Design Recommendations for Bonded Anchors under Fire Conditions Using the Resistance Integration Method

Fire design of cast-in place and post-installed anchors in concrete under fire is covered by EN 1992-4, Annex D, allowing steel- and concrete-related failure modes of anchors to be calculated. This informative annex of EN 1992-4 is limited to cast-in place or mechanical anchors, whereas post-installed adhesive anchors remain out of its scope. This paper presents a study of the applicability of the more flexible resistance integration method (RIM), proposed originally for the design of the pull-out resistance of post-installed reinforcement (PIR) by Pinoteau, on bonded anchors in uncracked concrete. This method is validated from a comparison of test results obtained from two research projects conducted at CSTB and TU Kaiserslautern on bonded anchors in uncracked concrete under ISO 834-1 fire conditions. The data considered include tests conducted on anchor sizes from M8-M30 using three different adhesives (two epoxy adhesives and one cementitious mortar). Design of the pull-out resistance under fire using RIM requires numerical calculation of temperature profiles considering models of concrete and steel elements; different assumptions about modeling these elements can produce vastly different end results. Finally, recommendations for assessment procedures for bonded anchors under fire conditions are provided as entry data for design.