The Behavior of Structural Steel Elements with Damaged Fire Protection Material

The rapid spread of high temperature within the steel material results in low fire resistance of steel structures. Various types of methods have been utilized in order to improve the stability and load-bearing capacity of the steel structure during fire incidents. Passive fire protection (PFP) is a popular method used in industrial and residential buildings to protect steel structures against fire. In PFP method a material with high thermal capacity is applied around the steel sections to reduce the heat transfer to structural steel elements. Spray-applied fire protection, concrete encasement, and gypsum boards are different types of PFP methods. Spray-applied fire-resistive materials (SFRM) are commonly applied material to protect steel structures from fire exposure. Some of the widely used SFRMs include CAFCO, Carboline, and Tyfo. SFRM offers many advantages over other types of fire insulation methods such as cost-effectiveness, lightweight, and ease of application. However, the applied fire protection material may be removed due to inappropriate applications and accidents. The direct exposure of the steel material at damaged regions can result in failure of the structural steel elements before the required fire rating of the structure is achieved. The primary goal of this study is to investigate the reduction in the fire resistance of steel beams with damages in the fire protection material. Steel beams protected with fully protected and damaged Tyfo, CAFCO, and Carboline fire protection material were simulated. The fire resistance of different steel beam sections with damaged fire protection has been investigated. The fire protections were designed for one-hour fire rating. Nonlinear thermal and structural finite element models of beams with damaged fire protection were developed. The temperature of various parts of steel beams, as well as mid-span deflection of damaged cases, were tracked and compared with cases with full protection. The results have shown that the fire protection loss can result in significant fire resistance reduction of the beams. This study’s contribution highlights the need for considering the influence of such damages in fire protection material in the design of fireproofing of steel structures.