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STRENGTHENING REINFORCED CONCRETE STRUCTURES BY

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STRENGTHENING REINFORCED CONCRETE STRUCTURES BY Powered By Docstoc
					                United Arab Emirates University
                    College of Engineering
              Civil and Environmental Department


          Graduation Project (1)
   Strengthening of an existing
   reinforced concrete structure
         Instructor: Dr. Ashraf Biddah
   Student Name                             ID No.
Nabil Raweh Qahtan                        980410066
Mohammed Eisa Al-Harrasi                  980710101
Hazem Bakri Al-Naser                      199901443
             Introduction

   Exclusive Summary

   The general idea of the project.

   Problems Facing reinforced concrete
    structures.
        Exclusive Summary

The main achievements:
 Studying the Strengthening Methods.

 Selection of an exiting building.

 Experimental Test.

 Beginning of Structural Analysis.
      The general idea of the project

   The owner of a residential building wanted
    to convert his building to a commercial
    building.

   According to change in the use of existing
    structure, the structural system of the
    building will be modified to fit the new
    changes.
   PROBLEM:     The old building cannot carry
    the new loads that come from the changes.

   DESIGN BRIEF : Design a strengthening
    system that can increase the capacity of the
    existing structural system to be able to
    carry the new loads that come from the
    changes.
      Problems Facing Reinforced
         Concrete Structures

   Load increases.

   Damage to structural parts.

   Improvements in suitability for use.

   Modification of structural system.

   Errors in planning or construction.
STRENGTHENING REINFORCED
CONCRETE STRUCTURES BY BONDING
STEEL PLATES:

    Strengthening is the process of
     adding capacity to a member of
     structure.

    Attachment of steel to concrete:
1.   Adhesive connecting mechanism.
2.   Bolting connecting mechanism.
            Explanatory Sketch




Fig. 1 Techniques of plating reinforced concrete beams.
      STRENGTHENING REINFORCED
      CONCRETE STRUCTURES BY
      PRESTRESSING CABLES:

   Post-tensioning is a technique
    used to prestress reinforced concrete
    after concrete is placed.
   The tensioning provides the member
    with an immediate and active load-
    carrying capability.
External Post-tensioned picture
     The advantages of External
           Prestressing
   Ability to restress, destress and
    exchange any external prestressing
    cable.
   Crack free members.
   Reduce deflection.
   High fatigue and impact resistance.
    The Disadvantages of External
            Prestressing
   Usually requiring a greater section
    depth.
   More exposed to environmental
    influences (fire, vandalism,
    aggressive chemicals etc.).
   Handling of the tensioning devices
    may be more difficult.
   High cost.
  Concrete Jackets
(Section Enlargement)
              Concrete Jackets
            (Section Enlargement)
   Enlargement is the
    placement of additional
    concrete and reinforcing
    steel on an existing
    structural member.
   Beams, slabs, columns,
    and walls, if necessary,
    can be enlarged to add
    stiffness or load-carrying
    capacity.
          Concrete Jackets

   In most cases, the
    enlargement must be
    bonded to the existing
    concrete to create a
    monolithic member for
    additional shear or
    flexural capacity.
Column Compressive strengthening by
       Section Enlargement
 •Enlarging the cross section of
 an existing column will
 strengthen the column by
 increasing its load carrying
 capacity.
 •A column can be enlarged in
 various configurations.
 •The drying shrinkage effects in
 the concrete used to enlarge the
 column must be considered.
            Section Enlargement
                 Method A
•In the illustration, Method A
will accomplish efficient load
transfer if the new portion is cast
with a bond breaker between the
new and old concrete.
•After most of the drying
shrinkage has occurred, the ties
that link the old and new
concrete can be installed.
            Section Enlargement
                 Method A
•The gap between the new
portion of the column and the
existing member (to be partially
supported by this column) can
be filled with dry packing
material.
•This will allow the new
material to share its portion of
the load.
           Section Enlargement
             Methods B & C
•When Methods B and C are used,
extreme care should be exercised to
select concrete mix designs with very
low shrinkage rates.
•Pre placed aggregate concrete
generally offers the lowest drying
shrinkage; it is, therefore, an
excellent material for column
enlargements.
     Disadvantages of the concrete
               jackets

   Increasing the size of the element, which make
    its usage very limited.
   Difficult to construct in some active buildings
    such as hospitals, schools because of the noise
    of equipments.
   Needs shuttering, formworks, reinforced steel,
    concrete, concrete pumps, vibrators, …etc.
Fiber Reinforced
    Polymer
Fiber Reinforced Polymer (FRP)

