Liang Gong

A novel assembled integral multi-ribbed composite floor system consisting of precast panels and a cast in situ topping has previously been validated through full-scale one-way and two-way slab experiments. Although the global load capacity of the system was initially verified, the experiments reveal that the concrete-to-concrete interfacial behavior between the precast panel and the cast in situ topping is a critical factor governing internal force redistribution and its post-cracking performance. To uncover the governing interfacial mechanism, this study develops a refined three-dimensional nonlinear finite element model using a coupled cohesive–frictional interface interaction, where a surface-based cohesive interaction captures the initial interfacial debonding and a penalty-based Coulomb friction model describes the subsequent shear-slip behavior. The model reproduces the cracking patterns, load-deflection relationship, and failure modes, with the relative error of load capacity, initial stiffness and crack load all less than 15%. Parametric analyses further indicate that the interfacial shear-transfer mechanism governs post-cracking stress redistribution across the multi-ribbed section, preventing premature delamination and ensuring efficient mobilization of the section’s flexural resistance. To effectively restrain this interfacial slip, an improved shear-key configuration is proposed to activate an enhanced mechanical interlocking mechanism. Numerical results confirm that the improved configuration effectively suppresses macro-sliding and redistributes local stress concentrations, thereby enhancing the structural integrity and flexural efficiency of precast composite floor systems.

The construction of highway suspension bridges has entered a new era, with the main span now exceeding 2300 m. However, the vertical stiffness design of such super-long-span structures remains a critical challenge, particularly regarding the selection of appropriate stiffness indices and the determination of their permissible limits. This study establishes an evaluation framework that integrates vehicle-bridge interaction (VBI) analysis to account for safety and comfort requirements with a systematic method for evaluating key stiffness indicators. Applying this framework to the 2300-m Zhangjinggao Bridge, the results demonstrate that local dynamic comfort at the girder ends governs the structural design. The results show that deflection, curvature, and girder-end rotation are strongly correlated, with Spearman correlation coefficients exceeding 0.92 within the investigated range. Among them, the maximum girder-end rotation is identified as the governing serviceability indicator. By combining the comfort threshold of 0.315 m/s² with the vehicle-bridge interaction results, a permissible girder-end rotation limit of 0.025 rad is proposed.

A new type of assembled integral multi-ribbed composite floor system with novel wet joint and steel sleeve connections, which exhibits satisfactory strength and stiffness, was proposed in the previous study. To further study the flexural performances of the joints, six groups of specimens, including two cast in situ concrete slabs and four composite slabs sized 4700 mm × 1200 mm × 300 mm and 2450 mm × 1200 mm × 300 mm, were investigated under four-point flexural tests. Four main influence factors were experimentally studied, i.e., casting methods, joint amounts, shear span lengths, and steel sleeve layout directions, on the failure modes, crack distributions, and deflection–load carrying capacity relationship. Test results indicated that the proposed composite slab system could provide the ultimate bearing capacity lower by 7% than that of the cast in situ concrete slabs, largely exceeding the code-predicted strength. No strain difference between the steel sleeve connections and steel rebars indicated good wet joint connection behavior. More hollow-core sections and long shear spans increased the potential of interfacial splitting cracks, leading to a shorter elastic stage and lower elastic stiffness. A finite element model was further parametrically conducted to explore the structural performances. Finite element results also indicate that the precast concrete slab had a more significant influence on the failure loads than the influences of concrete compressive strength and lap-splice steel rebar strength. These findings indicate that the proposed composite slab systems possess a satisfactory performance in the ultimate bearing capacity and deformability. Thus, such an assembled integral multi-ribbed composite floor system can be widely applied in construction.

An assembled floor system is a main step in the industrialization of construction in civil engineering, where the stiffness and anti-crack properties under designed loads and its self-weight are the main concerns. This paper presents a new type of assembled integral composite floor system, which is composed of precast ribbed bottom slab, lightweight infills, cast-in-situ upper slab and joints. Through the couplers for squeezing and splicing of longitudinal bars, shear keys and cast-in-situ joints between the precast panels and cast-in-situ upper part, the whole hollow floor system could not only exhibit satisfactory mechanical performance, but also lower the self-weight and shorten the construction time. To study its flexural behaviors, a full-scale specimen sized 9.2 m × 9.2 m was designed and tested under static area load. With the load increased to the designed loads of Chinese design code GB50010-2010, mechanical performance (i.e., crack distribution, deformation and stress distribution) were analyzed. To further study its load-carrying capacity and working mechanism, an effective finite element model was established in ABAQUS and compared with experimental and simulation results. It was found that the deflection of the floor under the normal service load and the crack width met the needs of normal use, and the finite element model could serve as a reliable method for the load-carrying capacity calculation.