RELIABILITY BASIS FOR EARTHQUAKE RESISTANT DESIGN

Abstract

This study addresses the limit behaviour of structures under different ground motions. The selection of ground motion records is one of the primary steps on which the dynamic behaviour of structures depends. Different ground motion time histories need to be scaled in a consistent way to facilitate direct comparison or averaging of structural response to these excitations. The scaling also provides a convenient way to enhance excitation intensity measure to different levels of severity. The structural model is subjected to the selected ground motion records and nonlinear dynamic analysis is performed. The incremental dynamic analysis (IDA) is used to find the structural performance index of the model. The objective of this thesis is to investigate the performance of the structure for different limit states by using the IDA. Using the spectral acceleration for fundamental mode as the ground motion intensity measure, a correspondence between ground motion intensity and performance levels, namely, immediate occupancy, damage control, life safety and collapse prevention limit states is established. The IDA is applied to a three-storey and eight storey reinforced concrete moment resisting frame. Two sets of ground motions were considered for performing the IDA. Out of the twenty-two ground motion time histories fourteen are Indian ground motion records having magnitudes (M>5) and remaining eight are other major earthquake ground motions occurred across the world having magnitudes (M>6). In the chosen ground motions some are from far-field and others are near fault records to study the influence of different seismic source characteristics on the outcomes of the IDA. Finally the performance of both the buildings has been compared to find the actual behavior under the IDA. The recurrence interval for ground motions corresponding to different performance levels to failure of the structure is found out for the specified seismic hazard curve for a region