International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 04 Issue: 07 | July -2017
p-ISSN: 2395-0072
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Performance Study of Elevated Water Tanks under Seismic Forces Furquan Elahi Shaikh1, B K Raghuprasad2, Amarnath K3 1M.Tech,
Department of Civil Engineering, The Oxford College of Engineering & Technology, Bengaluru, Karnataka, India 2,3 Professor, Department of Civil Engineering, The Oxford College of Engineering & Technology, Bengaluru, Karnataka, India ---------------------------------------------------------------------***--------------------------------------------------------------------Abstract – Elevated water tanks are frequently used in seismic active regions and because of that the seismic behavior of them needs to be carefully analyzed and dealt with. Due to lack of understanding most of the elevated tanks were damaged in the past earthquakes and hence there is a need to properly understand the different factors governing the design. At present, IS 1893:1984 describes the seismic force criteria for elevated water tanks. The code does not take into account for the convective and impulsive pressure in the analysis of the tank and also assumes the tank to be a single degree of freedom system. The objective of this work is to assess the impact of earthquake forces on two types of tank systems based on their support mainly classified as Framed Staging and Shaft Staging. Response Spectrum Analysis is carried out and behavior of these staging systems is studied as per draft code Part II of IS 1893:2006 and IITk’s GSDMA guidelines. Parameters such as Base Shear, Nodal Displacement, Overturning Moment, and Vibration Analysis are obtained from an FEM software STAAD-Pro.
Frame type and Shaft type using FEM software STAAD-Pro and compare their results and establish which one is better performing under seismic loads. The seismic design criteria in India is given by IS 1893-2002 (Part I) which illustrates minimum loading standards and IS 4326-1993 which gives the design and detailing requirements for constructions of building structures. 2. LITERATURE REVIEW Significant research was carried out on seismic design of liquid storage tanks and a few published works on seismic response characteristics of reinforced concrete water tanks. G.W. Housner [1] investigated the response of the tanks which were supported on ground and elevated tanks during the Chilean earthquake of May 1960. He studied that when an elevated water tank is completely filled or completely empty it may be treated as a single degree of freedom system. Whereas when the tank is partially filled with water the same idealization does not hold good and hence stated the convective effect in the tank which was primarily due to the sloshing of water to the tank wall. Jain Sudhir k [2] investigated that the IS code provisions and observed there was absence of a proper value which should take into consideration the performance factor of the tank. Analysis of few tanks suggested that the idealization based on the code is not adequate enough to counter the lateral forces differences and the final result depends heavily on the dimensions of the tank and the stiffness of support system. Durgesh C Rai [3] investigated that the current design of the circular shaft type staging was very poor and the tanks designed using those parameters were extremely vulnerable under lateral loads. He also studied the tanks which were damaged in 2001 Bhuj earthquake and that was taken as a benchmark in his study. Pavan S Ekbote [4] studied the response of the elevated tank and considered certain parameters and theories which were recommended by G.W Housner [1] which are more acceptable and are being adopted in many of the international codes. Their aim was to study the performance of the elevated water tanks under different kinds of staging patterns. Rupachandra J Aware [5] investigated and studied the seismic performance of circular elevated water tank as per the draft code of IS 1893:2002 (part 2). It was mentioned that complex pattern of stresses are developed in the staging and
Key Words: Frame Type Staging, Shaft Type Staging, Single degree of freedom, Impulsive pressure, Convective pressure. 1. INTRODUCTION The progress in the scientific research into the dynamic behavior of liquid storage tanks reflects the increasing significance of these structures. Early uses for liquid containers were found in the petroleum industry and in municipal water supply systems. As time progressed the use of these types of storage is not just limited to storage of flammable liquids or water but also extended to nuclear reactor installation and thus making the study of their vibration properties a matter of prime importance. Safety of elevated tanks is of significant importance as tanks carrying large volume of different types of liquids within them. Water tanks are circular, rectangular, square, conical or intze type. Based on their supporting system elevated tanks can be classified as framed staging and shaft staging tanks. Due to the importance of water in dire circumstances such as an earthquake this study is primarily focused on the seismic performance of an elevated water tank. The objective of this study is to analyze the two types of elevated water tanks namely
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