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Suspenders play a crucial role in transmitting loads from the bridge deck to the main cable in a suspension bridge. They are susceptible to fatigue due to repeated dynamic loads, particularly traffic loads. Traffic Load Models (TLMs), typically created using Monte–Carlo simulation and Weigh-In-Motion (WIM) data, are employed to evaluate this fatigue. However, these models often overlook practical vehicle trajectories and spatio-temporal distribution, which compromises the precision of fatigue assessments. In this study, we introduce a novel 2D Intelligent Driver Model (2D-IDM) that incorporates actual vehicle trajectories, with a particular focus on transverse vehicle movement. This enhancement aims to improve the fidelity of existing TLMs. To provide a clear, qualitative, and quantitative understanding of the effects of fatigue evaluation with or without actual trajectory characteristics, we have structured this paper as a comparative study. We compare our proposed model, denoted as TLM S-3, with two observation-based models (O-1 and O-2) and two simulation-based models (S-1 and S-2). We conducted an experimental case study on a long-span suspension bridge, where the actual traffic load trajectory was obtained using a WIM-Vision integrated system. To calculate fatigue damage considering both longitudinal and transverse directions, we established a multi-scale Finite Element Model (FEM) using solid element types to simulate the bridge girder. This model can generate the stress influence surface of the bridge and has been verified in both static and dynamic aspects. Our detailed comparative analysis demonstrates the consistency of the proposed 2D-IDM with the actual measured traffic load trajectories. This indicates that our approach can enhance the fidelity and precision of fatigue evaluations for bridge suspenders. [ABSTRACT FROM AUTHOR]

Crosswind is the primary external excitation source of the straddle monorail system. To ensure the ride quality of the monorail system under crosswind, based on multi-rigid body dynamics and finite element method, the coupling model of the monorail vehicle-beam is established, in which the track beam is considered as a flexible sub-model; the vehicle includes traveling/steering/stabilizing wheels and evaluate the characteristics of tire sideways and slip. Crosswind was obtained by the Davenport spectrum and loaded on the vehicle. Dynamic responses of the vehicle-beam system and the safe running/wind speed were studied. The study shows that, for a car, the wind loaded outside balances part of the centrifugal action and eliminates part of the overturning trend of the vehicle when it turns but makes the lateral ride comfort deteriorate in the straight line section. For the beam, the wind loads help reduce the track beam's transverse deformation when cars pass, and the vertical deformation is slightly improved. For operation, when the running speed is less than 50 km/h and the wind speed is less than 15 m/s, the monorail vehicle can operate safely. The straddle monorail wind-vehicle-beam model can conveniently update the design parameters for dynamic calculation and comfort evaluation. It can provide a specific theoretical basis or guiding principles for the safe operation of straddle monorail vehicles under wind loads. [ABSTRACT FROM AUTHOR]

The interface force condition on the cross section of parallel steel wire strands is an important basis for studying the longitudinal friction and slip behavior of wires. In this study, force-chain superposition was proposed to solve the transmission and distribution of transverse forces between parallel wires. The calculation rules for the basic parameters in the solution were determined, and a wire-drawing experiment was designed to verify their applicability. A two-dimensional discrete model corresponding to the cable cross section was established. According to the source and characteristics of the transverse load, the force system is decomposed into two directions to form two force chain analysis paths so that the model assumptions can be applied properly. A recursive algorithm was proposed to solve the two force chains, and symmetry conditions were applied at the coupling position to make the system self-consistent. The normal forces acting on the interface points were obtained by superimposing the results onto the two force chains and were verified against finite element analysis (FEA) results. A long-span cable-stayed bridge was considered as an example to investigate the interface force condition of its cables, based on which the approximate development length of the broken wires and the interface extrusion force of the multilayered beam model were established. The results indicate that the slight twisting of the parallel wire strands under the action of a large cable force provides 85% of the total interface forces, and the normal force is significantly concentrated in the central area of the cross section. The approximate development length of the central wire is only 25.9% of that of the outermost wire, and the minimum slip friction force between the layers accounts for only 21.2% of the maximum value for the multilayered beam model, confirming that the interface force condition has a significant impact on the longitudinal friction and slip behavior of cable wires. [ABSTRACT FROM AUTHOR]

Vortex-induced force (VIF) identification and modelling of a long-span bridge are often conducted in terms of aeroelastic sectional model tests in wind tunnels. However, there are uncertainties inherent in wind tunnel model tests so that vortex-induced vibration (VIV) still occurs in real long-span bridges designed according to wind tunnel test results. This paper presents a framework for VIF identification of a long-span bridge based on field-measured wind and acceleration data. The framework is composed of the four steps: (1) decompose field-measured acceleration response time histories using variational mode decomposition (VMD) method; (2) obtain velocity and displacement response time histories using frequency domain integration (FDI) method; (3) establish and update the finite element model and identify the generalized VIF time histories of the bridge; and (4) identify the parameters in the polynomial VIF models and decide the most suitable VIF model. The proposed framework is finally applied to a real suspension bridge with a recent VIV event. The results show that the proposed framework can accurately identify the generalized VIF acting on the bridge from the field-measured acceleration and wind data, and the derived most suitable VIF model can produce almost the same vortex-induced response (VIR) as the measured ones. [ABSTRACT FROM AUTHOR]

Aging, corrosive environments, and inadequate maintenance may result in performance deterioration of civil infrastructures, and finite element model updating is a commonly employed structural health monitoring procedure in civil engineering to reflect the current situation and to ensure the safety and serviceability of structures. Using the finite element model updating process to obtain the relationship between the structural responses and updating parameters, this paper proposes a method of using the wavelet neural network (WNN) as the surrogate model combined with the wind-driven optimization (WDO) algorithm to update the structural finite element model. The method was applied to finite element model updating of a continuous beam structure of three equal spans to verify its feasibility, the results show that the WNN can reflect the nonlinear relationship between structural responses and the parameters and has an outstanding simulation performance; the WDO has an excellent ability for optimization and can effectively improve the efficiency of model updating. Finally, the method was applied to update a real bridge model, and the results show that the finite element model update based on WDO and WNN is applicable to the updating of a multi-parameter bridge model, which has practical significance in engineering and high efficiency in finite element model updating. The differences between the updated values and measured values are all within the range of 5%, while the maximum difference was reduced from −10.9% to −3.6%. The proposed finite element model updating method is applicable and practical for multi-parameter bridge model updating and has the advantages of high updating efficiency, reliability, and practical significance. [ABSTRACT FROM AUTHOR]

In the wind tunnel test, the full-bridge aeroelastic model needs to simulate both the shape and dynamic characteristics of the real bridge, and modal parameters are key dynamic parameters. Therefore, it is essential to identify the modal parameters of the model accurately. To get accurate modal parameters of the long-span bridge model in the wind tunnel test, the applications of the Hilbert-Huang transform for modal parameter identification were analyzed in this paper. Then a band-pass filter is designed to filter the original signal so that the intrinsic mode function obtained by empirical mode decomposition can satisfy the single-component signal requirement and eliminate the mode mixing effect effectively. Meanwhile, the endpoint data extension method based on SVM (Support Vector Machine) was presented to restrain the end effects of empirical mode decomposition. Finally, taking the Oujiang Bridge as the engineering background, the improved algorithm was applied to modal parameter identification of the bridge under ambient excitation. The modal parameters such as modal frequency and damping ratio were obtained. The reliability of the improved method was verified by comparing the identified modal parameters with the results of the finite element method, and it turns out that the improved method can reduce the frequency identification error of vertical bend, lateral bend, and torsion to 1.01%, 4.07%, and 1.68%. The results indicated that the improved method based on the Hilbert-Huang transform can accurately identify the main modal parameters of the structure and can be better applied to identify the modal parameters of long-span bridge structures. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) has attracted significant attention over the past two decades due to its ability to provide real-time insight into the condition of structures. Despite the development of several SHM systems for long-span bridges, which play a crucial role in the assessment of these structures, studies focusing on short- or middle-span bridges remain scarce. This research paper presents an efficient and practical bridge monitoring and warning system established on a middle-span bridge, a key crossroad bridge located in Shenzhen. The monitoring system consists of sensors and measuring points that collect a substantial amount of data, enabling the close monitoring of various operational indicators to facilitate the early detection of threshold exceedances. Based on this system, the subtle condition of the bridge can be evaluated, and the operational condition of the bridge can be studied through the comparative analysis of the collected data. Over four months of monitoring, data including the strain and creep of the main beam, the strain and settlement of piers and the crack width of the bridge body are observed. Furthermore, the real-time operational status of the bridge is analyzed and evaluated through the combination of the collected data and the structural finite element model. [ABSTRACT FROM AUTHOR]

