Long-span Bridge Deck Research Articles

Simulasi Numerik Aeroelastik Model Seksional 2D Jembatan Bentang Panjang untuk Mengetahui Karakteristik Ketidakstabilan Flutter

Flutter is an aerodynamic instability on a long span bridge that can cause damage to the entire bridge deck structure. The interaction between wind and structure in long span bridges can be investigated by numerical simulation. In this study, an aeroelastic simulation was performed on a 2 DoFs sectional model of a long-span bridge deck with free vibration techniques to analyze flutter speed and determine the effect of deck shape on flutter instability characteristics using ANSYS software. The simulation result data was then extracted using the Modified Ibrahim Time-Domain Method (MITD) identification method to obtain the damping ratio and flutter derivatives coefficients. The damping ratio value is used to determine the critical flutter speed, whereas the coefficient flutter derivatives is used to determine the characteristics of flutter instability and the flutter mechanism that occurs in the bridge. The results showed that the rectangular shape (bluff body) is more susceptible to flutter instability than the streamlined shape, and has a lower flutter speed value than the other shapes. The flutter mechanism that occurs is torsional flutter, whereas in the streamline body is coupling flutter.

Using Deep Learning-Based Defect Detection and 3D Quantitative Assessment for Steel Deck Pavement Maintenance

Efficient distress detection and identification analysis are of great significances for long-span steel bridge deck pavement maintenance. This paper proposes a pavement distress recognition method based on road quality detection equipment and deep learning. Firstly, the sub-block image is used as the processing unit, and the three-dimensional image is divided into fracture surface element and background surface element. A pavement crack recognition network (PDRNet) based on convolutional neural network is proposed, which is used for automatic recognition of pavement background element and pavement crack element. Then, considering the pixel-level neighborhood characteristics of cracks in 3D pavement images, the PDRNet model is used to detect and quantitatively evaluate pavement cracks, which combines the crack elevation detection method to extract the complete contour of cracks in the crack surface element. Finally, the distress database containing three-dimensional markers is integrated into the pavement maintenance management platform. Results show that the PDRNet proposed in this paper has high prediction accuracy on the verification set and shows good robustness to various distress, and the average accuracy is above 88%. The established spatial-temporal integration platform overcomes the communication bottleneck between different types of data, and is important to improve the maintenance management level and predict the long-term development of distress.

Intelligent active flow control of long-span bridge deck using deep reinforcement learning integrated transfer learning

Aerodynamic forces of the Great Belt Bridge are mitigated using deep reinforcement learning (DRL) based active flow control (AFC) techniques at a Reynolds number of 5×105 in this study. The flow control method involves placing a suction slit at the bottom of the trailing edge of the bridge. The DRL agent as a controller is able to optimize the velocity of the suction to reduce the fluctuating coefficients of bending moment, drag, and lift by 99.1%, 73.7%, and 95.8% respectively. To reduce the high computational demands associated with DRL-based AFC training, this study integrates transfer learning technique into DRL, which calls transfer learning based deep reinforcement learning (TL-DRL) method. Specifically, the transfer learning method based on a DRL pre-trained model trained with a coarse mesh scheme is implemented. Results indicate that with TL-DRL method, the training cost can be reduced by 53%, while achieving the same control strategy and control effect as the DRL training from scratch. This study shows that the TL-DRL based flow control method is highly effective in reducing aerodynamic forces on long-span bridges. Furthermore, TL-DRL based flow control approach can adapt flexibly to different flow field environments, ultimately enhancing energy utilization efficiency.

Examination of occurrence probability of vortex-induced vibration of long-span bridge decks by Fokker–Planck–Kolmogorov equation

