SEISMIC PERFORMANCE OF CIRCULAR ELEVATED WATER TANK WITH FRAMED STAGING

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SEISMIC PERFORMANCE OF CIRCULAR ELEVATED WATER TANK WITH FRAMED STAGING Powered By Docstoc
					  International Journal of Advanced Research OF ADVANCED RESEARCH IN
  INTERNATIONAL JOURNAL in Engineering and Technology (IJARET), ISSN
  0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME
             ENGINEERING AND TECHNOLOGY (IJARET)

ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
                                                                         IJARET
Volume 4, Issue 4, May – June 2013, pp. 159-167
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2013): 5.8376 (Calculated by GISI)
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           SEISMIC PERFORMANCE OF CIRCULAR ELEVATED WATER
                    TANK WITH FRAMED STAGING SYSTEM

                     Gaikwad Madhukar V.1 Prof. Mangulkar Madhuri N.2
       1
         P. G. Student, Dept. of Structural Engineering, Jawaharlal Nehru Engineering College,
                               Aurangabad – 431003, Maharashtra, India.
       2
         Asst,Professor, Dept. of Structural Engineering, Jawaharlal Nehru Engineering College,
                                Aurangabad -431003, Maharashtra, India.



  ABSTRACT

          Water tank is used extensively for storage water, inflammable liquids, and other
  chemicals. The current analysis and design of supporting structures of elevated water tanks
  are extremely vulnerable under lateral forces due to an earthquake and the Bhuj earthquake
  provided illustration when a great many water tank staging’s suffered damage and a few
  collapses. The aim of this paper is to understand the behavior of Elevated Water Tank with
  the framed staging in lateral earthquake loading using IITK-GSDMA Guidelines by
  considering two theoretical theories given by Sudhir Jain &Sameer U. S. [1990] and Rapid
  Assessment of Seismic Safety of Elevated Water Tank with framed staging & Software
  STAAD Pro.-2007,for calculate the lateral stiffness. Same values of lateral stiffness Ks is
  used for further analysis. After details study it was found that the lateral stiffness Ksobtained
  by using Rapid Assessment of Seismic Safety of Elevated Water Tank gives the optimum
  value of Base Shear and Base Moment and hence it is economical. The design based on
  above gives the most economical section and also it is safe.

  Keywords –Elevated Water Tank, Lateral Stiffness, Seismic Analysis, STAAD. Pro 2007,
  Rapid Assessment of Earthquake safety.

  I.        INTRODUCTION

          Water supply is a life line facility that must remain functional following disaster.
  Most municipalities in India have water supply system which depends on elevated water
  tanks for storage. Elevated water tank is a large elevated water storage container constructed

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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME

for the purpose of holding a water supply at a height sufficient to pressurize a water
distribution system. These structures have a configuration that is especially vulnerable to
horizontal forces like earthquake due to the large total mass concentrated at the top of slender
supporting structure. So it is important to check the severity of these forces for particular
region.

1.1 Lateral Stiffness Ks of frame staging:
1.1.1. By considering Rapid Assessment of Earthquake safety of Elevated Water Tank:
        The design seismic forces for the water tank depends on its flexibility and hence on
the time period. Often, column stiffness is considered as 12EI/ L3, which is based on the
assumption that bracing beams are infinitely rigid. In practice, these beams are flexible and
therefore the assumption overestimates the staging stiffness.
        Most tank staging have identical bracing girders and equal panel heights. Moreover,
the top end of column in topmost panel and bottom end of column in bottommost panel are
fixed against rotation. For the most commonly used staging, having all the columns along the
periphery of a circle, panel stiffness is obtained as below-


Kpanel=                            For Intermediate panels, and ……. (1)


Kpanel=                            For Top & Bottom panels.…….. (2)


Lateral Stiffness of Staging Ks-
                        Ks =             . ……….. (3)


        When Tank structure is located on soft soil, the support is not rigid and hence
bottommost panel is no more fixed against rotation. Under these condition, the panel stiffness
is calculate using Eq. (1), which accounts for end rotations.

1.1.2. By considering Sudhir Jain &Sameer U.S. [1990]-
        Sudhir Jain and Sameer has given simple expression to evaluate the lateral stiffness of
framed type supporting system by considering the effect of girder flexibility. For tank staging
with equal panel heights, identical columns arranged along the periphery of a circle, and
identical bracing girders, the lateral stiffness of the staging Ks is calculated as below –

  =                    Where                  ………. (4)


          =

Kpanel=                        For Intermediate panel           …… (5)


Kpanel=                        For Topmost and bottommost panel …. (6)

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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME

Kaxial =                       ……… (7)

Where,
           H = Height of Panel from CG of container.
           h = Height of panel.

1.1.3. By using STAAD. Pro 2007 Software
        Lateral stiffness of staging is defined as the force required to be applied at the CG of
tank so as to get a corresponding unit deflection. From the deflection of CG of tank due to an
arbitrary lateral force one can get the stiffness of staging.STADD Pro software is used to
model the staging.




