The static performances of an assembled integral two-way multi-ribbed composite floor system have been studied experimentally and numerically, while the dynamic characteristics and comfort analysis under a human load have not been investigated. In this article, a 9.2 m × 9.2 m floor system, composed of 16 precast panels and integrated into a whole structure through six wet joints, was designed and tested under pedestrian loads. Dynamic performances related to its natural frequencies, vibration mode shapes, and maximum acceleration were analyzed. Theoretical formulas were proposed to predict its natural frequency and maximum acceleration under a single-person load. It was found that the dynamic behavior of this innovative floor system meets the requirements of GB50010-2010 and ISO 2631. Elastic plate theory could be applied to predict the natural frequency and acceleration, with the bending stiffness obtained from the experiment. Some design and dynamic test suggestions for this floor system and similar structures are proposed based on a parametric analysis.

The safety of the geotechnical environment around subways is vitally important for their sustainability. Ground settlement is a very common threat to the safe operation of subways and is related to subway traffic vibrations. Taking Nanjing subway line 10 as an example, field tests, discrete element simulations, and a grey relational analysis are carried out to study the deformation mechanism of the underlying sandy soil induced by vibrations. The results show that the vibration load of Nanjing subway Line 10 is mainly concentrated in the vertical direction. The particles’ coordination number below the subway increases under the vibration load, while the coordination number on the side of the tunnel decreases, which may cause a shear dilatancy effect. Among the five microscopic indexes, the local porosity and the coordination number are closely related to the deformation. Although the deformation of the underlying sandy soil is quite small under the subway traffic load, it will accumulate under frequent loading and then lead to urban engineering geological disasters.

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.