Evaluation of Seismic Performance Factors for High-rise Steel Structures with Diagrid System

Abstract

Diagrid system is a new tubular structural system in tall buildings which requires seismic performance factors (R, Ω0, Cd) for seismic design according to the loading and design codes. By considering the fact that the current codes do not include these factors, this paper aims to evaluate them based on the FEMA P695 methodology. For this purpose, five archetypes have been developed in a way that the structure story heights and span lengths are respectively equal to 4 and 6 meters; this makes the diagonal angles equal to 53.13 degrees. The response modification coefficient (R-factor) of the archetypes was calculated by the Uang method through iteration in analysis and design in OpenSees and ETABS software, respectively. Two types of analysis were carried out: non-linear static analysis (pushover analysis) and non-linear incremental dynamic analysis (IDA); the first evaluates ductility, μT, and over-strength factors, Ω, and the second evaluates “collapse margin ratio (CMR)”. At the end, computed “adjusted collapse margin ratio (ACMR)” was controlled by acceptable values of ACMR in the FEMA P695. Based on the results, the values of R-factor, over-strength factor, Ω0, and deflection amplification factor, Cd, are proposed to be 2.5, 2.0 and 2.5, respectively.