Steel Box Girder Bridge Research Articles

Design resistance strengths of composite steel box girder bridge using different codes

Bridges design based on prescriptive normative rules regarding loads and their combinations, safety factors, material properties, analysis methods, required verifications, and other issues that are included in design codes. In addition, Composite Steel Box Girder (CSBG) bridges present a prominent structural solution for straight and curved bridges with moderate spans, because of their large bending resistance and high torsional stiffness as well as rapid erection. This paper aims to perform a detailed theoretical comparative study between fundamental calculations of the design resistance strengths of shear, Vn or VRd, and flexure, Mn or MRd, in positive (sagging) and negative (hogging) moment regions, of CSBG highway bridges. The comparison is involved with design specification methodologies proposed by Egyptian Code of Practice (ECP-207-part 6), Bridge Design Specifications (BDS) presented by Association of State Highway and Transportation Officials (AASHTO), and European Standard (EC-4). On its turn, the study aims to standing on differences and similarities between considered standards in the design of such bridges.

Behavior of steel box girder bridges under blast loads and the possibility of reopening the bridge immediately following the explosion

Behavior of steel box girder bridges under blast loads and the possibility of reopening the bridge immediately following the explosion

Surface fatigue crack segmentation in steel box girder bridges using an improved Unet convolutional neural network

Despite the success of crack segmentation, the traditional segmentation strategy and networks are not necessarily suitable for fatigue cracks with unique visual features. Towards the indistinct crack features, a network named Fatigue Crack Unet (FC-Unet) was proposed, where the novel split attention mechanism was incorporated to boost diverse feature extraction. Scaled by various ratios, raw images were cropped and constituted three datasets to represent different segmentation strategies. FC-Unet was trained and tested on each dataset, where the class imbalance problem was alleviated by the adjustment of loss functions. Results showed that the segmentation performance is mainly limited to noise interference. Preserving abundant global contexts to distinguish noises, the global inference is the superior strategy to the previous local inference. Leveraging the wide receptive field in global inference, the down-sampling rate can be decreased to save resolution losses. Combining the focus-based and region-based loss functions, the accuracy of imbalanced data was further improved. Compared with nine classical networks, the proposed FC-Unet enjoyed a powerful backbone and achieved a superior metric of 83.1% mean intersection over union (MIoU).

Influence of ground motion parameters on seismic response of a large-longitudinal-slope and small-radius curved girder bridge.

The mechanical performance of curved bridges under the action of an earthquake is complex. To obtain the influence of seismic parameters on the seismic response of curved girder bridges, this paper relies on a large slope small-radius curved steel box girder bridge (LSCGB) and selects seismic wave incidence angle, vertical component of ground motion, and site category as seismic parameters to carry out nonlinear time history analysis. Based on the analysis results of the case bridge, it is shown that the torsional vibration of the first 10 modes of LSCGB is significant, the modes are dispersed, and the contribution of high-order modes of vibration cannot be ignored. The most unfavorable seismic wave incidence angle is in the direction of 45°∼60° counterclockwise Angle from the central connection line of Pier No. 1 and Pier No. 4 of the bridge. The seismic response of the curved bridge components increases with the vertical seismic intensity, and the influence on displacement responses is more significant. The basic vibration period of curved girder bridges built on soft soil sites is extended by approximately 18.23%, and the seismic response of key components increases with the softening of the site soil. Therefore, when analyzing the seismic response of LSCGBs, the influence of vertical component of ground motion and site category should not be ignored.

Probabilistic damage evaluation of isolated steel box-girder bridge excited by near-field earthquakes

