Investigating the behavior tall steel concentrically braced frames exposed to fire

Understanding the behavior of steel structures under fire loading is very important because many recent events indicate the vulnerability of steel structures to such a hazard. Extensive numerical and experimental studies have been conducted to investigate the behavior of different types of structural steel elements individually, steel structure connection, and steel moment frames in fire conditions. However, the response of concentrically braced frames in fire conditions has not yet been investigated. This paper examines the global response and the local behavior of the concentrically braced frames under a series of uniform fire scenarios considering the heating and cooling phases at different levels of floors by numerical analysis of finite element method. The analyzes show that the buckling of the beams and braces is exposed to high temperatures due to the large compressive axial force due to lateral constraints to expansion. Also, the fire resistance of the braced frames is affected by the position of the fire. As with increasing gravity load at lower levels, the effect of P-Δ, which is an effective factor in the destruction of the structure, has increased and thus the fire scenario in the lower levels could potentially risk the early destruction of the structure Increase. The results of analyzes can help engineers understand the local and global responses of steel bracing frames under fire loading.