The Zhanjiang Bay Laboratory R&D Building project aims to create a favorable working, research, and living environment. Zone II of the Zhanjiang Bay Laboratory R&D Building is equipped with a large-span, heavy-load transfer truss to obtain a large space on the ground floor. The overall structure adopts a steel frame-core tube structure system. In order to reduce the deflection of the large-span, heavy-load transfer truss, eight diagonal pull rods are installed between the large-span, heavy-load transfer truss and the core tube. The Q235 cross-shaped replacement section can consume construction load energy. Adopting replacement methods can reduce the stress and damage of diagonal pull rods caused by construction loads. The structure adopts a performance-based seismic design method for seismic calculation and analysis. In addition, a special analysis was conducted on the single frame structure. The major results can be summarized as follows: during small earthquakes, all structural components are in the elastic stage; during large earthquakes, frame beams yield first, but frame columns and core tubes do not yield; even without considering out-of-plane constraints, the structure can still meet the requirements.

The growing use of weathering steel in bridge engineering has highlighted the increasing impact of fatigue damage caused by the combined effects of welding residual stress and vehicular loading. This study investigates the fatigue performance of Q500qENH weathering steel bridge decks by proposing a coupled analysis method for residual stress and fatigue crack growth, utilizing collaborative simulations with Abaqus 2023 and Franc3D 7.0. An interaction model integrating welding-induced residual stress fields and dynamic vehicular loads is developed to systematically examine crack propagation patterns in critical regions, including the weld toes of the top plate and the weld seams of the U-ribs. The results indicate that the crack propagation rate at the top plate weld toe exhibits the most rapid progression, reaching the critical dimension (two-thirds of plate thickness) at 6.98 million cycles, establishing this location as the most vulnerable failure point. Residual stresses significantly amplify the stress amplitude under tension–compression cyclic loading, with life degradation effects showing 48.9% greater severity compared to pure tensile stress conditions. Furthermore, parametric analysis demonstrates that increasing the top plate thickness to 16 mm effectively retards crack propagation, while wheel load pressures exceeding 1.0 MPa induce nonlinear acceleration of life deterioration. Based on these findings, engineering countermeasures including welding defect control, optimized top plate thickness (≥16 mm), and wheel load pressure limitation (≤1.0 MPa) are proposed, providing theoretical support for fatigue-resistant design and maintenance of weathering steel bridge decks.