Nonlinear inelastic analysis of semi-rigid steel frames with circular concrete-filled steel tubular columns

Abstract

A reliable and effective method for the nonlinear inelastic analysis of frames using circular concrete-filled steel tubular (CFST) columns is developed in this paper. In the proposed method, the CFST columns and steel beams of the frame are modeled by using a fiber beam-column element that accounts for the nonlinear behaviors of both geometry and materials of the structure. The cross-sections of the elements are discretized into many small fibers and the stiffness matrix of the beam-column element is integrated through the Gauss-Labatto integration. The semi-rigid connections are modeled by using a zero-length element model where the nonlinear relationship of moment and rotation is formulated using a three-parameter power model. The accuracy and efficiency of the proposed method for modeling CFST columns are validated first by comparing the numerical results with multiple experimental results. Two CFST structures including the circular CFST column cantilever and the full-scale portal CFST frame with a variety of beam-to-column connections are then analyzed and verified with finite element models implemented in ABAQUS. The obtained results showed that the proposed method is highly accurate and can be utilized as an extremely useful tool for the nonlinear inelastic analysis of the CFST structures.