A numerical model for the fire response of steel structures

A method for quantitative evaluation of the response of unprotected steel frames exposed to a prescribed fire environment is presented. The beam- column theory is applied to formulate the analytic model, and the fire load specified by the standard fire curve is adopted for the temperature computation. The stiffness method with time increment is used for the numerical solution. The numerical results show that the collapse of a steel frame in a fire environment is controlled by the temperature variation as well as by the structural load. The fire loads induce thermal strain, creep, and plastic deformation of the structure. The creep effect becomes dominant when the structural temperature is high. The effective fire resistance time of the steel frame corresponding to a fire load history can be computed.