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.

The bridge discussed in this article is the first super-long bridge of the Zheng-Wan high-speed railway project to span the main channel of the South-to-North Water Diversion Project in China. The bridge is a 160 m beam–arch composite structure with concrete-filled steel tubes. To ensure water quality safety, a construction method of first the beam and then the arch was adopted, in which the steel tube arch ribs were constructed by vertical rotation. The construction monitoring of the vertical rotation of the arch ribs was conducted by numerical analysis to clarify the strength and stability of the arch ribs and tower in the construction of the vertical rotation of the steel tube arch ribs, and to evaluate the safety of the support and local components during construction. Finally, the vertical rotation construction of the steel tube arch ribs of the bridge was successfully completed under rigorous numerical analysis and precise construction monitoring.

In order to clarify the influence of hydrodynamic on dynamic response of bridge with complex piers submerged in reservoir, based on the continuous beam of a 4-column pile column frame pier in Xiaolangdi Reservoir of Yellow River, taking 4-column pile column frame pier and bridge as the object separately, the numerical analysis model of bridge (pier) - water interaction is established by ANSYS. The flow around deep-water piers is analyzed. For the single pier (SP) and the pier of the bridge (BP), the dynamic responses of different flow velocities, water depths and wave heights and the combined action are studied. The research shows that detouring flow analysis shows that velocity field and pressure field of each column are asymmetric. Specifically, for this bridge, due to the columns interfere with each other, the velocity difference of 1#, 4# column is more obvious than that of 2#, 3# column. Maximum and stability values of the dynamic response of SP and BP increase with the increase of flow velocity and depth. Specifically, as the water flow velocity increases, the maximum response of the dynamic response increases linearly, while the stable response of the dynamic response increases in the form of a quadratic curve. When the water depth does not exceed 50 m, the maximum and stable values of the dynamic response gradually increase in the form of a quadratic curve. When the wave acts alone, the dynamic response of SP and BP is the largest at the wave crest and the smallest at the wave trough. The maximum dynamic response at the wave crest and trough increases with the increase of wave height. With the increase of water depth, the dynamic effects of waves on SP and BP are more significant. Under the combined action of wave and current, the dynamic response of SP and BP increases with the increase of wave height and water depth. For different flow velocities, the maximum value of dynamic response at wave crest increases with the increase of flow velocity, and the maximum absolute value of dynamic response at wave trough decreases with the increase of flow velocity. Dynamic response under the combined action of wave and current is not the superposition of the dynamic response under the separate action of wave and current. The maximum value of dynamic response appears in wave crest and wave trough, indicating that the current does not change the action of wave field, and the wave still plays a leading role. Specifically, the influence of water on the dynamic response of BP is: pier bottom bending moment > pier bottom shear force > pier top displacement and the influence of water on the dynamic response of SP is: pier bottom bending moment > pier top displacement > pier bottom shear force.

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.

The shear design of a corrugated steel web box girder is important for structural reliability. Presently, corrugated steel webs bear all the shear forces, and the top and bottom concrete plates bear no shear force. Each steel web has equal force. This design is conservative and uneconomical and may sometimes be unsafe. The shear ratio and transfer efficiency of each corrugated steel web are investigated in this study through numerical analysis. Then, the distribution of shear stress in corrugated steel webs is verified through a static load test. Results show that the shear is shared by the top and bottom concrete plates and corrugated steel webs. The shear ratio presents a close relation with boundary, loading, and section position. The influence of a transverse diaphragm on the shear ratio is minimal, and this influence demonstrates a certain effect only on the steel webs located at the area of the transverse diaphragm.