Vortex-induced vibration (VIV) is a major concern for long-span bridge decks, which may happen especially for closed-box girders under certain environmental wind conditions. Traditionally, sustained VIV is observed as long as the wind speed falls within the lock-in region in wind tunnel tests. However, structural vibration monitoring of long-span bridges has indicated that frequency of VIV events may exhibit a probabilistic pattern. This paper proposes an analytical framework to evaluate the probability of VIV occurrence. First, a nonlinear aeroelastic model with multi-stability limit cycles is used to simulate the bridge deck VIV response within the VIV-triggering wind conditions. The first structural dynamic equilibrium point is usually unstable; the bridge deck instantaneous oscillation amplitude, which is excited by external environmental loads, must exceed this fixed point to trigger the VIV event. The external environmental excitation applied on bridge can be identified from the deck vibration without VIV occurring, then the VIV occurrence probability can be evaluated by Fokker–Planck–Kolmogorov equation. This study utilizes the field measurement data from the Humen Bridge, on which VIV event occurred the first time after 23-year servicing period, because water-filled barriers were placed along the two edges of bridge deck. Afterwards, VIV occurred frequently for over one month. The bridge deck VIV occurrence probability is evaluated by combining environmental wind information, stochastic deck excitation magnitude and a nonlinear aeroelastic VIV model. The results suggest that the proposed methods can approximate the VIV occurrence probability in comparison with empirical estimations using field measurements.

The effect of central gap and wind screens on the aeroelastic stability of long-span bridge decks: Comparison of numerical analyses and experimental results

As long-span bridges are usually built at exposed locations and high winds can cause disruptions to traffic, relatively tall wind screens are often used to protect vehicles which are prone to suffer from wind induced accidents. This paper presents the results of a series of two-dimensional discrete vortex method simulations of laminar incompressible flow past standard aerofoil mono-boxes and twin-boxes, conducted to investigate the aerodynamic impact of wind screens on bridge decks in relation to steady-state and divergent instability (classical flutter) behaviour. A comparison against the outcome of a series of parametric wind tunnel tests is also presented. The quality of the agreement between the numerical simulations and the observed experimental behaviour is such that designers, under certain conditions, could rely on computational bridge aerodynamics at feasibility or early design stages to identify potential instabilities and introduce mitigation measures aimed at optimizing the aerodynamic performance of the deck.

Large field monitoring system of vehicle load on long-span bridge based on the fusion of multiple vision and WIM data

Vehicle Load Monitoring (VLM) on entire long-span bridge decks presents significant challenges due to the spatial and temporal randomness of vehicles. Existing VLM systems often suffer from limited viewing coverage and poor continuity of multi-vehicle tracking methods. This paper proposes a VLM system consisting of multi-vision image pre-processing, modified YOLO-v4 model, kinematics-enhanced vehicle tracking algorithm, and data fusion method between vision and Weigh-In-Motion sub-systems. The system was tested on a long-span bridge using six cameras, achieving vehicle monitoring of entire deck. The precision of multi-vehicle tracking achieved 99.28% built upon YOLO-v4 model with 96.2% mean Average Precision (mAP). Comparative results demonstrate that the modified YOLO-v4 model outperforms state-of-the-art approaches, and our proposed tracking method surpasses other methods. Our proposed system offers a comprehensive solution for VLM on entire bridge deck, overcoming the limitations of existing methods. Future work could extend the system's capability to include complex traffic patterns.

Experimental investigation on mechanical behavior of T-type perfobond rid shear connectors under combined shear and tension

The stress of shear connectors becomes more complicated as the span length of steel-concrete composite bridges increases. To bear the great shear and uplift forces, a T-type perfobond rib (T-type PBL) shear connector with sufficient stiffness and ductility is proposed. While the shear behavior of T-type PBL connectors has been evaluated in previous studies, its mechanical performance under combined shear and tension is not well understood due to the particular shape and numerous impact factors. Therefore, one pull-out test considering pure tension and seven modified push-out tests considering combined shear and tension were carried out to investigate the failure mode, bearing capacity, and load-slip behavior of T-type PBL connectors under combined actions. The pull-out test was performed to determine the tensile resistance, followed by a series of modified push-out tests with constant horizontal tension to investigate the structural behaviors. Additionally, the effects of the rib height, flange width, and hole numbers were evaluated. Based on the test results, conical failure surfaces formed from the flange of the T-type PBL to the concrete surface for all specimens, and the concrete failure angle was approximately 32°. The bearing capacity of the specimen improved by 26% when the perfobond rib height increased from 100 mm to 120 mm, but the flange width barely had any effect. The capacity of 1-hole specimen dropped by 20% while 2-hole specimen increased by 8% compared to the standard specimen, which may relate to the distance between adjacent holes. Increasing the rib height by 25% and 50% reduced the initial relative slip (S90) by 30% and 32%, respectively, indicating the improvement in initial stiffness. Generally, the pull-out resistance of the T-type PBL shear connector was enhanced by increasing the flange width, rib height, and number of holes. An evaluation equation considering the hole number and hole spacing was suggested for the bearing capacity of T-type PBL shear connectors under the combined actions. The validity was verified by test results, with a calculated-to-test-result ratio of 1.12 and standard deviation of 0.15. This study could enhance the understanding of the behavior of T-type PBL connectors under the combined actions, and promote the potential application in long-span composite bridge decks.

