Explore the vast range of titles available.

In response to the frequent collapse of main girders caused by the breakage of suspenders on half-through and through arch bridges, a test specimen has been designed and fabricated with a through concrete-filled steel tube (CFST) arch bridge as the engineering background. A new electromagnetic disconnect trigger is employed to realize the rapid suspender breakage in the test specimen. Dynamic response tests of the residual structure of the arch bridge after suspender failures employing the test specimen have been carried out. A finite element model accounting for the suspender breakage dynamic process has been constructed by implementing ANSYS/LS-DYNA, and the results of the test and finite element analysis are compared. In order to simplify the dynamic response calculation process of the residual structure after hanger failures, the dynamic coefficient is introduced, and an equivalent static calculation method (ESCM) considering the dynamic effect of the suspender fracture is presented. Eleven kinds of CFST standard arch bridges with different spans are constructed, the static and dynamic effects of the standard arch bridge with various dynamic coefficients are compared, and then their corresponding dynamic coefficients for various suspender fractures are determined. The obtained results reveal that the proposed electromagnetic suspender breakage trigger can realize the hanger fracturing within 0.1 s, which accurately simulates the fracture process of an actual bridge suspender, and the influence on the value of the dynamic coefficient can be ignored when the duration for suspender fracture is less than or equal to 0.15 s. The influence of suspender fracture on the displacement and stress of the longitudinal beam is more notable than those of the arch rib. In particular, the long suspender breakage has the highest influence on the displacement and stress of the longitudinal beam and arch rib. The fracture of the second short suspender has a remarkable impact on the suspender force of the adjacent hanger. When the ESCM is utilized to assess the mechanical behavior of the half-through and through CFST arch bridge, the dynamic coefficients of the longitudinal beam (suspender) were evaluated to be, conservatively, 1.8 (1.8) and 1.8 (1.7), respectively.

Precise finite element modeling is critically important for the construction and maintenance of long-span suspension bridges. During the process of modeling, shape-finding and model calibration directly impact the accuracy and reliability. Scholars have provided numerous alternative proposals for the shape-finding of main cables in suspension bridges from both theoretical and finite element analysis perspectives. However, it is difficult to apply these solutions to suspension bridges with special components. Seeking a viable solution for such suspension bridges holds practical significance. The Nanjing Qixiashan Yangtze River Bridge is the first three-span suspension bridge in China. To maintain the configuration of the main cable, the suspension bridge is equipped with specialized suspenders near the anchors, referred to as displacement-limiting suspenders. It is the first suspension bridge in China to use displacement-limiting suspenders and their anchorage system. Taking the suspension bridge as a research background, this paper introduces a refined finite element modeling approach considering the effect of geometric nonlinearity. Firstly, based on the loop adjustment and temperature correction, the shape-finding and force assessment of the main cables are carried out. On this basis, a nonlinear finite element model of the bridge was established and calibrated, taking into account factors such as pylon settlement and cable saddle precession. Finally, the static and dynamic characteristics of the suspension bridge were thoroughly investigated. This study aims to provide a reference for the design, construction and operation of the three-span continuous suspension bridge.

This study proposes a method for evaluating the fatigue life of tied-arch bridge suspenders by considering the effects of random cyclic traffic loads and environmental erosion. To obtain cumulative fatigue load effects under traffic loadings, a multi-axle single-cell cellular automaton (MSCA) was used to analyze random traffic–bridge-coupled dynamics. Changes in stress amplitude caused by suspender sectional corrosion damage and degradation of suspender S–N curves owing to environmental corrosion were then used to update the relationship between load effect and resistance to obtain the fatigue limit states of the suspenders. To evaluate the dynamic performance and fatigue lives of typical suspenders, a case study involving a basket-type tied-arch bridge was conducted. The results indicated that, under the loading of a typical truck, structural vibration displacement was insignificant but suspender stress was very prominent, especially on the short suspenders. Parametric analysis of the vehicle–bridge interaction revealed that road surface roughness, vehicle weight, and traffic volume significantly affected the dynamic response of the bridge. Under random traffic loads, the shortest suspender experienced the most damage and had a fatigue life significantly shorter than those of the other suspenders. Ignoring corrosion, the shortest suspender fatigue life was 57.8 years; with fatigue corrosion accounted for, however, the shortest suspender experienced fatigue failure owing to cumulative damage after 30 years of service.

