Effectiveness of Damaged Fireproofing in Structural Steel Members Subjected to Fire

Fire incidents and elevated temperatures reduce the strength of structural steel members significantly. Passive fireproofing is a common method to protect steel structures against fire. In passive fireproofing method, a fire protection material is applied to structural members and connections to delay the heat transfer to steel in order to increase its fire resistance. However, during the service life of a structure, the fireproofing material may be damaged or removed due to accidents, improper applications or by connecting steel members to each other, which may happen after applying the fireproofing material. High thermal conductivity of steel material allows a fast spread of high temperature through the structural element at damaged regions. The concrete encasement is a typical passive fireproofing material to protect steel structures in oil and gas refineries and petrochemical plants. This study is focused on investigating the effect of the damaged concrete fireproofing on the structural response of structural steel members. Cases with different damage length, shapes and, penetration were studied to investigate the impact of such damages on the members’ structural response. Thermal and structural nonlinear finite elements analysis were performed. Finite element models were validated with experimental results from a published literature. Structural response of the damaged fireproofed beams was compared with the response of the fully protected beams subjected to ASTM E119 standard fire temperature. The deflection and strength failure limit states were investigated to determine the fire resistance of each studied case. It was observed that minor loss in fireproofing material dramatically reduces the fire resistance of the steel members. Damage length, size of beam and post-damaged fireproofing thickness influence the fire resistance of beams with damaged concrete fireproofing.