Critical Temperature Evaluation of Moment Frames by Means of Plastic Analysis Theory and Genetic Algorithm

Nowadays, deliberate or unwanted fire incidents have created much attention to the behavior of structures against these types of events. Since the properties of structural members are influenced by the increase in the temperature of the members, it is more difficult to predict the general and local behavior of the structures during the fire. In this research, a method has been proposed to calculate the critical temperature in two-dimensional structures at its collapse with desirable accuracy. In this process, the upper-bound theory of plastic analysis is used. The plastic analysis is performed by applying the initial fire scenario to the structure, and its collapse load factor with the corresponding collapse mode is determined. This operation continues until the critical temperature coefficient is acquired, and it occurs when its corresponding collapse load factor equals 1. In addition, the application of the genetic algorithm in the plastic analysis of structures has made this method more applicable to larger frames. Therefore, using this method, without using complex structural analysis and software, the critical temperature of the structures during its collapse, along with their collapse mechanism, both before and during a fire, can be calculated. The investigations on two case studies also confirm the decent accuracy of this approach.