Flexural Performance and Design of Steel-UHTCC Composite Bridge Decks with Different Composite Degrees under Hogging Moments

Due to the excellent tensile properties and long-term durability, using ultrahigh-toughness cementitious composite (UHTCC) at the hogging moment regions of long-span composite bridge decks is a new solution to the cracking issue. Composite degrees and the longitudinal reinforcement ratio have been suspected of influencing the flexural performance of steel-UHTCC composite bridge decks under hogging moments, but the extent of the influence remains unclear. This study aims to investigate the influence of these two core design parameters. Six specimens with different stud spacings and longitudinal reinforcement ratios were designed to investigate the failure modes, flexural capacity, deformation behavior, and cracking characteristics. The results show that the cracking stresses σ0.05 and σ0.1 in the steel-UHTCC composite bridge decks were 58.6%–216.8% and 58.9%–213.5% higher than those in the steel-normal-strength concrete (NSC) composite bridge decks. As the longitudinal reinforcement spacing reduced from 125 to 75 mm, the growth of the crack width was effectively restrained, and the cracking stresses σ0.05 and σ0.1 increased by 36.6% and 71.2%, respectively. Finally, a modified theoretical model is established to evaluate the influence of composite degrees on the elastic flexural performance of steel-UHTCC composite bridge decks. The dimensionless composite degree η is defined as a core parameter in this model. For practical elastic design, the threshold value of the dimensionless composite degree can be determined as 0.005.

Study on in-plane double-crack propagation in the rib-to-deck welded toe of steel-bridge

The fatigue problem of two in-plane cracks in rib-to-deck welded toe of orthotropic steel bridge decks is an important issue. Traditionally, related work focuses on single-crack propagation in these joints; however, many practical observations have shown that the initial weld cracks of structures are characterized by multiple cracks in a small range. Thus, the main goal of this paper is to investigate the mechanism of and guidelines for in-plane double-crack propagation in rib-to-deck welded toe of orthotropic steel bridge decks. In this paper, the rib-to-deck welded toes in the orthotropic steel deck of the Anqing Yangtze River Bridge are taken as the background. Based on extended finite element method theory, single-crack propagation theory and the multiple-crack coalescence law, the stress intensity factors at the crack tip are calculated by the interaction integral method, and the propagation directions are determined using the maximum energy release rate (Merr) criterion. The whole process of in-plane double-crack propagation, coalescence and failure in rib-to-deck welded toe of long-span steel bridge decks and their fatigue life are simulated according to the principle of an equivalent crack front. Meanwhile, the most unfavorable conditions of cracking parameters are determined by changing the spacing and shape ratio of the two cracks. Then, the fatigue loading experiment is carried out on equal proportion specimens under appropriate cracking parameters. The results reveal the whole process of in-plane double-crack propagation in rib-to-deck welded toe of orthotropic steel bridge decks, and the verification shows that experimental results agree well with the simulation results.

