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UNIT MAST AND OR SELF – SUPPORTING TOWER

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					     TECHNICAL SPECIFICATIONS




            FOR THE




          INSTALLATION OF




TELECOMMUNICATIONS MASTS AND TOWERS




                                      1
           Table of Contents
                                                       Page


Chapter One – General Principles of Practice              3

     1.1   Preamble                                       4
     1.2   Types of Structures                            5
     1.3   General Guidelines                             5
     1.4   Certification - Company and Employees          7
     1.5   Siting                                         8
     1.6   Environmental Requirements                     9
     1.7   Structural Certification                      14
     1.8   The Terrain                                   14
     1.9   Basic Wind Speed                              16



Chapter Two – Design and Construction                    20

     2.1   Service Life                                  21
     2.2   Superstructure                                21
     2.3   Structural Types for Self-Support Lattice     26
     2.4   Painting                                      55
     2.5   Obstruction Lighting                          55
     2.6   Substructure                                  56
     2.7   Earthing and Lightning Protection             75
     2.8   Safety Devices                                81


Chapter Three – Material Specifications                  85

     3.1   The Superstructure                            86
     3.2   Concrete                                      87
     3.3   Earthing and Lightning Protection             88
     3.4   Metals and Galvanizing                        88
     3.5   Earthing Clamps                               89
     3.6   U-Bolts                                       89
     3.7   Connector Clamps                              91

                                                              2
     3.8    Screw Down Clamps                      92
     3.9    Earth Bars and Disconnecting Clamps    93
     3.10   Lightning Arrestor                     95
     3.11   Copper Tapes                           96
     3.12   Connectors                             97
     3.13   Bi-metallic Connectors                 98
     3.14   Guy System Materials                   99
     3.15   Antenna Mounting Frames               101



Chapter Four – Maintenance and Testing            108

     4.0    First Line Maintenance                109
     4.1    Hot Dip Galvanization                 109
     4.2    Tower Maintenance                     109
     4.3    Maintenance Philosophy                110
     4.4    Routine Checks                        111
     4.5    Annual Maintenance Checks             113
     4.6    Testing                               115


     Glossary                                     121


     Index                                        124




                                                        3
         CHAPTER ONE




GENERAL PRINCIPLES OF PRACTICE




                                 4
1.1   Preamble

This document is intended to be a general, simple to read guide for
telecommunications services operators, fabricators and installers of
telecommunications towers and masts in the environmental, safety and
engineering practice that must be adhered to. It is intended to be a
handbook to be used by all who shall have anything to do with
telecommunications towers and masts whether as owners, fabricator,
installers and local authorities.

We have also provided comprehensive data on wind speeds for the entire
country that will form an easy reference material for engineers that are in
the business of designing masts and towers.

Responsibilities of telecommunications tower owners, users, builders are
set out in easy to read format, devoid of technical jargons. These
regulations consider towers from the different standard structures, the
perspective of their being made up of substructures and the
superstructures, public safety, safety of personnel and safety of equipment.
Compliance to the standards set out herein is mandatory.




                                                                              5
1.2     Types of Structures

Telecommunication towers may be of several types and range in height
from 30 to 300 meters or more. Three general forms of telecommunication
towers are

       Monopoles that consist of tapered steel tubes that fit over each other
        to form a stable pole,
       Guyed towers that are stabilized by tethered wires
       Self-supporting towers that are free-standing lattice structures.

These are illustrated in Figure 1 below.

                                   Guyed                   Self-supporting
              Monopole
        .




                               Figure 1 - Tower Types



1.3 General Guidelines

This specification applies to communication lattice towers and masts
constructed and installed in Nigeria.

        (a) It is assumed that the predominant load on these structures is
            wind load.


                                                                                 6
     (b) Each structure shall be made of hot dip galvanized steel sections.
     (c) Masts could be guyed or free standing
     (d) Free standing masts should not exceed 150 meters in height.
     (e) Masts and towers may be installed on a property with the written
        permission of the property owner and the approval of the Nigerian
        Communications Commission.
     (f) Structures above 30 meters in height may only be installed with a
        clearance certificate issued by the Nigeria Airspace Management
        Authority (NAMA).
     (g) No masts or towers (irrespective of the height) may be installed
        within 15 kilometers of any airport without prior approval and a
        permit from the Nigeria Airspace Management Authority (NAMA).
        This requirement also applies to such structures within the
        proximity of helicopter pads and their approaches.
     (h) The armed forces are exempted from this regulation in times of
        war only. At the cessation of hostilities any structures erected
        under this waiver must be submitted for reassessment and
        approval.
     (i) The open space available at the site of a proposed mast or tower
        installation must be at least three times the space required by the
        base of the structure.
     (j) A permit must be obtained from the Nigerian Communications
        Commission for the erection of any Masts or Towers whose height
        exceeds 20 meters and such structures shall be registered with
        the NCC on completion.


The following documents will be submitted to the NCC as part of the
application for a permit.



                                                                              7
 I. Site plan showing the proposed structure location in relation to
    adjoining structures.

 II. Evidence of ownership of the property on which the structure is to be
     installed or a written consent of the landlord.


III. Geographical coordinates of the proposed location of the structure and
     that of the nearest airport, heliport or helipad. In the alternative, a
     permit issued by the Nigeria Airspace Management Authority (NAMA)
     for the erection of the structure in the proposed location.

IV. Design of the structure showing its effective height, foundation, guys
    (where used), members, ladders, rest and work platforms, earthing,
    lightning protection and aviation lighting.


V. Detailed information on the software package used in the design to
   enable easy verification of the fidelity of the design of the structure.

VI. Certification of the proposed installer issued by the Nigerian
    Communications Commission (NCC).


The following guide-lines should be adhered to:

Each completed mast or tower must have a name plate bolted to each of its
legs on which the following particulars of the fabricator, operator and
installer are detailed

     Name of owner
     address of owner
     telephone numbers of owner
     Permit Number issued by the NCC for erection of the Mast at the
      location and in addition the following particulars pertaining to the
      antenna.

     date of erection
     height
     number of antenna
     Operating Frequencies


                                                                              8
    Location address
    Geographical coordinates
    a log book showing inspection dates and types of inspections
     performed

A tower or mast erecting crew must have a current Workmen’s
Compensation policy from a 1st Class insurance company to a minimum
value of five million naira or any such amount as may from time to time be
specified by the Nigerian Communications Commission, for any one claim
for third party claims. Responsibility for accidents during the installation
period shall be that of the installer and it shall revert to the owner of the
masts or towers on completion and handover.

 All masts and towers must be insured by their owners against third party
claims in the event of collapse.

1.4   Certification - Company and Employees

The minimum basic educational qualification for employees in the
fabrication, erection and maintenance of towers and masts shall be a four
year training programme in welding and machining from an accredited
Technical College and a City and Guilds Final Certificate. Installers who
meet the basic qualifications shall be licensed by the NCC. No installers
shall operate without the NCC license.

All checking visits and maintenance interventions have to be done by
employees with special qualification in telecom tower manufacture or
maintenance.

A tower fabricating company shall be licensed by the NCC upon
satisfaction that

    She has acquired enough capital equipment to enable her deliver
     safe and quality installation.
    She has in her employ, qualified and licensed fabricators.
    She has a good Workmen’s compensation insurance policy from a
     reputable insurance company
    She also has a good third party accident insurance policy
    She has a viable Health, Safety and Environment policy




                                                                                9
Tower and mast installation is an equipment based procedure. A company
applying to the NCC for an installation permit shall possess or demonstrate
easy access to the following capital equipment: -

       Packer
       Excavators
       Bull Dozer
       Forklift
       Long Boom Arm Crane
       Concrete Vibrator and Poker

1.5     Siting

This Section establishes siting the location of telecommunication towers
and masts with the objective of minimizing their number, protecting and
promoting public safety, and mitigating the adverse visual impacts on the
community whilst promoting the provision of telecommunications service to
the public.

Cities may not refuse the placement, construction and modification of tower
facilities on the basis of environmental or radio frequency emissions as
long as such facilities comply with the Nigerian Communications
Commission’s regulations concerning such emissions.

Telecommunications towers and masts, when permitted by the Nigerian
Communication Commission and the local authority, shall be regulated and
governed by the following use regulations and requirements.

1.6     Environmental Requirements

Height

The maximum height that may be approved for a telecommunication tower
in Nigeria is 150 meters. A tower, more than 50 meters in height, may be
approved by the National Communications Commission if the Commission
is satisfied that the increased height of the tower:

(1) Will not be detrimental to the public health, safety or general welfare.
(2) Will not have a substantial negative effect upon neighbourhood.
(3) Is in conformity with the intent and purpose of the planning of the area
      and the general plan of the community.

                                                                               10
(4) Will not impair the obligation to comply with any other applicable laws or
   regulations.

1.6.1 Space requirements.

a. One parking/loading space shall be required to serve a
   telecommunication tower site.

b. Any tower site lying 50 meters or less from a paved road shall be paved

c. If the site is more than 50 meters from a paved road, hard-surfacing of
   parking / loading spaces and driveways shall not be required for those
   portions of the site lying more than 50 meters from any paved road.

d. Stealth and/or camouflage design of towers and antennas are
   encouraged to reduce the visual impact of the structure.

1.6.2 Screening

An opaque screen at least 2.5 meters in height must surround the base of a
telecommunication tower. The screening shall also include landscaping
provisions for any portions of the development visible from adjacent
residential or used property or right-of-way. The use of barbed wire or other
security fencing material shall be allowed. Screening requirements may be
waived if the design of the tower is found to be compatible with the
adjacent land uses.

1.6.3 Removal of abandoned towers

A tower that has not been maintained for a continuous period of three years
shall be considered abandoned. The NCC will determine the date of
abandonment and may request documentation from the owner/operator
regarding the issue of usage.

Upon the determination of abandonment, the NCC will issue a removal
notice to the owner.

The owner shall dismantle and remove the tower from the property within
90 days of receipt of notice from the Nigerian Communications
Commission. An abandoned tower that is not removed within the 90 day



                                                                             11
period shall be removed by the NCC and removal costs plus a penalty shall
be paid by the owner.

1.6.4 Inspections

Telecommunication towers shall be inspected by a qualified tower
inspection service employed by the NCC once every six months to assess
the structural condition of the tower and support equipment. Owners of
towers which fail to meet the required standards will be notified to remedy
the situation within 30 days. Failure to remedy notified lapses shall attract
stiff penalties.

1.6.5 Authorization

 All telecommunications towers and masts shall be erected and operated in
compliance with Nigerian Communications Commission and Nigeria
Airspace Management Authority regulations.

1.6.6 Structure

Towers and masts shall be designed and located such that should any
structure fall, it will avoid habitable structures and public streets. This shall
be the major determinant factor in the issue of setbacks from adjacent
existing structures.

1.6.7 Co-location

Towers shall be designed and built to accommodate a minimum of three
service providers on the same structure, if over 25 meters in height. The
owner of the tower must certify to the NCC that the tower is available for
use by other telecommunications service providers on a reasonable cost
and nondiscriminatory basis. The Nigerian Communications Commission
will have the final authority for arbitration where any serious disagreement
that threatens collocation arises.

1.6.8 Fencing

Security fencing, if installed, shall be by a wrought iron, barbed wire, steel
chain link fence with evergreen hedge or a masonry wall not less than 1.8
meters in height. The exterior of equipment buildings and/or metal
equipment cabinets visible from residential areas or public rights-of-way



                                                                                12
shall be painted to reflect the color and character of adjoining structures or
blend with adjacent landscaping and other surroundings.

1.6.9 Setbacks

All telecommunication towers as well as guys and guy anchors shall be
located within the buildable area of the property and not within the front,
rear, or side building setbacks. Telecommunication towers in excess of 150
meters in height shall be set back a minimum of 50 meters from the right-
of-way of all controlled access, federal and state roadways designated as
freeways, to provide unobstructed flight paths for helicopters.

Towers shall be set back the greater distance of:

(a) 10 meters from any residential or used property;

(b) 25 percent of the height of the tower

(c) The distance specified as a potential hazard area by the designer of
    the structure.

Guy wire anchors and accessory structures shall not encroach into the
mandatory setbacks listed above.

1.6.10      Signage

No signage, lettering, symbols, images, or trademarks in excess of 1200
cm2 shall be placed on or affixed to any part of a telecommunications
tower, mast, antenna or antenna array fencing other than as required by
NCC for the purposes of Telco identification. No adverts will be allowed on
these structures.


1.6.11      Lighting

Telecommunication towers shall only be illuminated as required by NAMA
and/or ICAO. No signals, lights or illumination of any kind shall be permitted
on or directed towards any tower unless as required by the NAMA or any
other appropriate public authority. Security lighting around the base of a
tower must be shielded so that no light is directed towards adjacent
properties or rights-of-way.



                                                                             13
The purpose of obstruction lighting and marking is to ensure that an
obstruction to air navigation remains visible at a range sufficient to permit a
pilot to take appropriate action in order to avoid the obstruction by not less
than 305m vertically within a horizontal radius of 610 meters from the
obstruction.

A typical obstruction lighting kit shall include the following:

    Light with bulbs of a minimum of 10,000hrs service life
    Junction box
    Photo sensor
    Power cable (in conduit and armoured)
    Weather proof Light flasher. Flash rates of 40/min are allowable
     typical values.
    Assembly hardware such as U-bolts and connection bolts

Design of a lighting kit is regulated by governmental organizations.
One factor in determining lighting requirement is the height of the
structures. ICAO regulates the international industry whilst NAMA is
regulator of the Nigerian industry in line with ICAO recommendations.
Aviation lighting gear should be designed to have minimal serviceable
components so as to reduce the problems of regular ascent of towers to
service lamps.

1.6.12      Residential Areas

Telecommunications towers above 25 meters in height are, as a general
rule, not permitted within districts delineated as residential. Where they are
by exception allowed, they must be placed a minimum ratio of 3 to 1
distance to height to the nearest residential property.

Towers or masts or monopoles in excess of 25 meters in height are
permitted in the non-residential districts.

1.6.13      Tower to Tower Spacing

Any new telecommunications tower in excess of 55 meters in height must
be located a minimum of one kilometer from any other existing tower in
excess of 55 meters in height.




                                                                             14
1.6.14      Nearness to Power Lines

No tower or mast shall be installed in close proximity to High Voltage
electrical power transmission lines. The closest distance shall be that
equivalent to 120% of the height of the mast. In other words, the minimum
separation shall be the height of the mast plus 20% of the same height as a
safe margin.

1.6.15      Alternative Mounting Structures

Alternative Mounting Structures 30 meters or less in height shall be
permitted in residential areas.

Alternative Mounting Structures in excess of 30 meters in height are
permitted in the non-residential areas.

Alternative Mounting Structures must be similar in color, scale and
character to adjoining buildings or structures or blend with the landscaping
and other surroundings immediately adjacent to them so as to generally
avoid the creation of unique visual objects that stand out in the
environment.

1.6.16      Antenna Mounts

Antenna mounts must have structural integrity so as to guarantee public
safety.

(i)    Whip and Panel Antenna Mounts

       a.   Individual telecommunications antennas are allowed on existing
            low tension electric utility poles, light standards, and
            telecommunication towers in excess of 12 meters in height,
            provided that the total length of any antenna does not exceed
            15 percent of the height of the existing structure.
       b.   Telecommunications antennas and arrays are not allowed on
            existing high tension electric transmission towers.

       c.   Panel and whip antennas are permitted on billboard structures.