  FRP is a new class of composite
   material for the development and
   repair of new and deteriorating
   structures in Civil Engineering.
  Search for alternatives to Steel and
   alloys to combat the high costs of
   repair and maintenance of structures
   damaged by corrosion and heavy use.
    FRP Laminate Structure

•   FRPs are organized in a laminate
    structure.
•   each lamina (flat layer) contains an
    arrangement of unidirectional fibers
    fabrics embedded within a thin layer
    of light polymer matrix material.
   FRP consists of two main
    components:
    1.Fibers.
    2.Resin or Matrix.
FRP Laminate Structure
          Types of FRP

The three main types of fibers
  used are:
  • Carbon.
  • Glass.
  • Aramid.
     Suitability of FRP for Uses in
      Structural Engineering

   FRP properties and advantages makes it
    ideal for wide spread applications in
    construction worldwide.

   FRP has a few disadvantages.
    Advantages of FRP:
   Corrosion Resistance.
   Lightweight.
   Ease of installation.
   Less Finishing.
   Less maintenance.
   Ductility of FRP wrapped members
    improves dramatically.
   They are ideal for external
    application.
          Advantages of FRP
   They are extremely durable.
   They are available in various
    forms: sheets, plates, fabric, etc.
   They are available in long lengths
    that eliminates joints and splices.
   They cure within 24 hours.
   Versatility.
   Anti-seismic behavior.
        Disadvantages of FRP


   High cost, susceptibility to
    deformation under long-term loads
   Temperature and moisture effects,
    lack of design codes, and most
    importantly, lack of awareness.
                         Decision

Steel plates            Concrete                      FRP
                        jacketing
  High Corrosion      Medium Corrosion        Corrosion resistance


    Low Cost              High Cost                 High Cost

 High Installation   High Installation cost Ease of installation.
       cost
more Maintenance      more Maintenance          Less Maintenance


  Heavy Weight          Heavy Weight               light Weight
             Introduction



   M.S.Project gantt chart.
   Lab tests on FRP material.
   Cost estimation for G.P.1
M.S. Project Gantt Chart
M.S. Project Gantt Chart
Experimental lab test on FRP
        material.



   The main objective of this experiment
    was to study the effect of different
    environments on the behavior of FRP
    material.
              Beams Details
   This experiment consists of 16 beams and 6
    cubes.
   Beams were divided to 4 groups, each group
    consists of 4 beams with four different
    reinforcements.
   Beams dimensions were 10cm x 10cm x
    50cm.
   Minimum reinforcement of one bar with 6mm
    diameter (1Φ6) was used.
        Groups Environment
Each group was exposed to four different
  environments as follows:

Group 1:
 Room temperature with 26 C.
                             o

Group 2:
 Hot water tank with 100 % humidity at 45oC.

Group 3:
 Oven (0% humidity) at 45oC.
Group 4:
 Outside exposed to sun radiation and the
  variation in temperature through the 24
  hours.
                 Equipments
   Digital balance.
   Molds of beams and cubes.
   Mixer.
   Vibrator.
   Hot water tank.
   Oven.
   Cube test machine.
   Beam test machine.
              Materials
 Concrete mix: water,
  cement, sand, coarse
  and small aggregates.
 Plastic sheet.

 FRP strips.

 Strain gages.
                    Procedures
   Steel reinforcements were
    prepared.
   Strain gages were fixed on the
    steel reinforcement.
   Concrete ingredients were
    calculated, weighted and
    mixed using a big mixer.
   Concrete was poured in the
    molds of beams and cubes.
   Concrete was vibrated and
    covered by plastic sheet.
              Procedures