II.        CASE STUDY

    1. Numerical Problem Statement
        A RC circular water container of 200 m3 capacity has internal diameter of 8.50 m and
height of 3.82 m (including freeboard of 0.3 m). It is supported on RC staging consisting of 6
columns of 550 mm dia. with horizontal bracings of 300 x 550 mm at four levels. The lowest
supply level is 12 m above ground level. Staging conforms to ductile detailing as per IS
13920. Staging columns have isolated rectangular footings at a depth of 2m from ground
level. Tank is located on soft soil in seismic zone III. Grade of staging concrete and steel are
M20 and Fe415, respectively. Density of concrete is 25 KN/m3. Analyze the tank for seismic
loads.
        Elevated water tank can be analyzed by both the condition i.e. for tank full condition
and tank partially filled condition.



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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
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1.1 Preliminary Data

                            Table 1: Sizes of various components
                  Sr. No.       Components               Size (mm)
                       1        Roof Slab                175 Thick
                       2        Wall                     225 Thick
                       3        Floor Slab               225 Thick
                       4        Gallery                  110 Thick
                       5        Floor Beams              300 *600
                       6        Braces                   300 *550
                       7        No of Column             06
                       8        Dia. of Column           550

1.2 Formulation of Problem

                  Table 2: Constants which are considered for calculation
            Sr. No.     Constant       Values                 Remarks
               1           Z            0.16       Structure assumed in Zone III
               2           I            1.5              Importance Factor
               3           R            3.0         Response Reduction Factor
               4         M-20                            Grade of Concrete
               5        Fe- 415                            Grade of Steel

1.3 Details of Tank Geometry




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1.4 Change in Iteration with respect to volume:

                          Table 3: Table showing change in iterations with respective to volume

                                                                         Diameter of         Height of       Free Board
                                                       Volume in
       Sr, No.                        Iterations                         container in         tank in        of Tank in
                                                          Lit.
                                                                            meter              meter           meter
         01                               1             200,000             8.50                3.82            0.30
         02                               2                                 8.00                4.28            0.30
         03                               3                                 7.50                4.90            0.30
         04                               4                                 7.00                5.50            0.30
         05                               5                                 6.50                6.40            0.30

III.    ITERATION OF RESULTS BY GRAPHICAL METHOD

        Iteration of Results includes the graphical representation of output parameters which
are calculated as a solution.

                                                  Comparison of Lateral Stiffness
                              30000
                                                                     Rapid-        S. Jain       STAAD Pro
          Lateral Stiffness




                              25000
                              20000
                              15000
                              10000
                              5000
                                 0
                                              1          2               3              4             5
                                                             Iteration No

Graph No 01: Comparison of Lateral Stiffness obtained by Software & Theoretical Method


                                      Comparison of Base Shear for Static full condition-
                               375
                                                                    Rapid-       S. Jain       STAAD Pro.
              Base Shear




                               275


                               175


                                75
                                              1          2           3                  4             5
                                                              Iteration No

 Graph No 02: Comparison of Base Shear obtained by Software & Theoretical Method for
                               Static Full condition

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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME



                                Comparison of Base Shear for Static Empty condition
                      250
                                                             Rapid-        S. Jain         STAAD Pro.
                      200
             Base Shear

                      150

                      100

                          50
                                     1          2        Iteration No
                                                                3                   4                5


 Graph No 03: Comparison of Base Shear obtained by Software & Theoretical Method for
                              Static Empty condition

                                 Comparison of Base Shear for Hydrodynamic Full
                                                    condition
                          300
                                                            Rapid-        S. Jain         STAAD Pro.
         Base Shear




                          250


                          200


                          150
                                         1         2   Iteration No
                                                              3                 4                5

 Graph No 04: Comparison of Base Shear obtained by Software & Theoretical Method for
                           Hydrodynamic Full condition


                                Comparison of Base Shear for Hydrodynamic Empty
                                                    condition
                      250
                                                          Rapid       S. Jain           STAAD Pro.
         Base Shear




                      150



                          50
                                     1         2       Iteration No
                                                              3                 4                5


 Graph No 05: Comparison of Base Shear obtained by Software &Theoretical Method for
                          Hydrodynamic Empty condition




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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME



                                      Comparison of Base Moment for Hydrodstatic Full
                                                        condition-
                         5500
          Base Moment-
                                                                      Rapid    S. Jain       STAAD Pro.
                         4500


                         3500


                         2500
                                           1         2               3
                                                              Iteration No          4              5


Graph No 06: Comparison of Base Moment obtained by Software & Theoretical Method for
                             Hydrostatic full condition


                                      Comparison of Base Moment for Hydrostatic Empty
                                                         condition-
                               3500
                                                                  Rapid-       S. Jain       STAAD Pro.
                 Base Moment




                               3000


                               2500


                               2000
                                               1          2           3
                                                               Iteration No.             4             5


Graph No 07: Comparison of Base Moment obtained by Software & Theoretical Method for
                            Hydrostatic Empty condition


                                      Comparison of Base Moment for Hydrodynamic Full
                                                         condition-
                         5000
                 Base Moment