Aeroelastic instability and buffeting are two wind-induced phenomena for long-span bridges. In the traditional method, aeroelastic instability and buffeting are analyzed separately. If geometric and aerodynamic nonlinearity are required, aeroelastic instability is normally calculated based on finite-element methods, and buffeting is carried out based on linearization of structural and aerodynamic nonlinearity. Then, the standard frequency-domain methods are utilized on the eigenvalue decomposition. However, for ultralong-span bridges, aerostatic deformation, aeroelasticity, and buffeting are strongly coupled. During buffeting, the bridge deck pitching will change both structural stiffness and aerodynamic loads; therefore, the nonlinearity should be included in the long-span bridge buffeting analysis. This paper establishes a reduced-order modeling procedure to simulate the wind-induced buffeting vibration for long-span bridges including the nonlinear aeroelasticity and buffeting force. First, the mode-based vibration formulas are derived to consider both structural and aerodynamic nonlinearity through polynomial expansion. Next, the numerically simulated turbulence is imported into the vibration governing equation, and the structural response can be calculated using the time-domain integration method. [ABSTRACT FROM AUTHOR]

Structural displacement monitoring is one of the major tasks of structural health monitoring and it is a significant challenge for research and engineering practices relating to large-scale civil structures. While computer vision-based structural monitoring has gained traction, current practices largely focus on laboratory experiments, small-scale structures, or close-range applications. This paper demonstrates its applications on three landmark long-span suspension bridges in Turkey: the First Bosphorus Bridge, the Second Bosphorus Bridge, and the Osman Gazi Bridge, among the longest landmark bridges in the world, with main spans of 1074 m, 1090 m, and 1550 m, respectively. The presented studies achieved non-contact displacement monitoring from a distance of 600 m, 755 m, and 1350 m for the respective bridges. The presented concepts, analysis, and results provide an overview of long-span bridge monitoring using computer vision-based monitoring. The results are assessed with conventional monitoring approaches and finite element analysis based on observed traffic conditions. Both displacements and dynamic frequencies align well with these conventional techniques and finite element analyses. This study also highlights the challenges of computer vision-based structural monitoring of long-span bridges and presents considerations such as the encountered adverse environmental factors, target and algorithm selection, and potential directions of future studies. [ABSTRACT FROM AUTHOR]

In view of the insufficiency of bidirectional seismic control of long-span cable-stayed bridges as well as the limitations of existing schemes, a multi-direction damping system (MDDS) was proposed and investigated in this manuscript, which can provide seismic resistance bidirectionally. The new damping system owned a unique middle connecting structure, which overcomes the disadvantages that axial instability caused of excessive long rod and the demand of large installing space of traditional dampers. Both the performance stability and constitutive relationship of MDDS were verified by engineering tests, and the equivalent design method was then proposed and proved to be applicable. A detailed finite element numerical model of a super-long (main span over 800 m) column-type pylon cable-stayed bridge which equipped with MDDS in practice was established, the fragility curves of critical components were obtained by non-linear time history analysis, which exhibited the high efficiency of MDDS seismic performance in both transversal and longitudinal directions. Through extracting the median fragility value of 35 sections of the pylon under four damping cases, i.e. setting dampers transversely (TDS), longitudinally (LDS), bidirectionally (BDS), and MDDS, it can be concluded that MDDS performed far better on seismic resistance than LDS and TDS, and made the similar contribution with BDS. On account of half number of damper setting and the reduction in installing space demand, MDDS becomes the optimal choice in practical application for its economic efficiency and superiority. Furthermore, the optimal horizontal installing angle of MDDS was derived through six angle cases which was based on the system-level fragility curves comparison. [ABSTRACT FROM AUTHOR]

The nonlinear characteristics of bridge aerodynamics preclude a closed‐form solution of limit‐cycle oscillation (LCO) amplitude and frequency in the post‐flutter stage. To address this issue, a long short‐term memory (LSTM) network is utilized as the reduced‐order modeling of nonlinear aeroelastic forces on the bridge deck section, and it is repeatedly employed to generate force inputs at spanwise nodes of a three‐dimensional (3D) finite element model (FEM) of the long‐span bridge (using spatial beam elements). All LSTM networks are dynamically coupled through FEM, and the 3D nonlinear flutter response is accordingly obtained. To improve the simulation accuracy and reduce the required training data of the standard LSTM network, both general knowledge (motivated by the gating mechanism and mathematical models for information processing) and domain knowledge (resulting from the basic understanding of bridge aerodynamics) are leveraged to, respectively, customize the LSTM cell and network architecture. In addition, a fast‐training algorithm effectively combining the linear convergence of stochastic gradient descent and superlinear convergence of modified Broyden–Fletcher–Goldfarb–Shanno is developed to improve the training efficiency of the obtained knowledge‐enhanced LSTM network. To further advance the computational efficiency of the coupled LSTM‐FEM nonlinear flutter analysis, the convolution‐based numerical integration is adopted in the finite element modeling of long‐span bridge dynamics. A case study of a long‐span suspension bridge under strong winds demonstrates the proposed 3D nonlinear flutter analysis presents high simulation efficiency and accuracy and can be utilized to effectively obtain the nonlinear LCO characteristics in a wide range of post‐flutter wind speeds. [ABSTRACT FROM AUTHOR]

The dynamic performance and safety of both the train and the bridge are great concerns for long-span bridges subjected to crosswinds. For railway bridges, there is track laid on the bridge deck. The wind, train, track, and bridge subsystems form a complicated coupling system. This paper presents the dynamic responses of both the train and the bridge under crosswinds based on a wind-train-track-bridge coupled model, in which the vibration effect of the track structure involved in the coupling system is especially considered. For studying the dynamic responses of both the train and the bridge, models of railway vehicle dynamics are used for the train and a three-dimensional finite element model is used for the bridge. The train-track interaction and the track-bridge interaction are respectively considered. The wind action on the train and the bridge consists of a steady-state force and an unsteady-state force. Based on an in-situ test, the proposed numerical wind-train-track-bridge model involving the vibration effect of the track is validated. Then, the application of this proposed model on a long-span cable-stayed bridge on the Shanghai-Suzhou-Nantong HSR (high-speed railway) is presented as a case study. The typical running train and track currently serving in the Chinese railway transportation system are modeled in this study. Excitations from track irregularities are also taken into account. Finally, with the proposed wind-train-track-bridge coupled model, the dynamic performance of both the train and the bridge subjected to crosswinds are investigated. [ABSTRACT FROM AUTHOR]

The boundary conditions of the main girder are complicated for suspension bridges. And they have a significant impact on the static and dynamic response of the structure. This study proposes a model updating method based on influence lines considering boundary conditions. First, rotational and translational spring elements are used to simulate the boundary conditions of the main girder. Then, rotational spring stiffness is estimated by constructing a sensitive objective function based on the influence lines. Translational spring stiffness is estimated by constructing a sensitive objective function based on the temperature-induced displacements at both ends of the girder. To improve calculation efficiency, a Gaussian process model is used instead of the finite element model (FEM). The estimation of boundary conditions is expressed as an optimization whose main goal is to iteratively estimate the boundary conditions to minimize the objective functions. After the boundary conditions are determined, the influence lines-based model updating is carried out by using the adaptive metamodel global optimization method. To validate the proposed method, a long-span suspension bridge is taken as a case study. The results show that the boundary conditions of the main girder have been successfully estimated. The accuracy of the model updating is improved after the boundary conditions are considered. The updated FEM with accurate boundary conditions can be a benchmark model for bridge damage identification or condition assessment. [ABSTRACT FROM AUTHOR]

