Elastic and plastic methods for numerical modeling of steel structures subject to fire

An approach based on the elastic and plastic methods for fire resistance analysis is presented. It is intended to fill the gap between the simple calculation method and the finite element method currently being used by engineers. This approach can be applied to simple framed structures for which the failure temperature of the structure can be calculated, The elastic method includes the effect of interaction between the thermal loading and static loading. The load ratio in each member is calculated, resulting in a formulation whereby the Limiting temperature of each member can be obtained. The plastic method is based on the plastic hinge concept for the calculation of critical temperature of frames at collapse. The method makes use of the fact that the collapse load factor of a frame is a linear function of the collapse temperature for the same collapse mode. For situation where the collapse mode changes as the temperature in the frame increases, a demarcation collapse temperature multiplier is introduced to monitor the change. The main advantage of this approach is that the frame as a whole can be considered without using complex analytical technique. (C) 2000 Elsevier Science Ltd. All rights reserved.