   3 cubes were tested after 7 days.
   Concrete beams and cubes were
    removed from molds and cured in
    potable water for 14 days.
   Beams and cubes were exposed to
    air drying in laboratory.
                    Procedures
   FRP was applied with
    layer of epoxy.
   Beams were exposed to
    the different
    environments for 1000
    hours.
   3 cubes was tested after
    28 days.
   All beams was tested
    after 1000 hours.
Experimental Result
Experimental Results
Experimental Results
      Experimental Observations
1.   Effect of Fiber Reinforcement Polymer
     (FRP) on strengthening the beams:
    One FRP strip increased the beam's
     capacity by about 100% for all
     environments.
    Two strips of FRP increased the beam's
     capacity by about 200% for all
     environments.
    All reinforced beams strengthen with FRP
     failed on de-bonding of the FRP at the end
     of strips due to the shear force at this
     location.
     Experimental Observations
2.   Environmental effect on the
     beams:
    The effect of environment on reinforced
     concrete beams with steel only is
     negligible.
    Plain concrete with one strip of FRP
     (shear force) was affected in hot
     environments (humid and dry). Where
     the effect of outdoor and indoor
     environments was negligible.
     Experimental Observations
   The reinforced concrete beams strengthen
    with FRP; (bond capacity between the
    FRP and the concrete) was affected in hot
    and humid environment.
   Although the FRP in the outdoor
    environment was subjected to the Ultra
    Violet during the 1000 hrs exposure, no
    reduction in the beam capacity was
    noticed.
                Cost Estimation
Item # Item Description                   Manufacturers      Cost/    # units   Total
                                                             unit               Cost
                                                                                Dhs
1      5MM Steel Strain Gages Single      INSTALLATION       25       25        625
                                          middle east
2      Super Glue 5g Bottle               INSTALLATION       22       2         44
                                          middle east
3      Fiber Reinforcement Polymer Sika Company              75       7m        525
       strips (Sika Carbodur S type)                         Dhs/m
4      FRP Epoxy          (Sikadur     30 Sika Company       25       6         150
       normal)(6kg)
5      Reinforcement Steel Bars (#6)      Al-Moazam stores   2        12        24

6      Drawings Copying                                      4        17        68

7      Reinforcement Steel Welding                           5/beam   12        60


Total Cost = 1496 Dhs (within the budget)
       Analysis background
   The most important and most
    difficult task faced by the structural
    designer is the accurate estimation
    of the loads that may be applied to
    the structure during its life.
   The next problem is to decide the
    worst possible combinations of these
    loads that might occur at one time.
       Analysis background
   The loads that will be used in this
    project are dead and live loads.

   Dead loads are loads of constant
    magnitude that remain in one
    position.
   Live loads are loads that can change
    in magnitude and position.
       Analysis background
   ACI code (9.2) states that the
    required ultimate load carrying
    ability of the member U provided to
    resist the dead load D and the live
    load L must at least equal:

            U = 1.4D + 1.7L
         Analysis background
   The Loads carried by the structure are
    transferred from one structural element to
    another until it reaches its final destination
    to the supporting ground.

   The loads that come from slabs to beams
    can be estimated according to the slabs
    design system and the geometry of these
    slabs.
       Analysis background
   In one direction slabs the beam is
    carrying half of the slab as a
    rectangular or square shape.

   In two way slabs the each beam
    around the slab is carrying triangle
    or trapezoidal shape of the slab.
Prokon Structural Analysis & Design

   Prokon structural analysis and design
    is a useful tool for analysis and
    design of structures.
   The PROKON suite has two main
    components:

   PROKON Calcpad.
   PROKON analysis and design
    modules .
Prokon Structural Analysis & Design

   PROKON interface.
Prokon Structural Analysis & Design

   Input parameters.
Prokon Structural Analysis & Design

   Section dimensions.
Prokon Structural Analysis & Design

   Spans lengths.
Prokon Structural Analysis & Design

   Input loads.
Prokon Structural Analysis & Design

   Shear and Moment diagrams.
Structural system of the building
   Area = 750 m2.
   It consists of two stories.
   Types of slabs: One way Hurdy
    slabs, two way hurdy slabs and two
    way solid slabs.
   Types of columns: Rectangular and
    circular.
   There are projected beams and
    hidden beams.
Structural system of the building
   The Floor cover = 2 KN/m2.
   The Live load = 2 KN/m2.
           Hurdy slab load
   The unfactored loads calculation of
    the one way Hurdy slabs.
       Comparison between hand &
            Prokon results
   Hand results:
                     KN                      KN
    Self Weight  25      0.2 m  0.8 m  4
                     m3                       m
                       KN
    Wall weight  5.75
                        m

                 KN      KN             KN
Wu  1.4 ( 5.75      4       )  13.65
                  m        m             m
     Wu  (l ) 2   13.65  (5.2) 2
Mu                                46.137 KN .m
          8               8
     Wu  l    13.65  5.2
Vu                         35.5 KN
       2            2
Comparison between hand results
      and Prokon results
   PROKON results:
             Conclusion
   It was learned some modern
    technologies     in    strengthening
    concrete structures.
   It was learned a new computer
    software program.
   The a knowledge that we gained
    from structural analysis and design
    courses were applied.
              Conclusion
   From the experimental results, it was
    found that the FRP was effected by
    20 % in the hot (0% humidity)
    environment.
   It was decided to use FRP to strength
    the building.
   It was learned how to analyze one
    way Hurdy slabs and beams.
 Thank You
for Listening

				
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