Shaping Effects on Long Span Bridge Deck Aerodynamics

An aerodynamic circumstance of wind pressure surrounding the long-span bridge allocates many theoretical and experimental research to this topic. Determination of the materials and optimal cross-sectional shape of bridge decks that affected a dynamic behavior of long span bridge deck is still included in current research issues and works to be continued in this path. These include the Lack of sufficient awareness of wind forces, stemming from complex nature, and the unpredictability of the wind nature. In this study, in addition to recognizing the aerodynamic behavior of the flutter, the acting pressure forces on the bridge deck are investigated. The geometrical shape of decks, wind velocity, and flutter conditions are adopted as design variables that affected the dynamic forces exerted on bridge decks. A common type of geometric sections of the long-span bridge deck and effective aerodynamic phenomena are examined. The hollow box steel suspended deck and double cells box girder linked via upper flanges and cells linked via the top and bottom flanges are adopted for Computational Fluid Dynamic (CFD) approach. Thus, aerodynamic instability and turbulent torsional flutter flows, as well as a trail of shedding vortices around the bridge decks, are investigated. By changing some geometrical parameters of commonly used bridge sections, the optimal cross-section in terms of turbulence created above and below the deck section is examined and an optimal cross-sectional shape variable is proposed. The shape variable and section dimensions adopted for CFD-Simulations are similar to the dimensions and materials used in previous laboratory specimens of wind tunnels to be able to interpret the results and possibly verify them with the result of the current study.

Evaluation and improvement of wind environment and vehicle safety on long-span bridge deck under strong crosswind

Ensuring the safety of various vehicles or trains passing through the bridge deck under strong crosswind is one of the most important topics for a long-span bridge. Based on the project of Xihoumen Bridge, which remains open to vehicle traffic until the incoming crosswind at the mid span reaches up to 36.5 m/s, the wind profiles near the deck surface above different traffic lanes were analyzed through numerical simulation and checked by both wind tunnel test and field measurement. The crosswind loadings were evaluated by the equivalent wind velocities for different vehicle models, confirming the need of adopting appropriate wind barriers to reduce crosswind speed above the deck surface. A total of 14 types of wind barriers were evaluated by the crosswind reduction factor and the best scheme was determined. The flutter and vortex-induced vibration (VIV) performance of the girder with selected wind barrier were also checked. Finally, the optimum solution, an adjustable wind barrier was proposed to reduce the wind-induced drag forces at high wind speed, which has already been used in Xihoumen Bridges.

Stochastic Buffeting Analysis of Uncertain Long-Span Bridge Deck with an Optimized Method

The buffeting analysis of an uncertain long-span bridge deck was carried out in this paper. Due to the effect of strong spatial correlation of wind excitation, it should be assumed as partially coherent multiple excitations. The following includes a theoretical formula for the buffeting analysis of a long-span bridge deck with uncertain parameters, which was achieved mainly by a combination of the stochastic pseudo excitation method (SPEM) and response surface method (RSM). The SPEM-RSM was firstly applied to deal with the complicated spectral density function matrix of wind excitation. The buffeting response of the bridge deck was then calculated and verified by the results from the Monte Carlo simulation (MCS). The efficiency and applicability of the hybrid method for strong spatial correlation was proved. After the comparison, the effect of uncertain structural parameters and wind speed on the buffeting performance of the bridge deck were computed. The results showed that the whole uncertainties essentially affected the buffeting response of the deck. The uncertain wind speed played the most significant role in the vertical and lateral motion of the deck. The joint influences between structural uncertainties and uncertain wind speed further affect the random characteristics of the responses. Finally, the effects of different wind speed and wind angle of attack on the aerodynamic performance of the bridge are examined. The variance of the responses increased with the development of wind speed. The effect of different attack angles on the buffeting responses was significant.

UHPC-based strengthening technique for orthotropic steel decks with significant fatigue cracking issues

Fatigue cracking is a common drawback of orthotropic steel decks (OSDs), especially for long-span steel bridge decks, and it is difficult to repair such decks effectively. This paper proposes an ultrahigh performance concrete (UHPC)-based strengthening technique for OSDs with significant fatigue cracking issues. A multiscale finite element (FE) model based on the Wuhan Junshan Yangtze River Bridge is established. Analysis results show that the vehicle-induced stress values in the OSD are significantly reduced. However, the maximum tensile stress at the bottom of the UHPC layer is 12.9 MPa under the vehicle load, indicating that the UHPC layer is at risk of cracking. Two alternative retrofitting schemes for the UHPC layer are presented. One involves reinforcement by adding one-story transverse steel bars, and the other involves adding steel strips to strengthen the bottom of the UHPC layer. Transverse bending tests were conducted to compare these two schemes. The results show that the tensile strength of the UHPC layer strengthened with 80-mm-wide steel strips could reach 43.2 MPa, and that this was the superior scheme. A test involving 10 million fatigue-loading cycles was conducted to evaluate this steel strip strengthening scheme. The results indicate that the UHPC layer has a fatigue life of 8 million cycles. Thus, the fatigue life of OSDs with significant fatigue cracks can be improved using this strengthening technique.

