Finite Element Simulation of Concrete-Filled Double-Skin Tube Columns Subjected to Postearthquake Fires

Detailed finite-element (FE) analyses were conducted using commercial software to simulate the behavior of concrete-filled double-skin tube (CFDST) columns subjected to postearthquake fires. The main goal of these simulations was to replicate results from a series of experiments that first subjected CFDST columns to different levels of seismic damage by applying cyclic lateral loading, and then fire testing of the same specimens in a furnace. The numerical simulations paralleled the experiments in the loading sequence. Different material models and modeling techniques were assessed in terms of reproducing experimental observations including local failure modes such as steel tube buckling. Results from the cyclic loading simulations including residual deformations were maintained as initial conditions for the subsequent thermal-stress analysis to simulate the fire testing phase of the experiments. A sequentially coupled nonlinear thermal-stress analysis was conducted on the models of CFDST columns to study the effects of exposure to a standard fire (time-temperature) curve. Numerical simulations using material properties adopted from European general rules for structural fire design provided a reasonable comparison to experimental results for both during and postfire situations.