The thickness of steel plates used in the structure has gradually increased to meet the load-bearing capacity requirements of long-span steel bridges. Thick steel plate welded by arc welding process will result in considerable welding residual stress with complex distribution. Large welding residual stress will significantly impact the performance of steel bridges. At present; residual welding stress of thick steel plates is not considered enough in bridge engineering; which could lead to potential dangers in safety. In this paper; a butt welded joint with a thickness of 80 mm was designed; the residual welding stress was measured by X-ray diffraction method; and the distribution of residual stress in the direction perpendicular to the weld seam and along the direction of the weld seam is analyzed; and the distribution pattern of welding residual stress in thick steel plate is systematically studied. It is found that in the area near the weld; the stress in the direction along the weld seam is more significant than that in the perpendicular direction; the peak stress in the direction perpendicular to the weld seam usually appears in the weld seam and the heat-affected zone; and the maximum value tends to appear close to the last weld bead on the surface; on the path perpendicular to the weld seam; the stress in the direction perpendicular to the weld seam is distributed in a “Π” shape; the stress in the direction along the weld seam is distributed in an “M” shape; and the stresses in the direction along and perpendicular to the weld seam are symmetrically distributed; however the axis of symmetry may appear anywhere in and around the weld seam. The results could serve as a reference for welding residual stress analysis and guide optimization design of steel bridges made of thick steel plates.

To investigate the static performance of precast segmental hollow piers, two precast segmental hollow pier specimens were designed for static loading tests on the top of piers. The finite element model of precast segmental hollow piers was established by the finite element software Abaqus and verified based on the test results. Based on the experimental and finite element models, three optimal design solutions were proposed, and the calculation results of each solution were analyzed. The results show that precast segmental hollow pier mechanical behavior is similar to that of cantilevered bending members. The specimens present brittle damage characteristics after the destruction of the structure at the bottom of the pier pressure edge as the axis of the rigid body rotation. Following the test loading process, the bonding between the segments is good, except for the pier bottom damage surface of the rest of the bonding surface, which has no relative displacement. The calculation results of the finite element model are in good agreement with the test results and can effectively predict the load–displacement response of precast piers. Three optimized design solutions are proposed. The finite element simulation proves all three optimized design solutions show better overall ductility than the original solution and can effectively improve the performance of segmental precast hollow piers.

Accelerated bridge construction (ABC) has attracted much attention in China as a new and efficient construction method. However, the seismic performance of the connections between precast piers and other structures limits the application of ABC in medium and high seismic zones. In this paper, a quasi-static test was conducted to investigate the seismic performance differences between a cap–column socket connection (PSC) specimen, which reinforced an embedded RC column-to-precast cap beam with a socket connection, and a cast-in-place (CIP) cap–column specimen. A fiber-based finite element model that considers bond slippage between the connection reinforcement and wet joint concrete is proposed. The numerical simulation results compared with the experimental results show an error of about 12% in peak bearing capacity and about 2% in initial stiffness. The experimental and numerical results show that the PSC specimen demonstrates comparable seismic performance to the CIP specimen. Experimental results verified that the finite element model in this paper is adequate to predict the seismic responses of a precast column with a reinforcement-embedded socket connection. A reinforcement-embedded RC column-to-precast cap beam with socket connection can be an effective solution for construction in medium and high seismic areas.

Thick steel plates in bridges exhibit mechanical property gradients along their thickness, yet the underlying micro-mechanisms remain unclear. This study investigates an 80 mm thick 420 MPa-grade HSLA steel plate, and also quantitatively investigates the mechanism of its mechanical gradient behavior in the thickness direction through layered tensile tests combined with multi-scale microstructural characterization. The unique contribution of this work lies in establishing a quantitative correlation between the gradient in the dislocation density and the transition in yielding behavior. The results show that the surface layer area of the tested steel exhibited continuous yield characteristics, while all core layers exhibited pronounced discontinuous yielding. The mechanical properties showed a gradient distribution along the thickness direction, with the yield strength and tensile strength decreasing from 512.4 MPa and 545.9 MPa at the surface to 419.5 MPa and 520.4 MPa at the center (1/2t). Microstructural analysis shows that the full-thickness structure was composed of granular bainite (GB) and polygonal ferrite (PF). With respect to increases with depth, the average grain size increased from 6.86 µm at the surface to 11.57 µm at the center. Moreover, the surface region exhibited a broader grain size distribution range and higher size dispersity. The second-phase precipitates in the full thickness were mainly of two types, namely, Fe₃C and (Nb, Ti) (C, N) composite precipitates, and the precipitates in the surface layer had smaller sizes and higher distribution densities. Crucially, the dislocation density decreased sharply from the surface to 1/8t, then stabilized. While quantitatively elucidating the contributions of various strengthening mechanisms to the strength gradient, the mechanistic analysis also reveals a dislocation microstructure synergistic mechanism underlying the yield behavior differences.

High-strength steel wires in bridge stay cables are susceptible to chloride attack and wet–dry cycling during long term service. Furthermore, the resulting spatially non-uniform evolution of corrosion morphology can lead to the degradation of their static mechanical properties. In this study, high-strength steel wires with a nominal diameter of 7 mm were subjected to copper-accelerated acetic acid salt spray (CASS) exposure for 0–80 d, followed by 3D laser scanning and uniaxial tensile testing. Corrosion depth, surface roughness, and cross-sectional area loss were first quantified. Based on these morphological indicators, a 3D cellular automaton (CA) model incorporating an axially stationary correlated random field was developed. The maximum cross-sectional area loss ratio was subsequently adopted as the characteristic damage parameter for evaluating mechanical degradation, and a quantitative relationship between the CA simulation results and the degradation of static mechanical properties was established. The results show that, with increasing corrosion duration, the corroded regions on the wire surface progressively expanded, coalesced, and deepened, producing a spatially non-uniform morphology characterized by alternating zones of severe and mild corrosion along the axial direction. From 20 to 80 d, the maximum cross-sectional area loss ratio increased from 13.307% to 31.175%. Subsequently, the developed CA model successfully reproduced the evolution trends of the corrosion morphology indicators, with relative errors of less than 19% compared with the 3D scanning measurements. By incorporating the maximum cross-sectional area loss ratio obtained from the CA simulations into the mechanical degradation relationships, the mean prediction errors for Young’s modulus, yield strength, and ultimate tensile strength were 2.788%, 2.581%, and 3.198%, respectively, relative to the experimental results. These results demonstrate that coupling the CA model outputs with the mechanical degradation relationships provides an effective approach for predicting the residual mechanical properties of high-strength steel wires subjected to different corrosion durations.