PERFORMANCE-BASED SEISMIC DESIGN FOR IRREGULAR STRUCTURES

Abstract

Seismic design codes are generally based on strength philosophy, where structures are designed using a linear elastic force-based design (FBD) approach while accounting their nonlinear behavior by using a response modification factor (R). The main objective of this philosophy is a strength rather than a displacement capacity. This research reviews the Egyptian code-compliant design (CCD) to test their effectiveness, reliability, and structural performance, as well as it proposes an alternative performance-based design (PBD) approach for seismic design, by developing a performance factor (P) for different performance levels. A wide range of medium and high-rise regular and irregular RC moment frame structures of different properties are assessed using this approach in the elastic and inelastic stages through three-dimensional (3D) models where their capacity and susceptibility to deterioration is examined through nonlinear static pushover analysis, where the capacity curve, ductility ‘µ’ and overstrength ‘Ω’ are evaluated, then the performance of the different structures is investigated. Irregular structures were assessed in this study comparing their behavior under earthquake effects with the regular structures, to interpret the primary factors responsible for their performance and emphasize their negative impacts on the structural response. The correlation between FBD and PBD is carried out using the performance factor (P) and the correlation factor (ρ), which can be used in design codes to have a more reliable fulfillment of intended seismic performance and reduced construction costs while accommodating to the owner’s features.