Experimental Evaluation of Fully Prefabricated and Demountable Composite Steel Frame–Concrete Slab Joints

A bolt-connected precast concrete composite beam was designed in this study to realize a fully prefabricated and demountable steel frame composite structure. Three frame joint specimens each comprising two beam–column joints were fabricated and subjected to low-cycle reverse loading to investigate the effects of the composite steel H-shaped-beam–precast concrete floor slab and steel column form on their hysteretic behaviors, deformation mechanisms, and rotational capacities. Experimental results indicated that the failure mode of the steel-only joint consisted of yielding failure of the end plates and stiffeners, while that of the joints with composite beams also included concrete cracking failure. The use of a precast concrete slab significantly enhanced the moment capacity, initial rotational stiffness, and energy dissipation capacity of the joint. The H-shaped-column joint was more stable than the box-shaped-column joint. The moment capacity and initial rotational stiffness of the former were greater than those of the latter, whereas the energy dissipation capacity of the former was smaller. Strain results indicated that the precast concrete slab increased the strains in the H-shaped beams and end plates to a certain extent. Finally, methods for calculating the moment capacity, initial rotational stiffness, and rotational capacity of the joint in a fully prefabricated and demountable composite steel frame structure were derived and verified against the experimental results, showing excellent agreement and indicating significant engineering application value.