The prediction of suspender frequency and tension is difficult to solve due to the non-linear nature of suspender parameters. A method of predicting suspender frequency and tension using the generalized regression neural network (GRNN) model was proposed in this paper. It is necessary to select some suspender parameters as inputs into the model to solve the non-linear nature problem of the suspender parameters, such as length, mass unit per length, bending stiffness, fundamental frequency as well as tension, and to select the suspender frequency or tension as output. To consider the effect of different boundary constraints, analytical expressions of suspender parameters based on the singular perturbation method are derived and applied to train the models. Two different types of neural network models: back propagation neural network (BPNN) and radial basis function neural network (RBFNN), are also used to predict suspender frequency and tension to compare with the GRNN model. Datasets consist of measurements and literature samples are used to verify the models. Furthermore, R 2 , MAE, and RMSE are used to compare the performance of the models. The results showed that the application of GRNN achieves higher accuracy in predicting suspender frequency and tension compared to BPNN and RBFNN.

Suspenders are the crucial load-bearing components of long-span suspension bridges, and are sensitive to the repetitive vibrations caused by traffic load. The degradation of suspender steel wire is a typical corrosion fatigue process. Although the high-strength steel wire is protected by a coating and protection system, the suspender is still a fragile component that needs to be replaced many times in the service life of the bridge. Flexible central buckles, which may improve the wind resistance of bridges, are used as a vibration control measure in suspension bridges and also have an influence on the corrosion fatigue life of suspenders under traffic load. This study established a corrosion fatigue degradation model of high-strength steel wire based on the Forman crack development model and explored the influence of flexible central buckles on the corrosion fatigue life of suspenders under traffic flow. The fatigue life of short suspenders without buckles and those with different numbers of buckles was analyzed. The results indicate that the bending stress of short suspenders is remarkably greater than that of long suspenders, whereas the corrosion fatigue life of steel wires is lower due to the large bending stress. Bending stress is the crucial factor affecting the corrosion fatigue life of steel wires. Without flexible central buckles, short suspenders may have fatigue lives lower than the design value. The utilization of flexible central buckles can reduce the peak value and equivalent stress of bending stress, and the improved stress state of the short suspender considerably extends the corrosion fatigue life of steel wires under traffic flow. However, when the number of central buckles exceeds two, the increase in number does not improve the service life of steel wire.

The parallel steel wires used in arch bridge suspenders experience random corrosion damage on their surfaces during service. Corrosion damage, including micro-cracks, pitting, and a combination of both, leads to significant stress concentration under axial loading, which affects the performance of the steel wires. The change in the stress field caused by surface damage alters the stress intensity factor at the crack tip, and the presence of adjacent crack tips significantly amplifies the stress intensity factor, thereby accelerating crack propagation. The development of small surface damages in the steel wires is difficult to control and observe through experiments. By utilizing finite element methods for simulation, it is possible to intuitively analyze the crack propagation process, the trend of stress changes at the crack tip, and the interaction between damages. Numerical simulation results based on Paris’ law indicate that corrosion pits have a certain impact on the stress intensity factor at the crack tip. The propagation process of coplanar double cracks is highly sensitive to the initial crack size and the distance between adjacent crack tips. When the crack spacing is less than the crack depth, the stress intensity factor at the adjacent crack tips exhibits significant amplification. Based on this phenomenon, the coplanar double-crack system can be simplified to a complete single crack for analysis. By comparing the fatigue life of the double-crack system with that of the equivalent single crack, the effectiveness of the simplification rule has been validated.

