Seismic Performance Assessment of Code Compliant Building
Building codes around the world are predominantly based on force-based design philosophy. The force to be sustained is obtained from a uniform hazard spectrum which gives the peak design acceleration value. The force-based design approach considers reduction in applied seismic force on account of ductility due to inelastic behaviour of materials. A drawback of this approach is the difficulty to evaluate the damage a building may sustain under a seismic event.
For evaluation of damage nonlinear time history analysis is performed to ascertain the damage the structure may sustain during a seismic event. For time history analysis the structure is subjected to accelerations from natural ground motions. Nonlinear properties of structural elements are modelled with use of hinges and the response of hinges is studied to determine the damage a building may sustain. The expected damage of the structure is related to the rotation of hinges. Peak floor acceleration and inter-story drift is studied under different ground motions to study the impact on non-structural components of the structure.
For this study two 12 story RCC framed buildings, one with regular configuration and one having irregular configuration in the form of re-entrant corner are designed following the guidelines of Indian Standard (IS) design codes. ETABS software by Computer and Structure Inc. is used for the analysis and design of the buildings.
IS 1893 (Part 1): 2002, Criteria for Earthquake Resistant Design of Structures, mentioned that “It has been endeavored to ensure that, as far as possible, structures are able to respond, without structural damage to shocks of moderate intensities and without total collapse to shocks of heavy intensities”. For performance assessment, the same can be translated as Collapse Prevention for MCE events and Life Safety for DBE events. However, in IS 1893 (Part 1): 2016 this is removed and there is no discussion on the damage a building may suffer due to a seismic event. The aim of this study is to obtain the performance levels a structure fulfills when designed as per the Indian Standards.