(ii)   Dish Antenna Mounting Standards

                                                                           15
      a.    Ground mounted dish antennas in excess of five feet (1.5
            meters) height shall be screened from roadways and adjacent
            property by a minimum 1.8 meter high screening fence.

      b.    Building and roof mounted dish antennas of one (1) meter or
            less in diameter, are permitted in all areas. No permits are
            required for this category

       c.   Building/roof mounted dish antennas in excess of 1 meter in
            diameter, may be permitted on buildings on the condition that a
            structural engineer’s certification that the building will withstand
            the additional load is provided to the Nigerian Communications
            Commission.

1.7   Structural Certification

Prior to the installation of a telecommunications tower, mast and antenna
support structure on any building or roof the NCC shall be provided with a
structural engineer's certification that the structure will support and not be
adversely affected by the proposed mast, tower, antenna and associated
equipment.

1.8   The Terrain

The terrain for purposes of this specification is Nigeria and includes its
territorial waters and the continental shelf. In making designs for masts
and tower structures, this terrain is classified into three broad geographical
zones based on measured worst case wind speeds measured over a
period of 30 years.

   1) Exposed smooth terrain with virtually no obstructions and in which the
      height of any obstructions is less than 1.5m. This category includes
      open sea coasts, lake shores and flat, treeless plains with little
      vegetation other than short grass.

   2) Open terrain with widely spaced obstructions (100m apart) having
      heights and plan dimensions generally between 1.5m and 10m. This
      category includes large airfields, open parklands or farmlands and
      undeveloped outskirts of towns and suburbs with few trees.




                                                                              16
  3) Terrain having numerous closely spaced obstructions generally the
     size of domestic and high rise buildings. This category includes
     wooded areas and suburbs, towns and industrial areas, fully or
     substantially developed.

Wind loading shall be the predominant dynamic loading to be considered
outside dead weights since severe environmental conditions that lead to
additional seasonally variable loads are non-existent. Wind load rating is
based on the height of the tower and where it is located.




                                                                             17
                              Figure 1.1


Figure 1.1 above is a map of Nigeria showing the average wind speeds as
measured by the Nigerian Meteorological Agency. Wind loading for a
structure is to be considered over the full length of the structure and is to be
measured in Newtons per square meter (N/m2). The basic wind speeds
depicted in this map are measured at 10 meters above the ground. These
values increase with height and need to be so corrected when making
computations.




                                                                             18
Engineers are encouraged to consider and design for specific conditions
that might exceed these given standard values. Design philosophy shall be
based on two limiting states - strength and serviceability. The strength limit
considers the loading of a tower under extreme conditions; the
serviceability limit ensures the tower will provide the proper service under
normal conditions.
Towers shall be analyzed under three specific types of loading:

         (a)   wind
         (b)   environmental
         (c)   seismic

Wind effect on a tower must take cognisance of a number of external
conditions that might change the dynamics of the wind, such as terrain,
gusts, the method of wind-speed determination and the value of safety
factors needed for a specific tower type. The safety factor defines the
impact a failure of the tower would have to its operational integrity, human
life and property. A proportionate amount of over design must be applied to
take care of these.

1.9   Basic Wind Speed

The superstructure is really being designed to resist various pressures,
wind load, being the major one for Nigeria. Wind velocities constitute the
measured data generally available. A conversion has to be made from wind
velocity to wind pressure. Various existing standards define and measure
wind velocity in different ways and therefore the formulas used to convert
these velocities to pressure produce results that can vary as much as 25%.
That translates into a 25% difference in design loads that will produce
different foundation sizes all of which mean a totally different installed cost.

Engineers are therefore encouraged to use basic wind speeds in design of
wind loading. Basic wind speed approach assumes wind given winds
speeds from meteorological measurement to be at 10m above ground
level. Basic wind speed design escalates the wind load from 10 meters
above ground to the top of the structure.

For example, for a 90 meter tower with a basic wind speed design of 115
km hr-1, the wind load design at the top of the tower is 160 km hr-1.

Structures shall be designed to withstand forceful wind speeds that occur


                                                                             19
on the average of once every 30 to 50 years. This wind speed is then
escalated, with height, to a much higher wind speed at the top of the
structure. A gust factor to account for the varying nature of wind shall also
be incorporated into the design of the structure.


The wind speeds shown in figure 1.1 above were measured from the
stations listed in Table 1.1. Engineers who desire greater accuracy in their
wind speed calculations are encouraged to use figure 1 in conjunction with
Table 1.1.


                              Table 1.1

    STATION NAME            LAT.    LONG         STATE          ELEV.
S/N                                   .
 1 YELWA                   10.53’   04.45’                      244.0
                             N        E      KEBBI
 2    BIRNI KEBBI          12.28’   04.13’   KEBBI              220.0
                             N        E
 3    SOKOTO               13.01’   05.15’   SOKOTO             350.8
                             N        E
 4    GUSAU                12.10’   06.42’                      463.9
                             N        E      ZAMFARA
 5    KADUNA               10.36’   07.27’   KADUNA             645.4
                             N        E
 6    KATSINA              13.01’   07.41’   KATSINA            517.6
                             N        E
 7    ZARIA                11.06’   07.41’   KADUNA             110.9
                             N        E
 8    KANO                 12.03’   08.12’   KANO               472.5
                             N        E
 9    BAUCHI               10.17’   09.49’   BAUCHI             609.7
                             N        E
10    NGURU                12.53’   10.28’   YOBE               343.1
                             N        E
11    POTISKUM             11.42’   11.02’   BORNO              414.8
                             N        E
12    MAIDUGURI            11.51’   13.05’   BORNO              353.8
                             N        E
13    ILORIN               08.29’   04.35’   KWARA              307.4
                             N        E


                                                                            20
14   SHAKI        08.40’   03.23’   OYO
                    N        E
15   BIDA         09.06’   06.01’   NIGER     144.3
                    N        E
16   MINNA        09.37’   06.32’   NIGER     256.4
                    N        E
17   ABUJA        09.15’   07.00’             343.1
                    N        E      FCT
18   JOS          09.52’   08.54’   PLATEAU   1780.0
                    N        E
19   IBI          08.11’   09.45’   TARABA    110.7
                    N        E
20   YOLA         09.14’   12.28’   ADAMAWA   186.1
                    N        E
21   ISEYIN       07.58’   03.36’   OYO       330.0
                    N        E
22   IKEJA        06.35’   03.20’   LAGOS      39.4
                    N        E
23   OSHODI       06.30’   03.23’   LAGOS      19.0
     MET.AGRO       N        E
24   LAGOS (HQ)   06.27’   03.24’   LAGOS      14.0
     ROOF           N        E
25   LAGOS        06.26’   03.25’   LAGOS      2.0
     (MARINE)       N        E
26   IBADAN       07.26’   03.54’   OYO       227.2
                    N        E
27   IJEBU-ODE    06.50’   03.56’   OGUN       77.0
                    N        E
28   ABEOKUTA     07.10’   03.20’   OGUN      104.0
                    N        E
29   OSHOGBO      07.47’   04.29’   OSUN      302.0
                    N        E
30   ONDO         07.06’   04.50’   ONDO      287.3
                    N        E
31   BENIN        06.19’   05.06’   EDO        77.8
                    N        E
32   AKURE        07.17’   05.18’   ONDO      375.0
                    N        E
33   WARRI        05.31’   05.44’   DELTA      6.1
                    N        E



                                                       21
34    LOKOJA               07.47’   06.44’   KOGI              62.5
                             N        E
35    ONITSHA              06.09’   06.47’   ANAMBRA           67.0
                             N        E
36    PORT-                04.51’   07.01’   RIVERS            19.5
      HARCOURT               N        E
37    OWERRI               05.29’   07.00’   IMO               91.0
                             N        E
38    ENUGU                06.28’   07.33’   ENUGU            141.8
                             N        E
39    UYO                  05.30’   07.55’   AKWA IBOM         38.0
                             N        E
40    CALABAR              04.58’   08.21’   CROSS             61.9
                             N        E      RIVER
41    MAKURDI              07.44’   08.32’   BENUE            112.9
                             N        E
42    IKOM                 05.58’   08.42’   CROSS            119.0
                             N        E      RIVER
43    OGOJA                06.40’   08.48’   CROSS            117.0
                             N        E      RIVER

            Table 1.1 – Meteorological Stations in Nigeria




The above data obtained from the National Meteorological Services
indicate that the highest recorded wind speed over a period of 20 years is 7
ms-1, which translates to a mere 420 mhr-1. However, wind gusts of the
order of 55 km hr-1 have been recorded infrequently. Since these data form
our worst case scenario, masts and towers in Nigeria shall be designed to
withstand a minimum ground wind speed of 70 km hr-1.




                                                                          22
     CHAPTER TWO




DESIGN AND CONSTRUCTION




                          23
2.1 SERVICE LIFE

The expected service life of a tower shall be 25 years. The design, choice
of fabrication materials, fabrication methods, installation accessories, all
safety factors and tower loadings shall all be made to conform to standards
for this to be achieved.

Qualified professional engineers shall design and specify materials that
meet the requirements to give a minimum service life of 25 years in the
working environment. Qualified welders and skilled welding supervision
shall be deployed to give positive effect on the finished product. The
highest quality of welding must be built in. Poor quality welding will be
apparent shortly after installation by which time repairs will be very
expensive and time consuming. Proper welding means good quality
finishes and thus minimizes long term maintenance costs.
2.2 SUPERSTUCTURE
2.2.1 Finishes
All steel materials that are to be used in the superstructure shall as a
standard be hot-dip galvanized and later painted according to NAMA paint
schedule for obstructions. All aluminum materials shall have aluminum
finish and will be equally painted according to NAMA paint schedule for
obstructions.

2.2.2 Self-Support towers
Self support design is often the solution of choice when land availability is
limited. The tower uses tapered sections, and face widths will vary
according to height and load capacity required.

They are recommended for most applications in Nigeria anywhere it is
technically feasible to install them. They are designed and constructed in:

   1) Lattice structure

      Triangular or square structure
      With tube legs, angle legs, lattice legs or solid round legs
      Sections in steel angle steel or steel tubes
      Steel angle cross bracing.
      Tapered sections
      Face widths vary according to height and load capacity.


                                                                              24
    Rest platforms provided every 20 meters of height
    Work platforms provided at all height where antennas are to
     be installed
    Fitted with climbing ladder

Standard support forms for lattice structures are specified as follows:

   a) Lattice Leg
          cost-efficient, high-capacity design
          ideally suited for multi-carrier applications
          fast and easy assembly
          Bracings shall be of angle steel




   b) Angle Leg
       bolt-up construction
       constructed from steel angle steel
       Bracings shall be of angle steel




   c) Tube Leg / Solid Round Leg
       time-proven strong structural shape
       constructed from schedule 80 pipes
       Bracings shall be of angle steel
       bolt-up construction




                                                                          25
Towers legs shall be constructed from schedule 80 pipes or angle steel.
Hollow aluminum pipes shall be used for short towers. Bracings shall be of
angle steel construction or aluminum in case of aluminum towers.
Mast sections, when made from steel pipes, shall be
joined to each other through joint plates welded to the
base of each section. The width of the mast section joint
plates should be double the width of the wall of the pipe
they are supporting.

Gussets shall be used in the strengthening of the weld
joint between the base plate and the tower section.
Each plate shall have four 20mm diameter holes drilled
to accommodate four 18mm bolts, nuts and washers.
When bolting sections together, bolts shall be placed
upside down with washers and nuts on topside of plates,
the connecting face of plates shall not be painted. Lock
nuts must be used but nuts on bolts may be clinched if
lock nut is not utilized. Lock washers and lock nuts shall
on no account be omitted on antenna support steel work
and dish panning arms as that will directly result in loss of signals.

When a tower is made from angle steel, sections shall be joined to each
other through appropriately sized flanges, bolts, washers and lock nuts.
Bracing inhibits torque on a tower and its non adequate application
exposes towers to torque. This in turn results in loss of signal during strong
winds speeds.

2.2.3 Monopole Towers

   Monopole or Post Masts are to be made from galvanised hollow steel
   pipes or high strength steel. They shall be designed for a variety of
   multi-user configurations and finishes to meet local aesthetic
   requirements.

   The pipes are to be constructed tapered so that one pipe base fits into
   the top of another until the desired height is achieved. A joint in the
   arrangement has an overlay between the two adjacent pipes. The depth
   of the overlay, the base width and the number of pipes in a particular
   monopole shall be determined by height desired of the tower, the



                                                                            26
  thickness of the pipe walls, the base diameter and whether the tower
  shall be guyed or not.

  For a monopole,

   Sections shall be made from hollow, heavy duty, thick steel tubes,
    flanged steel tubes or low-alloy, high-strength steel.
   Each shaft section shall be a constant-tapered hollow steel section
   Slip joints are designed with a minimum of 11/2 times the pole
    diameter at the splice.
   Sections shall fit into each other with overlap
   Pipe diameter shall decrease from bottom to top
   Shall be guyed or self supported
   Shall be fitted with climbing rugs
   Usually not very tall structure in the self support design

Tapered steel and flanged steel poles feature designs that blend well into
the environment and require minimum space for installation.
Flanged steel poles are easy to handle and install. Connections shall be
precision fitted to allow quick assembly of modular sections and the top
platform, side arms or mounting frame. Pole sections shall be made with
identical base flange plates to permit simplified modifications of mounting
heights and antenna reconfigurations.
Tapered steel poles have comparatively smaller base diameters and so
demand minimal land space. Tapered poles can be installed quickly do
offer extremely efficient strength-to-cost ratio.

2.2.4 Guyed Towers

Guyed masts do also come in lattice, triangular or square, tapered or
straight, as well as monopole structural forms. Guyed masts are supported
and held in position by guy wires or ropes. Mast Guy Ropes shall be made
from pre-stretched steel only. For every mast, the specified minimum
strength of the guy wire shall be the maximum tension likely to occur in the
worst loading condition.
Guy wires must not be over tightened. Excessive tension may cause
alignment problems and even a cable rupture. It may cause permanent
wrapping of tower structural parts. Extreme precaution must be taken while
tightening because just 3 turns of a tightening device would increase the
tension of a 45m long guy wire by about 250kg.


                                                                              27
All sections must be straight square sections and eliminate any potential
problems with twisting or the need to shim the legs. Typical tower sections
shall have a brace configuration with horizontals (z, x or k) and pivot base
sections. These tower-structures are wholly of steel, modular and hot-dip
galvanized. Sections can be of the same face width but should the tapered
type be contemplated, it shall be designed with junction flanges. Tube or
solid legs with solid bracing increases the tower rigidity to allow for the twist
and sway.

In the guyed mode all the forces on a tower are supported by the guy wires.
Everything about the guy wire has to be engineered with precision and a
minimum safety factor of 2.0 applied to the design. The design, based on
the load calculations shall determine working load and the break strength
required of the guy wire and subsequently the choice of the size and grade
of the wire.

The choice of each guy earth screw anchor shall be dependent on its
holding power in the soil, which is a function of its diameter and length. This
is used to compute the minimum number of guys required.
As a general rule guys are planted in three directions at 120 o apart from
each other. The distance from the base of the tower to the guy anchor base
shall be one quarter of the height of the tower.

2.2.5 Roof Mounts

Roof mounting is an inexpensive way of elevating signals above roof
interference or any other obstruction. Structural checks must be made to
ascertain the capability of a chosen roof to withstand the additional load
being imposed on it by the structure and the entire antenna array it will
support. All roof mounted masts or towers must be certified by the
building’s structural engineer before installation.

As a general regulation roof mounts shall be limited to light weight
structures of low heights and support minimal dead and dynamic loads.
Roof mounts can be installed in the penetrating or non-penetrating modes.
They can be self support or guyed.