Study of experiment in field for long-span cable-stayed bridge

In order to provide the reasonable optimization measures for the construction of long-span steel bridge deck pavement in the alpine area, the actual pavement effect under the real load is studied by simulation simulation with the finite element analysis software relying on the construction of the bridge deck of No.1 Bridge of Haidong Avenue, Ledu District, Haidong city. Through different load positions and loading methods, the control load loading points are determined, and the parameterized analysis is carried out for the elastic modulus, thickness and temperature difference of the pavement, and finally the structural parameters of the pavement suitable for the bridge are obtained; the experimental analysis results show that the theoretical calculation idea adopted is feasible, and the measured value is within the expected range. It can be seen that the construction optimization measures and suggestions are of great significance to the construction of steel bridge deck pavement in the high cold area.

Structural Safety Evaluation of Precast, Prestressed Concrete Deck Slabs Cast Using 120-MPa High-Performance Concrete with a Reinforced Joint.

Prestressed concrete structures are used in various fields as they can reduce the cross-sectional area of members compared with reinforced concrete structures. In addition, the use of high-performance and strength concrete can help reduce weight and achieve excellent durability. Recently, structures have increasingly been constructed using high-performance and strength concrete, and therefore, structural verification is required. Thus, this study experimentally evaluated the structural performance of a long-span bridge deck slab joint, regarded as the weak point of structures. The specimens were designed with a 4 m span for application to cable-stayed bridges. To ensure the required load resistance and serviceability, the specimens comprised of 120 MPa high-performance fiber-reinforced concrete and were prestressed. The deck slabs satisfied all static and fatigue performance as well as serviceability requirements, although they were thinner than typical concrete bridge deck slabs. The study also verified whether the deck slabs were suitable to help implement precast segmental construction methods. Finally, the results confirmed that the structural performance of the developed prestressed concrete (PSC) deck slab was sufficient for the intended bridge application as it achieved a sufficiently large safety factor in the static and fatigue performance tests, relative to the design requirement.

Influence of geometric configuration on aerodynamics of streamlined bridge deck by unsteady RANS

Long-span bridge decks are often shaped as streamlined to improve the aerodynamic performance of the deck. There are a number of important shaping parameters for a streamlined bridge deck. Their effects on aerodynamics should be well understood for shaping the bridge deck efficiently and for facilitating the bridge deck design procedure. This study examined the effect of various shaping parameters such as the bottom plate slope, width ratio and side ratio on aerodynamic responses of single box streamlined bridge decks by employing unsteady RANS simulation. Steady state responses and flow field were analyzed in detail for wide range of bottom plate slopes, width and side ratios. Then for a particular deck shape Reynolds number effect was investigated by varying its value from 1.65x104 to 25x104. The aerodynamic response showed very high sensitivity to the considered shaping parameters and exhibited high aerodynamic performance for a particular combination of shaping parameters.

Non-stationary turbulent wind field simulation of bridge deck using non-negative matrix factorization

Numerical simulation of turbulent wind field is essential for the time-domain buffeting analysis of long-span bridges. However, recent field measurements captured strong non-stationary features during extreme wind events, which may pose questions on the current bridge aerodynamic analysis based on the stationary assumption. Therefore, it is both necessary and realistic to perform non-stationary simulation of turbulent wind fields of long-span bridges. In this study, a spectral-representation-based non-stationary process simulation algorithm, which takes advantage of the FFT technique, is proposed using non-negative matrix factorization. In addition, an appropriate scheme is recommended to search the initial matrices for the factorization. After factorizing the decomposed spectrum, the FFT technique can be utilized to enhance the non-stationary simulation efficiency. Numerical examples demonstrate the feasibility and effectiveness of the factorization of the decomposed spectrum. Then, the non-stationary turbulent wind field on the long-span bridge deck is simulated. The computational efficiency, accuracy and applicability of the proposed method are compared with alternative approaches. Results show that the factorization and simulation agree well with the target ones. Therefore, the proposed approach can be used to simulate the non-stationary turbulent wind field in practice.