In order to obtain a realistic heavy traffic load diagram of long-span steel bridge, a three-dimensional finite element model of heavy radial tire 10. 00R20 was established. The grounding shape, grounding area and pressure distribution of simulated tire under different axle loads on steel bridge surface under three load positions were analyzed. The results showed that the simulated tire inflation deformation, the ground area and pressure acting on the road surface were close to the measured results, which verified the reliability of the composite tire model established by the finite element method. The ground area of heavy-duty tire acting on steel bridge deck was similar to that of road surface, but the average ground pressure was higher, and the non-uniformity of pressure distribution can’t be ignored. Finally, the diagram of double-wheel rectangular uniform traffic load on steel deck was proposed and the non-uniform coefficient was given to characterize the most unfavorable response. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) systems have been widely applied in long-span bridges and a large amount of SHM data is continually collected. The harsh environment of sensors installed at structures causes multiple types of anomalies such as outlier, minor, missing, trend, drift, and break in the SHM data, which seriously hinders the further analysis of SHM data. In order to achieve anomaly detection from a large amount of SHM data, this paper proposes a long-short term memory (LSTM) network-based anomaly detection method. Firstly, the proposed method reduces the workload for preparing training sets. Secondly, the purpose of real-time anomaly detection can be met. Thirdly, the problem of high alarm rate can be avoided by utilizing double thresholds. To validate the effectiveness of the proposed method, a case study of finite element model simulation is firstly introduced, which illustrates the detailed implementation process. Finally, acceleration data from the SHM system of a long-span suspension bridge located in Jiangyin, China is employed. The results show that the proposed method can detect anomaly with high accuracy and identify abnormal accidents such as a ship collision quickly. [ABSTRACT FROM AUTHOR]

This document is a retraction note for an article titled "Virtual reality research on vibration characteristics of long-span bridges with considering vehicle and wind loads based on neural networks and finite element method." The article has been retracted by the Editor-in-Chief and the publisher due to concerns regarding compromised editorial handling and peer review process, inappropriate references, and not being in scope of the journal or guest-edited issue. The publisher was unable to obtain a current contact email address for the author, Feng-hui Dong. Springer Nature, the publisher, remains neutral in terms of jurisdictional claims and institutional affiliations. [Extracted from the article]

To explore a cost-efficient bridge structure system and expand the options for long-span bridges in mountainous regions, we propose an innovative cable-stayed deck arch (CSDA) bridge with significant potential benefits. This paper discusses the conceptualization, structural design considerations, and implementable construction methods of this bridge-type. We trial designed two CSDA bridges with span arrangements of 268 + 350 + 268 m and 280 + 3 × 380 + 280 m to demonstrate the versatility of our proposal in different topographic situations and its ability to accommodate both single and multiple main spans. The finite element analysis confirms the mechanical properties and structural feasibility of the conceptual designs. A comprehensive comparison with other types of bridges under identical conditions reveals that this new hybrid bridge is not only lightweight in structure, excellent in performance, and elegant in form, but also cost savings and with minor environmental impact. The preliminary study indicates that the CSDA bridges are suitable for the construction demand of high-rise pier and long-span bridges in mountainous terrain, and also an economical option for the main span between 350 to 400 m. • An innovative cable-stayed deck arch bridge is proposed, taking into account the design considerations and construction methods. • The bridge type accommodates different hilly terrain conditions and can be arranged with either single or multiple main spans. • The cable-arch load ratio is derived analytically and has proved the rationality of the structure system. • The proposed bridge exhibits excellent structural performance and other advantages. [ABSTRACT FROM AUTHOR]

• A comprehensive analysis is conducted to reveal the mechanism of widespread failure of light poles on an elevated bridge. • Large eddy simulation is performed to model the wind filed and aerodynamic pressures on the light poles. • Nonlinear Finite Element modeling is conducted to analyze the structure responses of the light poles. • The bridge superstructure can significantly enhance the local wind field, leading to increased wind loads (mean & fluctuating) on light poles. • Under enhanced wind loads, significant plastic strains/stresses develop at the bottom of the light poles. Light poles are critical secondary structural components that support the functionality and safety of transportation systems. However, they are tall slender structures vulnerable to wind load. This research attempts to analyze the mechanism of the widespread failure (69 poles failed) of light poles on an elevated highway bridge exposed to Category 4 Hurricane Laura (2020). First, large eddy simulation is performed to simulate the wind field and the aerodynamic pressure on light poles considering and without considering the presence of the bridge superstructure, respectively. Simulation result shows that the presence of the bridge superstructure strengthens the local wind field and the aerodynamic pressures. A nonlinear finite element model is created to simulate the structural responses. Research results indicate that, when considering the presence of the bridge superstructure, stresses at the pole bottom exceed the yielding strength and significant inelastic strains are developed, which is the main cause of the widespread pole failure. The present study can be used to evaluate the current design standard for luminaire pole structures on elevated bridges. [ABSTRACT FROM AUTHOR]

The present article proposes a novel framework for analyzing the dynamic responses of suspended monorail vehicles running over curved bridges under crosswinds. In this model, the curved bridge model is established with the finite element method and vehicles are simulated as a multibody system. Subsequently, a wind model is proposed with the wind tunnel test, spectral representation method, and yaw wind-decomposition method, taking into account the effects of the angle between the wind and vehicle changes when vehicles pass through the curved bridge. Finally, a suspended monorail curved bridge is analyzed to demonstrate the effect of the wind model on the vibration of the system. The results show that wind direction has a great effect on the lateral dynamic response of curved bridges, the lateral force of guiding tire, and the vertical force of running tire. The influence of crosswind on the dynamic response of the vehicle decreases with the increase of running time of vehicle on curved bridges. [ABSTRACT FROM AUTHOR]

This paper investigates the track–bridge interactions of the Wufengshan Yangtze Bridge, the longest high-speed railway suspension bridge in China. A finite element model of the track and bridge is built using the commercial software ANSYS. The longitudinal additional forces of the track under a single effect and combination effects of temperature rising load, bending load, and braking load are calculated. The numerical results show that strong additional forces appear in the continuously welded rail of the Wufengshan Yangtze Bridge. Temperature effect is the dominant factor for the residual internal forces. The maximum tensile stress is 115.5 MPa and the extreme compressive stress reaches 329.9 MPa. Rail expansion joints are needed for this long-span suspension bridge. [ABSTRACT FROM AUTHOR]

• A novel modeling methodology of monorail train and large-scale bridge interaction is developed and validated with a field test. • Convergence, accuracy, and computational efficiency of the proposed methodology are all discussed. • Comparison with traditional model illustrates the advantages and significance of the proposed methodology. • Effects of the varying bridge profiles on the vehicle-bridge interaction are elaborately evaluated. High–efficiency solutions for extremely long bridge structures are a challenge in vehicle-bridge interaction modelling. In the present work, a novel modelling methodology for a monorail train and large-scale bridge interaction system is developed based on moving element technology. First, the governing equations for the monorail train subsystem are derived by adopting the Newton-Euler method, and an extremely long bridge is modelled based on an improved component mode synthesis method in which a bridge unit with finite length is updated and moved as the train moves forward. The train and bridge subsystems are coupled together by a nonlinear wheel–track interaction model. Subsequently, the convergence of the proposed method is discussed in detail, and reasonable values of several crucial model parameters are determined. On this basis, the simulation results obtained by the proposed methodology are compared with those of the finite element method (FEM) and field test data, validating the reliability of the proposed methodology and revealing its remarkable advantages. Finally, by applying the proposed methodology, the dynamic performance of the monorail train-bridge system is evaluated under different operating conditions. Results indicate that the proposed methodology can achieve good calculation accuracy for the vehicle-bridge dynamic responses; additionally, its computational efficiency is much higher than that of the FEM. The variation of the bridge section profile has a notable effect on the dynamic performance of the monorail vehicle-bridge system, which becomes more significant with increasing train speed. [ABSTRACT FROM AUTHOR]

