Combining the advantages of cast-in-place hollow slabs and prefabricated reinforced truss composite concrete slabs, a novel hollow composite slab is proposed, characterized by the inclusion of hollow thin-walled boxes without reinforcement at the edges, referred to as the hollow composite slab. To further investigate the flexural performance and critical design parameters of the hollow composite slab, numerical simulations were conducted using the finite element software ABAQUS. Based on the actual specimen fabrication and test results, the rationality of the finite element modeling was validated. Using the finite element model, a parametric analysis of key parameters for the specimens was conducted. The results showed that the finite element model could effectively simulate the crack distribution, flexural performance, and deformation characteristics of hollow composite slabs. The influence of concrete strength and the longitudinal dimension of hollow thin-walled boxes on the flexural performance of hollow composite slabs was minimal, with ultimate bearing capacities changing by only 4.63% and 0.91%, respectively. In contrast, changes in slab thickness and span had a significant impact on the flexural performance, with ultimate bearing capacities changing by 20.46% and 42.09%, respectively. The bearing capacity of hollow composite slabs increased significantly with increasing slab thickness but decreased markedly with increasing span.

The performance of joint connections in composite slabs is crucial for ensuring their bidirectional load-bearing capacity and overall structural integrity. To effectively address the challenge of protruding rebar in precast components, a new structural form of a tightly connected hollow concrete composite slab without protruding rebar on the slab side is proposed. To investigate the mechanical performance and failure modes of this slab-side tight-joint connected hollow concrete composite slab, bending performance tests under monotonic load were conducted on three tightly connected hollow composite slabs and one seamless hollow composite slab. The analysis focused on the failure modes, crack distribution, bending capacity, and bending stiffness of additional steel bars at the joints of the slabs. The results indicate that, under normal operating conditions, the flexural performance development of concrete hollow composite slabs with tightly connected slab sides is generally consistent with that of the non-spliced cast hollow composite slab. Under ultimate conditions, tearing or brittle fracture failure at the joint interface is likely to occur in the composite slabs, leading to a reduction in flexural bearing capacity. With an increase in joints, the bending capacity of the hollow composite slab decreases by 17.1%, Conversely, when joints are positioned away from the most stressed section, the flexural stiffness of the section increases by 13.5%. A comparison of experimental data and theoretical calculations indicates that the additional rebar at the joints effectively contributes to the lateral load transfer in the hollow composite slab, achieving bidirectional load-bearing capacity. This further validates that the design of the single-joint, tight-joint connected hollow concrete composite slab without protruding rebar meets the requirements for bidirectional load-bearing performance.

A static performance experimental study was conducted on six simply supported reinforced concrete truss hollow composite slabs to analyze their flexural rigidity. The study investigated the effects of the slab thickness, the dimensions of the hollow thin-walled boxes, and the composite interfaces on the flexural rigidity of the hollow composite slabs. The flexural rigidity was calculated using methods from American standards, Chinese standards, and the relevant literature, and the results were compared with the experimental data. Based on the experimental findings, a method for calculating the flexural rigidity of hollow composite slabs using a reduced moment of inertia equation was proposed, and the calculated results showed good agreement with the experimental results. The research indicates that the composite interface and the size of the hollow thin-walled boxes have minimal influence on the flexural performance of hollow composite slabs, while the slab thickness significantly impacts their flexural performance. By employing the effective moment of inertia method and substructure calculation theory, a calculation method for the flexural rigidity of hollow composite slabs was established, demonstrating high accuracy.

Large-scale irregular cracks developed on the second-floor roof slabs of an industrial plant shortly after formwork removal. To identify the cracking mechanism and optimize the strengthening scheme, field inspection, X-ray diffraction (XRD) phase analysis, restrained-shrinkage stress calculation, and nonlinear finite element (FE) simulation were combined in a closed-loop study. The concrete strength, reinforcement arrangement, slab thickness, and flexural capacity all met the specification requirements, and XRD detected no crystalline sulfate-bearing phases within the 1–2 wt.% detection limit, ruling out structural overloading and sulfate-type chemical attack. The cracking was attributed mainly to excessive restrained drying-shrinkage stress caused by mix-proportion defects (a high water-to-binder ratio, excessive fly ash, and a high mud content in the fine aggregate); the calculated maximum restrained shrinkage stress of 3.19 MPa exceeded the concrete tensile strength. Preferential microcrack initiation in the aggregate–mortar interfacial transition zone (ITZ) is presented as a proposed mesoscale mechanism, because direct microstructural (SEM) observation was not performed. Under identical total CFRP consumption, a four-dimensional evaluation (bearing capacity, material utilization, crack suppression, and relative interfacial slip) showed that the grid-shaped layout outperformed the cross- and hash-shaped layouts, and a ±10% sensitivity analysis kept all predicted crack-width variations within ±5%. A composite remediation of low-pressure grouting plus grid-shaped CFRP was then applied; after 12 months of monitoring, the maximum crack width decreased from 0.32 to 0.04 mm, demonstrating the synergistic effect of the composite system rather than CFRP alone. This case provides a reference for the diagnosis and treatment of shrinkage cracking in comparable industrial roof slabs.