                                                                              28
       2.3 Structural types for Self Support Lattice

                                         Single Bracing




                            Panel Height


               Face width
                                                                                                  Redundant
        Type       S1                         S2                S3                                diagonal
                                                                          Redundant Horizontal
                                             X - Bracing


Panel Height



        Type       X1               X2                     X3        X4        X5                     X6


                                                K - Bracing


Panel Height



        Type       K1              K2                      K3        K4       K5                      K6


                            Figure 2.1 – Bracing Types

               Members shall be made from solid rod, pipe or angles.
               Engineer must specify wall thickness if design is of pipes and
               sizes and thickness of legs if of angles.


               Lattice Mast Bracing Types




                                                                                                 29
                          Diagonal Spacing




 Double K2 Down
 Double K3, K3A, K4                                         Double K 1 Down




             K – Brace Down                  K – Brace Up




                       Figure 2.2

Members shall be made from solid rod, pipe or angles.
Engineer must specify wall thickness if design is of pipes and
sizes and thickness of legs if of angles.




                                                                              30
                            Horizontal




                         Secondary Horizontal




          Diamond                               Double K




             Z bracing                                     M - Bracing

                          Figure 2.3
Members shall be made from solid rod, pipe or angles.
Engineer must specify wall thickness if design is of pipes and
sizes and thickness of legs if of angles.




                                                                         31
                                  K-Brace End Panel

                                                        K-Brace End panel




                                                        K-Brace End Panel

     Face A

Double Slope-Bracing




   Diagonal Up Z-Brace                      Diagonal Down Z-Brace

                         Figure 2.4

 Members shall be made from solid rod, pipe or angles.
 Engineer must specify wall thickness if design is of pipes and sizes
 and thickness of legs if of angles.




                                                                        32
                                            Horizontal




             X-Brace
            CX-Brace                                                         TX-Brace




Secondary Horizontal




                Horizontal




                               CX, TX-Brace with Secondary Horizontal             K-Brace
Left




                                      Redundant Vertical



                                Redundant Sub-Horizontal




              K1 Down                                         K2 Down
            K1 Up (Opposite)                                  K 2 Up (Opposite)

                           Figure 2.5
       Members shall be made from solid rod, pipe or angles.



                                                                                        33
       Engineer must specify wall thickness if design is of pipes and sizes
       and thickness of legs if of angles.




                                           Redundant Sub Horizontal




                      K 3 Down                                               K 3A Down
                       K 3 Up (opposite)                                     K 4 Up
(Opposite)




        Redundant Sub-Horizontal
                                                        Redundant Diagonal




        Redundant Sub-Diagonal




                                                K 1B Down

                                              Figure 2.6


                                                                                         34
     Members shall be made from solid rod, pipe or angles.
     Engineer must specify wall thickness if design is of pipes and sizes
     and thickness of legs if of angles.




                           Sub Diagonal
                          Working Point

       Sub Diagonal
                                                       Redundant Sub Horizontal


      Optional Vertical



                                                            Red Diagonal 3




                                                             Horizontal 3


                                                                    Diagonal 2


                                                                    Horizontal 2

                                                                    Diagonal 1


                                                                    Horizontal 1




                                 Diagonal



                                          Figure 2.7

Members shall be made from solid rod, pipe or angles.
Engineer must specify wall thickness if design is of pipes and sizes and
thickness of legs if of angles.




                                                                                   35
            Sub Diagonal
                                                              Redundant Sub Horizontal



      Optional Vertical



                                                                    Diagonal 3




                                                                     Horizontal 3


                                                                               Diagonal 2


                                                                            Horizontal 2


                                                                               Diagonal
                                                                1




                                                                Horizontal 1



                             Diagonal



                             Figure 2.8 Portal Bracing

Members shall be made from solid rod, pipe or angles.
Engineer must specify wall thickness if design is of pipes and sizes and
thickness of legs if of angles.




                                                                                      36
                                     Face width




                                                  Section height

                            Slope change




                        Height




                                     Face width


                                 Fig. 2.9

X-braced, self supporting, lattice design showing face width,
slope change and tower height




                                                                   37
                                Face width
                                               0.16




                           Section 15
                            Section 14

                           Section 13

                           Section 12

                           Section 11

                            Section 10
                                                                      This represents a generalized
                           Section 9                                  design of a 15 section, 6m length
                                                                      per section tower.
                           Section 8
                                                               300'
                                                                      Loading considerations to be
                            Section 7                                 taken into account in the
                                                      275.6'

                                                                      specification of bracing sizes,
                            Section 6                                 bracing configuration (double or
                                                                      single), bracing bolt sizes, leg
                           Section 5                                  size and type, face widths at top
                                                                      and base, etc are: -
                           Section 4                                      Wind speed to include gust
                                                                            factor if applicable
                           Section 3
                                                                          Total anticipated antenna
                           Section 2
                                                                            load
                                                                          Maximum Shear per leg
                           Section 1                                      Maximum uplift reaction
                                                                          Maximum compression

                                         34'




                                 Face width

                               Figure 2.10

Superstructure of a 15 section X - Braced Steel Tower showing antenna
mounts. Tower can be designed and fabricated as a three or four legged self
support structure. New sections that are intended to result in higher towers shall
be added below section 1 with the design philosophy as to face widths being
maintained.

                                                                                                      38
                                          Face width
                                               4




                             Section 13


                             Section 12


                             Section 11


                             Section 10


                            Section 9

                                                                    Generalized prototype design of
                            Section 8
                                                                    a 13 section, 6m length per
                                                                    section tower.
                            Section 7
                                                                H   Loading considerations to be
                           Section 6
                                                       23623'

                                                                    taken into account in the
                                                                    specification of bracing sizes,
                            Section 5                               bracing configuration (double or
                                                                    single), bracing bolt sizes, leg
                                                                    size and type, face widths at top
                           Section 4
                                                                    and base, etc are: -
                                                                        Wind speed to include gust
                           Section 3                                      factor if applicable
                                                                        Total anticipated antenna
                           Section 2
                                                                          load
                                                                        Maximum Shear per leg
                           Section 1                                    Maximum uplift reaction
                                                                        Maximum compression
                                        Face width




                              Figure 2.11

           Superstructure of a 13 section X - Braced Steel Tower
Tower can be designed and fabricated as a three or four legged self support
structure. New sections that are intended to result in higher towers shall be
added below section 1 and the design philosophy as to face widths maintained.
                                                                                                      39
               78 metre Tower                          100 meter Tower
                                       1.6m

        section 13                                                      section 16

        section 12                                                      section 15

         section 11                                                     section 14


        section 10                                                      section 13

        section 9                                                       section 12

        section 8                                                       section 11


        section 7                                                       section 10



        section 6                                                       section 9

        section 5                                                       section 8


        section 4                                                       section 7


        section 3                                                       section 6


        section 2                                                       section 5


        section 1                                                       section 4

                      Face Width
                       8.4metres
                                                                        section 3


                                                                          section 2
Two towers of different heights illustrating the
general relationships between lattice tower heights,
number of sections and the face widths at the top
and bottom. Both towers are of identical design but
have different heights.                                                   section 1


                                                          Face width
                                                          10.4 meters

                       Figure 2.12 - Self Support Lattice Towers of different heights
                                                                                        40
                 Structural Design of a 12-section self support tower in single or Z bracing.

                                                               Face width decreases from base to top of the tower


                                                                           12"                          15"                        18"                                 21"                                       24"                                27"
            9"



                      Top Frame
            7                                                              13                           19                           25                                31                                        37                                  43




            8                     X
                                                                            14                          20                               26                            32                                        38                                 44




            9              Lower Frame                                     15                           21                          27                                 33                                        39                                 45


L




                                                                                                                    LEG # 4
                                                                                            LEG # 3




                                                                                                                                                                                                                                       LEG # 7
                                                                 LEG # 2




                                                                                                                                                           LEG # 5




                                                                                                                                                                                                     LEG # 6
e           10                           H                                  16                          22                               28                             34                                       40                                  46
g
 #1                         6"

           11                                                              17                           23                          29                                                                           41                                  47
                                                                                                                                                                       35



                           24"

            12                                                              18                          24                               30                            36                                         42                                 48




            W                                                              15"                          18"                         21"                                24"                                       27"                                30"



          Section 1                                                  Section 2                        Section 3                  Section 4                           Section 5                                 Section 6                         Section 7




                  30"                                     33"                                                 36"                                   39"                                       42"




                 49                                       55                                                 61                                     67                                       73


                                                                                                                                                                                                                       25 1-/X''

                 50                                       56                                                 62                                     68                                      74




                  51                                       57                                                 63                                    69                                       75
LEG # 8




                                                                                                                              LEG # 11




                                                                                                                                                                             LEG # 12
                                             LEG # 9




                                                                                 LEG # 10




                                                                                                                                                                                                                         X'

                      52                                   58                                                 64
                                                                                                                                                                                                                                   H
                                                                                                                                                      70                                      76




                  53                                       59                                                 65                                     71                                      77



                                                                                                                                                                                                                       24"

                      54                                    60                                                 66                                     72                                      78




                                                          36"                                                 38"                                                                            45"
                                                                                                                                                   42"

           Section 8                                   Section 9                                      Section 10                              Section 11                                Section 12


                                  Figure 2.13
          A 12-section, single braced, lattice tower. Each section is tapered to produce an
          overall tapered structure. Additional sections, if the tower has to be higher shall
          be of greater face width than section 12 until the tower reaches required height.


                                                                                                                                                                                                                                                             41
  Design Data of a Ten Section Light Duty Self-Supporting Tower

                                             Table 2.1


                                        TOWER SCHEDULE
  Section       Spread Dimension         Tower Legs**          Tower Braces            Bolts
  Number      Upper         Lower      36 KSI Yield STR      36 KSI YIELD STR      A 325 GRADE
                                                  2
  1 (Top)     30 cm         30 cm          5.0 cm         2.5cm x 2.5cm x 0.32cm     8mm
                                                  2
    2         30 cm         30 cm          5.0 cm         2.5cm x 2.5cm x 0.32cm     8mm
                                                  2
    3         30 cm         50 cm          5.0 cm         2.5cm x 2.5cm x 0.32cm     8mm
                                                  2
    4         50 cm         72 cm          5.0 cm         3.2cm x 3.2cm x 0.5cm      10mm
                                                  2
    5         72 cm         94 cm          5.0 cm         3.2cm x 3.2cm x 0.5cm      10mm
                                                  2
    6         94 cm        114 cm          5.0 cm         3.2cm x 3.2cm x 0.5cm      10mm
                                                   2
    7        114 cm        135 cm         5.75 cm         3.2cm x 3.2cm x 0.5cm      10mm
                                                   2
    8        135 cm        156 cm         5.75 cm         3.2cm x 3.2cm x 0.5cm      10mm
                                                   2
    9        156 cm        176 cm         5.75 cm         3.2cm x 3.2cm x 0.5cm      10mm
                                                   2
10(Grnd) 176 cm            198 cm         5.75 cm         3.2cm x 3.2cm x 0.5cm      10mm
**Cross-sectional area




                                             Table 2.2


                                    SECTION HEIGHTS AND WEIGHTSD WEIGHTS
Section
             Height           Legs               Braces            Lap Links        Total
Number
  1           3.0 m          36 Kg               8.5 Kg              4.5 Kg         65 Kg
  2           3.0 m          36 Kg               8.5 Kg              4.5 Kg         65 Kg
  3           3.0 m          36 Kg               10 Kg               4.5 Kg         70 Kg
  4           3.0 m          36 Kg              17.7 Kg              4.5 Kg        101 Kg
  5           3.0 m          36 Kg              27.5 Kg              4.5 Kg        111 Kg
  6           3.0 m          36 Kg               29 Kg               4.5 Kg        127 Kg
  7           3.0 m          40 Kg               30 Kg               4.5 Kg        153 Kg
  8           3.0 m          40 Kg               33 Kg               4.5 Kg        162 Kg
  9           3.0 m          40 Kg               34 Kg               4.5 Kg        171 Kg
  10          3.0 m          40 Kg               37 Kg                N/A          216 Kg




                                                                                            42
                                                       Table 2.3

                            SUPERSTRUCTURE DESIGN AND LOADING
HEIGHT                     ALLOWABLE                          MAX COAX
                                             MAX COAX                        WIND LOAD TOP       WIND LOAD 9m BELOW
 ABOVE WIND SPEED         DEAD WEIGHT                         9m BELOW                2                      2
                                             QTY/SIZE                               (M )               TOP (M )
GROUND                    PER SECTION                          QTY/SIZE
               Km/ hr             Kg.                                        FLAT       ROUND       FLAT           ROUND

30 m            110               90             3 / 25mm      3 / 25mm          0.9      1.4       1.1             1.7
                125               90             3 / 25mm                    0.46         0.7


24 m            110               135            3 / 25mm      6 / 25m       1.67        2.51       1.86           2.79
                125               135            3 / 25mm      6 / 25mm      0.70        1.05    0.88              1.32
                145               135            3 / 25mm          ―         0.74        1.11       ―               ―


18 m            110               180            6 / 25mm      6 / 25mm      2.14      3.21        2.32          3.48
                125               180            6 / 25mm      6 / 25mm      1.11        1.67       1.25         1.88
                145               180            3 / 25mm      6 / 25mm      0.64        0.95       0.85           1.13


12 m            110               360        12 / 25mm             ―         4.83       7.25        ―               ―
                125               360        12 / 25mm             ―         3.35        5.30       ―               ―
                145               360            9 / 25mm          ―         2.69        4.04       ―               ―




  Table 2.4 FOUNDATION DESIGN AND LOADING

       HEIGHT            WIND             MAX            MAX              MAX           TOTAL
                                                                                                        AXIAL
        ABOVE           SPEED           VERTICAL        UPLIFT         SHEAR/LEG        SHEAR
                                                                                                        (KIPS)
       GROUND           Km / hr          (KIPS)         (KIPS)           (KIPS)         (KIPS)

        30 m             145              23.0              19.0          2.12           3.50           2.34

        24 m             145              22.0              18.2          1.92           3.42           2.09

        18 m             145              17.0              14.7          1.40           2.50           1.82

        12 m             145              24.1              22.4          1.73           3.30           1.52

  Below 145 ms-1 wind speed; shear, vertical and uplift forces are negligible.
  All foundation designs shall be in accordance with maximum reaction loads
  indicated above. Modification of loading locations and equipment can be made
  provided reaction loads do not exceed indicated values.
                                                                                                                        43
Design Data of a Fifteen Section Medium Duty Self-Supporting Tower

             Table 2.5

                             SELF-SUPPORTING TOWER SCHEDULE
Section         Spread Dimension             Tower Legs**                    Tower Braces            Bolts
Number      Upper           Lower            36 KSI Yield STR                36 KSI YIELD STR      A 325 GRADE
   1        46 cm           46 cm               5.0 cm2                  3.2cm x 3.2cm x 0.5cm       10 mm
   2        46 cm           46 cm               5.0 cm2                  3.2cm x 3.2cm x 0.5cm       10 mm
                                                       2
   3        46 cm           76 cm               5.0 cm                   3.2cm x 3.2cm x 0.5cm       10 mm
   4        76 cm          1.04 m              5.75 cm2                  3.8cm x 3.8cm x 0.5cm       10 mm
                                                        2
   5        1.04 m         1.32 m              5.75 cm                   3.8cm x 3.8cm x 0.5cm       10 mm
   6        1.32 m          1.6 m              5.75 cm2                  3.8cm x 3.8cm x 0.5cm       10 mm
   7         1.6 m         1.88 m              9.30 cm2                  4.4cm x 4.4cm x 0.5cm       12 mm
   8        1.88 m         2.16 m              9.30 cm2                  4.4cm x 4.4cm x 0.5cm       12 mm
   9        2.16 m         2.43 m              9.30 cm2                  4.4cm x 4.4cm x 0.5cm       12 mm
  10        2.43 m         2.72 m              10.8 cm2                    5cm x 5cm x 0.5cm         12 mm
  11        2.72 m          3.0 m              10.8 cm2                    5cm x 5cm x 0.5cm         12 mm
  12         3.0 m         3.27 m              10.8 cm2                    5cm x 5cm x 0.5cm         12 mm
  13        3.27 m         3.56 m               16 cm2                   6.4cm x 6.4cm x 0.5cm       16 mm
  14        3.56 m         3.84 m               16 cm2                   6.4cm x 6.4cm x 0.5cm       16 mm
  15        3.84 m         4.11 m               16 cm2                   6.4cm x 6.4cm x 0.5cm       16 mm



