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In this study, dynamic receptance analysis (DRA) is proposed and combined with hybrid finite element (FE)-statistical energy analysis (SEA) method to accurately predict structural noise from long-span cable-stayed bridge (LSCB) with steel box composite girder (SBCG) in urban rail transit (URT). To begin with, a vertical vehicle–track coupling model in frequency domain is established based on DRA, in which the rail is represented by an infinite Timoshenko beam supported by a series of fasteners that are regarded as springs with complex stiffness. The floating slab is regarded as the Euler beam with both ends free supported by steel springs. Using this model, the spectrums of the wheel–rail force and the forces transferred to the bridge can be efficiently obtained by taking rail roughness as the excitation. Due to the low modal density of the concrete deck, the hybrid FE-SEA method is introduced to establish the noise prediction model, in which the discontinuity caused by using distinct models for different frequency bands is avoided. Then the on-site noise tests of a LSCB with SBCG in URT are carried out to verify of the proposed method. Finally, based on the prediction method, the acoustic contributions of the bridge components are analyzed in detail. The force transfer characteristics as well as the noise reduction effects of different track structures are thoroughly investigated, so as to provide reference for the future research on bridge-borne noise control. [ABSTRACT FROM AUTHOR]

To excite sufficient vibrations of bridges for more effective modal experiments to take place, traveling vehicles were utilized in many bridge field inspection campaigns in history. However, the dynamics of a bridge subjected to the traveling vehicles are of changed resonant properties compared with those of the same structure with the ambient excitation in nature. Therefore, the field modal experiments employing vehicle excitations might unfavorably lead to shifted measurement results of low-order natural frequencies for long-span bridges of large mass. Using Xinjiang Bridge (a single-tower pre-stressed concrete cable-stayed bridge with spans 40m + 150m + 150m + 40m) as the engineering background, this paper validates this technical notion based on reliable physical experiments and numerical simulations and seeks a practical approach to deal with the issue. It is found that the maximum deviation between the low-order modal frequencies measured on Xinjiang Bridge for the vehicle excitation case and those measured for the ambient excitation case (the accurate values) reaches 0.65Hz, and the deviation between the lower limit of the usual vehicle excitation’s energy band and the modal frequency measured (factor 1) and the traveling vehicles’ speed (factor 2) are the two key factors influencing the modal frequency shifts. An empirical model to compensate for modal frequencies’ deviations is formulated considering the two key factors accordingly, which is of high-practical significance in future applications of the modal experiments using vehicle excitations to other long-span bridges. [ABSTRACT FROM AUTHOR]

Concrete bridge towers are widely used in long-span bridges. Aiming at the reinforcement process which requires the largest labor force and has the highest safety risk during the construction of the super high concrete bridge tower. The key technology of assembling design and construction of super high concrete bridge tower reinforcement characterized by "industrialized production of mesh, rapid section forming and on-site assembling installation" is creatively proposed. In terms of design, the three-dimensional bridge tower reinforcement is discretized into planar or 3D mesh. In order to facilitate the reinforcement segment, a new flush lapping is used for the circumferential connection of stirrup, and the tapered sleeve splicing is used for the connection of the reinforcement parts between the segments, and the reliability of the connection is verified by experiments. In terms of construction, industrial assembly lines are used for the production of steel mesh and overall bending forming. The bridge tower reinforcement segments are assembled on the special jig, and finally installed on the tower by the tower crane. At present, this technology has been successfully applied to projects such as Lingdingyang Bridge, reducing labor intensity, improving construction efficiency by 30%, and ensuring project quality. [ABSTRACT FROM AUTHOR]

The health monitoring of infrastructure is vital for ensuring the safety and structural integrity of bridges. Recently, ground-based real aperture radar (GB-RAR) systems have been successfully utilized in the dynamic and static monitoring of bridges. In this study, a comprehensive and innovative approach is presented to monitor the vertical deformation of a long-span metallic railway bridge and a reinforced concrete Shinkansen bridge in Japan using a polarimetric GB-RAR system. Distinct from conventional signal processing procedures, the proposed method omits the coherent scatterer selection step. Instead, polarization analysis is employed to evaluate the properties of scatterers and identify those corresponding to bridge sections requiring monitoring, while considering the structural characteristics of the bridge. Simultaneously, the signal-to-noise ratio for monitoring is enhanced by combining co-polarization responses from scatterers. Furthermore, the radar look angle is determined by accounting for the spatial configuration of the survey and the polarization orientation angle. Lastly, vertical deformation is assessed by projecting line of sight deformation in the vertical direction. The findings reveal the dynamic responses of the two bridges under diverse loading conditions, which include the transit of a low-speed train and a high-speed Shinkansen bullet train. The results demonstrate that the polarimetric GB-RAR interferometry technique, coupled with the developed algorithms, can be effectively applied to monitor any type of bridge with unparalleled spatial and temporal resolutions. [ABSTRACT FROM AUTHOR]

The design of suspension bridges predominantly emphasizes wind and earthquake loads, frequently overlooking the consideration of extreme events in the design stage, thus posing a threat to bridge safety. The purpose of this research is to spread awareness among engineers for identifying weak zones in a bridge and to provide a new insight into how much damaging the blast loading could be for the long-span suspension bridges if not designed properly under the blast loads. The current dynamic analysis procedures for bridges under blast loads are complex and computationally expensive, making them unsuitable, especially for long-span bridges. To address this, a simplified dynamic analysis approach is proposed to assess the structural response and extreme limit state of suspension bridges exposed to blast loads. The method involves a bilayer solution: blast loading is modeled as nodal loads, and the structural aspect is represented by a three-dimensional (3D) fishbone skeleton finite-element (FE) model. Time-history simulations of blast loads are conducted for various bridge locations and explosive sizes. The parametric dynamic analysis reveals that the tower top node is the most vulnerable location in the suspension bridge under blast loads, which potentially exceeds the stress limits of nearby main cable elements and triggers the zipper-type progressive failure of the entire suspension bridge. Similarly, blasting at the deck nodes nearby tower on the main span side as well as on the side span side significantly amplifies axial stresses in nearby suspenders and the main cable, i.e., demand-to-capacity ratios of C18 and C19 surpass unity under BS4-6W and BS4-8W, respectively confirming that the failure state has reached for C18 and C19 under medium- to large-sized explosives. Therefore, it is recommended that the maximum demand-to-capacity ratio for all bridge components under medium- to large-sized explosives shall be kept below 0.8 to ensure the safety of the entire structure under extreme limit state. Practical Applications: This paper provides a methodology to investigate the structural redundancy of suspension bridges under extreme limit state by providing a bilayer solution: the blast aspect, which is simulated as nodal loads on the bridge road surface and the structural aspect, is simulated as a 3D fishbone skeleton FE model. The implicit dynamic analysis approach is adopted parametrically by considering variable explosive weights and locations. For each blast scenario, the time-history of nodal loads is applied to various locations of the bridge considering small- to large-sized blasts. From a practical viewpoint, this study is relevant to develop comprehensive understanding of the dynamic behavior exhibited by long-span bridges when subjected to extreme loading scenarios. In essence, the aim is to explore the benefits and applicability of this research to the design of long-span bridges under blast loading conditions. The simplified approach presented in this paper, along with the corresponding bridge response results, allows a bridge design engineer to analyze a suspension bridge effortlessly. This method eliminates the need for intricate computations required to assess blast pressure over a solid bridge model, enabling a straightforward visualization of the anticipated behavior under blast loading. The research serves a crucial role in checking and verifying the extreme limit state, in addition to assessing the serviceability and ultimate limit states according to AASHTO's requirements. For existing suspension bridges, the study proves beneficial in formulating a comprehensive blast-resistant plan through retrofitting and strengthening identified weak zones. Consequently, this research holds practical significance, serving as a foundation for further exploration and investigation into the effects of blast loading on various types of long-span bridges. [ABSTRACT FROM AUTHOR]

