Rotational restraint stiffness of concrete beam-slab assembly exposed to fire

In real fire scenarios, fire-exposed reinforced concrete (RC) beams and slabs are restrained by the surrounding unheated components. Thus, evaluating the boundary constraints of concrete beam-slab assembly is particularly important for analyzing the fire performance of such assembly. In this study, the rotational restraint stiffness at beam end is re-checked first. Thirty finite element models are established for determining the distributed rotational restraint stiffness at slab edge. It is found that the distributed rotational restraint stiffness in the middle of slab edge increases with the increasing of both the slab thickness and the sectional size of beam, and decreases with the increasing of beam length. Finally, a regressive formula is proposed to determine the distributed rotational restraint stiffness at slab edge.