As flexible structures, suspension bridges usually undergo significant deformation under live load when carrying rail traffic, jeopardizing the safety of passing trains. In engineering practice, suspension bridges with short extended spans have been applied to reduce the beam-end rotation angle under live load. However, the extended span layout is still determined empirically, and optimizing the span layout of such bridges to reduce maximum deformation under live load requires further investigation. This study proposes an analytical method for solving the maximum deformation responses of suspension bridges with extended spans under live load based on deflection theory and the extreme value analysis method. The proposed method can accurately solve the deformation responses of suspension bridges with extended spans caused by live load. It also allows one to analyze the most unfavorable live load distribution and the maximum deformation under live load, avoiding the redundant search process of the finite element method. Furthermore, the proposed method is applied to analyze the influence of the extended span layout on the maximum deformation responses under live load. The results show that adequately increasing the length of the first extended span and decreasing the length of the second extended span is beneficial to reduce the maximum beam-end rotation angle and the maximum curvature of the main beam. • The method can effectively solve the deformation responses in extended-spans suspension bridges under specific live load. • The method can determine the most unfavorable live load distribution and the maximum deformation responses under live load. • An in-depth analysis is conducted on how the extended span layout influences maximum deformation responses under live loads. • The method merges the deflection theory with extreme value analysis method, laying the groundwork for structural design. [ABSTRACT FROM AUTHOR]

Accurate vehicle-induced deflection prediction is critical to bridge structural management and maintenance. However, most existing studies use finite element models and weigh-in-motion (WIM) system to predict the deflection of bridges, the cost of building finite element models is expensive. An accurate and low-cost vehicle-induced deflection prediction framework is developed in this study. In this framework, the calculation method of the spatio-temporal distribution matrix of the vehicle loads is proposed. A fusion attention mechanism bidirectional long short-term memory (ATT-BiLSTM) model is used to predict vehicle-induced deflection. Taking a suspension bridge in China as an example, the accuracy of short- and long-term vehicle-induced deflection prediction is tested, and different deep learning models are used for comparison. The results show that the proposed framework can predict short-term vehicle-induced deflection with a mean absolute error (MAE) of less than 2 mm, which can also accurately predict the extrema of vehicle-induced deflection within a certain time window. The proposed framework is independent of finite element models and lowers the cost of bridge deflection prediction. • An accurate and low-cost vehicle-induced deflection prediction framework is developed in this study. • The calculation method of the spatio-temporal distribution matrix of the vehicle loads is proposed. By using a fusion attention mechanism bidirectional long short-term memory (ATT-BiLSTM) model, the vehicle-induced deflection of the bridge is predicted. • Taking a suspension bridge in China as an example, the accuracy of short- and long-term vehicle-induced deflection prediction is investigated. [ABSTRACT FROM AUTHOR]

Framework of the proposed hierarchical Bayesian FEMU method. [Display omitted] • Effects of operational loads are considered in the hierarchical Bayesian FEMU. • Temperature-stiffness relationship and vehicle load estimation are established. • A two-step MCMC sampling and RSM are proposed to accelerate updating process. • Validated on a long-span arch bridge using two-year monitoring data. • An indicator is defined to assess structural states under operational loads. Excluding the variations of structural dynamic characteristics due to operational loads in finite element model updating (FEMU) is essential for response prediction and structural condition assessment. However, existing FEMU techniques for long-span bridges usually directly use modal parameters in the objective function without considering the effects of various operational loads, resulting in high variations of the updated model. To this end, this paper proposes a hierarchical Bayesian FEMU framework considering the effects of operational loads, including temperature and traffic loads. A linear temperature-elastic modulus relationship and a vehicle load estimation method based on weigh-in-motion (WIM) data are established to quantitatively consider the operational loads' effects on structural dynamic properties. In addition, the identified natural frequencies and measured expansion joint displacements are incorporated into the objective function to update structural static and dynamic properties simultaneously. A two-step Markov Chain Monte Carlo (MCMC) sampling method and a response surface surrogate model are proposed to accelerate the updating process. The proposed method is validated on a long-span arch bridge using two-year monitoring data. The updated model is then used to predict the structural static and dynamic responses by taking into account of operational loads, parameter uncertainties, and modelling errors, and the measured responses generally fall within the predicted 95% confidence interval. Finally, a structural state indicator, which has considered the effects of operational loads on structural properties, is defined to assess the structural condition and successfully detect the pavement replacement process on the bridge. [ABSTRACT FROM AUTHOR]

This work aims to develop a reasonable pre-camber design method for long-span cable-stayed bridges by investigating the high-speed train-bridge interaction under complex environmental loads, including ambient temperature, concrete creep, and concrete shrinkage (CCCS). First, an integrated dynamic model of the train-track-cable stayed bridge system (TTCSBS) is established using multibody dynamics and finite element theory and validated through field test. Then, the temperature change features at several key positions on the long-span bridge are investigated using long-term monitoring data. Temperature-induced bridge deformation is calculated by applying the established bridge finite element model (FEM) and compared with test results. CCCS-induced bridge deformation is determined through numerical calculations that consider the bridge's structural and material properties. On this basis, the effects of bridge deformation caused by environmental loads on vehicle-bridge dynamic interaction are investigated in detail, and a new bridge pre-camber design method is proposed to counteract the effects of both environmental and train dynamic loads. Results indicate that the proposed model's simulations align well with field test data. The long-span bridge deformation induced by the environmental loads intensifies the dynamic responses of a running vehicle, particularly the wheel-rail vertical force and car-body vertical vibration. However, it has slight influence on train-induced bridge vibration. The proposed pre-camber design method for long-span bridges, which accounts for long-term environmental load action, effectively ensures good vehicle service performance. The research results could provide useful guidance for the design of long-span bridge systems. • An integrated dynamic model of the train-track-cable stayed bridge system is established and validated by the field test. • An effective methodology for reconstructing long-span bridge temperature is developed and validated by long-term monitoring data. • Effects of the ambient temperature load and CCCS load on the vehicle-long span bridge interaction are revealed. • A new pre-camber design method is proposed considering both dynamic train loads and long-term environmental effects. [ABSTRACT FROM AUTHOR]

Finite element model updating (FEMU) is a frequent method for minimizing the differences between actual and predicted bridge structural behavior. However, static model updating for long-span bridges usually requires load tests to obtain the response under known static loads, which is costly due to long traffic interruptions. To offset this disadvantage, a static FEMU method based on long-term monitoring data is proposed to update the model in real-time by taking stochastic traffic loads with certain statistical characteristics as known static loads. First, the theoretical relationship between stochastic traffic flow statistical characteristics, static response statistical characteristics, and structural stiffness parameters is established. An objective function based on the probability characteristics of the long-term vehicle-induced response is constructed. Then, the FEMU process based on monitoring data is introduced, including the acquisition of the finite element model vehicle-induced response, the extraction of the actual vehicle-induced response based on the monitoring data, the selection of model updating parameters, and the application of the global-local parameter updating optimization method. Finally, the effectiveness of the proposed method is verified by applying numerical examples and real bridge examples to a long-span suspension bridge. It can be concluded that the proposed method can achieve FEMU based on long-term monitoring data, avoiding the inconvenience and large cost caused by load tests. The accuracy and efficiency of the model updating can meet the engineering requirements well through comparison with the result of the traditional load test method. • This paper presents a static finite element model updating method based on the statistical characteristics of long-term monitoring data during normal operation, avoiding the inconvenience and large cost caused by the previous model updating method based on the load test. • The proposed method takes stochastic traffic load with known probability characteristics as known static load, and can realize model updating well by reducing the error of the actual response probability characteristics and finite element model prediction response probability characteristics. • The probabilistic characteristics of long-term vehicle-induced static response are related to structural stiffness parameters and probabilistic characteristics of stochastic traffic flow. When the probabilistic characteristics of stochastic traffic flow are the same, the static response probabilistic characteristics are related to only the structural stiffness parameters. [ABSTRACT FROM AUTHOR]

The buffeting responses of sea-crossing bridges pose significant challenges due to the diverse terrain in the bridge region and intricate coupling effects between the environmental variables and structures. A novel Wind-Wave-Current-Bridge (WWCB) framework is proposed to assess the buffeting responses of coastal long-span bridges under coupled wind, wave, and current loads. By employing measured wind and wave data, the optimized C-vine copula and Ekman drift current theory are utilized to establish correlations among four environmental variables, namely wind speed, wave height, wave period, and current velocity. The nonlinear wave loads acting on the pile-cap foundations are computed using the potential flow theory and boundary element method (BEM). The interactions among wind, wave, current, and bridge involve both aerodynamic and geometric nonlinearity. The dynamic responses of the full bridge finite element model are iteratively solved until structural convergence is achieved using the Newmark-β method. Subsequently, the buffeting responses and the vibration mechanism of bridges are discussed in both the time and frequency domains. The results indicate that the nonlinear and correlation effects of wind, waves, and currents significantly affect the buffeting responses of the example bridge. Furthermore, the influence mechanism of wind and waves on the sea-crossing bridge is also discussed. • The C-vine copula and Ekman drift current theory are employed to establish the correlations among wind, waves and currents. • The nonlinear wave loads are computed using the 3D wave diffraction theory and boundary element method. • The aerodynamic and geometric nonlinearity are included in the interactions of wind, waves, currents and bridge. • Nonlinear buffeting analysis of a sea-crossing cable-stayed bridge under the coupled wind, wave and current loads. [ABSTRACT FROM AUTHOR]