Fabricated ballastless track has witnessed increasingly wide application in large-span bridges of municipal railways. The current ballastless track standard is applicable to bridges with a main span of 200 m to 400 m. For the main span is longer than 400 m, it is necessary to ensure the travelling safety and comfort on the fabricated tracks. In this study, static and dynamic analysis models of train-track-bridge are established to explore the influence of complex ambient temperature changes and concrete shrinkage and creep on bridge deformation, followed by the analysis of the deformation coordination between long-span bridge and fabricated ballastless tracks, thereby revealing the dynamic response of the train-track-bridge system under the complex influence of temperature. The results show that when a train runs at a speed of 160 km/h, the existing ballastless track design standard is still applicable to a bridge span of 688 m. Compared with CRTS type III track, the adoption of the novel prefabricated ballastless track on long-span urban bridges provides higher safety and greater comfort, with comprehensive power performance improved by more than 10%. This design comprehensively takes into account the deformation coordination and dynamic performance of the rail bridge, providing a basis for the design and application of fabricated ballastless tracks on long-span bridges of urban railways. [ABSTRACT FROM AUTHOR]

The excessive main girder displacement responses of the large-span cable-stayed bridges during seismic events may precipitate collisions between the main girder and the approach bridge. The viscous dampers (VDs) have been extensively employed in the seismic response control of long-span bridges, yet their effectiveness is limited. To augment the seismic-induced vibration control performance of the VD, inerter element, negative stiffness (NS) element, and spring element have been incorporated into the VD to achieve energy dissipation capacity enhancement. The equations of motion for the simplified cable-stayed bridge-damper systems are established under stochastic seismic excitation, and the design parameters of inerter and NS-based damper are optimized by using the genetic algorithm. The seismic control performance of the VD and five types of dampers are systematically compared, demonstrating that these dampers can substantially enhance the main girder displacement mitigation performance in cable-stayed bridges. Owing to the NS characteristics attributes of the inerter element and NS element and the tuning effect of the spring element, the tuned viscous mass damper (TVMD) with NS achieves a 24.56% higher efficiency in control performance compared to the VD. [ABSTRACT FROM AUTHOR]

Generalized structural and aerodynamic torsional stiffness of a suspension bridge with a main span length of 3000m are discussed first qualitatively in terms of analytical models. Two torsional divergence (TD) modes, symmetric and asymmetric, are compared in terms of the evolution of generalized torsional stiffness properties. It demonstrates that symmetric TD occurs prior to the asymmetric TD in a vast range of main span lengths. Numerical simulations of TD are then performed by the static finite element (FE) method. The results turn out a much lower critical wind speed of TD presented by the analytical model, due to stiffness degradation caused by main cable deformations. Finally, the effects of two types of countermeasures are examined. The replacement of the original deck section by a central slotted one can boost the critical wind speed of TD by 30%. Widening the main cable spacing enhances almost linearly the system’s critical wind speed. A combined countermeasure of a slotted bridge deck and widened main cable spacing stabilizes substantially the system’s aerodynamic static stability, resulting in a 45% increase in the critical wind speed of TD. [ABSTRACT FROM AUTHOR]

This work focuses on the dynamic analysis of road bridges under large microsimulated traffic flows, contributing an efficient dynamic analysis framework for future fatigue, comfort or driving safety studies in which realistic interactions between vehicles are considered. Different strategies to define the loading vector in the governing dynamic equations are presented for bridges discretized with beam and shell elements. The proposed interpolation techniques for beam-like models include a recursive binary search and a novel vectorized strategy based on shape functions expanded to the entire length of the deck. These are applied to a short simply supported bridge and a very long cable-stayed bridge under traffic flows generated with a cellular automata microsimulation model. The strategies presented here reduce the computational time required in conventional load interpolation algorithms, particularly in long bridges subject to dense traffic flows. Finally, the binary search algorithm is applied to the study of bridge decks discretized with shell elements under microsimulated traffic, demonstrating that high vehicle densities increase the contribution of the transverse vibration of the slab and the potential discomfort of pedestrians. [ABSTRACT FROM AUTHOR]

This paper aims to extend a previously developed probabilistic model for simulating extreme response scenarios to include congested traffic flow on long-span bridges, addressing the challenge of accurately modeling traffic loads under changing conditions. While the model was initially designed for free-flow traffic, this study demonstrates how it can be adapted for congested conditions, with the objective of improving the accuracy of traffic load models. To overcome the limitation of traditional Weigh-in-Motion (WIM) systems in capturing congested traffic, congested flow characteristics were inferred from available free-flow data. The cellular automata (CA) method was applied to generate realistic congested traffic scenarios, which were used as input for the probabilistic model. Key simulation parameters, such as cell length and vehicle weight distribution, were adjusted to reflect congested conditions. The results validate the model's flexibility, showing how, with the adaptation of some parameters, it can simulate both free-flow and congested traffic patterns effectively. This research provides a basis for improving traffic load models used in the design and assessment of long-span bridges, addressing the current limitations in existing codes and standards. [ABSTRACT FROM AUTHOR]

