Computer Analysis of Steel Frame in Fire

Based on an incremental variational principle, a computer program is developed to investigate in detail the large displacement elasto plastic thermal creep deformation behavior of a steel frame in the vicinity of a localized fire in a multistory building. Based upon a set of assumed time-temperature curves for the structural members and the available empirical stress-strain relation of structural steel at elevated temperature, the nonlinear problem is solved numerically by a finite element method. By assuming that the temperature remains constant during a time increment, the nonisothermal problem is approximated by step-wise constant temperature incremental processes. Numerical solutions of a number of structures are compared with available fire test results.