Prestressed concrete girder bridges are widely used worldwide due to their mature construction technology, economical cost, and low maintenance. After a certain number of years of service, prestressed concrete girders inevitably suffer from deterioration of their material properties, cracking, and reduced load-carrying capacity due to the natural environment and long-term vehicle loading. When the performance of a bridge declines to the point that it cannot meet the requirements of normal use, reinforcement and maintenance are required. In this study, a 5 × 45 m prestressed concrete continuous box girder bridge that has been in service for 25 years is taken as an example, and the causes of crack development and deterioration of the technical condition of the bridge are analyzed. Based on an analysis of the causes, reinforcement schemes for overall replacement of the girder and adding bridge piers are proposed. According to a comparison of the advantages and disadvantages, a decision analysis of the reinforcement scheme is carried out via the analytic hierarchy process (AHP). The vector weights of the two schemes were found to be 0.4288 and 0.5712, respectively, indicating that adding bridge piers is more advantageous than overall replacement of the girder. Thus, a scheme of adding five piers was adopted to reinforce the bridge. A load test was then performed after the reinforcement, and both the test deflection and strain calibration coefficients were found to be less than 1, indicating that the force state of the added piers and bearings was better than the theoretical calculations. The present study shows that the reinforcement scheme of adding piers can achieve the design goal. The working status of the box girder was significantly improved, the crack development of box girder was suppressed, and the service life of the bridge was prolonged.

This study investigates the dynamic amplification effect of the main girder of cable-stayed bridges after cable rupture. The expression for the dynamic amplification effect is derived using the modal superposition method, and the influence of the duration of cable rupture on the dynamic amplification effect is investigated. The results indicate that, for a single-degree-of-freedom (SDOF) system without damping, the displacement dynamic amplification factor (DAF) can reach a maximum of 2.0. For the main girder of cable-stayed bridges, the dynamic amplification factor can exceed 2.0 and is related to the weight of the projection components of the response on the mode shapes. Using the modal superposition method of calculation, the higher-order modes have the greatest influence on shear force, followed by the bending moment, while they have the least influence on displacement. The theoretical derivation is validated using a simplified model, and it is shown that the commonly used equivalent static load calculation method with a factor of 2.0 for the static cable force poses potential safety risks. Furthermore, this study shows that the shorter the duration of cable rupture, the more pronounced the dynamic amplification effect. It is recommended that the duration of the cable rupture should not exceed 0.01 times the fundamental period of the structure when the maximum impact effect is calculated to ensure the rationality of the calculation results.

Hinge joints in hollow slabs play a pivotal role in achieving effective lateral force coordination within structural systems. The detrimental impact of hinge joint damage on the overall load-bearing performance of bridges cannot be understated. In this study, a 23 × 16 m span hollow slab bridge was selected as the engineering background, and a rigorous load test methodology was employed to assess the condition of the hinge joints by analyzing the lateral load distribution coefficient. The evaluation analysis revealed a substantial deviation from the theoretical value of 1, with measured lateral load distribution coefficients ranging from 0.013 to 1.659 before reinforcement, indicating poor lateral connection, severe hinge joint degradation, and inadequate overall lateral stiffness of the bridge. To address these issues and enhance the overall lateral load-bearing capacity of the hollow slab beams, a novel hinge joint reinforcement method utilizing steel strip–tie rod clamping is proposed. The efficacy of this method was validated by comparing the measured lateral load distribution coefficients before and after reinforcement with the corresponding theoretical values. Numerical comparison and meticulous analysis demonstrated a promising improvement, with post-reinforcement ratios of the measured lateral load distribution coefficients ranging from 0.950 to 1.122, closely approaching the theoretical value of 1. These findings unequivocally illustrate the significant enhancement achieved in the lateral force coordination performance of the slab beams, thereby affirming the positive reinforcement effect.

Bridges are critical nodes in transportation networks, and the evaluation of their service performance is of vital importance. Rapid assessment techniques based on the theory of influence lines have become a significant research topic. This study proposes a rapid testing method for the influence lines of beam-type bridges, with the synchronous monitoring of dynamic vehicle positions and a wireless network of multiple sensors. Field testing on a 30 m span T-beam bridge revealed that the measured vertical displacement during slow continuous driving corresponded with the static load test data within a deviation of ±6%, with the entire testing process completed in only 5 min, demonstrating efficiency and minimal traffic interference. Based on the measured influence lines, rapid bridge bearing capacity assessments and finite element model updating were researched. A case study of a simply supported T-beam bridge composed of prefabricated prestressed concrete showed that the calculated values using the proposed rapid assessment method deviated from traditional load test values between −5.68% and 4.69%, indicating a small error margin. After applying this method to the model updating of a (25 + 45 + 25) m continuous beam bridge on a highway, the inversion errors of the concrete elastic modulus and prestress were 1.40% and 1.20%, respectively, confirming the reliability of the precision. The rapid testing method for influence lines can be applied to bridge inspection, evaluation, and model updating.

This study investigates the underlying causes of pier displacement and cracking in a highway link bridge. The initial geological assessment ruled out slope instability as a contributing factor to pier movement. Subsequently, a comprehensive analysis, integrating in situ soil investigation and finite element modeling, was conducted to evaluate the influence of additional fill loads on the piers. The findings reveal that the additional filled soil loads were the primary driver of pier tilting and lateral displacement, leading to a significant risk of cracking, particularly in the mid-section of the piers. Following the removal of the filled soil, visual inspection of the piers confirmed the development of circumferential cracks on the columns of Pier 7, with the crack distribution closely aligning with the high-risk zones predicted by the finite element analysis. To address the observed damage and residual displacement, a reinforcement strategy combining column strengthening and alignment correction was proposed and validated through load-bearing capacity calculations. This study not only provides a scientific basis for analyzing the causes of accidents and bridge reinforcement but, more importantly, it provides a systematic method for analyzing the impact of additional filled soil loads on bridge piers, offering guidance for accident analysis and risk assessment in similar engineering projects.

To address the severe threats posed by stay cable fractures, this study investigates a fatigue fracture of a fork-eye anchor head induced by excessive cable vibrations on a landscape cable-stayed bridge. A comprehensive methodology integrating field monitoring, theoretical analysis, and finite element simulation is employed to reveal the vibration characteristics, fatigue mechanism, and multi-factor coupled effects. Field tests identify wind-induced vibration and parametric resonance as the primary external triggers for fatigue damage. A simplified mechanical model of the fork-eye anchor head is established to evaluate the stress state under combined axial tension and bending moment. Fatigue analysis using the stress–life method elucidates how vibration-induced alternating stress significantly reduces the fatigue life of the connecting screw. The multi-factor coupled fracture mechanism is revealed, and practical mitigation measures including supplementary dampers and regular inspection are proposed. The findings provide a theoretical basis and engineering guidance for the design, maintenance, and safety assessment of similar landscape cable-stayed bridges.