The Wind–Vehicle–Bridge (WVB) coupling method is extensively applied in engineering practices for the dynamic analysis of railway bridges. However, research on the dynamic behaviors of the vehicle on curved bridges in wind conditions remains limited due to the complexities of interactions involved. In this study, the railway alignment and an actual curved bridge were chosen and modeled. The framework of the WVB system was detailed, and four excitation cases were investigated, considering mean wind, fluctuating wind and track irregularities. Three distinct scenarios, including vehicle on a curved bridge subjected to Inward Blowing Wind (IBW), Outward Blowing Wind (OBW) and vehicle on a straight bridge subjected to wind, were explored. The main conclusions are as follows: (1) wind direction significantly affects wheel unloading rate, lateral force, and derailment coefficient; (2) under mean wind condition, critical wind speed increases with the vehicle speed increasing under IBW, while it decreases with the vehicle speed increasing under OBW; (3) Combined wind and track irregularities reveal that wind direction significantly influences dynamic responses, and lower speeds are not necessarily equal to safer conditions for vehicles on curved bridges. [ABSTRACT FROM AUTHOR]

The construction duration of long-span arch bridges is excessively prolonged due to insufficient closing precision and the non-convergence of traditional cable adjustment calculation methods. This study investigates cable force management in long-span concrete-filled steel tubular (CFST) arch bridges during cable-stayed buckle construction, aiming to improve construction safety and precision in arch rib alignment. Using the Pingnan Third Bridge and Tian'e Longtan Bridge as practical examples, the research develops a multi-objective optimization method for cable forces that integrates influence matrices, constrained minimization, and a forward iterative approach. This method offers a robust strategy for tensioning and cable-stayed buckling, enabling real-time monitoring, calculation, and adjustment during the construction of large-span CFST arch bridges. The results reveal that the iterative approach notably enhances calculation efficiency compared to conventional methods. For instance, field measurements at the Pingnan Third Bridge show a minimal arch closure error of only 3 mm. Additionally, the study addresses concerns about excessive stress in exposed steel tubes during concrete casting. By optimizing the sequence of main arch closure and concrete casting, stress in the exposed steel tube is reduced from 373 MPa to 316 MPa, thus meeting specification requirements. In summary, the multi-objective cable force optimization method demonstrates superior efficiency in determining cable tension and controlling rib alignment during cable-stayed buckle construction of long-span CFST arch bridges. [ABSTRACT FROM AUTHOR]

This study aims to address the complexities in the calculation of the tangent stiffness matrix and the issues of divergence in iterative calculations in the shape-finding process of existing suspension bridge main cables. The research investigates the factors influencing the computational errors of existing cable element theories and the convergence or divergence of the main cable shape-finding calculations. First, a nonlinear equation for calculating the height of the cable element is constructed. Subsequently, a formula for cable height calculation is established according to the differential equations of the deformed cable element. Finally, considering the mass conservation principle before and after the cable deformation, a nonlinear system of equations for the configuration of the cable element is derived. Given the symmetric nature of the mid-span structure and loading in most suspension bridges, it is inferred that the point of the lowest slope of the main cable in the completed bridge state serves as the symmetry center of the structure. Consequently, a symmetric main cable shape-finding method is developed. A comparative analysis between the proposed method and existing iterative methods was conducted in terms of calculation accuracy and convergence behavior. The results indicate that the difference in horizontal cable force at the IP point between the two methods is 1.9 kN, and the difference in unstressed length is 2.5 mm. The calculation efficiency of the symmetric main cable shape-finding method is more than twice that of traditional iterative algorithms, with the number of iterations required for convergence generally being lower than that of traditional methods. For initial values that cause divergence in traditional iterative methods, the symmetric main cable shape-finding method achieved convergence within 10 iterations. The derived cable element theory and the symmetric main cable shape-finding calculation method can lay a theoretical foundation for the refined and efficient calculation of the main cable shape-finding process. [ABSTRACT FROM AUTHOR]

The traditional nonlinear aerostatic instability of long-span bridges is based on a two-layer iteration method that accurately predicts the structural equilibrium path before the critical buckling point. Due to strong nonlinearity after buckling, this traditional method cannot easily calculate the structural equilibrium and possible bifurcation using either Newton–Raphson or arc-length methods. In this study, a reduced order modeling (ROM) method for long-span bridge aerostatic deformation is proposed to approximate the bridge aerostatic equilibrium path after the critical point. The structural deformation mode shapes are extracted through singular value decomposition performed on the deformation matrix, and the nonlinear structural stiffness matrix is determined through the indirect displacement-based method on the finite-element method (FEM) platform. The ROM method is validated through comparison against the aerostatic deformation by the traditional two-layer iteration method based on FEM. By extending to higher wind speed, the ROM method can approximate the bridge deformation after initial buckling, and pitchfork bifurcation is observed after the structure undergoes rapid deformation growth. The stability of the equilibrium paths is examined through the Jacobian of restoring force vector, and the "snap-through" phenomenon exists for the equilibrium path before the bifurcation point. [ABSTRACT FROM AUTHOR]

Urban rail transit is rapidly evolving, with long-span cable-stayed bridges becoming increasingly popular among engineers because of their adaptability. However, as the operation time of bridges with tracks increases, the combined effects of repeated wheel loads and various bridge system excitations, including temperature changes and shrinkage–creep, gradually alter the alignment of the main beam. Similarly, the track structure on the bridge deck also undergoes vertical displacement, leading to corresponding degradation in rail alignment. This study applies singular function theory and verifies its effectiveness in bridge mechanical analysis. For the steel spring floating plate track cable-stayed bridge system, the mapping relationship between the deformation of the bridge’s main beam and the track’s deformation under bridge system excitation is derived, integrating singular function theory with the theory of train–track–bridge dynamic interaction. By analyzing the force transfer mechanism of the track–bridge system under system excitation, this research examines the effects of different excitations on the coupled dynamic response of the train–track–bridge. These findings suggest that system excitations increase the dynamic response of the train–track–bridge system, which is crucial for improving the durability and reliability of urban rail transit infrastructure. [ABSTRACT FROM AUTHOR]

