Mechanical Performance of Square Box-Type Core Mold Hollow Floor Slabs Based on Field Tests and Numerical Simulation

Aim: ing at the issues of the true mechanical performance and failure mechanism of large-span cast-in-situ hollow core floor slabs with square-box core molds under vertical loads, this study conducted systematic research combining in-situ tests and refined numerical simulations. Based on an actual project at the Hefei Xinluzhou Industrial Park, a distributed water tank loading system was employed to apply five-stage cyclic loading to an 8m × 8m slab section. The strains in both the reinforcing steel and concrete were monitored in real-time. Simultaneously, a coupled finite element model incorporating a concrete plastic damage constitutive model and an elastic-plastic model for steel reinforcement was established. This model was used to quantitatively analyze the stress distribution, stiffness evolution, and failure progression. The study shows that under a design load of 9.0kN/m², the floor slab operates in an elastic state, with stress distribution exhibiting “banded gradient” and “island-shaped loading” characteristics. This means a banded gradient in the middle span and localized concentration at the column capital edge. The strain-load relationship of the steel reinforcement and concrete is linear, and the bidirectional stiffness is similar. The finite element model accurately reproduced the experimental phenomena, confirming its reliability. Limit analysis revealed that the floor slab's load-bearing capacity reaches 27.2kN/m², with failure starting from diagonal cracks at the column capital edge and propagating to the positive bending cracks at the middle span bottom of the slab. The findings of this study reveals the bidirectional bending mechanism and failure path of box-shaped core mold hollow floor slabs, providing important theoretical and experimental support for optimizing the design of large-span floor slabs.