Mechanics-based approach for modeling delamination of fire insulation from steel structures

This paper presents a numerical model for evaluating internal fracture and delamination at the interface of fire insulation and steel surface in structural members. A cohesive zone model in combination with contact condition is employed in a 3D finite-element model to simulate the fire-insulation damage throughout the loading range, from initial loading stage until failure through fracture. The numerical model is validated by comparing model predictions, namely internal fracture and interfacial delamination of insulation, against test data generated at both material and structural levels. The validated model was applied to quantify the effect of critical factors on the extent of delamination between steel and fire insulation. Results from the parametric studies indicate that critical fracture energy at steel-insulation interface, insulation thickness, modulus of elasticity, and internal cohesion of insulation material have significant influence on the spread of delamination at steel- insulation interface. Further, delamination of insulation from steel surface occurs mostly in the plastic hinge zone and specifically in the tensile flange.