Research on the Failure Mechanism and Bearing Capacity Calculation of Lightweight Steel-Concrete Composite Cover Slabs

To effectively address the issue of excessive weight in traditional concrete power cover slabs， this paper proposes a new type of lightweight composite power cover slab. Four types of composite cover slabs were designed and subjected to vertical load-bearing failure tests. The failure modes， ultimate bearing capacity， and strain variation patterns of the slabs were obtained. The results showed that， compared with traditional steel fiber-reinforced concrete cover slabs， the weight of the new composite cover slabs was reduced by over 70%. The ultimate bearing capacities were 135 kN， 143.59 kN， 260.31 kN， and 550.65 kN， respectively， all meeting the requirements of <italic>Steel Fiber Reinforced Concrete Manhole Cover</italic>（GB/T 26537-2011）. Additionally， the composite slabs exhibited good deformability. The failure mode of the composite cover slabs was characterized by concrete compression-induced cracking and slab buckling in the area 1/4 of the slab length from the end. No slippage occurred between the concrete and the steel structure， indicating good overall integrity. To ensure effective collaboration between the two materials， it is recommended that the concrete thickness should not exceed 25% of the slab height. Finally， based on the experimental results and equilibrium theory， a method for calculating the ultimate bearing capacity was proposed.