                                                                   Rapid-      S. Jain       STAAD Pro
                         4000

                         3000

                         2000
                                           1          2              3
                                                               Iteration No          4              5


Graph No 08: Comparison of Base Moment obtained by Software & Theoretical Method for
                            Hydrodynamic Full condition




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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
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                                         Comparison of Base Moment for Hydrodynamic
                                                       Empty condition-
                             3400
                                                                  Rapid-         S. Jain      STAAD Pro.
           Base Moment-


                             3200

                             3000

                             2800

                             2600
                                              1               2                 3                4            5
                                                                           Iteration No

Graph No 09: Comparison of Base Moment obtained by Software & Theoretical Method for
                          Hydrodynamic Empty condition


                                                  Comparison of Hydrodynamic Pressure-
            Hydrodynamic Pressure-




                                     6
                                                                             Rapid-        S. Jain     STAAD Pro.
                                     5
                                     4
                                     3
                                     2
                                     1
                                     0
                                          1               2                    3                4             5
                                                                           Iteration No

  Graph No. 10: Comparison of Total Hydrodynamic Pressure by Software & Theoretical
              Method for Hydrodynamic Analysis of Elevated Water Tank


IV.    CONCLUDING REMARKS

        From above mentioned detailed study and analysis some of the conclusion can be
made as follow ……
        Graph No 1 clearly shows the comparison of Lateral Stiffness obtained from three
different methods. If we observe the graph, the value of Ks obtained from Sudhir Jain and
STAAD Pro. is higher than the Rapid Assessment of seismic safety. If we analyze the
elevated water tank by considering the higher value of Ks and same is used for Analysis &
design we will get the over stabilized or say over reinforced section, but it will be
uneconomical. Hence Ks by using Rapid Assessment of seismic safety is economical.
        Graph No 2 to 5 shows the comparison of Base Shear for Tank Full and Empty
condition by using three different methods for Hydrostatic& Hydrodynamic Analysis of

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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME

Elevated Water Tank. The values of Base Shear obtained from Tank full condition is greater
than the Tank Empty condition and hence considered for further analysis. If we observe the
graphs we find that the Base Shear obtained from Rapid Assessment of seismic safety is
lesser than the other two, and hence it is economical.
         Graph No. 6 To 9 shows the comparison of Base Moment for Tank full and Empty
condition by using three different methods for Hydrostatic & Hydrodynamic Analysis of
Elevated Water Tank. Base Moment obtained from Rapid Assessment of seismic safety is
lower than other two. If we design by considering the higher value we get over stabilized or
say over reinforced section. It is safe but uneconomical. That’s why Hydrostatics system of
designing of elevated water tank is not useful in seismic Zones. And hence, IS code provision
for static analysis is restricted for small capacities of tanks only. For Hydrodynamic analysis
the Base Moment obtainsfrom Rapid Assessment of seismic safety is lesser than the other
two, and hence it is economical.
         Graph No 10 shows the comparison of Hydrodynamic pressure on wall as well as on
base of Elevated Water tank. Total hydrodynamic pressure obtained from Rapid Assessment
of seismic safety is lesser than the other two, and hence it is economical.
         From detail study and analysis, it was found that the analysis and design based on
Lateral Stiffness Ks obtained from Rapid Assessment of Earthquake safety of Elevated Water
Tanks with Frame Staging is most economical and safe.

V.     ACKNOWLEDGEMENTS

      I wish to thank the Management, Principal, Head of Civil Engineering Department
and Staff of Jawaharlal Nehru Engineering College and authorities of Dr. Babasaheb
Ambedkar Marathwada University for their support.

REFERENCES

[1]. IITK-GSDMA Guidelines for Seismic Design of Liquid Storage Tanks Provision with
commentary and explanatory examples. NICEE, IIT Kanpur.
[2]. IS 1893-1984, Criteria for Earthquake Design of Structures, BIS, New Delhi.
[3]. IS 1893-2002 (Part-I) Criteria for Earthquake Resistant Design of Structure – Part-1,
General Provisions and buildings, BIS, New Delhi.
[4]. Sudhir Jain & Sameer U. S [1990] , Approximate method for determination of Time
Period of Water Tank staging’s, The Indian concrete journal, Vol-66, No-12
[5]. Rapid Assessment of Seismic Safety of Elevated Water Tanks with Frame Staging.
[6]. STAAD Pro. 2007, Structural analysis and design programing -2007 for analysis of
lateral stiffness.
[7]. Mangulkar Madhuri N. and Gaikwad Madhukar V., “Review on Seismic Analysis of
Elevated Water Tank”, International Journal of Civil Engineering & Technology (IJCIET),
Volume 4, Issue 2, 2013, pp. 288 - 294, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
[8]. Mangulkar Madhuri N. and Gaikwad Madhukar V, “Comparison between Static and
Dynamic analysis of Elevated water Tank”, International Journal of Civil Engineering &
Technology (IJCIET), Volume 4, Issue 3, 2013, pp. 12 - 29, ISSN Print: 0976 – 6308,
ISSN Online: 0976 – 6316.




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