DUCTILITY ANALYSIS OF R.C.C.(O.H.T)DESIGN AS PER IS 3370(PART II)

Abstract

Large capacity elevated intz tanks are used to store water for drinking and fire fighting. The liquid storage tanks are particularly subjected to the risk of damage due to earthquake-induced vibrations. A large number of overhead water tanks damaged during past earthquake. Majority of them were shaft staging while a few were on frame staging. Recently the Muzaffarabad earthquake 2005 and Bhuj earthquake 2001 also represented similar damage. Most of the damage was caused because of the tanks were either designed without considering the earthquake forces or inadequate seismic design considerations. To cope with this need the seismic design codes for over head water tanks have been revised and upgraded. The objective of this dissertation is to shed light on the difference in the design parameters of (a) over head water tanks (b) over head water tanks designd with earthquake forces, firstly based on Indian standard code 1893, (2002) i.e. adopting lumped mass modal method and second is based on draft code 1893-Part 2, (2005) considering two mass modal i.e. convective and impulsive mode method. Two types of elevated water tanks namely intz tank supported by frame staging and shaft staging have been considered in this study. These elevated water tanks are first designed and then designed considering earthquake forces. Their strength and ductility have also been evaluated and compared. It has been observed that time period in frame staging is higher then the shaft staging since the lateral stiffness of shaft staging is much larger. The tank supported on shaft staging has higher strength as compare to tank supported on frame staging but the ductility is low that may be the return of frequent failure of elevated water tank supported on shaft staging. In this dissertation work of 3D frame is being modeled in SAP 2000 VER. 11 (Advanced) & analyzed . The non-linear static procedure or simply push over analysis is a simple option for estimating the strength capacity in the post-elastic range. This procedure involves applying a predefined lateral load pattern which is distributed along the structure height. For evaluation of strength and ductility of frame staging, only staging portion has modeled in SAP. Here container portion is quite rigid there fore rigid link is assumed from top of staging to make rigidity. Mass of the rigid link has taken zero and stiffness is quite high compare to the other member of the staging.