Lumped plasticity model for simulating the inelastic earthquake response of CFT columns

Abstract

A simplified approach for simulating the seismic behavior of concrete-filled steel tube (CFT) columns using a lumped plasticity modeling approach based on a nonlinear spring model is proposed in this paper. Model parameters were calibrated considering plastic deformation, load–deformation during unloading and reloading cycles, and material strength degradation using an experimental database comprising 123 CFT column specimens (47 circular and 76 rectangular). 80% of the calibrated samples were used to develop predictive equations for the model parameters based on six input variables using multiple linear regression. The resulting equations were verified by the remaining 20% of all specimens; the verification results agreed with the experimental data and demonstrated better results compared to that of an existing fiber-based beam-column model. The proposed modeling approach was applied to model three frames with different stories (three, six, and nine stories) to perform nonlinear dynamic analyses. Then, their fragility curves were developed and compared with the curves obtained using existing fiber-based frame models. The proposed modeling approach increased the seismic vulnerability of the frames and reduced the analysis computational time.