The accurate prediction of the nonlinear flutter response is one of the important prerequisites for accurately evaluating the post-flutter performance of long-span bridges. In fact, as the vibration amplitude increases, the participation of lateral degree-of-freedom (DOF) will become more and more obvious and thus ignoring self-excited forces related to lateral vibration may no longer be applicable. To this end, based on 18 amplitude-dependent flutter derivatives (FDs), a 3-DOFs coupled nonlinear flutter analysis method was proposed in this study. Then, 18 amplitude-dependent FDs of two typical bridge decks were identified, and they were used to calculate the 3-DOF coupled nonlinear flutter responses based on the proposed flutter analysis method. Meanwhile, the correctness of the above flutter analysis method was also verified by compared with the numerical simulation results. Finally, the influence and mechanism of the lateral DOF, structural modal parameters and amplitude-dependent FDs on the nonlinear flutter of these typical bridge decks were investigated. The results show that when the torsional amplitude of the nonlinear flutter is large, the participation of lateral DOF will significantly increase the steady-state amplitude of the nonlinear flutter, and the larger the torsional amplitude, the more significant this increase is. The main reason is the participation of the lateral DOF introduces the negative coupled aerodynamic damping to the system, which then reduces the stability of the system. Besides, for the twin-box section, the influence of the lateral DOF on the nonlinear flutter is relatively smaller compared with the single-box section since the proportion of negative aerodynamic damping by the lateral DOF is smaller. Compared with the single-box section, the mass of the twin-box section has a smaller effect on the critical wind speed, and the torsional structural damping ratio of the twin-box section has a greater effect on the nonlinear flutter. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The continuous improvement of bridge construction technology has resulted in an ongoing expansion of bridge spans, which has concomitantly increased the difficulty of controlling the alignment of long-span bridges during construction. In order to address the issue of the grey prediction model exhibiting a significant discrepancy in its alignment predictions for long-span continuous girder bridges, a pre-camber prediction method for bridges based on a combination of the grey model (GM) and BP neural network (GM-BP) is proposed. Firstly, the parameters are identified according to their influence on the pre-camber, and the appropriate parameters are selected as the original data to improve the efficiency of prediction. Subsequently, the original data are preliminarily fitted by the GM(1,1) model, and the predicted values are used as inputs for training the neural network. Finally, the new predicted values are output using the nonlinear fitting ability of the BP neural network. To assess the efficacy of the model, it is applied to the prediction of the pre-camber of the girder segments of a bridge under cantilever construction. The pre-camber prediction for 11#–13# girder sections was based on 10 sets of monitoring data from constructed girder sections. The results demonstrated that the average relative error of the GM-BP combined prediction model was 3.01%, which was 5.68% less than that of the GM(1,1) model, and the overall prediction exhibited a closer alignment with the original data. The GM-BP combined prediction model is an effective method for ensuring the alignment control of bridge construction and is able to achieve high accuracy and stability in its predictions in the case of limited and irregular data. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Orthotropic steel bridge decks (OSDs) play a key role in long-span bridges, and full-penetration welding technology is crucial to improve their structural performance. This study proposes an innovative single-sided full-penetration welding rib-to-deck (RTD) joint technology. The accuracy of the numerical simulation in predicting the temperature field and stress field was verified by the combination of an experimental and numerical simulation, and the welding residual stress (WRS) of single-sided full-penetration welded RTD joints was analyzed. In addition, the effects of different welding parameters and RTD joint geometry on the WRS are discussed. The results show that the experimental results are consistent with the simulation results, indicating that the single-sided full-penetration welding technology without a groove is feasible. The WRS shows a peak tensile stress near the weld, which gradually decreases and transforms into compressive stress as the distance increases. In addition, the WRS of the roof surface and the U-rib surface increases slightly with the increase in the roof thickness and the welding speed. The research results are of great significance to optimize the welding process, improve the fatigue performance, and prolong the service life of steel bridge decks, providing a new technical method for bridge engineering. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accurate deflection prediction of in-service bridges can be used to assess the overall structural stiffness and detect abnormal states in advance. The bridge structures, especially long-span bridges, experience varying environmental and operational conditions, including temperature, humidity, wind excitation, and traffic loads, as well as long-term material deterioration and stiffness degradation mechanisms, and therefore, their deformation behavior shows complex variation phenomena, which pose challenges to many current deflection prediction methods. To address this subject, a Bayesian dynamic difference model (BDDM) to predict bridge deflection behavior online is proposed in this paper, explicitly considering the effect of the nonstationarity of time series data under varying environmental and operational conditions. A novel dynamic difference model is first proposed to include the nonstationary residual term and provide a linear approximation of a complex nonlinear process. Then, the formulas for recursively updating the dynamic difference model based on Bayesian inference are proposed. The proposed method is first validated through a numerical application using simulated nonstationary time series data with a nonlinear trend, indicating that it can adaptively capture nonstationary variations, update noise variance estimations, and improve prediction accuracy. To further demonstrate its performance, the BDDM is employed to predict the daily maximum deflection of a real-world cable-stayed bridge using measured data, and its performance is compared with several existing methods. The findings reveal that the proposed method outperforms other methods in terms of prediction accuracy, and can be potentially implemented for an online monitoring and early warning system. [ABSTRACT FROM AUTHOR]

The traditional multiscale model static updating method for long-span bridges requires load tests to obtain the correspondence between load and response, which leads to prolonged traffic interruption, with poor timeliness and low efficiency. Therefore, an efficient multiscale model dynamic calibrating framework based on stochastic vehicle-induced responses is proposed in this paper. The multiscale model is calibrated by monitoring data, and the dynamic calibrating efficiency is improved through the substructure–refined model combination modeling. First, the relationship between the structure and its corresponding response statistical characteristics is derived under stochastic traffic loads, and a statistical-based calibrating objective function of the multiscale model is established. Second, the framework for efficient multiscale model dynamic calibrating based on long-term monitoring data is presented, including efficient multiscale model establishment and dynamic calibrating based on stochastic vehicle-induced responses. Finally, the effectiveness of the proposed method is verified by its application to a long-span steel box girder suspension bridge. Comparison with the traditional load test method demonstrates that the proposed method effectively achieves multiscale model dynamic calibrating based on monitoring data during bridge operation, improving calibrating efficiency while ensuring multiscale modeling accuracy. [ABSTRACT FROM AUTHOR]

Wind tunnel tests or computational fluid dynamics (CFD) simulations of the aeroelastic model of a bridge deck section are currently used to make sure that significant vortex-induced vibration (VIV) of a long-span bridge will not occur after the bridge is put into operation. However, significant VIV still occurred in several long-span bridges in operation, indicating that the currently used wind tunnel tests and CFD simulations have some drawbacks or uncertainties. This study aims at establishing a digital twin by interacting CFD simulation with wind tunnel test for accurately and efficiently predicting the VIV response of a bridge deck. The measurement information of VIV of the deck section is collected from the wind tunnel test and fused with the CFD simulation. The optimisation for reducing uncertainties existing in wind tunnel test and CFD simulation is then carried out to make the CFD simulation as a digital twin. The digital twin is finally used to investigate the blockage effect of wind tunnel test and give an accurate and efficient prediction of VIV of the bridge deck. The flat closed-box steel deck section used in the Xiangshan Harbor cable-stayed bridge is selected as a case study. The results from the case study show that the digital twin can be established and used for an accurate and efficient prediction of VIV of the bridge deck section. [ABSTRACT FROM AUTHOR]