• Correlation of vibration data is found to be mode-related and traffic flow independent for linear time invariant bridges. • Vehicle load can be modeled as a uniformly modulated non-stationary process (UMNSP) under the invariant weight distribution. • RoMS is employed as correlation-based damage indicator under UMNSP assumption and proven effective in real-world application. Structural damage identification and condition assessment is the most direct goal in structural health monitoring (SHM). Vibration-based methods (VBM) using the global dynamic responses (displacement or acceleration), including modal-based methods and statistical methods, have been comprehensively investigated in the last few decades in the SHM community. These two types of methods face challenges in practice due to the indicators being sensitive to the environment and insensitive to local damage. It is curious whether new features of data in high-dimension space can be found and the new features can be used as damage indicators. This study proposes a method based on the correlation of the global dynamic responses in high dimensional space for damage identification. It is proved that the ratio of mean square (RoMS) between any two responses (two-dimensional space) is dependent on the modal parameters of the structure only and changes only with the damage of the structures. Therefore, it can be used as a damage indicator. The proposed method is validated through a finite element numerical analysis on a cable-stayed bridge and the monitored acceleration of a real-world suspension bridge, and is further compared with the modal analysis methods. The results show that the proposed method can accurately identify the damage and is sensitive to local damage compared to modal parameters. [ABSTRACT FROM AUTHOR]

Long-span cable-stayed bridges are subjected to the risk of collision from passing ships. Conducting experimental study on the collision of bridges and vessels is difficult due to high cost and limited space. In this paper, the behavior of a 1 018-m long-span cable-stayed bridge subjected to ship collisions is numerically studied. Finite element models of the entire bridge and ships are established. Four different dead weight tonnages (DWT), namely, 2 700, 12 000, 30 000, and 75 000 t, with impact velocities of 1 m/s to 6 m/s are investigated. The complete collision process under different loading scenarios is simulated, from which the collision force, bridge responses and local damage are obtained. The calculated collision force is significantly affected by the impact velocity and DWT, and exhibits a linear relationship with the impact velocity. Comparison with design codes shows that different codes vary significantly in estimating the collision force and Eurocode provides most accurate results. The effect of the material model on the collision force is also studied. This numerical study provides a reference for the ship collision design of long-span cable-stayed bridges. [ABSTRACT FROM AUTHOR]

In the wind tunnel test of a long-span bridge model, to ensure that the dynamic characteristics of the model can satisfy the test design requirements, it is particularly important to accurately identify the modal parameters of the model. First, the stochastic subspace identification algorithm was used to analyze the modal parameters of the model in the wind tunnel test; then, Grubbs criterion was introduced to effectively eliminate outliers in the damping ratio matrix. Stochastic subspace identification algorithm with Grubbs criterion improved the accuracy of the modal parameter identification and the ability to determine system matrix order and prevented the modal omissions caused by determining the stable condition of the damping ratio in the stability diagram. Finally, Oujiang Bridge was used as an example to verify the stochastic subspace identification algorithm with Grubbs criterion and compare with the results of the finite element method. The example shows that the improved method can be effectively applied to the modal parameter identification of bridges. [ABSTRACT FROM AUTHOR]

• The temperature distribution of a cable-stayed bridge is obtained by integrating heat-transfer analysis and monitoring data. • The heat-transfer analysis and structural analysis share a unified FE model, resulting in an efficient and accurate analysis. • The numerical results have a good agreement with the field monitoring data. Varying temperature is a major load of long-span cable-stayed bridges. The temperature effect on the structural behavior may mask the influences of other loads. Conventional studies on the thermal behavior of bridges are limited to regression analyses based on measurement or numerical studies of 2D or local 3D models. This study investigated the global 3D temperature behaviors of a three-tower cable-stayed bridge through the integration of field monitoring and unified numerical simulation. A 3D refined model of the bridge with thermal elements was built, and the thermal boundary conditions were determined from environmental field monitoring data for the global 3D heat-transfer analysis. The calculated temperatures agreed well with the field monitoring counterparts. The temperatures were then input into the same global finite element model with mechanical elements for structural analysis. The temperature-induced structural responses, including the structural displacements and forces, agreed well with the measurement counterparts. The temperature-induced structural response variation pattern and sensitivity were summarized and quantified. This unified numerical simulation enables an efficient and accurate analysis of the global 3D thermal behavior of bridges, as compared with the conventional 2D or local 3D simulation. [ABSTRACT FROM AUTHOR]

• An innovative precast concrete-encased concrete-filled steel tube column-to-column connection is proposed. • Five connection tests were conducted to investigate compression behaviour of the precast connection. • The proposed precast connection exhibited comparable compression resistance to continuous CECFST columns. • Comprehensive finite element modelling was performed to identify key variables that affect compression resistance of the connection. • A simplified analytical model was proposed to evaluate compression resistance of the precast connection. Concrete-encased concrete-filled steel tube (CECFST) is a new type of composite member featuring superior structural performance and high construction productivity. This form of structural members has been increasingly used as columns in high-rise buildings and as piers in long-span bridges. Recently, to promote the application of CECFST columns in countries short of labour, e.g., Singapore, North America and Europe, an advanced precast CECFST column-to-column connection with rapid construction and excellent tensile performance was developed by the authors. However, behaviour of the developed precast connection subjected to axial and eccentric compression has not been studied so far. In this paper, an experimental programme including five connection tests was conducted to investigate compression performance of the developed precast connection. The test results showed that compression resistance of the precast connection could achieve that of CECFST columns, indicating that it is feasible to connect CECFST columns by the newly proposed precast connection to enhance construction productivity. Furthermore, an extensive finite element (FE) modelling programme was carried out to generate more numerical data by conducting parametric studies. The experimental and numerical results showed that connection configuration plays a pivotal role in load-carrying capacity of the precast connection. Based on EN 1994-1-1, one simplified strength prediction model was proposed for the proposed precast CECFST column-to-column connection. Compared with experimental and numerical results, the predicted strength was conservative and consistent, indicating that the proposed approach can be used in the design of the precast connection. [ABSTRACT FROM AUTHOR]

Introduction: During masticatory loading, dental bridges are subjected to various forces that might generate deflections in the bridge framework. For this reason, designing long-span bridges require great care about flexions that happen during the function. This can be compensated could be compensated by increasing occluso-gingival height, using rigid materials, and enhancing resistance to deflection by modifying the abutments' preparations. The current study hypothesied that the stress, deflection, strain, and deformation of the fixed partial dentures are guided by the three-dimensional configurations of the pontic areas, and all other parameters could be mutually changed with different influence on the overall outcome. Aim: The study aimed to evaluate the difference in the amount of stress, deflection, strain, and deformation on using different materials and configurations in the pontic and connector area of the dental bridge using the 3D Finite Element Analysis (FEA). Materials and Methods: An invitro virtual biomechanical analysis using 3D FEA method was conducted. 3D models were created from the Cone Beam Computed Tomography (CBCT) of a dentulous patient and two materials were selected for this study, Zirconia and enhanced graphene-based polymer. The study models were assembled into four groups as the following: Group I: 3-unit Zirconia fixed-fixed bridge; Group II: 3-unit Graphene fixed-fixed bridge; Group III: 4-unit Zirconia fixedfixed bridge; Group IV: 4-unit Graphene fixed-fixed bridge. Using FEA software a 600 N load was applied and the resultant normal stress, deflection, maximum equivalent strain and total deformation data were monitored, collected and interpreted. Results: The findings of the current study showed higher values of normal stress, deflection, equivalent elastic strain, and total deformation in Graphene-based bridges (group II and IV) than the Zirconia-based bridges (group I and III). It should also be mentioned that normal stress, deflection, equivalent elastic strain, and total deformation showed higher values in the threeunit bridge (group I and II) than their corresponding 4-unit bridge groups (group III and IV). Conclusion: This biomechanical analysis confirmed that the stress concentration and deflection of the fixed bridge are influenced by material characteristics. However, configuration of the pontic area could influence the studied mechanical parameters regardless the length of the dental bridge. [ABSTRACT FROM AUTHOR]

