SEISMIC ASSESSMENT OF REINFORCED CONCRETE BRIDGE

Abstract

There is always a matter of care when the behaviour of bridge is considered when the seismic load is taken into consideration. Not only for seismic loads but for normal service loads also the dynamic characteristics are complex in nature. So understanding the behaviour of the bridge had become a challenge for the overall benefit of the society. In this study 3 bridges of varying heights are taken to examines the seismic responses of a three — span continuous concrete i-girder bridges. Bridges taken for this study is a three span with two bents each having three circular columns. 3-D finite element models is Id to the seismic performance of the bridges. Thin shell elements having DOF 1 deck and column are modelled with beam Gused for modelling elements or commonly known as frame element. The base of intermediate bent columns is assumed to be fixed. Material non-linearity in frame elements is in the form of hinges. The load cases,, i.e7 those of dead load is taken initially. Modal and Pushover analysis is performed. The dead load is applied to entire structure to determine the "cracked section properties". Based on the cracked section properties the modal analysis is performed. Non linear static analysis is performed as per ATC-40, FEMA-356, FEMA-440(Equivalent Linearization), FEMA-440(Displacement Modification). Finally from pushover analysis for both bents in transverse and in longitudinal direction to get the demand capacity ratios which is comming less than one and varying with the change in length of the column. Various other design results had been obtained.