To study the influence of the Chinese high-speed railway ballastless track spectrum and the German low-interference spectrum on riding comfort, a long-span highway-railway suspension bridge is studied as an example, and a passenger–train–bridge coupling model is established based on the structural dynamics. The vibration responses of the passenger–train–bridge system during the CRH2C train running on the bridge are studied by a combination of the self-written computer program and general finite element software, considering the hunting movement, and the riding comfort of trains and passengers is evaluated using NMV and ISO-2631 standard, respectively. The results show that track irregularity has a few effects on the lateral vibration of the bridge. Compared with the German low-interference spectrum, the Chinese high-speed railway ballastless track spectrum has less exciting effects on the vibration of the passenger–train–bridge system and better riding comfort. Passengers in the middle of the train and on the middle seats of the same train have better riding comfort, and with the increase of train speed, the riding comfort of passengers will gradually reduce. Instead of passenger responses, the riding comfort classification based on the car body is overestimated. [ABSTRACT FROM AUTHOR]

Novel loss functions for seismic response prediction, such as physics-informed loss functions, have attracted considerable attention. However, existing loss functions are based on the time domain and do not consider the frequency domain differences contained in structure response signals. This study accordingly designed three loss functions based on frequency domain information — one pure frequency domain loss function and two combined frequency- and time-domain loss functions — using Fourier transforms. The proposed loss functions were applied using a trusted publicly available dataset for a frame structure, and their performances were compared with those obtained using the conventional mean squared error (MSE) loss function. The proposed frequency domain loss function exhibited superior performance, accelerating the convergence of learning curves for long-period signals while simultaneously enhancing their frequency domain accuracy and facilitating the prediction of high-sampling-rate response signals. In addition, the designed loss functions exhibited more stable performances and superior accuracy than the MSE when random dataset partitioning was employed. Finally, the combined time- and frequency-domain loss functions were shown to predict the seismic displacement time-history of tall, long-span bridges more accurately than the MSE by training the model to predict structural acceleration responses, then integrating them to predict displacement responses. [ABSTRACT FROM AUTHOR]

Stage-built long-span bridges deform with temperature, affecting alignment to design needs. In this paper, a model for predicting temperature time series is proposed, which can predict temperatures in engineering practice and utilize the predicted results to adjust the elevation of stage construction. The model employs convolutional neural networks (CNNs) for initial feature extraction, followed by bidirectional long short-term memory (BiLSTM) layers to capture temporal dependencies. An attention mechanism is applied to the LSTM output, enhancing the model's ability to focus on the most relevant parts of the sequence. The Crested Porcupine Optimizer (CPO) is used to fine-tune parameters like the number of LSTM units, dropout rate, and learning rate. The experiments on the measured temperature data of an under-construction cable-stayed bridge are conducted to validate our model. The results indicate that our model outperforms the other five models in comparison, with all the R2 values exceeding 0.97. The average of the mean absolute error (MAE) on the 30 measure points is 0.19095, and the average of the root mean square error (RMSE) is 0.28283. Furthermore, the model's low sensitivity to data makes it adaptable and effective for predicting temperatures and adjusting the elevation in large-span bridge construction. [ABSTRACT FROM AUTHOR]

Aiming at the problems of large capacity, narrow transverse width, large excitation, high safety level, and difficulty in accurately grasping the working state of the cable-stayed bridge for the long-span track, this research obtains the structural response data in real time by establishing a health monitoring system. The adaptive filtering method was employed to separate the train load response and the temperature load response. Then, a train load effect analysis method based on the influence line and a temperature load effect analysis method based on the correlation were proposed to assess the operational status of the bridge in real time and objectively. The Chongqing Nanjimen Railway Track Bridge (hereinafter Chongqing Nanjimen track bridge) project was utilized as a case study to demonstrate the application of these methods. The results show that the adaptive filtering method can effectively separate the response of train and temperature loads. The normalized cross-correlation (NCC) results of the measured train load response and the influence line's finite element calculation show a high degree of fit between the measured values and the theory, proving that no significant anomalies are found in the bridge. There is a strong correlation between the ambient temperature difference and the Pearson correlation coefficient of structural response, which indicates that the Chongqing Nanjimen track bridge is currently in normal working condition. [ABSTRACT FROM AUTHOR]

Concrete shrinkage and creep significantly affect the serviceability of bridges, especially long-span bridges. To investigate the long-term shrinkage and creep behaviors of low-shrinkage and low-creep C60 high-performance concrete (hereinafter referred to as LSLC HPC C60), 76 LSLC HPC C60 specimens are designed and subjected to shrinkage and creep tests for 270 days. The results indicate that the LSLC HPC C60 exhibits a similar trend in shrinkage and creep development as ordinary C60 concrete but with smaller creep and shrinkage values. New parameters for the two commonly used creep models are recommended based on experimental data. By comparing the measured data, it is determined that the parameter-recommended creep models are more suitable for predicting the creep performance of the LSLC HPC C60. A finite-element model of a long-span bridge is established, and the recommended models are imported into the bridge model. The multidecade deflections of the main span of the bridge are analyzed considering different creep models. The calculated results indicate that the parameter-recommended creep models can be used to predict the long-term deflections of long-span bridges with the LSLC HPC C60. [ABSTRACT FROM AUTHOR]

This study employs advanced techniques, namely the improved multi-synchrosqueezing transform (IMSST) and the Fouriersynchrosqueezed transform (FSST), to extract the instantaneous frequency of the Humber Bridge, in the UK, in operational conditions. First, a brief overview of the relevant theories behind the techniques used is provided. These techniques are then applied to track the instantaneous frequencies within the monitored vertical acceleration data of the bridge. The instantaneous frequencies extracted by both techniques are verified against each other. The investigation further encompasses the development of three distinct regression models: a simple regression model, an expanded regression model and a regression model based on principal component analysis (PCA). The efficacy of the PCA-based model is scrutinised by generating and testing datasets that mirror the monitored data, with the Kolmogorov-Smirnov (KS) test confirming theirvalidity. The findings of this research indicate a statistically significant inverse relationship between modal frequency and acceleration intensity. Furthermore, by incorporating wind effect considerations into the regression analysis, the R-squared values in both the expanded and PCA-based models exhibit substantial improvements. This demonstratesthe performance of the enhanced model in capturing the dynamics of the bridge. The robustness of the PCA-based model is furthercorroborated by its performance during testing, proving its potential as a reliable tool in structural health monitoring (SHM). [ABSTRACT FROM AUTHOR]