• Fatigue loading tests on notched steel wires are performed. • A three-dimensional solid model of notched steel wire is established. • A critical region-based fatigue life prediction method is proposed. • Theoretical predictions agree well with the experimental observations. Huge uncertainty exists in the corrosion process, and the dimensions of corrosion pits are quite random in practical engineering. Corrosion pit-induced stress concentration accelerates the initiation of fatigue cracks, ultimately reducing the fatigue life of bridge sling. This paper proposes a critical region method to predict the fatigue life of notched steel wires. This method considers the critical distance and the average stress amplitude of notched specimen. Fatigue loading tests on various notched steel wires are performed to simulate the effects of corrosion pit morphologies on the performance of steel wires. The relationships between notch dimensions and the fatigue lives of specimens are discussed. Following that, a fine-mesh three-dimensional solid model of notched steel wire is established by finite element method. The stress concentration coefficients and the stress distribution near the notch root are investigated, and the critical distance is also determined according to the local stress gradient of notched steel wire. The critical region-based fatigue life prediction method is validated using experimental fatigue life results of notched steel wires. A good agreement is observed between the theoretical predictions and experimental observations. [ABSTRACT FROM AUTHOR]

Engineered Cementitious Composites (ECC) with high ductility has been recognised to be a high performance and durable alternative to the construction material in civil engineering field. In this paper, ECC material was proposed to be applied on the long-span steel bridge deck overlay. Herein we studied the feasibility of this application via integration of ECC's material performances and stress response of structure using finite element analysis. The results show that ECC material could overcome the brittleness of normal concrete, featuring high tensile strain/deformability capacity under tension/flexural load, as well as higher flexural strength and fatigue life, compared with normal asphalt/concrete materials. Furthermore, the self-healing capacity in ECC helps the crack seal itself, as a result, recovers its water permeability coefficient and resistance to chloride ion penetration to nearly the same level as undamaged ones. By integrating ECC's flexural fatigue behaviour and finite element analysis, it can be concluded that ECC is feasible to be a candidate material for the steel bridge overlay. The application of ECC is expected to greatly extend the service life of steel bridge overlay meanwhile be with thinner thickness compared with normal bridge deck overlay structure, resulting in a more sustainable overlay. [ABSTRACT FROM AUTHOR]

Ship collision is rare, yet it leads to serious consequences once it occurs, in particular for long-span bridges. This study investigates dynamic responses of a long-span, rail-cum-road cable-stayed bridge under ship collision through finite element analysis. Three ship tonnages were investigated, which are 3000, 5000, and 8000 t, respectively. The displacement, velocity, and acceleration of the bridge under ship collision are analyzed. The collision process is simulated in two explicit steps to improve the computational efficiency. First, the collision force is determined through a collision simulation of the ship to a rigid body that simulates the massive bridge pier. The collision force is then applied to the bridge to analyze the dynamic responses of the bridge. The simulation results of the collision force are compared with four different design codes. Analysis results from different codes show significant discrepancies, demonstrating lack of reliability of the formula recommended by the codes. The results indicate that the maximum displacement and acceleration occur at the top of the bridge pylon. The bridge's responses under ship collision decrease as the collision angle increases from 0° to 20°. [ABSTRACT FROM AUTHOR]

• The numerical analysis method of tornado-induced vibration of the stay cable is developed. • The dynamic performance of the stay cable in the downburst and the tornado are compared. • The frequency characteristics of the cable vibration induced by small-scale extreme winds are investigated. The wind-induced vibration and its mitigation of ultra-long stay cables are critical to the safety of long-span bridges. Remarkable progress has been made in understanding and mitigating the vibration of stay cables in normal wind, while the cable response in small-scale extreme winds such as downbursts and tornadoes remains unclear. This study compares the dynamic performance of an ultra-long stay cable in a downburst and a tornado. Firstly, a downburst and its induced vibration of an ultra-long stay cable of a kilometer-level cable-stayed bridge are introduced based on the data recorded by the structural health monitoring system (SHMS). A tornado with the same intensity as the measured downburst is then simulated analytically at the bridge site. The tornado-induced vibration of the stay cable is obtained based on the finite element method. The dynamic performance of the cable under the downburst and the tornado, including the acceleration characteristics, displacement characteristics, and frequency characteristics, are investigated and compared. The result shows that large-amplitude cable vibration is found during the two extreme winds and the out-of-plane acceleration is larger than the in-plane acceleration. For the same wind intensity in this study, the acceleration of the cable caused by the downburst is much larger than that caused by the tornado. During the tornado, the in-plane displacement of the cable is much larger than the out-of-plane displacement, which is the opposite during the downburst. The frequency range of the cable vibration induced by the small-scale extreme winds is similar and it is about 2.5 ∼ 6 Hz, and the mode order is from the 10th to the 25th. [ABSTRACT FROM AUTHOR]

Long-span suspension bridges are subjected to wind-induced vibrations due to their large flexibility and low damping. Damped outriggers have been proposed recently to supplement damping and suppress multimode vibrations of main girders of long-span bridges, e.g., vortex-induced vibrations. However, when installed at multiple positions including tower-girder junction points and girder ends to further improve multimode damping effect, damping effects of the damped outriggers are interdependent. Additionally, the frequency curves of adjacent modes with respect to varying parameters of the damping devices could approach and intersect with each other, making it difficult to track mode orders and modal damping variations in design optimization. This study therefore proposes an optimization method to design damped outrigger parameters for maximizing multimode damping of the bridge. First, the bridge with damped outriggers is modeled generally using finite element method for dynamic analysis. Subsequently, two critical issues in the design, i.e., the mode tracking and multi-objective optimization, are respectively addressed by using the modal assurance criterion and the genetic algorithm. The proposed method is then applied to the Xihoumen Bridge with a main span of 1650 m. The results show that through the proposed optimization, 6 out of 7 modes vulnerable to vortex-induced vibrations can reach a damping ratio over 1.0%, which cannot be achieved by using damped outriggers of a uniform size. Furthermore, the required damper coefficients are decreased by 49.4%. The flexibility of the outriggers has been considered in the design. The developed method is promising in the design of other types bridge damping devices, e.g., multiple tuned mass dampers. • A method proposed for optimizing multiple damped outriggers for a suspension bridge. • Mode tracking in optimization addressed using the Modal Assurance Criterion. • Damper size reduced by 50% through optimization in the case study of a suspension bridge. • Balanced damping improvement for multiple modes achieved through the optimization. [ABSTRACT FROM AUTHOR]

Highlights • Two scaled field tests in reticulated dome under blast loading were conducted. • The deformation modes of specimens were identified and discussed. • Strain rate sensitivity of material were considered in numerical evaluation. • The deformation history and energy absorption of the structure were also discussed. Abstract Long-span spatial structures are commonly used as landmarks in modern cities and may be potential targets of terrorist attacks; thus, it is important to study the dynamic behaviour of such structures under blast actions. In this study, experiments were conducted on two reduced-scale models which were designed and manufactured. The aims of the experiments were to (i) assess the accuracy of a numerical approach for simulating the structural dynamic responses based on the finite element software, "ANSYS/LS-DYNA", and (ii) survey the various failure modes of single-layer reticulated domes under an external blast loading. The numerical results showed a good agreement with the experiments when the empirical load model was used to study the elastic and inelastic deformation of a multi-curved shell. Additionally, the deformation, development of plasticity, and energy absorbing behaviour of each component were examined, and the following four major response patterns were identified: elastic vibration, slight damage, local failure, and global collapse. [ABSTRACT FROM AUTHOR]