        Table 2.6


                              SECTION HEIGHTS AND WEIGHTS
  Section
                    Height          Legs                        Braces              Brace Plates     Total
  Number
    1               3.0 m           36 Kg                       25 Kg                    N/A         65 Kg
       2            3.0 m           36 Kg                       25 Kg                    N/A         65 Kg
       3            3.0 m           36 Kg                       29 Kg                    N/A         70 Kg
       4            3.0 m           40 Kg                       57 Kg                    N/A        102 Kg
       5            3.0 m           40 Kg                       67 Kg                    N/A        112 Kg
       6            3.0 m           40 Kg                       78 Kg                    N/A        127 Kg
       7            3.0 m           65 Kg                       79 Kg                    N/A        153 Kg
       8            3.0 m           65 Kg                       88 Kg                    N/A        162 Kg
       9            3.0 m           65 Kg                       98 kg                    N/A        171 Kg
       10           3.0 m           76 Kg                       123 Kg                 8.0 Kg       216 Kg
       11           3.0 m           76 Kg                       134 Kg                 8.0 Kg       227 Kg
       12           3.0 m           76 Kg                       145 Kg                 8.0 Kg       246 Kg
       13           3.0 m           111 Kg                      148 Kg                 12.7 Kg      288 Kg
       14           3.0 m           111 Kg                      156 Kg                 12.7 Kg      296 Kg
       15           3.0 m           111 Kg                      166 Kg                 12.7 Kg      306 Kg

                                                                                                             44
Table 2.7

                        SUPERSTRUCTURE DESIGN AND LOADING
                                                      MAX COAX     WIND LOAD        WIND LOAD
                       ALLOWABLE DEAD     MAX COAX
 HEIGHT   WIND SPEED                                  9m BELOW        TOP         9m BELOW TOP
                       WEIGHT PER LEVEL   QTY/SIZE
                                                      QTY/SIZE      (SQ. M)           (SQ. M)
            KPH             KGS.                                 FLAT    ROUND   FLAT     ROUND

             110             135          3 / 22 mm 3 / 22 mm    2.09     3.14   3.07      4.60
  45 m       125             135          3 / 22 mm 3 / 22 mm    1.40     2.09   2.42      3.62
             145             135          3 / 22 mm 3 / 22 mm    0.37     0.56   0.56      0.84


             110             205          3 / 22 mm 3 / 22 mm    2.14     3.21   3.16      4.74
  39 m       125             205          3 / 22 mm 3 / 22 mm    1.58     2.37   2.60      3.90
             145             205          3 / 22 mm 3 / 22 mm    1.02     1.53   1.30      1.95


             110             270          6 / 22 mm 6 / 22 mm    2.23     3.34   4.09      6.13
  33 m       125             270          6 / 22 mm 6 / 22 mm    1.58     2.37   3.25      4.88
             145             270          6 / 22 mm 6 / 22 mm    1.20     1.81   2.32      3.48


             110             360          6 / 22 mm 6 / 22 mm    2.23     3.34   4.09      6.13
  27 m       125             360          6 / 22 mm 6 / 22 mm    1.53     2.30   3.25      4.88
             145             360          6 / 22 mm 6 / 22 mm    1.02     1.53   2.32      3.48


             110             400          9 / 22 mm     ―        2.14     3.21   ―          ―
  21 m       125             400          9 / 22 mm     ―        1.95     2.93   ―          ―
             145             400          9 / 22 mm     ―        1.72     2.58   ―          ―


             110             400          9 / 22 mm     ―        2.14     3.21   ―          ―
  15 m       125             400          9 / 22 mm     ―        1.49     2.23   ―          ―
             145             400          9 / 22 mm     ―        1.11     1.62   ―          ―




                                                                                                  45
          Table 2.8 TOWER FOUNDATION DESIGN & LOADING



      TOWER     WIND      MAX               MAX        MAX       TOTAL
                                                                          AXIAL
      HEIGHT   SPEED    VERTICAL           UPLIFT    SHEAR/LEG   SHEAR
                KPH       (KIPS)            (KIPS)     (KIPS)    (KIPS)   (KIPS)

       45 m     145      63.13             48.14        6.9      13.54     7.5


       40 m     145        51                40         5.1       10      5.39


       35 m     145        40                33        4.45        7      4.27


       30 m     145      29.21             24.21       2.92       4.68    3.97


       25 m     145      17.29             14.02       1.79       2.65    2.53


       20 m     145      15.94              12.9       1.73       2.6     2.14




Below 145 ms-1 wind speed; shear, vertical and uplift forces are negligible.
All foundation designs shall be in accordance with maximum reaction loads
indicated above. Modification of loading locations and equipment can be made
provided reaction loads do not exceed indicated values.


Table 2.9 Footing Assembly Weight Table

               Weight       Weight x 12
               (Kg/m)        (Kg/m)
                43                 17.16
               1.43             17.16
               1.43             17.16
                2.23               26.76
                2.40                28.8
                2.40                28.8
                 1.61              19.32
                3.06               36.72
                3.02               36.24



                                                                                   46
Table 2.10 Lap Link Weight Table
   Weight          Weight x 3
   (Kg/m)           (Kg/m)
   55.63            166.89
   58.01            174.03
   62.63            187.89
   65.55            196.65




Table 2.11
STRUCTURAL DESIGN DATA FOR A TYPICAL LATTICE TOWER

              80 meter Tower (Pipe) Configuration
 Section      Height      Leg Size (cm)                       Brace
                m       Grade A500 steel        Configuration     Size (mm)
    1           6        20 Schedule 80        Double Angle A     90 x 80
    2          12        20 Schedule 80        Double Angle A     90 x 80
    3          18        20 Schedule 80           Single 2x       100 x 100 x 4
    4          24        20 Schedule 80           Single 2x       100 x 100 x 4
    5          30        15 Schedule 80           Single 2x       100 x 100 x 4
    6          36        15 Schedule 80           Single 2x       100 x 100 x 4
    7          42        13 Schedule 80           Single 3x       75 x 75 x 1.5
    8          48        13 Schedule 80           Single 3x       75 x 75 x 1.5
    9          54        13 Schedule 80           Single 3x       60 x 60 x 6
   10          60         8 Schedule 80           Single 3x       60 x 60 x 6
   11          66         8 Schedule 80           Single 4x       60 x 60 x 6
   12          72       6.5 Schedule 80           Single 4x       50 x 50 x 5
   13          80       6.5 Schedule 80           Single 3x       50 x 50 x 5

       All brace connections shall be bolted and provided with locking pal nuts.
       Sections are in typical 6 meter lengths
       Leg strength minimum 46 KSI yield.
       Max Share/Leg: 40.11 KIPS
       Max Uplift: 288.26 KIPS
       Max Compression: 345.76 KIPS
       Design Wind Speed is 120 Km hr-1



                                                                                    47
Table 2.12
STRUCTURAL DESIGN DATA FOR A TYPICAL LATTICE TOWER


                       100 metre Configuration Lattice Tower
Section     Height   Leg Thickness
             ( m)     (cm) 50 KSI              Brace                        Redundant
                                      Bolt Size    Diag. Config.    Size (mm)         Size (cm)
   1          6           16         (2) 20mm        Double A       90 x 75 x 6       6 x 6 x 60
   2         12           16         (2) 20mm        Double A       90 x 75 x 6       6 x 6 x 60
   3         18           16         (2) 20mm        Double A       90 x 75 x 6       6 x 6 x 60
   4         24           16         (2) 20mm        Double A       90 x 75 x 6       6 x 6 x 60
   5         30           13           22mm          Single 2A      10 x 10 x 6       6 x 6 x 60
   6         36           13           22mm          Single 2A      10 x 10 x 6       6 x 6 x 60
   7         42           13           22mm          Single 2A      10 x 10 x 6       6 x 6 x 60
   8         48           13           22mm          Single 2A      75 x 75 x 8       6 x 6 x 60
   9         54           10           22mm          Single 2A      75 x 75 x 8       6 x 6 x 60
  10         60           10           20mm          Single 2A      75 x 75 x 8       6 x 6 x 60
  11         66            9           20mm          Single 3A      75 x 75 x 8       6 x 6 x 60
  12         72           7.5          20mm          Single 3A     60 x 60 x 600      6 x 6 x 60
  13         78           7.5          20mm          Single 3A     60 x 60 x 600      6 x 6 x 60
  14         84            5           16mm          Single 4X      50 x 50 x 6            -
  15         90            5           16mm          Single 5X      25 SOLID               -
  16         96            5           16mm          Single 1X      25 SOLID               -

                                           BRACE
                                                                    Internal
                                                                    Traingle
  1           6                                                    75 x 75 x 6
  2          12                                                    75 x 75 x 6
  3          18                                                    75 x 75 x 6
  4          24                                                    75 x 75 x 6



         Sections are in typical 6 metre lengths
         All brace connections shall be bolted and provided with locking pal nuts.
         All X-Braces shall be center bolted.
         Structure is designed for a maximum wind speed of 160 Km hr-1
         Total structure design weight (unloaded) is 38,000 Kgs
         Maximum design shear / Leg is 80 KIPS
         Total shear at the Base is 155 KIPS
         Maximum design uplift is 627 KIPS
         Maximum design Compression is 733 KIPS




                                                                                                   48
                          Monopole Tower – Structural Form


                                        Platform
             Platform Height

                 Section 1


                                    d              d

              Section 2
                                                              d – section overlap
                                    d                d
              Section 3

                    Height
                                    d                    d
              Section 4

                                d                      d
             Section 5                                       Section Height




                                        Base Plate

                               Figure 2.14

Sections fit into each other with an overlap (d). Base diameter, section height,
depth of overlap between sections and total mast height are all structural
stability issues determined by the structural design engineer. For higher towers,
additional sections are added below section 5 until the required height is
reached but there must be corresponding increases in base width as the
number of sections and consequently the height increases.


                                                                                    49
Table 2.13    Design details of a four section, 45 meter Monopole (Typical)


             Section                   4           3           2           1
Length (m)                           13.7          12         12         11.2
Number of Sides                       18           18         18          18
Thickness (mm)                        10           8          6.5         5.5
Lap splice / section overlap (m)                  1.7        1.45        1.14
Top Dia (cm)                         106           80         75          56
Bottom Dia (cm)                      130          110         93          75
Grade of Steel                                      A572-65
Weight (Kg)                          8.4          5.3         3.5        2.3
Material Strength                   80 ksi       80 ksi     65 ksi      65 ksi

    Tower above is designed for a 100 Km hr-1 basic wind




                                                                                 50
             Antenna carrying Monopole (Self Supporting)




                              Figure 2.15

Pictorial of a self-supporting monopole tower fully fitted with antenna support
bracket and carrying antennas




                                                                                  51
Section of a Typical Guyed three-legged Mast
            (Single or Z-bracing)




                A – Face Width (uniform throughout the mast)
                B – Vertical brace height
                C - Bolt spacing
                D – Steel member width
                E – Section height


              The design of a guyed mast must be such that it is very
              straight, easily connected and erector-friendly.


Figure 2.16




                                                                    52
                 N-section Guyed Pole Mast

                                     Triangular guy wire support
                                                                           Antenna support
                                                                           and outrigger




                                                                                       1
                                                                                           2   H

                        Turn buckles for Guy wire tension fine tuning




                                                                           1
                                                                               4   H
                                                              Base Plate
Base Plate




                                      Figure 2.17

    A four section guyed monopole illustrating the relationship between tower height
    (H) and the horizontal distance from tower base to the guy anchor
    (1/4 H). Tower can be installed in many sections.
    This design of masts is ideal for the installation of HF-SSB dipole antennas.




                                                                                                   53
                  Triangular Guy Wire support
                  Fits into the top portion of the
                  Mast




     Galvanised stake for attachment of
     buckles
     Used for Guy tension fine tuning




                         Figure 2.18
Details of parts of the guyed pole mast in figure 2.17 above




                                                               54
              Figure 2.19

Shows in detail, the antenna support outrigger shown in figure 2.17 above.




                                                                             55
Roof Mounts - Pictorial




                      Figure 2.20
Different ways of implementing roof mounts showing acceptable installation
standards that guarantee safety.
                                                                             56
                      Figure 2.21

              Examples of Non-Penetrating Roof Mounts
These can be implemented where possible with mass or reinforced concrete
bases.




                     Figure 2.22
       Penetrating Roof Mounts showing acceptable craftsmanship



                                                                           57
2.4 Painting

All skeleton type structures must be painted to ICAO stipulations on obstruction
painting.

ICAO stipulates that
   For structures up to 212 meters, the structure shall be given seven equal
    bands of red and white paint or orange and white paint.
   For structures above 212 metres nine bands of paint in alternating red and
    white or red and orange.
   In all cases the top and bottom of mast or tower must be painted red or
    orange.
   Paint shall be non gloss finish (matt).

In addition mast and towers shall be painted with base primer paint, one
suitable under coat of red and white or orange and white followed by two coats
of non gloss (matt) paint.

2.5 Obstruction Lighting

All mast and tower structures in Nigeria must conform strictly to ICAO / NAMA
regulations with respect to obstruction lighting of tall structures as follows:

   For every fifty meters of height above ground level, a tower shall have
    installed on it, one lamp on top and two lamps at the sides.
   Obstruction lamps shall be fitted and shall be maintained in a working
    condition at all times on all structures within 15 kilometers of an airport or
    helipad.
   Light intensity and colour as follows:

  Tower Height              Light Intensity                 Light Colour

  Below 45 m               not below 10 candelas            Red and fixed

  Betw 45 and 150m         not below 1600 candelas          Red and flashing

  Greater than 150m        4,000 to 20,000 candelas         White Flashing




                                                                                     58
            NAMA / ICAO Lighting Regulation


          105 - 150 m                                              Single light




        45 - 107 m

                                                                   Double
                                                                   lights
      0 - 45 m




                     Figure 2.23
Schamatic representation of the ICAO / NAMA obstruction lighting regulations.


2.6 Substructure

Foundations for the tower and mast structures shall be designed to withstand
the full expected dynamic loads - antennae, feeders, wind loading, etc. It shall
take cognisance of the complete findings of the site conditions (geotechnical
investigation of soils and wind conditions). This may call for different types of
foundation which may take the form of reinforced concrete blocks, standard pad
and column, raft, preset rock anchors or piles. Engineers must compute the
weight of tower structure, weight of antenna feeders and all associated steel
work then calculate effects of wind loads on total surface.