Modern civilization regards bridges as lifelines, and their failure due to significant earthquakes in the past has raised concerns about their seismic vulnerability. The effect of near-fault earthquakes on the bridge vulnerability is a significant problem that has not been well explored. The present work utilizes fragility analysis to assess the probabilistic seismic risk evaluation of a continuous isolated steel box girder bridge exposed to near-field ground motions (NFGMs). Probabilistic seismic demand models (PSDMs) of the bridge are explored to reliably associate key demand and intensity measures to capture the seismic performance of the system. This study examines a steel box girder bridge in Guwahati, India, isolated with lead rubber (LRB) bearings and a friction pendulum system (FPS). To achieve a comparable seismic response, each bearing system is designed for a similar isolation period. The PGV/PGA ratio is a useful metric for classifying ground motion suites and estimating their frequency content by classifying the input excitations into low- and high-frequency motions. To perform probabilistic seismic risk assessments, two ensembles of forward directivity records with PGV: PGA >160 cm/s/g (high frequency) and PGV: PGA <160 cm/s/g (low frequency) are considered. Moreover, one ensembles of near-field incorporating the fling effect and far-field are also utilized. The failure probability under the seismic hazards for isolated bridges is assessed utilizing different damage measures (DM) such as maximum displacement ductility of pier (DDP), displacement of deck (MDD), drift ratio of pier (PDR), and rotational ductility (RDP). The near-field earthquake damage probability is significantly impacted by the PGV/PGA ratio, as a high PGV/PGA ratio results in a greater probability of damage than a low PGV/PGA ratio. In conclusion, guidelines are provided that will help the design engineers for designing bridges with LRB and FPS isolators for seismic isolation in the event of varying ground motion characteristics.

Vibration-based system identification of a large steel box girder bridge

Vibration-based system identification of a large steel box girder bridge

Fire effect of steel bridge structure with consideration of leaked combustion fuel on asphalt bridge deck

In this paper, a fire load model is introduced for steel bridge decks considering asphalt pavement layers, aimed at exploring the consequences of fire arising from fuel leakage on the bridge pavement. Temperature data, mass loss rates, and radiation measurements from the pavement during fire tests are collected. The fire process on the bridge deck is categorized into four distinct stages, based on the mass loss rate. The temperature-time model is constructed by fitting the temperature data from the first two stages on the top surface. This model is then validated by comparing the temperature data obtained from various temperature-time load inputs with the experimental data from the middle and bottom surfaces. Additionally, a finite element numerical model is developed for a steel box girder bridge, enabling a comparison of different temperature-time models to establish the rationality of the bridge deck temperature-time model. Finally, the thermal mechanical coupling method is employed to investigate the impact of fire on the bridge's mid-span, revealing a close alignment between the simulation temperatures derived from the bridge deck temperature-time curve and the experimental results.

Effect of material characteristics of lead rubber isolators on seismic performance of box girder bridge

Near-field (NF) earthquakes have distinct ground motions, forward directivity pulses, and fling-step motions, causing structural responses to differ from far-field (FF) earthquakes. Seismic isolation is regarded as a developed and successful technology that may be applied to enhance a structure’s functionality and safeguard it against catastrophic earthquake effects. The variation in mechanical properties of seismic isolation also significantly influences bridge seismic response. The study investigates the influence of lead rubber (LRB) isolators and the characteristics of ground motions on seismically isolated bridges, aiming to determine optimal parameters for minimal earthquake response. Key parameters include ground motion characteristics, characteristic strength (Q), and isolator flexibility. The study modeled the force-deformation behavior of isolators using bilinear behavior, reflecting the Bouc-Wen hysteric model. CSI Bridge was used to model seismically isolated steel box girder bridges, with eight natural accelerograms assessing a 2% probability of exceedance in 50 years. The peak responses of pier displacement (MPD), isolator hysteric energy (HED), base shear, and deck acceleration are chosen as the response parameters for the comparison. To evaluate the response parameters, the earthquake data are scaled to the three studied peak ground acceleration (PGA) levels of design level (0.2 g), extreme level (0.4 g), and rare-extreme level (0.8 g). The findings offer insight on the relevance of isolator stiffness and its influences on the seismic performance of isolated bridges. The study identifies minimum values for pier displacement, hysteric energy, deck acceleration, and base shear at specific Q/weight sustained by isolator (W) and time period (T) values. Recommendations are made for the preliminary seismic isolation design of bridges with LRB isolators, highlighting the importance of PGV to PGA ratio in earthquake damage assessment.

