Creep Buckling of Steel Beam-Columns Subjected to Fire

摘要

This paper presents highlights of a computational study to investigate the influence of thermal creep of steel on the ultimate strength of steel beam-columns at elevated temperatures. W12x 120 wide flange beam-columns with the unsupported length of 240 inches are used in the simulations. A Pin-pin end-support condition, and an initial geometric imperfection having the shape of the first buckling mode with the amplitude of L/1000 formed the geometric boundary conditions. Beam-columns are subjected to a single end-moment, and are bent about the weak axis of their cross section. Thermal creep of steel is modeled following equations proposed by Fields and Fields for the creep of ASTM A36 steel. Thermal restraints, both axial and rotational, were ignored in the analyses. Representative results from creep buckling tests simulated at 500 are presented and discussed. Presentation of the results in the form of Creep Buckling Curves and Isochronous Strength Interaction Curves are proposed to quantify the effects of axial loads and end-moments on the time- and temperature-dependent behavior of steel beam-columns. Results from creep buckling simulations presented in this paper indicate that the combination effect of axial loads and end-moments have a significant impact on the predictions of the time-dependent ultimate strength of steel beam-columns subjected to fire.