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The threat of rockfall impacting bridges in mountainous areas poses a great risk to the safety of passing trains. This study delves into the dynamics of rockfall impact and its implications on the interaction between train vehicles and bridges. Leveraging LS-DYNA, this study first captured the force–time history of rockfall impact on bridge structures. Subsequently, there was a comparison with the impact forces generated at various speeds with those predicted by established formulas, validating the accuracy of simulations. Employing BANSYS software, the dynamic responses of both bridge structures and the vehicle–bridge coupling system to falling rocks were analyzed. The investigation encompassed parameters such as impact speed, position, and train location. The findings reveal that escalating impact speeds correlate with increased average and maximum impact forces from falling rocks. Notably, the average impact force does not linearly correspond with rock speed and often exceeds values calculated by conventional formulas. Impact position minimally affects maximum impact force, yet alterations in position prolong impact duration, consequently reducing average impact force. Rockfall-induced impacts precipitate notable spikes in train lateral acceleration, lateral wheelset force, wheel unloading rate, and derailment coefficient, albeit with a comparatively lesser impact on vertical acceleration. Increasing impact speed and altering position intensifies the vehicle’s response, particularly when the train is in close proximity to the impact site.

This paper presents an accurate analysis of the natural frequency and mode shape of carbon fiber-reinforced steel–concrete composite beam with double-slip surfaces. To study the flexural vibration of the composite beam, a governing differential equation considering the shear-slip effects of two interfaces is formulated. Based on this formulation, the natural frequency and mode shape of carbon fiber-reinforced composite beams are calculated. For comparison purpose, numerical simulations of the composite beams are conducted using the ANSYS in order to verify the present results. High consistency in the two calculation values is revealed. In addition, carbon fiber-reinforced composite beams are fabricated and tested. It is found that the experimental values agreed well with the theoretical results. The findings from this study may provide the benchmark reference for engineering analysis and design of carbon fiber-reinforced steel–concrete composite beams.

The $\mathrm{\Pi }$-shaped open section girder is a very common section, which has been widely used in the construction of modern bridges. However, compared with a streamlined box girder, it is easy to cause vortex-induced vibration (VIV) in bridges due to its bluff section shape and poor aerodynamic stability.

In this paper, a typical open section with a height–width ratio of 10:1 is taken as the research object. Through wind tunnel tests and numerical simulation technology, the time-history data of VIV of the $\mathrm{\Pi }$-shaped section are obtained. By selecting three different neural network models to establish the relationship between external parameters (wind attack angle, wind speed, turbulence) and structural response parameters (the onset wind speed of VIV, the length of the lock-in interval). After comparing different machine learning methods, the most suitable machine learning model is selected to predict the VIV response characteristics of the main girder. The research results show that the typical open section has a serious VIV phenomenon. The BP neural network model has the best performance in predicting the VIV performance of the open section in terms of calculation speed, prediction accuracy and solving nonlinear adaptability. At the same time, it is found that different characteristic parameters of the incoming wind field have different influences on the prediction results of the VIV response. Among them, the wind attack angle is the key parameter that affects the onset wind speed of VIV, but the turbulence intensity has a greater impact on the maximum amplitude of VIV. At the same time, the optimized BP model can predict the characteristic parameters of VIV response under unknown wind fields. This paper provides a new idea to study the effect of different incoming flow parameters on the performance of section VIV and further improves people’s understanding of VIV system.

The field load test is a direct and effective method for evaluating the performance of bridge structures. However, the existing bridge static load tests on site are costly, inefficient, and obstruct traffic; moreover, improper loading may also cause some damage to the bridge structure. This paper proposes a random model update method based on bridge dynamic load tests and the Bayesian inference as an alternative to the static load test. The Gaussian process model was used instead of the finite element model to reduce the cost of model calculation. Furthermore, choose the Markov Chain Monte Carlo (MCMC) method based on delay rejection adaptive Metropolis algorithm for Bayesian inference to improve the speed of the Bayesian method inferring the posterior probability density of updated parameters. First, the parameters to be updated for the bridge structure analysis model were determined based on the global sensitivity analysis method. Second, a uniform design sampling method was used to establish the Gaussian process optimization model to update the random model of the bridge structure. Finally, a reinforced concrete truss arch bridge was used to verify the correctness of the static load results of the bridge predicted by the random model update method based on dynamic load testing and Bayesian inference. The results show that the predicted results of the bridge static load test based on the dynamic load test and Bayesian reasoning method have an excellent agreement with the measured results, and this method can effectively overcome the adverse effects of the existing bridge static load test.

Different micromechanics models are researched though the Finite element analysis of FRP bridge deck, and the result is compared with the load test of the deck. The results show that, the elastic modulus along the fiber direction of the deck calculated by the selected micromechanics models are the same. The holistic deformation and the local deformation computed by the finite element model, whose elastic modulus is computed by the rule of mixture, are very close to the load test values. The fiber reinforced cloth can’t increase transverse modulus of the pultruded profiles. The rule of mixture model is the best model to simulate the pultruded FRP deck.

To study the lateral dynamic responses of a 64-meter steel truss bridge under train loads at different speeds, the structural model test was employed. The parameters of the bridge model, the rail model and the train model were determined by the similarity principle. The different speeds were applied on the train model to measure the lateral vibration signals at the designated positions of the bridge model. The results show that: when the train is passing the bridge at different speeds, torsional mode contributes a lot to the lateral displacements. The lateral displacements and accelerations of the bridge increase with the increasing train speeds and there are abnormal values at some speeds.

The load limitation standard of trucks has an immediate influence on the actual vehicle load level and its probability distribution characteristics. Further, the standard may affect the serviceability of constructed infrastructures, for example bridges. To investigate the truck load limitation issue of small-medium span bridges, a probabilistic model of load limitation analysis was firstly established. In the second part, the truck load characteristics were discussed based on long-term WIM data and the truck types were extracted. Subsequently, the higher limit of truck mass was obtained through inverse iteration based on the established flexural functions and selected multi-level target reliability index. The effect of target reliability index and differences in regional load characteristics on the limited truck mass were discussed based on the analysis results. Further, the applicability of current standard was analyzed through a comparison. The following conclusion were obtained based on the former analysis: the limited truck mass decreases linearly with the increasing of target reliability index. Besides, the influence of differences in regional load characteristics on the results is non-ignorable. The current standard of overload control is suitable for small-medium span bridges. Nonetheless, it is ideal for different regions to refine regional standards based on actual conditions.

Based on construction experiences, test results and active criteria, the causes breeding cracks in anchored ends of prestressed concrete hollow slab beams were analyzed and considered as smallness of dimensions of bearing plates, unreasonableness of beam pre-camber, local compression to the concrete in the anchored ends and largeness of the reaction forced by obtuse angle supports of oblique slabs. The effects of cracks on bearing capacity and normal service were charecterized and related prevention measures were proposed. At last, differences between current and old codes were emphasized in order to ensure safety during construction.