Nonlinear inelastic dynamic behaviors of composite framed structures subjected to seismic loads

Abstract

This paper proposes a new method using stability functions and a distributed plasticity model to analyze the dynamic nonlinear inelastic behaviors of concrete-filled steel tubular (CFST) composite framed structures subjected to seismic loads via the Fortran programming language. The advantage of this method is the ability to accurately study the nonlinear behavior using only one beam-column element per member instead of using solid and shell elements as in traditional methods, thereby improving the model analysis time. A nonlinear algorithm based on the Newmark-β direct integration scheme has been developed to solve the governing differential equations of motion. The element stiffness matrix is integrated through the Gauss-Lobatto numerical integration scheme, while the nonlinear geometric effects P-Δ and P-δ are considered using stability functions and corresponding geometric matrices. The reliability and accuracy of the proposed method are verified by comparing the analysis results with those obtained from Abaqus. The results demonstrate that, by using beam-column elements for simulation, the proposed method provides accurate results, while significantly reducing computational time. For the CFST framed structure, the analysis time using the proposed method has been reduced by almost 128 times compared to the Abaqus program. Therefore, the proposed method promises to be a useful tool for the practice of designing and analyzing CFST structures subjected to seismic loads.

Keywords: Nonlinear inelastic analysis; CFST; Beam-column element; distributed plasticity model; dynamic behaviors; seismic loads.