INCREMENTAL NONLINEAR DYNAMIC ANALYSIS OF COMPOSITE SPECIAL MOMENT FRAMES (C-SMF)

Abstract

In this research study, the seismic performance and collapse risk of composite special moment frames (C-SMF) are evaluated using the FEMA P695 methodology [5]. To address this objective, several 2D prototype building configurations of 3, 6, 8, 12, and 16 stories were designed based on a typical floor plan, located in different seismic zones and soil types, following the Chilean standard NCh 433 [1]. Geometric nonlinearity (P-Delta effect) and material nonlinearity were incorporated by implementing fiber-based concentrated plasticity models using effective stress-strain curves for this purpose. The software SAP2000 version 19.1.1 was used to conduct the entire research work.

Subsequently, incremental nonlinear dynamic analyses (Time-History) were performed to determine the median collapse intensity​, the collapse margin ratio (CMR), and to evaluate seismic performance by comparing the calculated adjusted collapse margin ratio (ACMR) with the allowable values proposed by FEMA P695 [5]. Based on the results, the recommended seismic performance factors for code-compliant use in C-SMF are: Ωo=3.0, R*=6.0, and Cd=5.5. The performance evaluation was satisfactory for all individual and group cases; however, in the authors’ judgment, the C-SMF structural system ensures life safety and may be incorporated into national regulations with a recommended height limitation of 12 stories.