Investigation of effective parameters on seismic performance of steel frames with CFST columns

Abstract

The seismic performance of steel frames with composite columns is evaluated by the seismic performance factors. Despite the essentiality of appropriate coefficient values, there are limitations in the building code regarding seismic performance factors of composite structures. These values have been presented in the regulations based on engineering judgment and comparison with similar steel and concrete structures. However, limited research exists on the determination of seismic performance factors for composite structures, where these coefficients are affected by numerous parameters. This article aims to cover the existing gaps and examine the parameters that have received inadequate attention in regulations and articles, despite their significance in the seismic design of composite structures. The present study conducts a nonlinear static pushover analysis of steel structures with concrete-filled tubular steel columns (CFST) to investigate the influential parameters in seismic performance factors. The variables studied in this research encompass the height of the structure, soil type, lateral force-resisting system, and structural irregularity. The findings demonstrate that changes in structural height influence the value of the response modification factor in all examined soil types for IMFs and SMFs. Also, the response modification factors provided in ASCE 7 prove to be conservative for the studied lateral force-resisting systems excluding SMFs in composite structures. In addition, the seismic performance of the studied models has dropped due to the geometric irregularity of the plan and the irregularity of non-parallel systems. Besides, the response modification factor values for composite structures surpass those specified for similar steel structures, while Eurocode 8 and ASCE 7 consider these values to be equal and similar to steel structures, respectively.