Cohesive zone model properties for evaluating delamination of spray-applied fire-resistive materials from steel structures

•Delamination of fire insulation from steel structures is discussed.•Properties governing delamination of SFRM from steel structures are evaluated.•Cohesive zone model is applied to simulate delamination phenomenon.•Effective properties of SFRM to mitigate delamination are quantified.

This paper presents cohesive zone model (CZM) fracture properties of spray-applied fire-resistive material (SFRM) for modeling delamination of fire insulation from steel structures. For characterizing cohesive zone properties, namely cohesive strength, cohesive fracture energy and cohesive displacement ductility, a set of experiments are conducted on three types of commercially available SFRM namely medium density Portland cement-based, medium density gypsum-based and mineral fiber-based. Data from experiments is utilized to develop a cohesive stress–displacement relationships in both mode-I and mode-II delamination. The recorded stress–displacement relationship indicates noticeable strain-softening zone verifying that SFRM is not a completely brittle material, rather, it is quasi-brittle.