Due to the asymmetrical cross section of long-span rail-cum-road twin-girder bridges, the aerodynamic interference effect and flow characteristics of the twin girders in the gap are complicated. To study the influence of spacing on their aerodynamic characteristics, section model wind tunnel tests were conducted on a long-span rail-cum-road twin-girder cable-stayed bridge. This study considered the two conditions of bare and completed girders and the two inflow directions of 0° and 180°, with a spacing ratio range of L/Br = 0.1–2.0, and tested the surface wind pressures of the twin girders. Their aerodynamic and flow characteristics were analyzed, and the influence of spacing on their aerodynamic interference was clarified. The results show that for asymmetrical twin girders, the spacing and direction of incoming flow are still the key factors affecting their wind pressure distribution and flow characteristics. Due to the asymmetry of twin-girder sections, the influence of spacing on the wind pressure distribution and flow pattern varies with different flow directions. Furthermore, the attachments to completed girders enhance the asymmetry, making the aerodynamic and flow characteristics more complex than those of bare girders. Finally, three flow patterns are summarized: the upstream girder lower surface wake acts on the downstream girder fairing lower surface, acts on its fairing upper surface, and acts at its fairing. [ABSTRACT FROM AUTHOR]

The development tendency of lightweight and higher-speed regarding trains goes against the safety and comfort requirement of high-speed trains, especially in the scenario of the train running on bridges within crosswind environments. Wind barriers have been proven to be an effective measure to guarantee the train's operation security. In this paper, a new type of wind barrier consisting of the fence-type wind barrier form and open hole-type wind barrier form has been proposed. Then, a series of wind tunnel tests about the large-scale section model of a large-span suspension bridge installed with different wind barriers have been conducted. The effects of three different forms of wind barrier including fence-type, open hole-type, and combined-type on the aerodynamic characteristics of the train-bridge system have been analyzed. The windproofing effectiveness and the protection mechanism of the combined-type wind barrier on the train-bridge system have been revealed through the measured aerodynamic characteristics. The results show that the installation of open hole-type, fence-type, and combined-type wind barriers at a height of 4 m and a ventilation rate of 19% yields a maximum reduction in the train drag coefficient of 67.70%, 72.92%, and 97.21%, respectively. Moreover, the combined-type wind barrier can improve the train-bridge system's aerodynamic performance and trains' running safety on bridges when comparing with the open hole-type and fence-type wind barriers. The proposed combined-type wind barrier can provide a more efficiency and practical way for the high-speed train's running safety on the bridge. [ABSTRACT FROM AUTHOR]

Bridges are fundamental facilities in the transportation system, and their operational performance is crucial for economic and social development. Many large bridges are now equipped with structural health monitoring (SHM) systems that collect various types of real-time data. However, our user study found that despite the accumulation of massive amounts of monitoring data, current analysis methods cannot efficiently process large-scale, high-dimensional data. To address this, we have developed BOPVis, a visualization system for bridge monitoring data. BOPVis allows users to intuitively locate sensors and extract corresponding data from a 3D digital model of a bridge. It also provides convenient and flexible interactions for examining trends over time and correlations across hundreds of monitoring channels. A real-world long-span suspension bridge in China is used as a case study to demonstrate the advantages of the BOPVis system for operational performance mining. Through BOPVis, the global temperature deformation behaviors of the bridge are explored and found to align with the physical mechanism documented in the SHM literature. The BOPVis system, with its interactive visualization analysis capabilities, offers a new method for analyzing bridge monitoring data. [ABSTRACT FROM AUTHOR]

The fatigue provisions for bridge design in North America and Europe are highly simplified for the sake of practical implementation, in comparison with the state of the art in understanding of the true fatigue behavior. Historically, one significant simplification in the calibration of damage equivalence factors has been to assume that trucks cross the bridge one at a time, when in reality trucks are known to platoon, and multiple truck presence is not uncommon on longer span structures with higher traffic volumes. While code writers have taken steps more recently to consider multiple presence effects, these efforts have been limited, and a clear understanding of the influence of key design parameters on multiple presence effects has not yet been fully established. Against this background, the present work considers real-time multilane weigh-in-motion (WIM) data and compares fatigue damage from recorded loading events over years to the damage resulting from the same vehicles crossing the bridge individually, to better understand the significance of multiple vehicle presence effects on fatigue damage. For both finite and infinite life fatigue design, the results show that multiple vehicle presence effects can be significant, depending on traffic volume, road configuration, and influence line characteristics. Multiple presence factors are therefore defined, allowing practitioners to consider multiple presence effects appropriately when designing bridges where they may be relevant. [ABSTRACT FROM AUTHOR]

Utilizing the high strengths, toughness, and durability of ultra-high-performance concrete (UHPC), a segmentally prefabricated orthotropic steel–UHPC composite deck (POSUCD) system has been developed for long-span cable-stayed bridges. The deck system combines an orthotropic steel deck (OSD) with a reinforced UHPC layer using notched perfobond strips (NPBLs). The UHPC layer is prefabricated onto the OSD of the girder segment in the factory to form the POSUCD. After the precast UHPC layer is cured, the girder segments are transported to the bridge site and assembled. The precast UHPC layers are then connected via transverse wet joints before tensioning stay cables. Against the background of the Danjiangkou Reservoir Bridge with a main span of 760 m, finite element (FE) analysis was conducted to examine the stress state and flexural tests were carried out on local full-scale models to verify the feasibility of POSUCD. The results show that the prefabricated UHPC layer reduces the maximum static compressive stress of the steel deck in the girder system by 21%, and the stress ranges at fatigue-prone details of the steel deck are decreased by 28%–90% compared to traditional OSDs with asphalt overlay. Since the prefabricated UHPC layer helps withstand dead axial load in the main girder, the high compressive strengths of UHPC can be utilized more effectively than in deck systems with UHPC only used as a cast-in-situ overlay to resist vehicular wheel loads. The transverse wet joint interfaces were identified as the weakest aspect of the POSUCD, whether under tension or compression; however, their nominal flexural strengths along the longitudinal direction meet the required design standards. The shear resistance of NPBLs was also well confirmed by the minimal interfacial slip on the specimen when it reached the ultimate capacity under positive bending moment. [ABSTRACT FROM AUTHOR]

