Soil Structure Interaction Analysis of Elevated Water Storage Tank.

IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 05, 2016 | ISSN (online): 2321-0613

Soil Structure Interaction Analysis of Elevated Water Storage Tank Miss V. J. Ghadage1 Prof. A.H. Kumbhar2 Prof. T.F. Mujawar3 1 B.E. Student 2,3Assistant Professor 1,2,3 Department of Civil Engineering 1,2,3 Dr.Daulatrao Aher College of Engineering, Karad, MH Abstract— In day to day life, one cannot live without water.

The elevated liquid storing tank is the most effective storing competence used for domestic or even industrial rationale.

The water must be stored and be available whenever needed by community and industry. Thus there is an acute need for large efficient and economical storage facilities. When a structure is built on soil some of the elements of the structure are in direct contact with the soil. When the loads are applied on the structure, internal forces are developed in both the structure and as well as in soil. The aim of this study is to understand the soil structure interaction analysis of a water tank supported by system of column and bracing.

Key words: Elevated Water Tanks, Stagging System, Staad pro, Soil Structure Interaction I. INTRODUCTION The water is source of every conception. Depending upon the location of the water tank, the tanks can be name as overhead, on ground and underground water tank. The tanks can be made in different shapes like rectangular, circular and types.

The elevated water tanks are built for direct distribution of water by gravity and are usually of smaller capacity.

In the rapidly expanding world today there is an ever increasing need to preserve and store water. The water must be stored and be available whenever needed by community and industry. Thus there is an acute need for large efficient and economical storage facilities. As of today water tank have taken on many layouts and configuration. most common among them is a cylindrical tank with a roof of either a one way slab or a two way slab or a partial spherical dome. As of today water tank are analyzed and designed by considering the earthquake forces and wind forces imposed over the water tank body. The response of water tank and staging for earthquake and wind loading is different for than for static loading. When earthquake forces and wind forces are developed the resulting horizontal trust which constitute a major load is of complex nature.

Frame type staging are generally regarded superior to shaft type staging for lateral resistance because of there large redundancy and greater capacity to absorb seismic energy. Soil structure interaction is a challenging multidisciplinary subject which covers several areas of civil engineering. In this paper Soil Structure Interaction analysis of elevated circular water tanks is performed by using of staad pro software.

B. “Finite element analysis of post-buckling dynamics in plates—Part I” Hue Chen, Lawrence N. Virgin ASCE 2005 In this paper various static and dynamic aspects of postbuckled thin plates, including the transition of buckled patterns, post buckling dynamics, secondary bifurcation, and dynamic snapping (mode jumping phenomenon), are investigated systematically using asymptotical and nonstationary finite element methods.

C. “Determination of Natural Frequencies and Mode Shapes of Structures Using Subspace Iteration Method with Accelerated Starting Vectors” Byoung-Wan Kim Sang-Won Cho Chun-Ho Kim and In-Won Lee ASCE 2005 In this paper natural frequencies and mode shapes of structures are determined from eigenvalue analysis. This paper proposes a subspace iteration method with an accelerated Lanczos starting subspace for the efficient eigenvalue analysis of structures.

D. Ketan Bajaj, Jitesh T. Chavda, Bhavik M. Vyas (2013) [3] This paper studied the buildings are subjected to different earthquake loading and behaves differently with the types of condition, such as soft, medium and hard soil. Different soil properties can affect seismic waves as they pass through a soil layer. With the change in soil property from hard to medium and from hard to soft the shear force has increased by respectively for flexible base.

III. CONVENTIONAL ANALYSIS A. General Features of the Tank

II. LITERATURE REVIEW A. Dr. G. Ravi, Dr. H. S. Prasanna, Vinay M. L. Gowda (December 2015) [1] The focus of this paper is on potential effects of SSI o framed structure with shallow foundation resting on clayey soils.

This analysis provides results in the form of stresses and displacements values, deformation, story drift which are realistic values than those provided by analysis.

Fig. 1: shows - Elevated Water tank 1) Shape – Circular water tank supported on column, bracing staging.

2) Capacity – 4, 00,000 liters.

3) Height of staging – 16 m

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Soil Structure Interaction Analysis of Elevated Water Storage Tank (IJSRD/Vol. 4/Issue 05/2016/025)

