SEISMIC PERFORMANCE AND VULNERABILITY OF IS CODE DESIGNED RC FRAME BUILDINGS

Abstract

Significant developments have taken place in the last three decades in the field of Earthquake Resistant Design. Concepts of Capacity Design, Performance Based Design, and Displacement Based Design have been developed and are being adopted by many national codes. Indian standard seismic design practice is based on Force Based Design combined with some aspects of Capacity Design. This Dissertation examines the Seismic Performance and Vulnerability of RC frame buildings designed as per Indian Codes of Practice. Examples of conventional gravity load designed, and seismic load designed buildings, with and without ductile detailing are presented and their Performance and Seismic Vulnerability have been evaluated. The seismic design codes, including the IS code, are traditionally based on Force Based Design approach, which incorporates effect of hysteretic damping through a Response Reduction Factor used for reducing the design loads. This factor includes the effect of Overstrength and Ductility. Two types of RC frame design — OMRF, without ductile detailing of reinforcement, and SMRF, with ductile detailing of reinforcement, are specified by the Indian codes. The efficacy of the Indian code design specifications are examined in this dissertation. It has been shown that the buildings designed and constructed properly for the gravity loads alone, have significant Overstrength available to sustain the MCE level seismic action corresponding to Zone-IV, without collapse. The RC frames designed as SMRF have much higher ductility but lesser strength as compared with OMRF and the seismic performance of the two designs has been observed to be comparable.