Fatigue damage is the most dangerous failure behavior for gearbox suspenders in urban railway vehicles, and passenger capacity is crucial to the dynamic load characteristics of the traction transmission system. Therefore, in this paper, a dynamic model of the motor car is established, and a numerical simulation is carried out under different speeds and curve radii to investigate the effect of passenger capacity on fatigue life. The research results show that passenger capacity is an essential factor affecting the fatigue life of suspenders. As the vehicle runs at an average speed, the fatigue life of the suspender is 1.07 × 106 km when the passenger capacity is 120 people; when there are 240 people, the fatigue life reduction is 60%, while it is 86% at 339 people and 92% at 389 people. The per capita fatigue damage under a straight line is 7.27 × 10−10 at 20 km/h but 1.23 × 10−8 at 60 km/h. The per capita fatigue damage under a curved line is 7.18 × 10−9 in the 600 m curve but 9.00 × 10−9 in the 400 m curve. It can be concluded that the effect of speed is more significant than the curve radius. This research achievement can provide theoretical support for vehicle design and maintenance decisions.

The corrosion of the rotating axis pins of the short suspender will lead to the rotating restriction of its end, which will lead to the corrosion of the parallel wires and affect the performance of the short suspender. In this study, the technical condition of the rotating restricted short suspender unfixed from the suspension bridge was carefully detected. An axial tensile performance test was carried out on these short suspenders, and the subsequent availability of the rotating restricted suspender was evaluated based on the size of the fracture gap. The rotationally limited working conditions of these short suspenders were skillfully simulated by the specially designed tooling, and the fatigue performance test of the rotating restricted short suspender was carried out. A simplified simulation method was proposed based on the random traffic theory. By introducing traffic data obtained from the WIM system, the stress response of the short suspenders caused by vehicles on each lane was simulated, and the simulation results were converted by the rain flow counting method. The residual life of the rotating restricted short suspender was predicted by the comparison between the fatigue test results and the fitting curve of the simulation results. From this study, several of the following conclusions can be summarized: The measured fracture gap size is negatively correlated with the effective area of the suspender, and the gap size of 8mm is a key value. When the fatigue load cycle reaches 345,000 times, the suspender is already in a dangerous state. Additionally, the fractured gap size is considered as the judgment basis for the usability of rotating restricted short suspenders. When the gap size is less than 8 mm, the suspender can be continually used after maintenance and should be updated after 6 years. Otherwise, the suspender needs to be replaced immediately.

The half-through arch bridge short suspender is more prone to damage due to its high linear stiffness and special force characteristics. To analyze the vehicle-induced vibration characteristics of the short suspender during service, a half-through arch bridge finite element model and a three-axis vehicle model were established to realize the coupled vibration of the suspender axle under bridge deck unevenness excitation. The suspender was simulated using LINK element and BEAM element and separated along its axial and radial directions, and its tension-bending response characteristics was studied. The study found that the short suspender’s amplitude and frequency are higher than those of the long suspender as vehicle critical duration increases. Influenced by the tensile bending effect, the vibration, cross-section equivalent force amplitude, and impact coefficient at the anchorage end are larger than those at the center, and the lower anchorage end’s cross-section peak stress is biased towards the direction of the side column. The internal force of the short suspender is consistent with the deformation trend; its internal force coincides with the deformation trend; and its axial alternating load is generated by the axial relative deformation between the arch rib and the bridge deck, while the bending alternating load originates from the rotational deformation of the short suspender.

To meet the demand of not interrupting traffic during the replacement of suspenders in long-span railway suspension bridges, this research proposes for the first time the application of the unsupported replacement method to the suspender replacement of self-anchored railway suspension bridges. Based on the basic principle of suspension bridge, the safety control index in the process of boom replacement is proposed. Midas Civil 2024 software is used to analyze the structural response of the boom after removal under static force and train load, including the change of cable force of adjacent boom, the displacement of main cable and stiffening beam. The real bridge test was carried out based on the special bridge of Chongqing Egongyan Track. The results show that after the removal of the boom, the cable force of the adjacent boom increases by 42–55%, the main cable is partially twisted but the adjacent joints change little, and the displacement of the stiffened beam meets the specification requirements. When the train is fully loaded, the maximum increase of the cable force of the adjacent boom is 150 kN, the stress increment of the operating boom is far less than the design strength, the increase of the downtorsion of the main cable is only 2.22%, and the displacement of the stiffening beam is within the allowable range. The safety control index and real bridge test results show that the unsupported replacement method is feasible and safe in the replacement of the suspenders of long-span rail suspension bridges, which provides an important reference for related projects.