                                                                                    59
Constructional materials and installation methods must conform to the
conditions prevalent at the site.
Worst case load design condition shall always constitute the initial factor of
safety against overturning for complete foundations or any part thereof.
Standard foundation designs are to be made for normal soils. They may be
modified to suit the soil conditions at the installation site. Soil investigations
must be carried out at each site to determine the bearing pressures (vertical and
horizontal) and other subsurface conditions. The final foundation design shall be
made to suit the soil conditions at the site.
Normal soils are defined as dry cohesive soils having


   a) an allowable net vertical bearing capacity 192kPa
   b) an allowable net horizontal pressure 63kPa per linear meter of depth to a
        maximum of 192kPa.
   c) unit weight of compacted soil greater than 16kNm-3
   d) water table is at a depth greater than 2.5m below the surface
   e)   coefficient of passive earth pressure greater than 3.2
   f)   coefficient of active earth pressure of approximately 0.3
   g)   non acidic properties
   h)   no organic materials are present in the soil

Three basic physical forces shall be taken into consideration whilst designing
tower and masts foundations. They are: -

          a. Vertical down load
          b. Base shear
          c. Uplift load

Proper soil borings shall be made by competent soil testing specialists and they
must go deeper than the probable depth of the foundation to make sure of soil
type consistency a little deeper.



                                                                                     60
For guyed towers, borings are also to be taken at all guy locations and at the
base pier location. Conditions can vary widely on the site. Watch out that the
concrete mix specified by engineer is adhered to.

2.6.1 Foundations and Anchors

Foundations and Anchors shall be designed to support the structures and
specified loads for specific soil conditions. Pile, raft or specially designed
foundations or anchors are to be considered in submerged, marshy or peat soil
conditions. Foundation designs shall be made and certified by qualified and
registered professional engineers.

2.6.2 Standard Foundation

Standard foundations and anchors may be used for construction when actual
soil parameters equal or exceed normal soft parameters. Geotechnical
investigation to verify that actual site soil parameters equal or exceed normal
soil parameters must be made before standard foundations and anchors are
utilized in final designs.

Foundations and anchors shall be designed for the maximum structure
reactions resulting from the anticipated worst loading conditions. When
nonstandard foundations and anchors are to be used for construction, the soil
parameters recommended by the geotechnical engineer should incorporate a
minimum safety factor of 2.0 against ultimate soil strength.

2.6.3 Rock Anchors

Rock anchors shall be of type to permit long life and shall be treated against
corrosion to last over the design life of the tower. Pre-stressed rock anchors are
to have their upper terminating steel work in such a way as to have a steel-to-
steel connection between the structure footing and the rock anchor tendon. The
upper end termination of rock anchors shall not be encased in concrete but shall
be protected against corrosion so as to allow any subsequent checking of the
tension in the tendons during the life of the structure.

2.6.4 Anchor Bolts Template

Templates provide proper anchor bolt orientation at the time of foundation
forming. Templates shall be precisely fabricate and used in constructing tower
foundations to design specifications. Use of templates eliminates problems
associated with misalignment. A minimum of two anchor stirrups shall be
                                                                                  61
provided around each leg of a tower. Each stripe shall have a safe working load
(SWL) of 100KN.

2.6.5 Uplift

Anchors are to be dimensioned to provide sufficient safety against overturning. A
qualified geotechnical engineer shall design foundations especially when they are
to be sited in non-standard soils and the application of prototype designs for
normal soils becomes undesirable.

Standard foundations, anchors, or drilled and buried piers shall be assumed to
resist uplift forces by their own weight plus the weight of earth enclosed within
an inverted pyramid or cone whose sides form an angle of 300 with the vertical.
The base of the cone shall be the base of the foundation if an undercut or toe is
present or the top of the foundation base in the absence of the foundation
undercut. Earth shall be considered to weigh 16kN/m3 and concrete 24kN/m3.

Straight shaft drilled piers for standard foundations shall have an ultimate skin
friction of 31 kPa per linear meter of depth to a maximum of 48kPa of shaft
surface area for uplift or download resistance.

Nonstandard foundations, anchors, and drilled piers shall be designed in
accordance with the recommendations of a geotechnical report. A mat or slab
foundation for a self-supporting structure shall have a minimum safety factor
against overturning of 1.5.

The effects of the presence of water shall be taken into account in the design of
nonstandard foundations. Reduction in the weight of materials due to buoyancy
and the effect on soil properties under submerged conditions shall be
considered.

2.6.6 Concreting

Loose material shall be removed from bottom of excavation and the sides of
excavation shall be rough and free of loose cuttings before concrete placement.
Concrete shall be placed in such a way that will prevent segregation of concrete
material and any occurrence that may decrease the strength or durability of the
foundation. Concrete placement shall be continuous. No construction joints
shall be allowed. Weight of concrete mixture shall be 24kNm-3.
Concrete mixture must be such as to enable the concrete develop a minimum
compressive strength of 30Nm-2 in 28 days. Reinforcement steel shall be grade
50 deformed bars and shall be covered with concrete overlay of a minimum
thickness of 75mm. Spacers shall be used to achieve this minimum cover on
                                                                                    62
reinforcement. Concrete should always be thoroughly mixed prior to putting in
place, and any water which, seeps into excavation should be removed prior to
placing concrete. A concrete vibration machine must be used until all concrete
is in place.

The concrete column of foundation must always be installed inside wood or
steel formwork and left in place for 24 hours before removing. When the
formwork is removed concrete must be kept wet for first seven days of drying in
the south of the country whilst a ten-day period is recommended for the north.
Aggregate size shall be 20mm.

Mechanical vibration shall be used in making concrete so as to eliminate
honeycombs and voids. Welding and splicing is prohibited on reinforcement
steel and embodiments. Concrete curing time should be 28 days.
The surface level of mast foundation, guy anchor and tower foundation blocks
shall be between 150mm and 300mm above the highest point of the existing
ground level.

When separate blocks of foundation for each leg of tower are employed, the
upper surface of each must be at the same level. The upper surfaces of all
foundations are to be given a gentle slope to ensure water run off. They are to
be painted further with bituminous paint to avoid dampness around the
foundation bolts, sole plates and guy attachment steel works. All loose materials
are to be removed from the excavation before placement of concrete. A curing
time of four weeks (28 days) is to be allowed before erection of steel on the
concrete base.

Structural backfill shall be compacted in 225mm maximum layers to 95% of
maximum dry density at optimum moisture content. It must have a minimum
compacted weight of 1.6kNm-3.
Top of the foundation shall be sloped to drain with a floated finish. Exposed
edges of the concrete shall be chamfered.

If power cables, feeders, grounding tape must pass through concrete base,
appropriately sized diameter plastic or asbestos pipe shall be imbedded in
concrete works.

Where land for structure is limited, grounding tapes and rods may be placed
below or to the side of foundation.



                                                                                63
2.6.7 Raft Foundation

The dimensions of the raft are to be chosen so that the pressure distribution
under maximum design loads will be such that tensile forces will not develop
under a significant part of the raft area. Raft foundations shall be designed by
certified foundation engineers using geotechnical data for the site. A name plate
giving details of the designer and the builder shall be placed in conspicuous
location at the tower base.

2.6.8 Piles

In swamps and peat soils, pile foundations are recommended in order to
overcome catastrophic effects of uneven settlement in other types of foundation.
Pile foundations shall be designed by certified foundation engineers using
geotechnical data for the site. A name plate giving details of the designer and
the builder shall be placed in conspicuous location at the tower base.

2.6.9 Drilled foundations

Foundations can be drilled in any type of soil formation. In normal soils it is a
straightforward and easy task. Drill the hole. Drop in a pre-wired rebar cage.
Place the concrete with a pump tube. The roughness of the sides of the hole
provides the necessary resistance against pullout.

For sandy soils, it is a little more tricky. The hole will usually cave in as its being
drilled. A casing can be used and pulled out as the concrete is placed so the
concrete is in contact with the sides of the hole. Or drilling slurry could be used.
The hole is kept filled with "mud". As the concrete is pumped into the bottom of
the hole, the mud is pumped out at the top. The concrete likewise makes
intimate contact with the soil and the foundation provides the support that the
engineering calls for.

2.6.10 Reinforcement

Main reinforcement bars shall have a minimum concrete cover of 75mm.
Sufficient auxiliary reinforcement shall be included to minimize the occurrence
of cracking whilst the integrity of the foundation remains intact. Reinforcement in
block type foundations shall be such as to ensure that the total weight of
concrete can be fully utilized to give the specified resistance to uplift forces.
                                                                                      64
2.6.11 Factors of safety

The factors of safety of the complete foundations and any component thereof
against overturning shall be made for the worst design load condition.

In the case of guy anchor blocks, a safety factor of 2 shall be applied to the
maximum design guy tension. In calculating the resistance to shear (for the
foundation only) the friction between the bottom face of the concrete and the
soil shall be taken into account. In the case of guy anchor blocks, the earth
resistance in the direction of the horizontal force may be assumed to be utilized,
in which case the soil shall be checked against the possibility of shear-friction
failure. The soil surrounding the foundation shall not be included in the
calculation of resistance to uplift and overturning.

2.6.12 Foundation Drawings

Foundation drawings shall indicate structure reactions, material strengths,
dimensions, reinforcing steel and embedded anchorage material type, size and
location. Foundations designed for normal soil conditions shall be so noted.
Every foundation design shall include site soil data as a footnote.




 Typical Guy Anchor footing               Typical footing of self support Tower
                                               (K – Bracing)
                       Figure 2.24
                                                                                  65
                    Foundation design for Self- Supporting Post Mast
      Infill between base and
                                                    Base Plate
      plate (concrete or epoxy)
                                                             Studding


4 no. studding assembly                                        Levelling nut
are used on a post mast           Y
                                                            Retaining plate



                                           X

     Dimensions of X and Y
     are dependent on soil
     conditions, dead weight
     of mast and wind loading


                                                            .Square and level shuttering
                                                            .Template laid across
                                                              shuttering
                                                            .Studding fitted
                                                            .Infill of concrete


                                      Figure 2.25




                                                                                           66
   SECTION VIEWS – SHOWING SUBSTRUCTURE ARRANGEMENT
                (Raft Foundation)

                                              X1
                                              X




                                                                A
                                                           Horizontal Ties
                 X4         X3
                                                           Vertical Bars

                                                            A


                                        FOUNDATION PLAN




                                                          Tower Base
                                   D2

                              D1                          Ground Level
                                                          Horizontal Ties
                                                          Vertical Bars
                      D
                                                          Foundation stub leg

                          1"-3"
                  L
                          SECTION THROUGH FOUNDATION

                                    Figure 2.26

This foundation type can be used for all types of towers. It is applied for individual
legs for a three or four legged structure. Type of soil and the overall dynamic
loading determine the dimensions. These shall be determined for each particular
site by the geotechnical engineer.

                                                                                         67
            BASIC RAFT FOUNDATION DESIGN FOR TOWERS



                                                 Center of pad and Tower
                             X
                                 A                        A




                                      ½X

                                             X

                                           Plan View


             19mm chamfer on 4                          Horizontal Levelling Brace
             sides
                                                                   Short Base Section
  Adequate projection of
  leg above concrete top
  to enusre good
  clearance for bottom
                         Y
  tower brace                                                              Y-z
  attachment




                    Bar Clearance
                                      Horizontal bars, spaced according to engineer's design
                                             Section AA

                                     Figure 2.27

All dimensions, reinforcement steel sizes and quantities shall be according to
the engineer’s design which will be dependent on the soil characteristics, dead
loading of mast, its height and worst case calculated wind loading




                                                                                               68
Traditionally reinforced concrete is the choice option for tower guy anchors. A
concrete block, in the size determined by the design engineer, is placed against
undisturbed earth to hold the guys. Construction involves digging, forming and
pouring the concrete, then backfilling and tamping. The equipment required
includes backhoes, forming equipment and concrete mixers, etc.

                    Steel reinforcement for
Floor mat             Tower leg
                                                       Completed tower footing
                                                       showing leveling bolts




         Figure 2.28A                                     Figure 2.28B

        Construction of raft foundation for a Tower in a sandy soil




                                                                               69
                    Basic Foundation Design - Four Legged Tower

                   Projection above concrete base
                               Levelling nuts Lock nuts
                                                          Studding (4 No. on each leg)


                     Y
                                                             Z




                                            X

                                          SECTION


                                                       Stud holes
                                                                                            Anchor Plates



                   X2(All sides)
                                                                               Studding Details



                                      X1 (All sides)

                              Mild Steel Base Plate

                               Figure 2.29
           Design for light weight mast in normal soil
Foundation design for one leg in a three or four legged tower configuration.
This is a galvanised steel tower socket base for installation on a concrete foundation. Each
corner of the base is provided with a clearance hole for studs that provide a leveling method.
Typical values for a lightweight tower in a normal soil are as follows:


                         Concrete Depth                          1.2 meter

                         Concrete Width                          1.8 meter

                         Face Width                              0.65 meter

                         Base Width                                 1. meter




                                                                                                            70
             Drilled Pier Foundation Design for Towers in Swamps
                             (Three Legged)


                                                                                                           32' - 6"



                  Braced anchor bolts
                                                                             16' - 3"
                                                                                                                                                                          A


                                               A


                                                                                                                                     A

                                9' - 4 9/16"




                                                                         A
                                                                                         60o 60o     60°              60°




                                                                                                                                Tower Center
                                                                                                                                               18' - 9 1/18"
                                                                                              120°




                                                                                              o
                                                                                        120
                                                                                                                                                               Tower Leg Base Plate
                                                                                                                            A
                                                                                                                                                                                                          Double Nut
                                                                                                                                         Drilled Pier
                                                                                                                                                                                 Anchor bolt projection
                                               Form Top. Drilled Pier with
                                               galvanised sheet metal                                                                     Non shrink grout                 135




33" - 0"MINIMUM
                                                                                                                                                                           Drain plate



                                                                                                                                                                                           BASE DETAIL
                                                                                                                            A

                                                                                        FOUNDATION PLAN

                  SECTION A - A .




                                  Figure 2.30
           Plan of a typical foundation type for unconsolidated soils.
      All dimensions are to be specified by a geotechnical engineer and are strictly
      dependent on the site soil characteristics, expected maximum dynamic loads,
      shear stress, uplift and compression.




                                                                                                                                                                                                                   71
             Typical Micropile in an unconsolidated Formation




                                                         Helical screw pile
Helical pier extension
shaft


                                                        Single or multi helix

     Lead section with
     bearing plates




                                   Figure 2.31
                         Section of drilled Pier Foundation

                                                                                72
Typical Anchor Assembly

This is easily deployed in unconsolidated              Extension
formations for guy anchors, in drilled pier
and micro-pile foundations. They exist in
                                                     Forged Couplings
a lot of configurations.
Lengths can be varied according to the soil
characteristics. Lengths are increased by
                                                      Helical Extension
the use of extensions.




                                                   Lead Section




                          Figure 2.32: TYPICAL ANCHOR ASSEMBLY




                                                                          73
              Figure 2.33
   Typical Pier and Pad foundation construction




                   Tower Base




                                                  Guy stay blocks
            Figure 2.34
Completed Guyed Tower foundation site

                                                                    74
     Basic Foundation Design for a Three legged slim lattice Mast


                                       W          Ground Level




                    Y                                  Expansion fillet
                                                       A393 wire mesh to side faces
                                                       Nominal Cover to all faces



                                       X
                               Section View

                                       X
                              X/2          X/2
                                                        W – Lattice face width at the
                                                            base
                        X/2                             X – Foundation dimension
                                                            (square)
                X


                        X/2




                                    Plan View

                                    Figure 2.35

All dimensions are to be specified by a geotechnical engineer and are strictly
dependent on the site soil characteristics, expected maximum dynamic loads,
shear stress, uplift and compression.