This paper introduces a new accelerating algorithm, efficient match slimmer (EMS), specifically designed to lighten computational loads of sophisticated template matching algorithms, enabling these algorithms to be effectively run on single‐board computers. Utilizing EMS in conjunction with a robust template matching algorithm, we have developed Raspberry Vision—a compact, cost‐effective, and real‐time vision‐based system. Its compactness and portability facilitate a practical measurement strategy that not only minimizes the camera‐to‐target distance but also simplifies the camera calibration process in bridge displacement monitoring, thereby enhancing measurement accuracy. The performance of the system is estimated on two operational suspension bridges. The results demonstrate that Raspberry Vision, equipped with the measurement strategy, can significantly improve the measurement accuracy in the long‐span bridge test and is also suitable for cross‐sea bridge measurements. [ABSTRACT FROM AUTHOR]

The First Egongyan Bridge in Chongqing, China was opened to traffic on December 27, 2000. It carries six-lanes of city traffic and two pedestrian paths, one on each side. It is a 600 m span suspension bridge. It was planned that the two pedestrian paths might eventually be converted to transit tracks in the future. However, with the rapid increase in urban traffic, the deck was transformed into an 8-lane bridge instead. Therefore, a new bridge parallel and adjacent to the old bridge was built for the rail transit. For aesthetic reasons, the city decided that the new bridge should also be a suspension bridge, with the same span length and tower height as the first bridge. The First Egongyan Bridge was a true suspension bridge with main cables anchored to ground anchors. However, the new bridge bridge's proximity to the first bridge necessitated the construction of a self-anchored suspension bridge that did away with a second set of ground anchors. This 600 m span happened to be the world's longest span for a self-anchored suspension bridge. [ABSTRACT FROM AUTHOR]

The San Michele Bridge in Paderno, Italy, is a prime example of the refurbishment of a historic structure. An architectural and historical landmark, it is the last of a remarkable group of trussed arch bridges built in the late XIX century to be fully operational, and serves the Seregno-Bergamo railway line and the provincial road SP54/166 connecting Paderno d'Adda and Calusco. In 2014, after 130 years of service, the bridge was subjected to an extensive survey and inspection campaign to acquire a more profound knowledge of the structure and its reliability. Overall, the inspections revealed that the bridge was still in a decent state but needed refurbishment. This article will briefly present the challenges faced in the design and execution of the refurbishment works. [ABSTRACT FROM AUTHOR]

The transverse seismic behavior of a long-span cable-stayed bridge with two inverted Y-shaped reinforced concrete towers is investigated in this study. To accomplish this, a 1/35-scale model of a cable-stayed bridge with a span of 1088 m was designed, constructed, and tested until failure on four shake tables; the test was conducted at Tongji University, China. A site-specific artificial wave was applied in the transverse direction. Moreover, the input peak ground acceleration was increased from 0.1 g to 1.3 g until the test model failed. The transverse displacement, force, rebar strain, and curvature responses of the bridge model are obtained and studied. The test results showed that the transverse displacement response of the tower was significantly affected by high-order modes. This resulted in the maximum seismic displacement of the tower at the middle – upper level of the middle column except for the tower top. The ratio of the transverse seismic forces acting on the towers significantly exceeded that of the forces acting on the piers. In the final test case, severe damage, including concrete crushing and rebar exposure, occurred at the bottom of the middle column – the most critical part of the tower – leading to the inclination of the tower. Damage to the cables or deck was not observed. The finite element model captured the elastic transverse seismic behavior of the test model. [ABSTRACT FROM AUTHOR]

An accurate prediction of the future service state of long-span bridges is crucial for the structural reliability evaluation, maintenance planning, and further life-cycle cost analysis. By extending the average conditional exceedance rate (ACER) statistical model and applying input–output data collected through a structural health monitoring (SHM) system, this paper proposes a novel methodology for predicting the future service state of long-span bridges. The advantages lie in the consideration of the main excitation load as the structural input and the strain response of the bridge as the output. Therefore, a mapping relationship between the extreme excitation load and extreme strain could be established, and the future service state of long-span bridges could be predicted. The proposed method comprises three steps: (1) extraction of the ambient temperature-induced strain and vehicle-induced strain from the measured strain series through the SHM system using the baseline estimation and denoising with sparsity (BEADS) method, (2) establishing statistical models of the extreme values of different excitations (input) and structural strains (output) using a cascade of conditioning approximations and the ACER to obtain the tail trend of the data and extrapolating it, and (3) establishing a functional relationship between the input and output extreme values based on the same conditions of the regression period at the target prediction level, after which the future service state of long-span bridges can be predicted. The proposed method is applied to a case study of the Jinchao Bridge in Guangdong Province, China, and the results are expected to provide a scientific reference for the design of new bridges and in the maintenance of existing ones in service. [ABSTRACT FROM AUTHOR]

Viscous dampers are widely used as passive energy dissipation devices for long-span cable-stayed bridges for mitigation of seismic load-induced vibrations. However, complicated finite element (FE) modeling, together with repetitive and computationally intensive nonlinear time-history analyses (NTHAs) are generally required in conventional design methods. To streamline the preliminary design process, this paper developed a simplified longitudinal double degree of freedom model (DDFM) for single and symmetric twin-tower cable-stayed bridges. Based on the proposed simplified longitudinal DDFM, the analytical equations for the relevant mass- and stiffness-related parameters and longitudinal natural frequencies of the structure were derived by using analytical and energy methods. Modeling of the relationship between the nonlinear viscous damper parameters and the equivalent damping ratio was achieved through the equivalent linearization method. Additionally, the analytical equations of longitudinal seismic responses for long-span cable-stayed bridges with nonlinear viscous dampers were derived. Based on the developed simplified DDFM and suggested analytical equations, this paper proposed a simplified calculation framework to achieve a simplified design method of nonlinear viscous damper parameters. Moreover, the effectiveness and applicability of the developed simplified longitudinal DDFM and the proposed calculation framework were further validated through numerical analysis of a practical cable-stayed bridge. Finally, the results indicated the following. 1) For the obtained fundamental period and longitudinal stiffness, the differences between results of the simplified longitudinal DDFM and numerical analysis were only 2.05% and 1.5%, respectively. 2) Relative calculation errors of the longitudinal girder-end displacement and bending moment of the bottom tower section of the bridge obtained from the simplified longitudinal DDFM were limited to less than 25%. 3) The equivalent damping ratio of nonlinear viscous dampers and the applied loading frequency had significant effects on the longitudinal seismic responses of the bridge. Findings of this study may provide beneficial information for a design office to make a simplified preliminary design scheme to determine the appropriate nonlinear damper parameters and longitudinal seismic responses for long-span cable-stayed bridges. [ABSTRACT FROM AUTHOR]

