Performance Evaluation of RCC Building: A Direct Displacement Based Approach

Abstract

Current seismic design codes used for seismic design of structures are based on Force-Based Design approach. The traditional seismic design of structure is primarily based on forces. This methodology completely misses an important parameter, structural displacement, which is a measure of damage in structures subjected to earthquake excitations. Strain and drift can be integrated to give displacement. Therefore, both structural and non-structural damage can be related to displacement. Many researchers have shown that Direct Displacement Based approach performed well in predicting seismic demands of the structure.

The present study is done to close the gap between existing research on Displacement- Based Design (DBD) and its implementation for the design of conventional reinforced concrete (RC) frame structures. This approach has been utilized on reinforced concrete regular moment resisting frame structure. Story drift ratios were chosen as deformation limits to define the performance levels for specific earthquake hazard levels. In this study frames designed using DBD approach has been utilized in compliance with response spectra of IS 1893 (Part 1). Nonlinear Static (Pushover) Analysis and Time History Analysis has been carried out to evaluate whether the postulated performance criteria are met. The Base Shear forces and the top displacements, in addition, for each frame were also checked with the ones obtained through DBD approach. Comparison of buildings designed using DBD approach has been done with the same building designed using FBD. Buildings analysed with DBD approach gives high time period as a result low stiffness and low base shear compared to FBD.

Also effect of the Site Specific Response Spectrum on analysis of Reinforced Concrete regular frame structure is presented. Present study includes ground response analysis of of Ahmedabad and Delhi site using one dimensional Equivalent Linear Analysis based software ProSHAKE. Acceleration Time History of Bhuj Earthquake (0.106g) and El Centro Earthquake (0.344g) are considered as input motion to get response spectra at ground surface for low and high PGA. Various sites considered in Ahmedabad are Paldi, Chandkheda, Thaltej and Passport Office at same soil depth of 15m. Delhi site is considered with varying bedrock depth of 10 m, 30 m, 60m, 100 m and 200 m taking account of effect of soil depth. Seismic response of 3 and 6-storey regular RC frame structures are analysed using DBD methodology at Ahmedabad and Delhi site for low and high PGA earthquakes.