Fire resistance of integral composite beams with superposed slabs

摘要

The uniform-load fire behaviors of four full-scale integral composite beams with superposed slabs were tested, considering the post-cast-slab thickness, shear-connector spacing, and precast-slab overlap length on the steel-beam upper flange. The concrete temperature distribution along the slab thickness, the temperature of the rebar inside the slab, the temperature distribution along the steel-beam height, the bending stiffness, and the overall integrity of the superposed slabs and steel beam were studied. ABAQUS simulations of the temperature-field and deformation behaviors of the composite beams with superposed slabs under coupled thermal and mechanical loading were performed. No damage to the post-cast and precast slab bonding interface during the heating process was apparent. The post-cast joint had no obvious influence on the structure, which could still bear loads. The composite-beam temperature field and bending stiffness were not significantly affected by the bonding interface of the new and old concrete and the post-cast joint. Overall, the post-cast slab thickness and shear-connector spacing predominantly influenced the composite-beam fire resistance. The experiment and numerical results agree well, verifying the numerical-model validity and feasibility.