                                                                                        75
                                         C   L
                                                              Tower axis and centre pad



                                                          C       L
                          A                                   A



                                     Square
                                       (W)


                                   PLAN VIEW
                                                 Tower section

                 Grade



                                                                      Y




                     d1                             d

                  #7 Steel bars
                                                        Drainage bed of compacted gravel and sand
                                  ELEVATION VIEW - section AA


                                    Figure 2.36
                 Tower Foundation using micropiles

All dimensions are to be specified by a geotechnical engineer and are strictly
dependent on the site soil characteristics, expected maximum dynamic loads,
shear stress, uplift and compression. Typical values in normal soil for a 45
meter light weight steel tower are:

                      Concrete Depth                                   1.2 meters
                      Concrete Width                                   1.8 meters
                      Face Width                                      0.57 meters
                      Base Width                                      1.0 meters

This design does not give room for leveling after concrete has been poured



                                                                                                    76
Foundation Design for a Self –Support Monopole Tower

                            Section




           Plan


                                        Design basic wind speed is 100 Km hr-1
                                        Plate thickness is 6
                                        Plate grade is A36.
                                        Anchor Bolt Grade is A325 X.
                                        Yield Strength is 4 ksi.
                                        Bolt Length is a minimum of 1meter.
                                        Base Plate outer diam is 1.5 m
                                        Base plate inner diam is 1.1 m




                     Figure 2.37
Dimensions given above vary with the peculiarities of the monopole and the soil


                                                                                 77
2.6.13 Foundation in Swamps

Guyed tower erection in swamps can be performed more quickly, more
efficiently and less expensively with modified construction techniques and an
alternative method for anchoring.

One alternative method is the ‘simple marsh anchor’ method. This technology
uses square rods with screw helices at one meter intervals on the initial three to
six meter length. These rods are then screwed into the ground with one, two, or
three meter extensions being added until the proper depth and torque are
reached. This method is analogous to driving in earth rods into the earth except
that here, hydraulic screwing is used. The torque and final depth are determined
by the soil and by the pulling strength required. Each anchor is then topped with
an eye to attach one guy wire.

Using screw anchors requires only the availability of an auger machine to screw
the anchors into the ground. No digging of holes, forming, and pouring concrete
for the guy anchor is required.

With this method, just one anchor per guy wire would do. The anchors are
simply screwed into the ground until a layer of earth is encountered that is
resistant enough to achieve the required installation torque. Anchors could be
screwed into the ground for a few hundred meters. The depth could be
shortened considerably by using multiple anchors with load-distributing
linkages.

This method has unique advantage of ease of adding extensions or additional
anchors at a later date, should guy wire capacity need to be increased for
additional load requirements or for the addition of torque arms.
The only concrete needed is for the tower base foundation.

2.7 Earthing and Lightning Protection

All masts shall be grounded. The earth resistance measured at the earth
terminal block shall be less than 2 ohms. A lightning air terminal (Faraday Rod)
shall be mounted on mast top and a vertical copper earth wire or tape run down
the side of one mast leg to ground and connected to the earth at the terminal
box.

The most important in getting a good earth is the use of right and good quality
materials for installation.

                                                                                  78
Tapered Base, Guyed Tower - Grounding                    Guyed Tower Leg Grounding




  Twin Lightning rod connection                        Leg grounding for self-support Tower




        ALTERNATE WAYS OF GROUNDING AT GUY - ANCHORS


                                                                                              79
                          Figure 2.38
        Earthing and lightning protection methods




Tower          TOWER FOUNDATION AND LEGS
Leg                                                 Equipment Room
Earth

                                                2



                                                1




                                                                     Earth Bar
        1   Antenna Cable Bulkhead separately
            earthed to Tower                                         Earth Tape - Copper
        2                                                            Buried Earth Rods
            Other Equipment Earth bonded to
            Tower


                        TOWER EARTHING DESIGN - TYPICAL
                                                                                           80
                        Figure 2.39



2.7.1 Earthing

Earthing and Lightning protection shall be provided in all completed towers sites
to protect equipment from damage and personnel from harm which may result
from excessive voltages during a lighting strike. The arrangement shall be such
that lightning discharge current must be prevented from entering equipment
rooms. Equipotential conditions shall be maintained throughout the site by
bonding.

The resistance achievable in an earth installation is directly proportional to the
resistivity of the soil at the depth to which the earth rod has been driven. When
the soil resistivity of a site is not known it can be measured without excavation,
by using a direct reading meter and earth spikes. It can also be read out from
tables, such as Table 2.1 below, if soil type is accurately known.

Resistivity at any depth is related to the diameter of the earth rod, the target
resistance and the depth to which the earth electrode is driven into the soil by:

            R = (p ⁄ 275L) ×log10 (400L ⁄ d)

                        Where    R    is the target resistance
                                 p     is the resistivity of the soil
                                 L     is the length of electrode in meters
                                 d     is the diameter of electrode in cm


An accurate assessment of the soil resistivity should be made around the tower
base using a direct reading resistance meter to determine the appropriate depth
to drive in the copper earth rods, the number of rods, the need for an earth mat,
etc.

Table 2.1 gives typical values which can be used for computation but shall not
serve as a substitute for actual measured values.




                                                                                     81
      Table 2.14 – Resistivity Values for different Soil Types

        Soil                         Resistivity, ohm, cm

        Marshy Ground                200 – 270
        Loam and Clay                400 – 15,000
        Chalk                        6,000 – 40,000
        Sand                         9,000 – 800,000
        Peat                         20,000
        Sandy Gravel                 30,000 – 50,000
        Rock                         100,000




2.7.2 Construction of an Earth

Lightning rod is clamped to the highest point on the mast. Ground wire is
connected to the lightning rod and shall, most desirably, be one continuous
piece all the way to the earth ground rod. Sometimes, the antenna type may
not permit the use of a lightning rod point. In such cases, the ground wire shall
be taped or wire-tied to the mast as far up as practical. Ground wire shall run
from the tip of the mast, be connected to the tower, and then run all the way to
the ground.

Copper bond earth rods made up of copper electrolytically bonded onto a high
tensile steel core shall be driven into the ground at varying depths dictated by
earth resistivity measurements. Several lengths of the rod may have to be so
driven in. Each length is coupled to the next through coupling threads. The rod
is driven in by hammering on the driving high tensile steel head. Each leg of a
mast or tower shall have at least one earth rod driven into the ground beside it.
The leg of the mast is tied to the earth rod through a flat copper tape.

The number of earth rods to be driven into the ground at the optimum depth
shall be such that is necessary to achieve a suitably low resistance.
Where a good grounding cannot be obtained at a reasonable depth, a three
meter pit should be dug and partly filled with layers of carbon, salt and manure
and backfilled firmly.

The maximum permissible resistance to earth is 2 ohms.

                                                                                    82
2.7.3 Protective Grounding

Structures shall be directly grounded to a primary ground.
A minimum ground shall consist of two, 1.2 meter long, 16 mm diameter
galvanized steel ground rods driven not less than 2.4 meters into the ground,
180° apart, adjacent to the structure base. The ground rods shall be bonded
with a lead of not smaller than 5 mm tinned bare copper connected to the metal
base of the structure of each leg of a tower.

A similar ground rod shall be installed at each guy anchor and connected to
each guy at the anchor in case of guyed towers.

Self-supporting towers exceeding 1.5 m in base width shall have one ground
rod per tower leg. All the earth rods shall be tied together to maintain an
equipotential all over the structure. Top ground strap are to be bonded at both
ends. Bottom ground strap are also to be bonded at both ends. All equipment
on a structure (antennas, antenna supports, warning safety lights, etc) shall be
connected by a secondary ground.

The earth of the tower shall be bonded to the general earth of any adjoining
equipment room and all shall form a single earth. The maximum permissible
resistance to earth is 2 ohms.


2.7.4 Lightning Protection

Separate down conductors shall be installed
from each air terminal (lightning spike). In
addition, the structure shall also be a return
path to the earth. These two systems shall
to be bonded together. Lightning spikes
should be long enough to give 450 cone of
protection over all aerials. Air terminations are
to be copper rod, hard or medium – hard drawn,      Air Terminal – Lightning Spike
12mm in diameter. Down conductors shall be                   Figure 2.40
made from 25mm by 3mm soft annealed copper strip.
The earth termination shall be independent of the foundation reinforcement.
When rods are used as earth electrodes these should be driven into the ground

                                                                                   83
to a depth of at least 2.4m in normal soil or the depth predetermined for the site
from measurements. Longer lengths should, when necessary, be built up of
1.2m lengths screwed onto each other with internal screw and socket joints. If
one earth electrode cannot obtain the specified resistance, additional electrodes
should be connected in parallel. Such additional electrodes may be those
provided for other down conductors. The distance between any two driven
electrodes should be about equal to their driven length.
All connections between earth conductors and steelwork shall be via sacrificial
legs or brackets where copper would be in contact with concrete. It shall be
painted with bitumen or separated from the concrete with itemized paper.
Earth conductor runs shall be straight as far as is practicable. Any bends that
may be unavoidable shall be smooth and of maximum radius.
The resistance to ground of the earth system shall be below 2 ohms.

2.8 Safety Devices
Safety devices shall be installed on every tower above 45 meters high. Of
importance are the fall arrest systems, climbing ladders or step bolts, guard
rails, work / test platforms, rest platforms and anti-climb systems.

Fall Arrest Safety System




                             Figure 2.41

                                                                                84
A complete fall arrest system consists of the rail and the trolley.



2.7.1 Trolley

      Locking brake pawl attaches to climber’s harness
      Moves freely along the Safety Rail with climber in normal climbing position
      In case of a slip trolley brakes remain locked until the force is removed

Falls are instantly arrested when a sudden downward motion is applied to the
Trolley. Trolley remains stationary once disconnected from the harness.




                               Installed anywhere on the tower leg, and
                               adaptable to most structures. It is to be
                               fabricated from lightweight high tensile
                               Aluminum


         Safety Rail


2.7.2 Anti Climb Shields

Anti Climbs consist of metal sheets bolted
to tower legs. They are constructed to prevent
unauthorized persons from climbing a tower.
It is ideal for tower sites around schools and
public areas where public safety is a concern.




                                                                                85
2.7.3 Climbing Facilities

  (a)     Access Ladders
        To be made from hot dip galvanized steel
        or aluminum sections. Mountable on all tower
        types and monopoles. Amenable to inside or
        outside mounting. Climbing Ladders shall be of
        steel or aluminum depending on tower material and
        shall be provided with the following:

         (a)    Safety cages
         (b)   Landing places – rest and work platforms
         (c)   Protective finishes

Ladders are to be attached to the tower structure.

The lowest point on the ladder shall be at a height of 3m to 4.5m above ground
level and it shall run all through to the top of the structure. The ladder shall be
so located that a clearance of at least 150mm at the rear of the ladders exists
between the ladder and the structure.

Anti climbing devices shall be provided on the structure to prevent access
except from the climbing ladder.

The vertical separation between rest platforms shall be 20m. Work and test
platforms shall be located at those points where antennas are to be installed.

Platforms – Work / Rest / Test

All platforms shall be readily accessible from the climbing ladder.
The access to all platforms and walkways from the vertical climbing ladder shall
be from one direction only. Platforms and walkways shall be designed to carry a
point load of 150kg at any point without a deflection exceeding 6.0mm.

Guard-rails

These shall be of height between 0.9m and 1.1m and shall be provided on all
platforms, stairways and horizontal members used as walkways. They shall
have an intermediate rail at half this height and a toe board not less than
150mm high. The distance between any toe-board and the lowest guard – rail
                                                                                 86
above it shall not exceed 750mm. Widths of walk-ways and platforms should not
be less than 650mm. Walk-ways and surface used as working platforms or
traversed to gain access to platforms or traversed to gain access to working
positions are to be provided with anti-slip surface.

Guard rails and toe boards shall be attached at each vertical stanchion. They
shall be secured to prevent rotation.


Step Bolt

They are climbing facilities ideally suited
to fixing on monopoles.




Safety Enhancement

Safety in the installation and use in service of masts and towers are enhance by
the following practices which shall be mandatory on all tower owners and
installers

      (1)   Tower assembly parts shall be standardized e.g. fasteners for the
            main structure should ideally be of only one size, length and
            material.
      (2)   Manually handing over of parts or tools between installers during
            tower erection is totally forbidden.
      3)    All parts must be fully labeled especially where the method of
            assembling is not obvious.
      (4)   Towers must be structurally designed for simple assembly - ease of
            fit, elimination of small loose parts, etc.
      (5)   On-site welding and riveting is prohibited. All site connections shall
            be by bolt and nut with a means provided for locking the nut against
            loosening by vibration. All nuts bolts and washers shall be
            galvanized. Such galvanizing shall be done so as to permit the
            ready assembly of nuts and bolts after galvanizing. Taper washers
            shall be used whenever the steel section shape requires their use.
            Bolt lengths shall be such that with the locking device in place a

                                                                                87
minimum of one complete thread shall protrude beyond the nut. Bolt
threads shall protrude inside the structure only.




                                                                88
  CHAPTER THREE




MATERIALS SPECIFICATIONS




                           89
3.1 The Superstructure

3.1.1 Members’ Sizes

The sizes of members in compression shall be such that the maximum
slenderness ratios are:

Ladder                   120
Bracing members          150
Subsiding members        180

No load-carrying angle shall be smaller than 50 x 50 x 6mm. The minimum
thickness of gussets and similar plates on the main structure shall be 8mm.

3.1.2 Intersecting Bracings

Where a gusset plate connects bracings that cross, at least one of the bracings
shall be continuous between the main members to which it connects.

Towers and Masts shall be manufactured from the following materials

  a) Steel with hot dip galvanized finish

  b) Stainless Steel with # 4 or # 7 finish

  c) Aluminum - polished, anodized and painted finish


3.1.3 Lattice Structures

  1. Legs    - Tubular
             - Angular
             - Solid Round Leg
  2. Members - Tubular pipes
             - Angles
  3. Bracing - Angles
             - Tubular pipes
             - Steel rods

3.1.4 Monopole Structures

  1. Sections - hollow, heavy duty, thick steel pipes
                                                                             90
                - hollow, heavy duty, flanged steel pipes

3.1.5 Guys

  1. Wires               - Extra High Strength stainless steel or galvanised
                            steel cable.
  2.   Earth Screw Anchor – Galvanised steel or stainless steel.
  3.   Thimble            -- Galvanised steel or stainless steel.
  4.   U-Bolt              - Galvanised steel or stainless steel.
  5.   Turnbuckle          - Galvanised steel or stainless steel.

Both lattice and monopole structures shall be made from steel for tall, heavy
load bearing towers or aluminum for lightweight light duty towers. Tower
components shall be of the following classification: -

   All steel members shall be fabricated from Grade 50 or 42, A36 or A 572-
    50.
   All steel tubes shall be fabricated from Grade 43C.
   All structural pipes shall be fabricated from Grade 42 or Grade C steel.
   Anchor rods shall be fabricated from Grade B7 steel.
   Rebar shall be fabricated from Grade 400 steel.
   Diagonals shall be fabricated from Grade 43A steel.
   Structural Bolts fabricated from Grade A325 steel.
   Steel angles shall have a minimum strength of 56ksi for tower legs and
    36ksi for tower members.
   Round legs shall be fabricated from schedule 40 pipes.
   Braces shall be fabricated from Grade A36 or A 572-50 steel

3.2 Concrete

Ordinary cement shall be used. Cement of different types may not be mixed.
High Alumina (HA) cement may not be used for concrete mixing. Additives that
hasten the setting of cement or give a denser concrete shall not be used.
All sand shall be clean, sharp, gritty, and free from loam earth, salt and other
impurities like humic acids. Sand shall not contain more than 15% clay or silt.
The sand shall contain grains from the finest sizes up to 4.75 mm. Grains
smaller than 0.25 mm in size shall not constitute more than 15% of the total
weight of the sand to be used.




                                                                                   91
Aggregate shall be clean screened river ballast gravel, graded in size and free
from dirt, floury stone dust, loam or earth or any other impurities. The maximum
size of aggregate to be used shall be 19 mm.

