Extending substitute frame model as a rapid supersede for moment frames and X-braced structures in seismic response estimations

Abstract

Substitute Frame (SF) model is a recently introduced equivalent simplified MDOF model by the authors which is applicable to moment-resisting frames, facilitating the modeling efforts and output management besides reducing the analysis time. The use of this model is deliberated only in the code-based OpenSEES software generally used by researchers and is not suitable for the practical works of engineers. This paper aims to develop the SF model to be usable in the practical engineering platforms that are widely used by engineers, and authenticate its accuracy and applicability in such platforms. Moreover, another objective is to develop this model to be applicable to concentric X-braced steel frames with equal or non-equal bay lengths. These objectives will be fulfilled with different examples, and the accuracy of the simplified models will be comprehensively evaluated by means of modal, nonlinear static, and nonlinear dynamic analyzes. The nonlinear time history analyses (NTHA) are performed with 20 real ground motion records. It has been shown that the proposed simplified model can estimate the responses of moment frames and X-braced systems with acceptable accuracy in a considered practical engineering platform. The proposed model could estimate the natural periods of all the original models with less than 1% error. In addition, the proposed SF model could predict the overall behavior of the original models in the pushover curve and estimate the maximum IDRs, PFAs, and story shears of all stories with acceptable accuracy in nonlinear dynamic analysis. Moreover, the use of the SF model can considerably reduce the computational time (by about 85%) for performing the analyses, and also facilitate the modeling efforts and output management. The supplementary example files for the present study would be shared through the link “https://web.nit.ac.ir/∼h.hamidi/software_data.htm”.