Investigation on temperature effect of local structural stress during non-uniform cross-section steel bridge deck pavement paving

During the process of gussasphalt concrete paving on the orthotropic steel bridge deck of a non-uniform cross-section box girder bridge, the high-temperature asphalt mixture often produces temperature stresses that can affect bearings safety. In this study, a refined model of a steel box girder bridge with a 660 m scale was developed and numerical simulations were conducted using the finite element software. The temperature field was applied to the orthotropic steel bridge deck in a quasi-dynamic fashion, leading to the determination of a safe width for concrete paving. To assess the accuracy of the computational predictions, field paving was performed under the safe width condition determined from the calculations, and the temperature and local stress data were measured in the field. The results demonstrate that the finite element predictions are in good agreement with the yield strength of the bearing’s local structure, and the measurements also show a close correspondence with the structural yield strength, validating the reliability of the quasi-static simulation approach. The proposed method offers a computational tool and a reliability criterion for future finite element analyses of large-span non-uniform cross-section steel box girder bridges, as well as a safe width example for subsequent gussasphalt mixture paving on orthotropic steel bridge decks.

Evaluation Method of Fatigue Life for Asphalt Pavement on the Steel Bridge Deck Based on the Inhomogeneous Poisson Stochastic Process.

The paving layer on the steel box girder bridge deck is widely used when constructing pavements for steel bridges. Owing to the orthotropic feature of steel decks, a transverse clapboard and rib can lead to a concentration of stress. Consequently, fatigue cracks are often identified in asphalt concrete pavement layers due to re-compaction caused by heavy vehicles. This study aims to derive an evaluation method of fatigue life for asphalt pavement based on the inhomogeneous Poisson stochastic process in view of the highly random and uncertain working conditions of layered composite structures. According to the inhomogeneous Poisson stochastic process, along with Miner's fatigue damage accumulation theory and the linear elastic fracture mechanics theory, the fatigue life formula could be deduced. Meanwhile, fatigue experiments for asphalt concrete are designed to investigate the correlation between the theoretical formula and the actual fatigue damage life of the material. Compared with the test, the accuracy error is within 10%, which is better than other traditional methods. Therefore, the fatigue life prediction model could better reflect the loading order effect and the interaction between loads, providing a new path for the fatigue reliability design of steel bridge deck asphalt pavement.

Refined Analysis of Spatial Three-Curved Steel Box Girder Bridge and Temperature Stress Prediction Based on WOA-BPNN

Bridges often improve the visual appeal of urban landscapes by incorporating curve elements to create iconic forms. However, it is noteworthy that curved bridges have unique mechanical properties under loads compared to straight bridges. This study analyzes a spatial three-curved steel box girder bridge based on an actual engineering case with a complex configuration. Initially, the finite element software Midas/Civil 2021 is utilized to establish a beam element model and a plate element model to examine the structural responses under dead loads in detail. Then, two different temperature gradient distribution models are employed for the temperature effect analysis. The backpropagation neural network (BPNN) optimized by the WOA algorithm is trained as a surrogate model for finite element models based on the results of temperature stress simulation. The results reveal that the bending–torsion coupling effect in the second span of the spatial three-curved steel box girder bridge is pronounced, with the maximum torque reaching 40% of the bending moment. The uneven distribution of cross-section stress is particularly significant at the vertices, where the shear lag coefficient exceeds 3. Under the action of temperature gradients, the bridge displays a warped stress state; the stress results obtained from the exponential model exhibit a 21% increase compared to BS-5400. Optimization of the weights by the WOA algorithm results in a significant improvement in prediction accuracy, and the convergence speed is improved by 30%. The coefficient of determination (R2) for predicting temperature stress can reach as high as 0.99.

Engineering Mechanics Methods in Stability Studies of Bridge Structures and Innovations in Future Bridge Designs

Abstract With the development of science and technology and transportation, high pier and large-span bridges are rapidly rising. Due to the increase in span diameter and pier height, nonlinear and stability problems of bridges become more and more important. In this paper, the stability of large-span steel box-girder suspension bridges is investigated using engineering mechanics methods. Based on the finite element analysis method to solve the bridge structure of the first type of stability problems and the second type of stability problems, the use of the response spectrum method for bridge seismic response. Taking “Xiling Yangtze River Bridge” as the engineering background, the seismic response is analyzed by establishing a finite element model. The axial force of the bridge tower generated by the downstream earthquake is larger than that generated by the transverse earthquake. In the transverse direction, the bending moment MZ is larger than the bending moment MY in the transverse direction, and the bending moment of the pile foundation is larger than the bending moment of the pile foundation in the longitudinal direction. The Xiling Yangtze River Bridge plays a dominant role in transverse seismicity, and its downstream seismic excitation plays a dominant role in longitudinal seismicity. However, the energy-demand ratio corresponding to the transverse moment MY is only 1.83, and the strength of the pile section needs to be further improved. For the future innovation of bridge design, a high-performance bridge structure based on UHPC is an important direction for future development.

