Intumescent coating applied to a steel tension bar with circular solid section after the fire test
Source: BAM, division Fire Engineering
Steel tension members are generally used for bracings, suspensions and underbracing systems. Typically, slender sections with circular solid section are used. Because tension members often serve to stabilize the structure, in the event of a failure of these members, a collapse of the entire structure can happen. Under fire exposure, unprotected steel structures lose their load-bearing capacity at an early stage due to rapid heating. Therefore, appropriate fire protective measures are required to prevent a rapid heating of the steel members and thus to ensure the load-carrying capacity for a corresponding fire resistance time.
Taking advantage of the profile-following application and the low coating thicknesses intumescent fire protection coatings can fulfil both fire protection and architectural requirements. In the event of fire, intumescent coatings form a thermal protective layer around the steel member. However, due to the slender cross-sections typically used for tension members, high demands are placed on the performance and reliability of the intumescent coatings. The effects of various parameters on the thermal protection performance of the intumescent coating are analysed, including the geometry of the section, dry film thickness of intumescent coating, load utilisation level as well as the orientation of the tension member. Based on theoretical considerations and results of the real scale fire tests, it is evidenced that mechanically loaded fire tests are essential to assess accurately the contribution of intumescent coatings to the fire resistance of steel tension members with circular solid sections. Furthermore, the research is used to develop a new European test standard from series EN 13381 for the determination of the fire resistance of steel tension members with intumescent coatings based on loaded fire tests, which will enable an expansion of the approval-based scope of application in the future.
Performance of intumescent fire protection coatings applied to structural steel tension members with circular solid and hollow sections
Dustin Häßler, Sascha Hothan
published in Fire Safety Journal, Vol. 131, page 1-12, 2022
BAM Safety of Structures department
BAM Fire Engineering division