Water to be used for concrete mixing shall be free from oil, salt, and organic
substances. It shall be clear. Cement shall have a mixture of 1:2:4.
The concrete shall be thoroughly mixed by machine.
3.3 Earthing and Lightning Protection Installation Materials

Air Terminals shall be made from copper.
Saddles (ridges, flat, light duty or heavy duty) shall be made from gunmetal or
aluminum.

Clamps shall be made from gunmetal or aluminum. Bi-metallic clamps shall be
employed when joining aluminum earth rods to copper earth conductors.

Earth bars shall be made from high conductivity copper.

Copper Earth rods shall be made from:

   High tensile steel core with copper film electrolytically bonded to it to a
    minimum thickness of 0.25mm.
   Solid copper earth rods for extremely high corrosive environments
    U-bolts could be of copper but with gunmetal back plates.

3.4 Metals and Galvanising

The following metals and alloys shall be used in tower fabrication, construction
and for foundation reinforcement: -

        Magnesium
        Zinc
        Aluminum
        Lead / Tin
        Brass / Copper / Bronze
        Silver
        Graphite




                                                                                   92
3.5 Earthing Clamps




                         Figure 3.1
              Typical clamps for installation of earth tapes



3.6 U-Bolts




                                                               93
Multi-Point Air terminal              Elevation Rods                   Mounting Brackets




                                         Figure 3.2
                           Earth and lightning protection materials
           Rod to Tape Coupling                    Building in Rod Holdfasts




                                                                                           94
3.7 Connector Clamps


                   Square Tape Clamp




             Oblong Box Clamp/7




                           Figure 3.2
       Installation Materials – Earthing and lightning protection




                                                                    95
3.8 Screw down Clamp




Plate Type Clamp




                             Figure 3.3
         Installation Materials – Earthing and lightning protection

                                                                      96
  3.9 Earth Bars and Disconnecting Links




         Insulator                       Wooden base disconnecting link




 6-way disconnecting link                Disconnecting link channel Iron base

               Inspection Housing




                            Figure 3.4
These materials are used for earthing installation to make testing easy

                                                                                97
                            Figure 3.5
These materials are used for earthing installation to make testing easy

Conductor inspection housing shall be installed at test points to protect the earth
rod and earth connections and make them available for testing. It shall be made
from high grade, heavy duty polypropylene and ultra violet stabilized to prevent
degradation by sunlight. It shall be non-brittle.




                                                                                 98
3.10 Lightning Arrestor Installation Materials




          Pointed Air Rod                         Flat Saddle




                         Light Duty Saddle




                        Figure 3.6
            Pointed Air rod and installation saddle

                                                                99
3.11 Copper Tapes – Can be Tin or lead covered


                   Copper Tape




                     Flexible Copper braid




                      Figure 3.7
       Flat Copper Tape and Flexible Copper Braid




                                                    100
3.12   Connectors

       Circular cable connector




               Cable to Tape Junction Clamp




                    Cable To Cable Test Clamp




                  Figure 3.8
                Cable connectors
                                                101
3.13   Bi-Metallic Connectors




                       Metal Tape Clip




                     Non-Metallic Clips




                  Figure 3.9
              Cable and Tape clips


                                          102
   3.14      Guy System Materials




                                                     Earth Screw Anchor




          Turnbuckle                            Guy Wire




                            Figure 3.10
                            Guy materials

Guying materials shall conform to the sizes, mechanical strengths and
capacities shown below in Tables 3.1 (1-4)




                                                                          103
              Table 3.1.1 Guying Cable

           Size & Grade               Working Load Break Strength Wt. / 100 strands
   3.5mm x 7 x 7 Galvanised Steel       154 Kg         771 Kg          1.27 Kg
   10mm x 7 x 19 Galvanised Steel      1306 Kg        6532 Kg          1.10 Kg
  8mm x 7 x 19 Stainless Steel(304)     245 Kg        1089 Kg          2.27 Kg
5mm x 7 x 19 304 Stainless Steel(304)   336 Kg        1678 Kg          4.10 Kg
 6.5mm x 7 x 19 Stainless Steel(304)    581 Kg        2903 Kg          5.00 Kg

              Table 3.1.2 Turnbuckles

     Working Load (Kg)           Diameter & Take Up          Unit Wt. (Kg)
             750                    10mm X 15cm                   0.45
            1,000                  12.5mm X 22cm                   0.9
            1,500                   15mm X 30cm                    1.8
    Turnbuckles shall be made from drop forged steel, be of hot dip galvanized
    Finish and have Eye and eye construction

              Table 3.1.3 Earth Screw Anchors
                              Helix     Holding Power
Overall Length Rod Dial. In.                                 Unit Wt(Kg)
                            Diameter in Normal Soil
    75 cm      12.5 mm       10 cm        1,135 Kg.              3.2
   120 cm        16 mm       15 cm        1,815 Kg.              5.5
   173 cm      17.5 mm       20 cm        5,000 Kg.               12
   12.5mm Link from earth anchor to turnbuckle. Hot dip galvanized finish.


              Table 3.1,4 U-Bolt Clips and Thimbles
                    Description                              Kgs. Per 100
    3mm Galvanized Steel U-Bolt Clip                             4.54
    8mm Galvanized Steel U-Bolt Clip                             8.16
    6.5mm Galvanized Steel U-Bolt Clip                           8.16
    8mm Galvanized Steel U-Bolt Clip                             13.6
    10mm Galvanized Steel U-Bolt Clip                            21.8
    6.5mm Galvanized Heavy Duty Thimble                          4.54
    8mm Galvanized Heavy Duty Thimble                            6.35
    10mm Galvanized Heavy Duty Thimble                          11.34




                                                                                      104
3.2   Antenna Mounting Frames

Frames for mounting antennas on towers or masts shall be designed in
sympathy with the type of tower structure, the type and weight and size of the
antenna.
They shall be made from galvanised steel, stainless steel or aluminum. There
shall be no welded parts. All joints shall be implemented with bolts and nuts.


Some basic designs exist for certain tower structural forms. A few are shown
below.



                                             Tower
                                             structure




                                                           Antenna Mount on Self-Support Tower




                                  DETAIL B




                        A     A




                                                         Plan View


                                                                             Section View



         Side Antenna Mount




                                                                                                 105
Side Antenna Mount




                     SADDLE- BRACKET




                                       106
    Side Mount




                                       Plan View

Section View




 Antenna Mount on Self-Support Tower




                                                   107
108
            Antenna Mount on Self-Support Tower




Plan View


                                        Section View




                                                       109
metal clip




             110
             metal clip




metal clip                metal bracket




                                          111
      CHAPTER FOUR




MAINTENANCE AND TESTING




                          112
4.0   First Line Maintenance

In tower design, it is assumed that the worst case scenario is a total mechanical
failure. This can be caused by stress, extreme overload, use of defective and
poor quality materials, fatigue, corrosion, poor workmanship, insufficient
maintenance, sabotage, as well as any combination of these factors. Every
design must attempt to foresee all possible combinations of these that can
occur in the installation environment and incorporate protective answers to them
in the design. This is the first line of maintenance.

4.1   Hot Dip Galvanization

Unprotected steel can be seriously damaged due to environmental factors as
rain, salty humid air and extremes of temperature. Corrosion transforms steel
back to its natural state of iron, which is very fragile and can prove to be deadly
in structures like towers which support heavy pressures. The best way to avoid
this phenomenon is through a process called "hot dip galvanization".
This process consists of dipping steel in melted zinc at 450°C. At this
temperature iron and zinc share great affinity, and allow an alloy to form where
pure zinc prevails to the outside. The final product is a steel surface protected
with a zinc coating.

Due to the difference of electrochemical potential between zinc and steel
(cathodic protection), a zinc coating protects steel in such a way that slightly
exposed surfaces due to cutting, scratching or piercing are equally protected
against corrosion.

What considerably affects the appearance and gauge of galvanization is the
contents of alloy elements that are present in steel: carbon, magnesium, and
silicon. The greatest effect is produced by silicon in concentrations higher than
0.12%.

Most steels can be galvanized: high-strength steel, low-carbon steel, low-alloy
steel, and steels with as much as 0.20% copper content; the most appropriate
being low-carbon steels.

4.2   Tower Maintenance

Towers require regular maintenance. Regular maintenance is especially
important for the purposes of public safety, network availability, environmental
aesthetics and life time quality of the structures.
Maintenance is as important to self supporting masts and towers as it is to
                                                                                   113
guyed masts. For masts and towers, maintenance is mandatorily preventive as
any breakdown comes usually with catastrophic consequences. Maintenance
and inspection of steel antenna towers and antenna supporting structures
should be performed by the owner on a routine basis.

Major inspections shall be performed, at a minimum, every 3 years for guyed
towers and every 5 years for self-supporting towers.
Ground and aerial procedures should be performed only by authorized
personnel, experienced in climbing and tower adjustments.

All structures shall be inspected after severe winds or other extreme loading
conditions.

Shorter inspection intervals of 2 years for guyed towers and three years for self
supporting towers shall be obligatory for structures in coastal salt water
environments, in corrosive atmospheres, and in areas subject to frequent
vandalisation. At every tower site, the owner shall keep a maintenance log book
in a thick cellophane folder. This folder shall be readily accessible to the
regulators inspectors. It shall have the following information: -

      Installation Date
      Inspection due dates
      Painting due dates
      Minor Maintenance due dates
      Major Maintenance due dates
      Name and address of Inspector

For each of the due dates, the log must show whether the inspection or the
maintenance was carried out and by whom.
4.3    Maintenance Philosophy

The external condition of Towers and Masts must be regularly inspected with
intent to detect deterioration. Necessary maintenance works must be carried out
timely.
Periodic checks and inspection of the structure must be carried out:
At regular intervals of time during the service life of the structure
After the installation of an additional load like antennas on the structure
After each serious climatic event like tempest, hurricane, tornado
                                                                                114
The first thorough check of the structure should be carried out 6 months after its
installation and erection.
Maintenance checks should be carried out yearly henceforth
4.4      Routine Checks

4.4.1 Main structure

Check that there are no structure components missing
Check that bars are neither warped, holed nor spitted. Replace all defective
parts.
Check structure components for corrosion
Check that draining holes on pipe leg members, pipe lattice parts are not
blocked.
Check the climbing facilities, platforms, catwalks for integrity

4.4.2 Tower Base Foundation

Check for settlements or movements
Check for erosion
Site condition (standing water, drainage, trees, etc.)
Check bolts, nuts and lock nuts for tightness
Grout condition

4.4.3 Guy wires

Check that each cable that is part of the guy wire is neither broken nor warped
Measure the tension of each guy wire using a strand dynamometer and
compare result with the installer's stated values.

Check guy wires condition (corrosion, breaks, nicks, kinks, etc)
Check that the guy wire tightening system is properly greased.
Check for loose or missing fasteners
Check base for settlement, movement or earth cracks
                                                                                115
Check backfill heaped over concrete for water shedding
Check anchor rod condition below earth
Check for signs of corrosion and take remedial timely steps
Ensure anchor head is clear of earth

4.4.4 Bolting parts

Check that no bolts or nuts or any bolting part like washers, pins, etc is missing.
Replace these immediately.
Check bolts tightening.
Check bolts, nuts and bolting parts for corrosion.
Check anchorage rod in the concrete.

4.4.5 Verticality

Check with the appropriate devices such as theodolite that the structure stands
vertical. There shall be no tilts. Take two measurements in two different planes
with a 90' angle difference.

4.4.6 Antennas and Accessories
Check antennas and antenna supports good condition
Check coaxial cables good condition
Check fixing clamps good condition.

4.4.7 Safety components
Check that access ladder is in good condition
Check rest and work platforms for defects, wear and tear
Check that all safety components are existing and complete
Check the correct functioning of the fall arrestor system

For a fall arrestor system with cable, check that the cable has not been over
tightened.

Check that the anti climbing door is functioning.

4.4.8 Lightning and Earthing system
Check that all lightning and Earthing components are existing and complete
including lightning arrestor, copper strip, connection plate,
                                                                                 116
Check the Earthing connection of coaxial cables,
Measure the resistivity of the Earth and confirm conformity to expected values.
4.4.9 Aviation Safety Lights
Check that all components are in place,
Check condition and well functioning of components (Light bulb, energy cables,
fixing parts, photoelectric cell, connections)
Check earthing of the light wiring.

4.4.10      Anti corrosion protection
Check all galvanised members for integrity
Check paint condition.
Check for signs of corrosion on the structure, of the bolts, bolting accessories,
harnesses, antenna supports, etc
For guyed masts, check for corrosion on the entire guy assembly.



4.4.11      Salty environment
Wash the structure and accessories with clean water once every six months to
eliminate residue salt particles which may not be washed away by rain.
4.4.12      Concrete blocks
Check the good condition of above ground concrete block parts.
There must not be any water collection, cracking or splitting, chipped or broken
concrete.
Check the condition of anchor setting in the concrete block.
Check anchor-bolt corrosion.

4.4.13      Tower loading
Check types, numbers and installed heights of all antennas currently on the
structure and confirm that the loading does not exceed structure design load.


                                                                                    117
4.5   Annual Preventive Maintenance Checks
4.5.1 Structure
Tension of Guy wires using a dynamometer.
Geometry of the structure.
Re-tighten main structure and accessories bolted parts (10%)
Geometry of the Bars.
Rigidity of Antennas and Accessories.

4.5.2 Safety
Ensure anti climb door can open and close. Clean and grease all hinges.
Ensure the work platform's trap can open and close. Clean and grease all door
hinges.
Fixing of the fall arrestor system
Check tower ladder for any signs of weakness, re-tighten all bolts
Check the riggers’ safety gear, take inventory and record it
Right placing and right installation of safety components.
Test of the fall arrestor system with individual equipment.


4.5.3 Earthing
Physical condition of the lightning rod
Physical condition of the lightning arrestor
Physical condition and installation of the copper strip
Connection of the concrete block copper belting onto the copper strip
Connection of coaxial cables earthing onto the copper strip
Connection between the bottom coaxial cable earthing and the collection
Copper bar fixed on the concrete block
Tightening of the brass bolts of the lightning protection electrodes
Resistivity the lightning protection electrodes

                                                                            118
Earth resistance
4.5.4 Aviation Safety Lights
Functionality of controllers, flashers, alarms and photo control
Condition of electrical wires, connectors and earthing
Condition and fixing of energy cables
Conduit, junction boxes, and fasteners weather tight and secure
Bulb condition - change all bulbs at one time immediately before the rated
service hours is achieved.
Condition and fidelity of the power supply systems

4.5.5 Coating
Discrepancies in galvanization
Paint coating. Repaint every three years
Rust and/or corrosion conditions
ICAO / NAMA Color marking conditions
Water collection in members - unplug drain holes, etc.


4.6   TESTING

Measurement of Guy Tension

Tension should be measured when wind is relatively still. Measurements in wind
velocity above 25 m/s (90km/h) will yield misleading results. Tension results can
be considered satisfactory if they fall within 15% of the tension value stated by
the manufacturer and/or installer. Excessive tension may cause alignment
problems and even a cable rupture. It may even cause permanent wrapping of
tower structural parts.

There are two basic methods of measuring guy tensions in the field:

         1. the direct method
         2. the indirect method.
                                                                              119
4.6.1 The Direct Method (see Figure 4.1)

A dynamometer (load cell) with a come-along (length adjustment device), is
attached to the guy system by clamping onto the guy just above the turnbuckle
and onto the anchor shaft below the turnbuckle, thus making the turnbuckle
redundant. The come-along is then tightened until original turnbuckle begins to
slacken. At this point the dynamometer carries the entire guy load to the anchor,
and the guy tension may be read directly off the dynamometer dial.
This method is used to set the correct tension by adjusting the come-along until
the proper tension is read on the dynamometer.

