Second-order analysis of 2-D steel frames at elevated temperatures

At elevated temperatures, the stress-strain relationship of steel will be nonlinear. When one of the columns of a steel frame is subject to a local fire, the material properties of the column will deteriorate locally. Although the column is weakened, the steel frame will not collapse immediately if the frame is robust enough so that the excessive internal forces of the column can be redistributed by its connecting members. Structural design with robustness consideration can prevent a steel building under local fire from collapse. This paper is to propose a second-order analysis and design method for 2-D steel frames considering the nonlinear stress-strain relationship of the material under elevated temperatures. Results are found to be in line with the Eurocode 3 predicted failure loads.