Influence of Separation Interference Method on Aerodynamic Responses of a Pentagonal Shaped Bridge Deck

Long-span bridges often exhibit vibration under wind action. Various aerodynamic countermeasures have been developed over the years to enhance the aeroelastic responses of the long-span bridge deck and Separation Interference Method (SIM) is one of these. Engineers should have sound knowledge about the flow mechanism of the aerodynamic countermeasures of the bridge deck for further improvement of the aerodynamic responses and better design of the bridge deck. In the present study, a numerical investigation was carried out to disclose the flow mechanism of SIM on a pentagonal bridge deck. Simulation was conducted by using unsteady RANS for a pentagonal bridge deck with and without SIM techniques and their aerodynamic responses were compared. In the first part performance of unsteady RANS was evaluated to predict the dynamic responses for a pentagonal bridge deck. Then, the steady state responses and flow fields were explored for a bridge deck with and without SIM. Later, the dynamic responses such as flutter derivatives and unsteady pressure characteristics were evaluated and compared. It was found that SIM can improve the aerodynamic responses of the bridge deck. The addition of the curb affected the flow field around the bridge deck and the important flow features noticeably. The leading-edge top and bottom surface separations and the trailing-edge bottom surface separation are the most significant flow features to control both the steady state and dynamics responses of the bridge deck.

Numerical simulation of windless-air-induced added mass and damping of vibrating bridge decks

The windless-air-induced added mass/mass moment of inertia (ma/Ia) and damping (ca) effects on mechanical parameters of a vibrating bridge deck are usually ignored in wind tunnel tests. In this paper, for three typical deck sections, computational fluid dynamics simulations are carried out to study the vertical/torsional single degree-of-freedom forced vibration under windless conditions, and further to reveal the effects of ma, Ia, and ca on the modal parameters. The influences of turbulence model, computational domain size, grid resolution, and time step size are analyzed. For the addressed issue, the Reynolds stress equation model (RSM) is found to be more suitable than the shear stress transportation (SST) k-ω model. A mathematical model for aerodynamic forces at zero wind speed is presented by using the dimensionless ma, Ia, and ca, and they can be extracted by combining the motions and the numerically simulated aerodynamic forces using the least squares method. The numerically simulated results for an ideal plate under small amplitudes are very close to the theoretical values, and consequently verify their accuracy. The causes for the non-zero values of flutter derivatives H4∗ and A3∗ at zero wind speed are revealed. In the windless air, the added damping almost linearly increases with the vibration amplitude. Five existing long-span bridge deck models are taken as examples to investigate the effects of ma, Ia, and ca on structural frequencies and damping ratios.

Fatigue endurance limit of epoxy asphalt concrete pavement on the deck of long-span steel bridge

Fatigue crack damage in the epoxy asphalt concrete pavement of long-span steel bridge deck is still one of the most severe problems even though the fatigue endurance performance has been studied for a long time. In this study, it aimed at exploring the mechanism why the fatigue damage of the epoxy asphalt concrete occurred, as well as finding out the reason why fatigue test results in laboratory were different from those in practical engineering application. A finite element mechanics method was first applied to analyze the maximum strain value of the epoxy asphalt concrete pavement at different load positions, then fatigue performance of the epoxy asphalt concrete was investigated using a four-point bending fatigue testing method, and finally a three-parameter fatigue equation model, which was demonstrated to be feasible and rational, was utilized to determine fatigue endurance limit for the first time. The fatigue damage of the epoxy asphalt concrete occurred in a short time once the strain level with driving load was larger than fatigue endurance limit. In contrast, the fatigue damage did not appear in a long time if the strain level was less than the fatigue endurance limit. It is suggested that the fatigue endurance limit be adopted as a control parameter in the design phase of epoxy asphalt concrete pavement. These findings advance previous design specifications in the world, and could help extending service life of epoxy asphalt concrete pavement of long-span steel bridge deck.