4) Steel – all reinforcement shall be HYSD. 5) Water density – 9.81 KN/m3 6) Seismic zone – III 7) wind speed – 39 m/ Capacity = 400 m3 π/4 x D2 x H = 400 Let h = 3.75 m Free board = 0.25 m H = h + free board = 3.75 + 0.25 = 4.0 m π/4 x D2 x 4 = 400 Cylindrical Wall Determination of hoop tension according to IS 3370 part IV Dia. of tank = 11.7 m, H=4m T = (30 H + 50) = 30 x 4 + 50 T = 170mm M = coefficient x WH3 Design Of Top Dome Rise = 0.15 D Thickness of 100 mm is provided for dome D/2 x D/2 = h x (2R – h) 1. Self weight of dome = 1 x 1 x 0.1 x 25 KN/m2 2. Live load / sqm = 1 x 1 x 1.5 Hoop stress at any angle is given by = WR/t x [(cos2θ+ cos θ – 1 )]/ [1+ cos θ] D = 11.65 m Let D = 11.7 m Meridonial stress = WR(1-cosθ)/tsin2θ Design Of Top Ring Beam Hoop tension = Ft = (TiCosq x D/2) Meridional thrust = WR/ (1+ cos θ ) Design Of Slab Wt of water Wt of slab Diameter of base slab = 11.7 m Effective span = 11.7 + 0.3 = 12 m Circumferential moment = (Mθ)c = 1/16 ( Pa2 ) Radial moment = (Mr)c = 1/16 ( Pa2 ) IV. RESULTS AND DISCUSSIONS A. Analysis Using Conventional Method Vibration serviceability has became a governing design criteria for many new building structures water tank is the typical case for dynamically exited structure by earthquake and wind loading.In conventional structure we get the seismic forces on structure based on the zone factor, importance factor, response reduction factor and spectral acceleration .the frequency is calculated based on lateral deflection caused at the top of tank due to seismic load .in conventional analysis we get the moment at different location given by IS code with respect to height.As per conventional analysis maximum bending moment is occurring at the middle of ring girder and at support location ,maximum shear force occur at the face of support, while twisting moment will occur in between centre of span and face of support .Due to arch effect of dome the thickness of dome required is nominal. Lateral force is occurring maximum at the bottom of tank lateral force at the

staging level is small compared to the top lateral force .lateral force is increased as per the height.

B. Analysis Using Staad Pro Software In this analysis of elevated circular water tank has been done by using finite element analysis software. Finite element analysis provide the six component of forces at every nodal point in line element ,while in plate element it provides the bending and membrane stresses. It is observed that frequency of vibration is reduces with increase in staging height. Tank vibrate in fundamental mode shape as mass participation in percentage is higher than ninety percent when tank is full at various staging height. Stresses in tank wall increases with increase in the wall depth, stresses observed in dome of tank is small due to arch effect of dome. In calculating the frequency of structure it is found that zone factor, Importance factor response reduction factor damping does not influence on frequency of elevated water tank. Soil structure interaction affect the frequency of the structure due to stiffness of the water tank staging is altered. The water tank has that much of mode shape equal to number of exiting masses, higher mode are found to be not effective in vibration as the mass participating is negligible

Fig. 2: Frequency verses water depth for various modes for 16m staging height Maximum deflection at the top of tank is found to be directly proportional to water depth at different staging height,

Fig. 3: Max deflection with water depth for various staging height

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Soil Structure Interaction Analysis of Elevated Water Storage Tank (IJSRD/Vol. 4/Issue 05/2016/025)

Maximum base shear in single column with water depth for various staging height. Base shear increases directly proportional to water depth.

Fig. 6: Frequency with water depth for various staging height for soft rock Fig. 4: Max base shear with water depth for various staging height Soil structure interaction for water tank structure if found by giving spring support to the water tank structure.

For first mode frequency increases by 70 percent for medium soil compared to soft soil, while frequency increases by 30 percent for soft rock compared to medium soil.

Soft soil Ks=10000KN/M2/M Medium soil Ks=30000KN/M2/M Soft rock Ks=50000KN/M2/M

Fig. 7: Frequency with water depth Above graphs are shown for frequency with water depth for conventional method, finite element method.

Frequency is maximum in conventional analysis.

V. CONCLUSION Fig. 5: Frequency with water depth for various staging height for soft soil

In soil structure interaction analysis frequency of vibration increases with increase in modulus of sub grade reaction.

REFERENCES [1] Dr. G. Ravi, Dr. H. S. Prasanna, Vinay M. L. Gowda (December 2015) [1] [2] “Finite element analysis of post-buckling dynamics in plates—Part I” [3] “Determination of Natural Frequencies and Mode Shapes of Structures Using Subspace Iteration Method with Accelerated Starting Vectors”.

[4] Ketan Bajaj, Jitesh T. Chavda, Bhavik M. Vyas (2013) [3].

[5] Dimitrios Vamvatsikos2 and C. Allin Cornell, Direct Estimation of Seismic Demand and Capacity of Multidegree-of-Freedom Systems through Incremental Dynamic Analysis of Single Degree of Freedom Approximation,ASCE3,ASCE 2005

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Soil Structure Interaction Analysis of Elevated Water Storage Tank (IJSRD/Vol. 4/Issue 05/2016/025)

[6] Emrah Erduran and Ahmet Yakut, Vulnerability Assessment of Reinforced Concrete Moment Resisting Frame Buildings, ASCE 2007.

[7] Erol Kalkan and Vladimir Graizer, Coupled Tilt and Translational Ground Motion Response Spectra , ASCE 2007 [8] Farrashkhalvat and J.P. Miles ,Basic Structured Grid Generationwith An Introduction To Unstructured Grid Generation , Butterworth-Heinemann, oxford,2003 [9] FFT analyzer manual Gregory A. Kopp and David Surry, Wind Tunnel and Uniform Pressure Tests of a Standing Seam Metal Roof Model, ASCE 2005.

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