Many very large bridges with high piers and long spans are under rapid construction in mountainous regions especially in Western China. However, the current seismic design methods in China are based on a code which only applies to bridges with span up to 150 m. To evaluate the risk of the inapplicable design method and the influence of spatially variable ground motions (SVGM) on the seismic response of very large bridges, a high-pier, long-span, continuous RC frame bridge is numerically studied. This study considers whether multiple support excitation can be simplified into specific uniform excitation cases while guaranteeing the conservative seismic demands for this bridge. Non-stationary SVGM on both bedrock and the surface of multiple soil layers are simulated including wave passage effects, coherency effects and site amplification effects. The nonlinear dynamic finite element model of the bridge is analysed for two groups of earthquake motions, namely group 1 - bedrock and group 2 - ground surface excitations. Each group contains three different excitations, i.e. i) multiple support excitation ii) the largest and iii) the smallest accelerations from the SVGM. The relative displacements, internal force responses and ultimate damage modes are obtained and compared. For this bridge the uniform ground motion input with the largest accelerations provides conservative seismic demands for most structural components when the site amplification effect is not considered (group 1). However, for the ground surface motions, where site amplification needs to be taken into account (group 2), in several cases the uniform ground motion with the largest accelerations results in lower response than that predicted when considering SVGM. The present results indicate that only when the bridges are located on ideal simple topography where site effects have little influence, the uniform excitation with the largest accelerations taken from the SVGM may be an alternative input for seismic analysis. However, for bridges on complex terrain, where site effects can significantly amplify the ground motions at the bedrock, SVGM need to be applied as input for the seismic analysis. As spatial variability of input motion is not a mandatory requirement in the Chinese bridges design code, these results suggest that the existing design code for very large bridges should be modified accordingly. [ABSTRACT FROM AUTHOR]

This study presents the general features of the structural health monitoring (SHM) system of the long-span cable-supported bridges in Turkey, namely the First Bosphorus Bridge, the Second Bosphorus Bridge (Fatih Sultan Mehmet Bridge), the newly constructed the Third Bosphorus Bridge (Yavuz Sultan Selim) and the Osman Gazi Bridge (Izmit Bay Bridge). Due to the critical function of the bridges in the transportation networks of Istanbul, structural health under extreme and operational load cases without interruption of their operation is essential. The SHM systems are already available and in use for the First and Second Bosphorus Bridges; however, the Yavuz Sultan Selim and the Osman Gazi Bridges, only have the preliminary SHM systems established. General preferences of the current and planned SHM systems of the bridges are given based on the monitoring objectives and requirements. Data collected from the SHM systems are also exhibited as an illustration for structural modal identification of the First Bosphorus Bridge. Based on the experiences from the current SHM systems, future works and planning are recommended to effectively design new SHM system and to efficiently update the current ones. [ABSTRACT FROM AUTHOR]

This paper investigates congested traffic loading on long-span bridges through the use of traffic microsimulation. Six months of Weigh-In-Motion free-flow traffic data (including cars) are used as input for the microsimulation of congested traffic. Key parameters that affect traffic loading are identified in the output of the microsimulation, and these parameters form the basis for a more computationally efficient ‘pseudo-microsimulation of congested traffic’ (PMCT) model. This PMCT model is shown to replicate the traffic loading from full microsimulation accurately and allows long-run simulations, equivalent to 1000 years of congested traffic, to be performed with an acceptably short duration. This reduces the significant uncertainties associated with extrapolating short-run simulation results to long return periods. The 1000-year simulated results from the PMCT are compared with the extrapolated results from full microsimulation, and with the traffic loading from some design codes, for different bridge lengths. Both types of microsimulation are also applied to calculate maximum lifetime loading for two typical long-span bridges – one cable-stayed and one suspension bridge – using influence lines determined from finite-element models. [ABSTRACT FROM AUTHOR]

Determining ground motions is essential for seismic analysis of long-span bridges located at complex sites. However, there is a lack of earthquake records for local site conditions. Thus, this study focused on the effect of local site conditions on the stochastic response of long-span high-pier rigid frame bridges crossing a valley with an overlying water layer. For this purpose, a hybrid boundary element and finite element method (BEM-FEM) is proposed to investigate the stochastic seismic response of long-span bridges at such a complex site. First, a simulation method for 3-D spatially varying ground motions ascribed to wave scattering from irregular surface topography, sedimentary soil, and water layers was established based on the BEM combined with the spectral representation method. Furthermore, the statistical properties of the bridge response were explored based on the FEM and Monte Carlo simulations. The advantage of this work is that it reveals how the seismic wave propagation in this particular valley topography and water layer affects the stochastic response of the bridge considered. Moreover, the results indicate that seismic wave scattering leads to a significant energy redistribution of the input waves in the tri-directions related to the surface location, and a decrease in the coherency loss functions at all frequencies. Owing to this change, the peak ground accelerations (PGAs), bridge response means, and response variability are doubled. The beneficial effect of the water layer on the PGAs is weakened, while the adverse effect of hydrodynamic pressure dominates. The parameter analysis results demonstrate that a 10-m-deep sedimentary soil layer produces a 47% increase in the internal force of the pier bottom. The solid-liquid dynamic coupling effect should be accurately quantified for bridges located at saturated sites. Considering the local site conditions, the coefficient of variation (COV) of the response of the pier top exceeded 0.3, indicating strong randomness. • Lack of earthquake records of valley site with irregular topography, sedimentary soil, and water layer. • Seismic scattering effect by valleys produces 3-D spatially varying ground motions. • Dynamic response of long-span bridges evidently varies owing to local site condition. • Valley effect leads to more significant randomness of bridge response. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of wind non-uniform characteristics in mountainous terrain on the dynamic analysis of a vehicle-bridge (VB) system, a typical bridge site for a terrain model was established in a wind tunnel. Six typical flow directions, such as parallel to the river direction and perpendicular to bridge axis and ridge, were adopted to study the mean wind speed of experimental monitoring points at the bridge deck. Owing to the local ridge at the bridge site, the distribution of wind speed along the bridge deck shows obvious non-uniform characteristics. Seven monitoring points were set on the bridge deck, and the linear interpolation method was adopted to obtain the time histories of the wind speed at every point. A scaled wind tunnel model was also applied to conduct the three aerodynamic coefficients of the vehicle and bridge. Based on the experimental wind characteristics of mountainous terrain, the numerical framework of the wind-vehicle-bridge (WVB) system was established considering the effect of non-uniform wind, where a railway cable-stayed bridge was simulated using the finite element model, and a multi-body dynamic model of the vehicle was used. The influence of fluctuating wind excitation on the WVB system was discussed, and it played an essential role in vehicle vibration. • The non-uniform characteristics of wind field in the mountain area are investigated in the wind tunnel. • Based on the conducted results, the safety of vehicle moving through the bridge is studied. • With or without fluctuating wind excitation, the dynamic responses of vehicle-bridge system are also computed. [ABSTRACT FROM AUTHOR]

This paper presents a framework based on the endurance time (ET) method to evaluate bridge seismic fragility and resilience in the life-cycle context by considering corrosion effects. The ET method has been widely used for seismic analysis of structures in recent years due to its high precision and low computational effort. However, the traditional ET method does not provide any information about the dispersion of seismic responses and can only predict the median of responses. Therefore, a framework for quantifying the record-to-record (RTR) uncertainty through the ET method is proposed. Firstly, a three-dimensional finite element model of a three span bridge in OpenSees was constructed and subjected to the ET intensifying functions. The proposed methodology was then applied to predict the bridge's probabilistic seismic response distribution. The results were compared with those obtained using incremental dynamic analysis (IDA) as a benchmark method. It was demonstrated that the proposed methodology can significantly reduce computational costs while maintaining acceptable seismic response accuracy (both median and dispersion). Next, the life-cycle fragility and resilience of the bridge were evaluated considering the chloride-induced corrosion effects using the proposed framework, which may be challenging to address using the IDA method due to its time-consuming nature. The results show that the seismic resilience decreases, whereas the uncertainty increases with the increasing seismic intensity and age of the bridge. Therefore, it is of great importance to incorporate aging effects into an accurate evaluation of bridge resilience. • Life-cycle resilience of the aging bridge is evaluated using the ET method. • The ET method is extended to probabilistic assessments by introducing a framework for quantifying the response distribution. • Corrosion can significantly affect the functionality and resilience of bridges. • The uncertainties in the functionality and resilience of the aging bridge are investigated. [ABSTRACT FROM AUTHOR]