Research on the Overall and Local Mechanical Behaviors of Steel Box Girder Cable-Stayed Bridge via Incremental Launching Construction

In this paper, a large-span cable-stayed bridge with double pylons and double cable planes is employed to study the overall and local mechanical behaviors. The steel box girder bridge is constructed by incremental launching with the maximum span of 50 m. Through the overall stress analysis, the most unfavorable stress position of the structure in the incremental launching construction is identified; the refined local stress analysis is carried out for the girder section at this position, and the local stress characteristics of the structure are studied. The mechanical performance and the applicability of incremental launching are determined by comparing four kinds of elastic cushion. This paper aims at improving the safety of incremental launching construction of steel box girder bridge, and can provide reference for similar projects.

Temperature-induced response reconstruction for the dynamic reliability assessment of bridge girders

Assessing the dynamic reliability of bridge girders under data missing of long-term structural responses still remains a challenge. The conventional methods are often inadequate to analyze the structural dynamic behavior from the incomplete data, resulting in the inability to accurately assess the dynamic reliability of bridge girders. Therefore, this paper presents a new temperature-induced response reconstruction model for the dynamic reliability assessment of bridge girders. Considering that the strong spatial–temporal correlation exists between the air temperature and the structural response, the temperature-induced response reconstruction model, namely Conv-SCINet, is established in this paper by combining the three one-dimensional convolutional layer-based block (Conv-Block) and the sample convolution and interaction network (SCINet) layers to reconstruct the long-term missing structural responses. The corresponding state parameter (i.e., the variance of the normal distribution) of structural responses can be evaluated by Bayesian probability recursion to form the limit state function for the dynamic reliability assessment of in-service bridges. Finally, the validity and feasibility of the proposed method are demonstrated using a prestressed concrete bridge and a steel box-girder suspension bridge. The results show that the Conv-SCINet model has better reconstruction performance of long-term structural responses and higher evaluation accuracy of dynamic reliability for bridge girders compared to the four currently acknowledged high-precision models. In addition, the proposed method also confirms the feasibility of using the air temperature to reconstruct missing structural responses and further evaluating the dynamic reliability of in-service bridges.

Experimental study on optimization of continuous steel box girder bridge deck

ABSTRACT In order to accurately optimize the structural parameters of steel bridge deck(OSD), an optimal design method of continuous steel box girder bridge deck based on response surface method is proposed. Optimization design process includes full scale model test, finite element analysis, response surface function fitting and design parameter optimization. The orthotropic steel bridge deck’s deck thickness, stiffener thickness, diaphragm thickness, stiffener height, and diaphragm opening form are chosen as independent variables, and the internal forces of important structural components discovered are used as dependent variables. Design-Expert software created a five-factor, three-level response surface test. A multivariate quadratic response surface regression model between structural parameters and target response values was developed after the objective function and constraint criteria were identified. Numerical theory’s variance analysis was used to find the best combination, and Design Expert software was used to confirm it to make sure the design value was accurate. The findings indicate that optimized structural parameters are trustworthy because the difference between the predicted value and the theoretical value is less than 5%. An orthotropic steel bridge deck’s structural parameters can be optimized using the response surface approach. It serves as a reference for subsequent steel bridge deck design and construction.

Equivalent Vehicle Model Based on Traffic Flow of Long-Span Steel Box Girder Bridge

Equivalent Vehicle Model Based on Traffic Flow of Long-Span Steel Box Girder Bridge

Updating method on geometric shape control of continuous steel box girder bridges by incremental launching construction