Two control points are marked, one above the clamping point on the guy and
one on the anchor shaft, and the control length is measured. The dynamometer
and come-along are then removed, and the original turnbuckle is adjusted to
maintain the control length previously measured.




         Dyanamometer            Turnbuckle
         Come - Along
                                               (1) Dynamometer Method
                                                  As come-along is tightened,
                                                  dynamometer carries all
                                                  the load




                                                 a



                                                                                120
(3) Pulse Method                                              (2) Swing Method
          Pulse travels up and                                Guy swings from a to b and
         down the guy N times                                 back N times in p seconds
              In p seconds



                              Figure 4.1
                      Measurement of Tension of Guy


4.6.2 The Indirect Method

There are two common techniques for the indirect measurement of guy initial
tension - the pulse or swing method (vibration) (Figure 4.2) and the tangent
intercept method (Figure 4.3).

(a) The Pulse Method




                                   L




     V




 V                                     L              TM



                                                W



                                                  T
                                                  A
                                                       2L V
                                                         W




 T
 A                                               W
                                                      M
                                                      T




                                               2L H


                                           H




                                                                                           121
                                 H

                       Figure 4.2

Relationship between Guy Tension at Anchor and at Mid-Guy

One sharp jerk is applied to the guy cable near its connection to the anchor
causing a pulse or wave to travel up and down the cable. On the first return of
the pulse to the lower end of the guy cable, a stop watch is started. A number of
returns of the pulse to the anchor are then timed, and the guy tension is
calculated from the following equations:




  where
     TA = Guy tension at anchor
     TM = Guy tension at mid-guy
     W = Total weight of guy, including insulators, etc.
     L = Guy chord length
      N = Number of pulses or swings counted in P seconds




V = Vertical distance from guy attachment on tower to guy attachment at anchor
H = Horizontal distance from guy attachment on tower to guy attachment at
anchor
N = Number of pulses or swings counted in P seconds
P = Period of time measured for N pulses or swings (s)
Instead of creating a pulse that travels up and down the guy, one may achieve
the same result by causing the guy cable to swing freely from side to side while
timing N complete swings. The formulas given above will also apply for this
approach.

                                                                              122
(b) The Tangent Intercept Method


                                                    C




                                                           I
                                                               I




        V   V




                                                    ight
                                           e   of s
                                        Lin



                                      W
                       α

         T
         A


                                  H
                                  H




                              Figure 4.3

A line of sight is established which is tangential to the guy cable near the anchor
end and which intersects the tower leg a distance (tangent intercept) below the
guy attachment point on the mast. This tangent intercept distance is either
measured or estimated and the tension is calculated from the following
equation:




where

C = Distance from guy attachment on tower to the center of gravity of the weight

W
                                                                                123
I = The tangent intercept

If the weight is uniformly distributed along the guy cable, C will be approximately
equal to 1-I/2. If the weight is not uniformly distributed, the guy may be
subdivided into n segments and the following equation may be used:




where




Wi = Weight of segment i

Ci = Distance from the guy attachment on the tower to the center of gravity of
segment i

If the intercept is difficult to establish, one may use the guy slope at the anchor
end with the following equation:




   where
   cz = Guy angle at the anchor
Note that




   and that




and that WC in equation (7) may be replaced with S, as was done in equation
(5).
                                                                                  124
Glossary of Terms

Plumb -- The horizontal distance between the vertical centerlines at any two
elevations shall not exceed .25 percent of the vertical distance between the two
elevations.

Twist -- The twist (angular rotation in the horizontal plane) between any two
elevations shall not exceed 0.5 degrees in 3 m and the total twist in the
structure shall not exceed 5".

Length -- For tubular steel pole structures with telescoping joint, butt welded or
flanged shaft connections, the overall length of the assembled structure shall be
within plus 1 percent or minus 1/2 percent of the specified height.

Normal Soil -- A cohesive soil with an allowable net vertical bearing capacity of
192 kPa and an allowable net horizontal pressure of 63 kPa per linear meter of
depth to a maximum of 192 kPa.

Twist -- The angular rotation of the antenna beam path in a horizontal plane
from the no-wind load position at a specified elevation.

Sway -- The angular rotation of the antenna beam path in a vertical plane from
the no-wind load position at a specified elevation.

Displacement -- The horizontal translation of a point relative to the no-wind load
position of the same point at a specified elevation.

Grounding is the means of establishing an electrical connection between the
structure and the earth, adequate for lightning, high voltage, or static
discharges.

Primary Ground is the conducting connection between the structure and earth
or some conducting body, which serves in place of the earth.

Secondary Ground is the conducting connection between an appurtenance and
the structure.

Climbing Facilities -- Components specifically designed or provided to permit
access, such as fixed ladders, step bolts, or structural members.

                                                                                125
Climbing Safety Devices -- Equipment devices other than cages, designed to
minimize accidental falls, or to limit the distance of such falls. The devices
permit the person to ascend or descend the structure without having to
continually manipulate the device or any part of the device. The climbing safety
device usually consists of a carrier, safety sleeves, and safety belts.

Working Facilities -- Work platforms and access runways.

Guy Connection - the hardware or mechanism by which a length of guy strand
is connected to the tower, or guy anchor.

Lux is lumens/sq m

Candela is light intensity. Its unit is the lumen

 Alternative Mounting Structure - man made tree, clock tower, church steeple,
bell tower, utility pole, light standard, identification pylon, flagpole, or similar
structure, designed to support and camouflage or conceal the presence of
telecommunications antennas.

Antenna - structure or device used to collect or radiate electromagnetic waves,
including directional antennas, such as panels, wireless cable and satellite
dishes, and omni-directional antennas, such as whips, but not including satellite
earth stations.

Antenna Array - An arrangement of antennas on their supporting structure.

Dish Antenna - A parabolic or bowl shaped device that receives and/or
transmits signals in a specific directional pattern.

Panel Antenna - An antenna which receives and/or transmits signals in a
directional pattern.

Antenna, Stealth - A telecommunications antenna that is effectively
camouflaged or concealed from view.

Telecommunications Antenna - An antenna used to provide a
telecommunications service.

Whip Antenna - An omni-directional dipole antenna of cylindrical shape which is
no more than 15 cm in diameter.

Co-location - single telecommunications tower and/or site used by more than
one telecommunications service provider.
                                                                                       126
Identification Pylon - A permanent ground mounted sign consisting solely of a
single monolithic structure used to identify a development.

Guyed Tower - Any telecommunications tower supported in whole or in part by
cables anchored to the ground.

Tower Height - The distance measured from ground level to the highest point of
any and all components of the structure, including antennas, hazard lighting,
and other appurtenances.

Monopole - A self-supporting telecommunications tower which consists of a
single vertical pole fixed into the ground and/or attached to a foundation.

Self-supporting Lattice - A telecommunications support structure which consists
of an open network of metal braces forming a tower which is usually triangular
or square in plan.

Telecommunications Tower - A self-supporting or guyed structure more than 5
meters in height, built to support one or more telecommunications antennas.




                                                                                127
Index

      A

     Access Ladders                                            83, 112
     Accidents during the installation period                         7
     Aggregate                                                  59, 87
     Air Terminal                                        75, 80, 88,90
     Airport                                                      6, 55
     Alternative Mounting Structure                            13, 122
     Aluminum – polished, anodized and painted finish                86
     Anchor Bolts Template                                           58
     Angle leg                                                  21, 22
     Annual preventive maintenance checks                          113
     Antenna Mounting Frames                                       101
     Anti Climb Shields                                              82
     Anti Corrosion protection                                     112
     Authorization                                                   10
     Aviation Lighting                                            6, 12
     Aviation safety lights                                   112, 114

      B

     Base Plate                                                   23, 74
     Basic Foundation Design for Slim lattice mast                    72
     Basic wind speed                                         15, 16, 74
     Bi-metallic                                                  88, 98
     Bolting                                          23, 111, 112, 124
     Bolt-up construction                                             22
     Bracing                   21, 25, 26, 27, 28 29, 33, 35, 49, 62, 86
     Building and roof mounted dish antennas                          13
     Bull Dozer                                                        8

      C

     Cable and Tape clips                                             98
     Cable Connectors                                                 97
     Certification                                          6, 7, 13, 14
     City and Guilds                                                   7
     Clamp                                      88, 89, 91, 92, 97, 112
                                                                            128
   Clearance certificate                                             6
   Climbing                24, 81, 82, 83, 84, 110, 111, 112, 121, 122
   Coating                                                    109, 114
   Co-location                                                 10, 122
   Concreting                                                       59
   Copper-Tapes                                                 79, 96

    D

 Dish Antenna Mounting Standards                                   13
 Drilled pier Foundation design                                    67
 Dynamometer                                       111, 113, 115, 116

    E

   Earthing              75,76, 78, 88, 89, 91, 92, 93, 94, 112, 114
   Effective height                                                6
   Elevation Rods                                                 90
   Environmental requirements                                      9
   Excavators                                                      8

    F

   Fabricators and Installers                                       4
   Face width                  21, 34, 35, 36, 37, 38, 49, 67, 72. 73
   Factors of safety                                               61
   Fall Arrest Safety System                                       81
   Faraday Rod                                                     75
   Finishes                                                21, 23, 83
   Flat saddle                                                     96
   Flexible copper braid                                           96
   Footing Assembly                                                43
   Foundation Design and Loading                                   40
   Foundation Design                       40, 43, 57, 58, 67, 72, 74
   Foundation Engineers                                        60, 61
   Foundation in swamps                                            75
   Free standing masts                                              5




                                                                          129
    G

   Geographical coordinates                                        6, 7
   Graphite                                                         88
   Ground mounted dish antennas                                     13
   Guard-rails                                                  81, 84
   Gust factor                                         16, 35, 36, 126
   Guy Anchor               11, 25, 50, 60, 61, 6, 66, 70, 75, 80,122
   Guy materials                                                    99
   Guy wires                                          24,25, 111, 113
   Guyed Towers                                     5, 24, 57, 80, 110
   Guys                                              6, 11, 25, 66, 87

    H

   Height of Towers                                                 8
   HF-SSB dipole antennas                                          50
   High Alumina (HA)                                               87
   Hot Dip Galvanization                                          109
   Humic Acid                                                      87

    I

   ICAO                                           11, 12, 55, 56, 114
   Inspections                                             7, 10, 110
   Installation permit                                               8
   Insulator                                                  93, 118
   Intersecting bracings                                           86

    J

 Junction box                                                 12, 114

  K
 K-bracing                                      26, 27, 28, 29, 30. 31
 KNm-3                                                      57, 59, 60
 Kpa                                                      57, 59, 121

    L


                                                                           130
   Lap Link Weight Table                                              44
   Lattice 5, 21, 22, 24, 26, 27, 34, 37, 38, 44, 45, 73. 86, 67, 111, 123
   Saddle                                                         86, 95
   Lighting                                   6, 11, 12, 55, 56, 78, 123
   Lightning and Earthing system                                     112
   Lightning Arrestor                                      95, 112, 114
   Lightning protection          6, 75, 76, 78, 80, 88, 90, 91, 92, 114
   Log book                                                       7, 110
   Long Boom Arm Crane                                                 8

    M

   Magnesium                                                   88, 109
   Maintenance                            7, 8, 21, 108, 109, 110, 113
   Maximum compression                                          35, 36
   Maximum shear                                                35, 36
   Measurement of Guy Tension                                      115
   Monopole structures                                          86, 87
   Monopole Towers                                                  23
   Multi-Point Air Terminal                                         90

    N

   Name plate                                                  7, 60, 61
   Nearness to power lines                                            12
   Nigeria Airspace Management Authority                            6,10
   NAMA                                         11, 12, 21, 55, 56, 114
   Nigerian Communications Commission                    6, 7, 8, 10, 13
   NCC                                            6, 7, 8, 9, 10, 11, 14
   Nigerian Meteorological Agency                                      15
   Non-Metallic clips                                                 98
   N-Section Guyed Pole Mast                                          50

    O

   Oblong Box Clamp                                                  91
   Obstruction lamps                                                 55
   Obstruction lighting                                      12, 55, 56
   Open terrain                                                      14
   Operating Frequencies                                              7
                                                                              131
 Out rigger                                                       50, 52

    P

   Packer                                                              8
   Painting                                                     55, 110
   Panel Height                                                      26
   Permit Number                                                       7
   Photo sensor                                                      12
   Pier and Pad foundation construction                              71
   Piles                                                         56, 61
   Plate Type clamp                                                  92
   Platform height                                                   45
   Platforms                                  6, 21, 81, 111, 112, 122
   Pointed Air Rod                                                   95
   Post Masts                                                        23
   Property Owner                                                     6
   Protective Grounding                                              80
   Public Health                                                      9
   Public Safety                                      4, 8, 13, 82, 109

    R

   Radio frequency emissions                                            8
   Raft Foundation                                             60, 64, 66
   Redundant Diagonal                                                  31
   Reinforcement                               59, 60, 61, 65, 66, 80, 88
   Removal of abandoned towers                                           9
   Residential Areas (towers in)                               11, 12, 13
   Resistivity values for different soil types                          79
   Resistivity                                          78, 79, 112, 114
   Rest platforms                                               21, 81, 83
   Rock Anchors                                                     56, 58
   Roof Mounts                                                  25, 53, 54
   Routine checks                                                      111

    S

 Safe Working Load (SWL)                                               58
 Safety components                                                112,113
                                                                              132
   Safety Devices                                           81, 122
   Safety Enhancement                                             84
   Safety of equipment                                              4
   Safety of personnel                                              4
   Salty environment                                            113
   Screening                                                   9, 13
   Security Fencing                                            9, 11
   Self Support Lattice                                       26, 37
   Service Life of Towers                               12, 21, 110
   Setbacks of Towers                                         10, 11
   Side Antenna Mount                                            103
   Signage                                                         11
   Silver                                                          88
   Site Plan                                                        6
   Siting                                                           8
   Slip Joints                                                     24
   Slope change                                                    34
   Solid Round Leg                                        21, 22, 86
   Space requirements                                               9
   Square structure                                                21
   Standard foundation                                        58, 59
   Steel member width                                              49
   Step Bolt                                                 64,121
   Structural certification                                        14
   Substructure                                            4, 56, 64
   Superstructure                      4, 16, 21, 35, 36, 40, 42, 86
   Superstructure Design and Loading                          40, 42

    T

   Tapered sections                                               21
   Technical College                                               7
   Terrain                                               14, 16, 128
   Thimble                                                   87, 100
   Total anticipated antenna load                             35, 36
   Tower Base Foundation                                     75, 111
   Tower loading                                             21, 113
   Tower maintenance                                             109
   Tower schedule                                             39, 41
   Tower to Tower Spacing                                         12
                                                                         133
 Tube leg                                                         21, 22
 Turnbuckle                                              87, 99,100, 115

    U, V

   U-Bolt clip                                                    99, 100
   U-Bolts                                                     12, 68, 89
   Uplift                   35, 36, 40, 43, 45, 57, 59, 61, 62, 68, 72, 73
   Verticality                                                        112

    W

   Weather proof light flasher                                          12
   Wind flow map                                                        15
   Wind Load                                              16, 40, 121, 14
   Wind loading                                                         14
   Wind Speeds              15, 16, 17, 19, 35, 36, 40, 42, 43, 44, 45, 74
   Work platforms                                                        21
   Workmen’s compensation                                   6, 21, 83, 112

    X, Y, Z

 X-braced, self supporting, lattice design                          34, 45
 Z bracing                                                              38
 Zinc                                                              88, 109




                                                                               134

				
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