Seismic Analysis and Retrofitting Strategies for an Existing Building

Abstract

Seismic protection is a widely accepted concept aimed to improve the performance of any structure under future earthquakes. Seismic protection primarily includes seismic rehabilitation, seismic retrofitting and passive protection system. Earthquakes of varying magnitude have occurred in the recent past in India, out of which worth mentioning are Latur (1993) and Bhuj (2001). Such seismic activities caused extensive damages to life, property, and had raised concern among civil engineering profession. Structures including buildings, hospitals, communication towers, industrial structures and chimneys etc., that suffered damages can be retrofitted to with stand safely seismic demand of the future earthquake. Recently developed materials and techniques play vital role in seismic retrofitting of existing structures. Most widely used seismic retrofitting strategies in Indian subcontinent are Jacketing and FRP wrapping of structural elements. Present work is focused on assessing adequacy of an existing school building in Ahmedabad against seismic demand of future earthquake. Seismic vulnerability of the school building is carried out by Visual Inspection and primary assessment through data collection, rapid visual screening, condition assessment and quick checks for strength and stiffness. On the basis of primary evaluation decision about requirement of detailed evaluation of the structural element is taken. For deficient structural members, Non-Destructive Test (NDT) and core cutter test are carried out. Seismic demand of a school building was estimated through lateral load analysis and Demand Capacity Ratio (DCR) calculations. Existing capacity and seismic demand of the school building is evaluated through Non Linear Static (Pushover) analysis using ETABS. Deficient members are identified and grouped to provide uniform retrofitting schemes. Two retrofitting strategies like column jacketing and FRP wrapping is suggested for column and beam respectively.