A new method of deviation vector transformation of geometric shape was proposed to improve the accuracy on geometric shape control of continuous steel box girder bridges by incremental launching construction.The method correct the transfer matrix method in the ideal state where the lateral and vertical deviations of longitudinal axis at the segments can be adjusted periodically.By firstly constructing a spatial coordinate system for identifying the geometric shape of the box bridge and taking the elevation and horizontal coordinates of the control points at both ends of the installed bridge segment as the basic variables, the actual and design coordinates of the control points will be obtained in the constructed coordinate system, constructing the vector of deviation system on geometric shape and the sum of vector squares, and then the extremum problem of the partial differential equation is solved to obtain the "transformed shape" with the lowest dispersion of overall deviation.The modified term appended to transfer matrix method aforementioned for bridge segment to be installed can be obtained ultimately by deriving from the "transformed shape" and "designed shape".Engineering practice shows that the horizontal and vertical maximal deflections on the axis of the whole bridge at post construction are less than 5 and 15 mm, respectively, by using the proposed method to control the geometric shape of a continuous steel box girder bridge by incremental launching construction method, meanwhile, the horizontal and vertical deflections on the axis of the segments above the permanent piers are less than 4 and 10 mm, respectively. The theoretical method has been verified with good effect in requirement of the code.

Multitask fatigue crack recognition network based on task similarity analysis

For fatigue cracks in steel box girder bridges, comprehensive perception is urgent and practical since it provides diverse damage information. Multitask learning networks, which learn multiple tasks jointly, could realize various detection tasks simultaneously. However, multitask networks are hard to avoid task conflicts, thus limiting recognition performance. In this study, the representational similarity analysis method was introduced to quantify task similarity, which helps decouple the parameters of unrelated tasks. Considering task correlation, a multitask network called CrackFormer was developed to recognize the initiation location, repair scene, and region morphology of fatigue cracks. From the perspective of learning difficulty, multiple tasks were trained and coordinated dynamically. Finally, the trained model was evaluated by comparative tests. Results showed that task similarity analysis was verified to be reasonable by transfer learning test. Compared with isolated tasks, CrackFormer demonstrated superior accuracy, efficiency, and robustness by mutual complementation of task knowledge. After optimizing the parameter sharing design, detection performance was further improved.

The Multi-Scale Model Method for U-Ribs Temperature-Induced Stress Analysis in Long-Span Cable-Stayed Bridges through Monitoring Data

Temperature is one of the important factors that affect the fatigue failure of the welds in orthotropic steel desks (OSD) between U-ribs and bridge decks. In this study, a new analysis method for temperature-induced stress in U-ribs is proposed based on multi-scale finite element (FE) models and monitoring data First, the long-term temperature data of a long-span cable-stayed bridge is processed. This research reveals that a vertical temperature gradient is observed rather than a transverse temperature gradient on the long-span steel box girder bridge with tuyere components. There is a linear relationship between temperature and temperature-induced displacement, taking into account the time delay effect (approximately one hour). Then, a multi-scale FE model is established using the substructure method to condense each segment of the steel girder into a super-element, and the overall bridge temperature-induced displacement and temperature-induced stress of the local U-rib on the OSD are analyzed. The agreement between the calculated temperature-induced stresses and measured values demonstrates the effectiveness of the multi-scale modeling strategy. This approach provides a valuable reference for the evaluation and management of bridge safety. Finally, based on the multi-scale FE model, the temperature-induced strain distribution of components on the OSD is studied. This research reveals that the deflection of the girder continually changes with the temperature variation, and the temperature-induced strain of the girder exhibits a variation range of approximately 100 με.

Continuous bridge displacement estimation using millimeter-wave radar, strain gauge and accelerometer

Monitoring of bridge displacement is essential for providing critical information regarding the health of bridge structures. However, continuous and accurate monitoring of structural displacement remains challenging. This study proposes a bridge displacement estimation technique that combines an accelerometer, a strain gauge, and a millimeter-wave radar considering intermittent radar target occlusion common in long-term displacement monitoring. The technique primarily estimates displacement using radar and accelerometer measurements but switches to using strain and acceleration measurements when radar targets are occluded. A radar target occlusion detection algorithm is developed to automatically achieve this switching. Automated initial calibration is performed to select suitable targets from all radar-detected targets and estimate the conversion factor for converting radar-based displacement from the line-of-sight direction to the actual movement direction. An artificial neural network model is automatically trained for strain–displacement transformation without the need for any pre-knowledge of a target structure. The proposed technique was validated via a laboratory test on a 10-m-long beam-type structure and a field test on a pedestrian steel box-girder bridge. The proposed technique correctly detected the intermittent radar target occlusion, and continuously estimated displacements for up to 75 min. The intermittent radar target occlusion leads to errors of a few millimeters in the displacements estimated using radar and accelerometers. However, the proposed method accurately estimates displacements with errors of less than 0.1 mm.