Chao Liu

Vehicle loads play a critical role in the performance and safety assessment of in-service bridges, making accurate perception of their spatial-temporal distribution a fundamental task in bridge health monitoring. However, traditional contact-based and indirect measurement approaches are constrained by high costs, limited spatial coverage, and insufficient real-time capability. In contrast, computer vision technologies provide a promising non-contact alternative for vehicle load perception. This paper presents a comprehensive review of computer vision-based algorithms for identifying vehicle load spatial-temporal distributions on bridges, tracing the technological evolution from basic vehicle detection and tracking to advanced load modeling and post-processing techniques. First, traditional vehicle weighing methods are contrasted with computer vision-assisted bridge weigh-in-motion systems, highlighting the paradigm shift from contact-based measurements to visual perception. Subsequently, mainstream vehicle detection and tracking algorithms are reviewed and compared, and their applicability to different traffic monitoring scenarios is discussed. The core of the review focuses on three hierarchical levels of vehicle load modeling and perception, including equivalent point loads, axle loads, and wheel loads, the corresponding identification algorithms are examined in detail, demonstrating increasing levels of refinement achieved through detection, segmentation, and geometric inference. Furthermore, key post-processing challenges in vehicle load spatial-temporal distribution identification are analyzed in a structured manner, including homography estimation, trajectory optimization, and robustness under complex conditions such as lighting variation and occlusion. Through a comparative analysis of existing approaches, the advantages of deep learning-based methods over traditional digital image processing techniques are highlighted, while current limitations, particularly in terms of computational efficiency and generalization to the specific load distribution identification tasks, are also identified. Finally, future research directions are proposed, emphasising the development of efficient model architectures, benchmark datasets, and algorithmic adaptability. This review aims to serve as a reference for researchers and engineers engaged in the development and application of vision-based vehicle load spatial-temporal identification systems.

This study explores the explosion protection measures and the subsequent residual load‐bearing capacity of prestressed concrete box girders following an explosion. Four prestressed box beams were tested at a scale of 1:5 to assess their blast resistance. Various protective materials were utilized, including a steel plate, an ultra‐high‐performance concrete (UHPC) layer, and a composite protective layer, to strengthen the box girders. The findings indicated that when subjected to a deck explosion, the top plate of the box girder experienced localized penetrating damage, demonstrating punch‐through failure. In contrast, the web and bottom plate mainly showed signs of bending. When compared to the unprotected girder, the reinforced girder's top plate sustained less damage, whereas its bottom plate suffered more extensive harm. During the research, the authors conduct post explosion bending performance tests on each box girder, analyze the remaining bearing capacity, ductility index, and failure cracking of each box girder after explosion. The findings indicated that the protective coating mitigated the explosion‐induced stiffness degradation in the box girder. Additionally, the load–displacement curves for the protected box girders displayed steeper slopes compared to those of the unprotected box girders. A finite element model for box girder explosions was developed, and the accuracy of the numerical analysis was confirmed. Through precise numerical simulations, a parametric analysis was conducted on various protective layers of the box girder. Analysis indicates that increasing the thickness of the protective layer can enhance the blast resistance of the box girder, reduce damage to the top slab, and improve the post‐blast flexural load‐bearing capacity of the structure. When the thicknesses of the steel plate protective layer, UHPC protective layer, and aluminum foam protective layer are increased from 4 to 7 mm, 1.5 to 3.0 cm, and 1 to 4 cm, respectively, the damage area of the box girder's top slab is reduced by 23%, 31%, and 26%, respectively.

With the increasing urbanization in China, the scale of urban elevated bridge construction continues to expand. Conventional ground-supported formwork systems face significant challenges in the construction of high-pier, large-span prestressed bent caps. These traditional systems, characterized by large site occupancy and high material consumption, often lead to low construction efficiency. Particularly in space-constrained urban centers, their bulky support structures severely disrupt surrounding traffic and fail to meet urban bridge construction demands. In this paper, a lightweight, ground-free formwork support system for high-pier bent caps is systematically investigated. By employing novel materials and structural forms, such as acrylonitrile-styrene-acrylate (ASA) polymer-reinforced alloy formwork and ground-free steel supports, the system achieves lightweight, modular, and green construction. It innovatively addresses multiple technical difficulties inherent in traditional methods, significantly reduces carbon emissions during construction, improves material reusability, and embodies the concept of sustainable construction. Engineering practices in typical projects, including Wenzhou Wenrui Avenue, Hangzhou Shidai Avenue, and Ningbo Jiulong Avenue, have demonstrated the marked effectiveness of this system. It has significant advantages in terms of construction efficiency, cost control, resource conservation, and environmental impact, indicating substantial potential for broader application.

In recent years, there have been an increasing number of examples of using ultrahigh-performance concrete (UHPC) as a pavement layer to form an ultrahigh-performance concrete–normal concrete (UHPC–NC) composite structure to improve the bearing capacity of bridges. In order to study the flexural performance of this kind of structure, this research studied the flexural performance of UHPC–NC composite slabs, with UHPC in the compression zone, using experiments, numerical simulation, and theoretical analysis. The results showed the following. Firstly, after the UHPC–NC interface had been chiseled, there was no obvious slip between the two materials during the test, and the composite plate was always subjected to synergistic stress. Secondly, the composite slabs in the compression zone of the UHPC were all subjected to bending failure, and the cooperative working performance of each part under the bending load was good, indicating that the composite slab had a unique failure mode and a high bearing capacity. Thirdly, increasing the thickness of the UHPC significantly improved the flexural capacity of the composite plate, and the maximum increase was about 15%. Increasing the reinforcement ratio of the tensile steel rebars also had an increasing effect, with a maximum increase of about 181%. Finally, the proposed formula for calculating the flexural capacity of composite slabs with UHPC in the compression zone could accurately predict the bearing capacity of said slabs. The calculated results were in good agreement with the experimental values, and the error was small.

The use of UHPC enables reducing the height of composite slabs, which may decrease the punching shear capacity. This paper investigates the punching shear behavior of steel‐normal concrete‐UHPC composite slabs with experiments and theoretical analyses. Results indicated that a 50 mm UHPC layer makes the nominal punching shear strength increase by 24.91%. Utilizing UHPC and increasing loading area can effectively enhance the punching shear capacity. Besides, theoretical punching shear model proposed based on rigid‐plastic theory can reliably predict the punching shear capacity of composite slabs. The punching shear angle derived from strength theory closely matches the experimental values.