The accurate installation of long-span arch bridges' arch ribs remains a challenge due to the complex calculations required for cable forces and arch rib displacements, as well as the significant influence of environmental and construction loads. In this study, we propose a practical approach to alignment and error feedback control for long-span arch bridges. Cable forces were optimized using multiple control objectives based on influence matrix principles. The impact of temperature on the next segment to be installed was analyzed using the metastatic GM(1, 1) model and fitting results. Several tunable parameters were employed to account for parameter errors and environmental interference. These parameters were adjusted based on the deviations between practical and theoretical alignments for different arch rib segments, achieving a model output of an offset-free-tracking arch rib structure. This technology was applied to monitor the construction of the Tian'e Longtan Grand Bridge. Compared to conventional alignment control approaches, the proposed method achieved excellent arch ring alignment after the closure of the high-accuracy arch rib and cable release, as well as effective control of cable force uniformity and tower deviation. Field measurement data indicate that the closing deviation of the arch ring is only 3 mm. This study provides a valuable reference for the construction control of long-span arch bridges. [ABSTRACT FROM AUTHOR]

Various approaches have been proposed for bridge structural health monitoring. One of the earliest approaches proposed was tracking a bridge's natural frequency over time to look for abnormal shifts in frequency that might indicate a change in stiffness. However, bridge frequencies change naturally as the structure's temperature changes. Data models can be used to overcome this problem by predicting normal changes to a structure's natural frequency and comparing it to the historical normal behaviour of the bridge and, therefore, identifying abnormal behaviour. Most of the proposed data modelling work has been from long-span bridges where you generally have large datasets to work with. A more limited body of research has been conducted where there is a sparse amount of data, but even this has only been demonstrated on single bridges. Therefore, the novelty of this work is that it expands on previous work using sparse instrumentation across a network of bridges. The data collected from four in-operation bridges were used to validate data models and test the capabilities of the data models across a range of bridge types/sizes. The MID approach was found to be able to detect an average frequency shift of 0.021 Hz across all of the data models. The significance of this demonstration across different bridge types is the practical utility of these data models to be used across entire bridge networks, enabling accurate and informed decision making in bridge maintenance and management. [ABSTRACT FROM AUTHOR]

The cable saddle structure is the main support component for long-span bridges to transmit cable force, which is of great significance for the structural force system. Nowadays, the main cable saddle structures used in long-span bridges are mainly traditional anti-slip saddles and innovative rolling saddles. To clarify the characteristics of the saddles in long-span bridges, the design principles, mechanical properties, and casting process of these two types of saddle structures were researched. A rolling saddle in a bridge project was taken as an example and its mechanical situation in the roller area was investigated. The results showed that the stress concentration phenomenon is prone to occurring in the rolling saddle because of the line contact in the contact area and the rolling saddle is mainly subjected to vertical force. Thus, attention should be paid to the von Mises stress in the contact area between the saddle base and the roller shaft, the lower surfaces of both ends of the roller shaft, and the top surface of the tower, to avoid material damage. Furthermore, the casting process of the anti-slip saddle structure is mature, but also faced with problems due to the welding of thick plates, and urgently needs to be improved and upgraded. The rolling saddle is used with the all-welded casting process, but its technology is relatively immature and the requirements for the roller shaft material performance are strict. The research results can provide a reference for the selection and design of the saddle structure in long-span bridges. [ABSTRACT FROM AUTHOR]

In the actual structural health monitoring system of suspension bridges, only part of suspenders tension can be monitored, but not all the suspenders tension can be obtained. To solve this problem, a method for suspenders tension identification of bridges based on the spatio‐temporal correlation between the girder strain and suspenders tension is proposed. By using actual monitoring data of vehicle loads, a spatio‐temporal correlation model of the girder strain and tension forces of all suspenders is constructed based on the combined application of stacked denoising autoencoder and convolutional neural networks‐long short‐term memory model, so as to realize the preliminary identification of suspenders tension. On this basis, by using the actual monitoring data of suspenders tension and the strain monitoring data obtained through the distributed optical fiber sensors, the delicate identification of tension forces of all suspenders is realized based on the error interpolation of preliminary identification results. The results of the example bridge show that the method in this paper can effectively identify tension forces of all suspenders of the suspension bridge, and identification results are more accurate than the method using only the monitoring data of suspenders. [ABSTRACT FROM AUTHOR]

Combined with computational fluid dynamics analysis method and coupled vibration analysis method, the aerodynamic shielding effect of tower of long-span sea-crossing bridge on high-speed trains is analyzed from the aspects of flow field distribution, aerodynamic characteristics, and dynamic response. Based on k–omega shear stress transport turbulence model, a three-dimensional numerical simulation model of train-tower-girder is established. Considering the influence of bridge tower width, train speed, and crosswind speed, how the bridge tower changes the aerodynamic characteristics of the train by causing local sudden wind is discussed, and the average fluctuation amplitude ( Δ m ) and influence width (d) are defined to quantify the tower-induced aerodynamic shielding effect. Meanwhile, the further influence of shielding effect on train dynamic response is discussed by the comprehensive wind-train-track-bridge coupled analysis system. The results show that the bridge tower greatly changes the wind environment around the train with it passes through the bridge tower area, resulting in a significant and sudden change in the aerodynamic characteristics of the train. Larger tower width and smaller yaw angle (e.g., higher train speed and lower crosswind speed) will increase the influence width and sudden change amplitude of tower-induced shielding effect on trains' aerodynamic coefficients. The further influence of tower-induced sudden wind on car body acceleration and wheel load reduction ratio of high-speed train shows a wider width than that on train aerodynamic characteristics. [ABSTRACT FROM AUTHOR]

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The reasonable expression of live load and its accuracy are important to the safety and design rationality of highway bridge structures. In this study, the optimization issue of the traffic load model for the suspenders of large-scale suspension bridges is studied. Taking a 2300-m main span suspension bridge as an example, a method for suspender classification based on the geometric feature of the influence lines is proposed, and the extreme traffic load effect scenarios are analyzed and used as an optimization reference. Multi-objective optimization based on a genetic algorithm is used to explore the improvement of the traffic load model of the suspender. The traffic load model of the suspender is optimized with three objectives, i.e., accuracy, convenience, and improvement, and the optimization results regarding the load value and loading length are obtained. The value of the uniformly distributed load of the optimized model ranges from 6.4 kN/m to 8.9 kN/m, and the maximum value of the concentrated force could reach 1433 kN. By comparing the obtained optimized model with the current specification model and the extreme load effect scenario model, the improved applicability of the optimized model in the analysis of the load effect of the suspender can be verified. The optimized method and relevant conclusions can provide useful references for the improved design and operation management of similar bridge structures. [ABSTRACT FROM AUTHOR]