Evaluation of the performance of special steel moment frames under fire conditions

Steel structures are vulnerable to fire and material properties such as modulus of elasticity, ultimate strength and yield strength will change with increasing temperature. In this study, the effect of fire on the performance of special steel moment frames is investigated. For this purpose, different scenarios such as changing the location of the fire in different bays and floors were considered. Thermal analysis and nonlinear analysis and finally the performance of the structures were performed using modified thermal steel materials. The results indicate that the fire in the outer opening of the building will create a critical situation. the performance of the structures was evaluated based on the thermal analysis and using the modified thermal steel material. The results indicated that the fire in the exterior bays will be a critical situation. The variation trend of the ratio of collapse loads to design loads as soon as the temperature reaches 300 ° C is different. In different locations and at temperatures below 300 ° C, The increase rate of collapse loads to design loads is approximately 25%. While at temperatures above 300 ° C, with regard to the fire location, the rate of increase will reach 60%. The trend of collapse load variations under high temperatures and different fire locations is such that it converges to a certain value. Based on the results of nonlinear analysis, a design procedure was proposed to predict the collapse load of steel frames under fire conditions.