CA (Cellular Automaton) model was applied to the simulation of random traffic flow to develop a model considering the randomness of traffic flow and apply it to wind-vehicle-bridge coupling vibration. Finite element and neural network models were adopted respectively to numerically compute the vibration characteristics of bridges under wind and vehicle loads, verify the correctness of model. Subspace iteration method was used for the modal analysis of bridges. Natural frequencies of the top 8 orders were 0.21 Hz, 0.27 Hz, 0.36 Hz, 0.45 Hz, 0.56 Hz, 0.66 Hz, 0.87 Hz and 1.02 Hz respectively. The vibration frequency of the long-span bridge was consistent with the vibration characteristics of large-scale complex structures. Natural modes mainly reflected the torsion and bending of main beam and the swinging vibration of side and main towers. Fluctuation wind time-history presented periodic characteristics. The maximum and minimum values of fluctuation wind were about 20 m/s and -20 m/s respectively. The target and simulation values of power spectral density of wind speed were basically the same in change trend, which indicated that the fluctuation wind time-history computed in this paper was reliable. The model of dense traffic flow based on CA more truly described the running status like accelerating, decelerating and changing lanes of vehicles on the bridge, also contained the density information of vehicles and more truly reflected traffic characteristics. Vibration accelerations of the long-span bridge were symmetrically distributed. Vibration acceleration of central position in the left main span was the largest and near 50 cm/s²; vibration acceleration on the main tower was the smallest. The curve of vibration displacement with considering wind loads presented some fluctuations, while the vibration displacement of bridges without considering wind loads was very smooth. In addition, the amplitude of vibration displacement without considering wind loads moved laterally towards the left compared with that with considering wind loads. Therefore, wind loads must be considered when the vibration characteristics of the long-span bridge were computed. Otherwise, the accuracy of computational results would be reduced. It only took 0.5 hours to use neural network to predict the vibration acceleration of the long-span bridge. In the case of the same computer performance, it took 5 hours to use finite element model to predict the vibration acceleration of the long-span bridge. The advantage of neural network model in predicting the performance of large-scale complex structures like a long-span bridge could be obviously found. In the future, we will consider using neural network model to systematically study and optimize the long-span bridge. [ABSTRACT FROM AUTHOR]

This paper presents a diagnostic case study of a long-span bridge, which uncovered the root cause of unsymmetric vibration performance that appeared to point to deterioration. In this case study, two iterations of the structural identification (St-Id) process were applied to (1) develop a comprehensive finite-element (FE) model (inclusive of approach spans) representative of the general dynamic properties (frequencies and mode shapes), and (2) check that the response magnitudes were consistent with those expected from vehicular traffic. More specifically, this research confirmed the perceived vibration discrepancy with direct measurements, conducted a comprehensive (including approach spans) ambient vibration monitoring of the bridge, updated an FE model to match measured modal parameters, and performed a series of simulations to both validate the updated model and understand the root cause of the unsymmetric vibrations. Through this process, it was determined that the unsymmetric vibrations resulted from the approach span designs, which provided significantly different levels of lateral stiffness to the primary bridge. Additionally, upon repeating the test following the replacement of all expansion bearings with neoprene bearings, similar levels of vibration asymmetry were observed, which further supported the diagnosis that this behavior is an inherent characteristic of the bridge. In addition to introducing an iterative St-Id process that makes use of both modal parameters and magnitude information (derived from an ambient vibration test), this paper illustrates the importance of explicitly including the approach spans within the St-Id of long-span bridges. In this case, ignoring the influence of the approach spans would likely have resulted in the erroneous conclusion that some damage or deterioration within the main spans was causing the unsymmetric vibrations observed. [ABSTRACT FROM AUTHOR]

Long-span bridges have low vibration frequencies and small intrinsic damping, and hence are subjected to large-amplitude vibrations, e.g., vortex-induced vibrations (VIVs), which jeopardize the serviceability and safety of the bridge structures. This study proposes a novel concept to supplement damping to such bridges for multimode vibration mitigation, by damping rotations of the bridge girder during vertical and torsional vibrations instead of translational displacements that have been previously the focus of relevant studies. A salient advantage of the concept is that bridge girder rotations near its ends are relatively large during vibrations enabling adequate supplemental damping and also convenient implementation. The concept is realized by a damped outrigger, consisting of a stiff outrigger rigidly connected to the bridge girder and horizontal dampers connecting the end of the outrigger to a bridge tower or a pier. A tensioned beam with rotational constraints is first used to demonstrate damping effects of damped outriggers on suspension bridges. Considering practical parameter ranges, the maximal damping ratio provided by one damped outrigger to a specific mode is about 1.0%. Influences of the relative importance of axial tension and bending stiffness and outrigger stiffness are studied. Furthermore, finite element analyses of an existing suspension bridge with damped outriggers are conducted to verify the damping performance. Numerical results show that by installing one damped outrigger, 6 out of 7 modes that have been involved in VIV events of the bridge can achieve a damping ratio of approximately 1.0% or above. By installing damped outriggers at the two towers, more modes can achieve a relatively large damping ratio, suggesting excellent performance of damped outriggers in suppressing multimode vibrations of long-span bridges. • Damped outriggers proposed for vibration mitigation of long-span bridges for the first time. • Damping effect studied via a simplified model of a suspension bridge with damped outriggers. • Excellent performance in multimode vibration mitigation verified via finite element analyses. • Demonstration via a case study of an existing long-span suspension bridge. [ABSTRACT FROM AUTHOR]

• A novel steel-concrete joint is proposed for long-span high-speed railway arch bridges. • The joint combines the shear connectors, steel skeleton with outsourcing concrete and diaphragm. • A model test of the proposed SCJ specimen with a scale of 1/5 was conducted and investigated. • A nonlinear finite element model of the SCJ was established with high accuracy. • The experimental and numerical results indicated great mechanical properties of the SCJ. Steel-concrete joint is often used to connect steel and concrete structures in bridge engineering. In this paper, a novel steel-concrete joint, consisting of shear connectors, steel skeleton with outsourcing concrete and solid concrete diaphragm, is proposed for long-span high-speed railway arch bridges. The joint has the advantage of convenient construction and the concrete diaphragm at joint can ensure the smooth stress transmission of the arch. The mechanical behavior of the steel-concrete joint is investigated by conducting a down-scale model test with a scale of 1/5 under four loading cases. The stress distributions and crack patterns of the experimental specimen model are listed and analyzed. Then based on the experimental results, a nonlinear finite element model of the steel-concrete joint is established. Utilizing the local stress analysis of the model, the stress concentration near the concrete corner could be decreased by reducing the inclination size of corner. The results indicate that the proposed steel-concrete joint shows great mechanic properties, as well as reasonable force transfer behavior without damage during loading. The test and analysis of the joint are expected to develop the design of steel-concrete joints in arch bridges with complex structural composition. [ABSTRACT FROM AUTHOR]

• Investigate pounding performance of long-span girder bridges under earthquakes. • Seismic isolation bearings can reduce the probability of pounding by tuning responses of adjacent units. • Pounding is more likely to happen when considering near-fault motions and wave passage effect. For girder bridges located in regions with a high seismic hazard level, seismic isolation bearings are usually implemented to suppress the seismic inertial force transmitted from the superstructure to substructures, protecting the pier columns and foundations. However, whether potential pounding might happen for these seismic-isolated girder bridges between adjacent units are scarcely considered, especially for those with long spans where the wave passage effect is of great significance. This paper develops a finite element model for a typical hybrid truss-girder bridge, based on which the influence of seismic isolation bearings and wave passage effect on pounding is carefully investigated considering both near-fault and far-field motions. The results show that for this type of long-span girder bridges, pounding may happen even the adjacent bridge units are designed with similar vibration periods, especially when near-fault motions and wave passage effect are considered. Under non-uniform excitations with different apparent wave velocities, the employment of isolation bearings can reduce the relative displacement at expansion joints and thus improve the performance against pounding; however, the occurrence of pounding and damage of expansion joints cannot be fully avoided. Further, motions with lower apparent velocities generally correspond to more devastating responses, which should be particularly considered during engineering practice. [ABSTRACT FROM AUTHOR]