Search Results (61)

Unlike conventional asphalt pavements, steel bridge deck pavement (SBDP) is directly constructed on orthotropic steel deck plates characterized by relatively low flexural stiffness, rendering it more susceptible to rutting deformation under elevated temperatures and repeated loading. To investigate the mesoscopic mechanism underlying rutting formation in SBDP, a three-dimensional (3D) discrete–continuous coupled model of a steel–asphalt composite structural specimen (SACSS) was developed and employed to conduct virtual rutting simulations, which were subsequently validated against laboratory test results. The impact of surface cracking on rutting progression was then explored. In addition, the spatial motion and contact interactions of particles during the rutting process were monitored and analyzed. The influence of steel plate stiffness on the rutting resistance of SBDP was also evaluated. The numerical analyses yielded the following key findings: (1) Under three steel–asphalt interface bonding (SAIB) failure conditions (0%, 17%, and 100%), the virtual simulation results exhibited strong agreement with experimental trends in rutting depth over time, thereby confirming the validity and reliability of the coupled modeling approach. (2) At 30 °C, the presence of surface cracks is found to increase the rutting depth by 35.77%, whereas this effect is mitigated at 45 °C. (3) The meso-mechanical mechanisms governing rutting deformation in SBDP are further elucidated under different temperature conditions. (4) Moreover, at elevated temperatures, the use of a steel plate with an elastic modulus of 206 MPa effectively inhibit rutting development. This study offers mesoscopic-level insights into the effects of temperature, SAIB conditions, steel plate stiffness, and surface cracking on the macroscopic rutting behavior of SBDP, thereby providing a theoretical foundation for the design and optimization of long-lasting SBDPs. Full article

The welded joints in steel bridges have a complicated structure, and their fatigue life is mainly determined by the real stress under the coupling effect of vehicle load stress, as well as weld-induced residual stress and its relaxation. Traditional fatigue analysis methods are inadequate for effectively accounting for weld-induced residual stress and its relaxation, resulting in a significant discrepancy between the predicted fatigue life and the actual fatigue cracking time. A fatigue damage assessment model of welded joints was developed in this study, considering weld-induced residual stress and its relaxation under vehicle load stress. A multi-scale finite element model (FEM) for vehicle-induced coupled analysis was established to investigate the weld-induced initial residual stress and its relaxation effect associated with cyclic bend fatigue due to vehicles. The fatigue damage assessment, considering the welding residual stress and its relaxation, was performed based on the S–N curve model from metal fatigue theory and Miner’s linear damage theory. Based on this, the impact of variations in traffic load on fatigue life was forecasted. The results show that (1) the state of tension or compression in vehicle load stress notably impacts the residual stress relaxation effect observed in welded joints, of which the relaxation magnitude of the von Mises stress amounts to 81.2% of the average vehicle load stress value under tensile stress working conditions; (2) the predicted life of deck-to-rib welded joints is 28.26 years, based on traffic data from Jiangyin Bridge, which is closer to the monitored fatigue cracking life when compared with the Eurocode 3 and AASHTO LRFD standards; and (3) when vehicle weight and traffic volume increase by 30%, the fatigue life significantly drops to just 9.25 and 12.13 years, receptively. Full article

Orthotropic steel box girders and steel bridge decks are commonly applied to bridges. Because of the coupling of original defects and alternating forces, fatigue cracks are likely to appear in the structures. In order to ensure the life span of bridges, methods for automatic crack identification are needed. In this paper, we present a novel approach for crack detection and bridge condition monitoring by integrating convolutional neural networks (CNNs) with graph attention networks (GATs). At first, the original large-sized images are divided into small-sized patches, and these patches are input into a CNN architecture to extract features by decreasing dimensions. Then, the output features of the CNN model are considered as nodes of the graph. Considering the spatial relationship among the patches in the original image, the node from the central patch is connected to the nodes from its neighboring patches to constitute a graph structure, which can be input into a GAT model to learn the relationship among the nodes and update the features. Finally, the output features of GAT can judge whether the central patch contains cracks. Forty original large-sized images are cropped into abundant patches for the training of the CNN-GAT model. With the use of a sliding window technique, the trained CNN-GAT model is capable of finding the patches containing cracks in the test images with large sizes. From the test results, the location and the size of the cracks are exhibited, which indicates that the proposed approach is effective for crack identification in bridge structures. Full article

Orthotropic Steel Bridge Decks (OSBDs) are often used in long-span bridges due to their high performance and ease of installation. However, issues such as fatigue cracking and the deterioration of asphalt overlays due to their local stiffness inefficiency necessitate innovative solutions. Orthotropic Steel–Ultra-High-Performance Concrete Composite Bridge Decks (OS-UHPC-CBDs) have enhanced OSBD performance; however, they have disadvantages such as a heavier weight and high initial cost requirements. In this study, an Orthotropic Steel–Lightweight Ultra-High-Performance Concrete Composite Bridge Deck (OS-LUHPC-CBD) is proposed as a solution that integrates a novel Lightweight Ultra-High-Performance Concrete (LUHPC) with a high-strength Q425 steel deck and trapezoidal ribs. A comprehensive experimental investigation, including full-scale four-point bending tests, was undertaken to evaluate the flexural behavior of the proposed OS-LUHPC-CBD compared to the OS-UHPC-CBD. The experimental results show that the proposed OS-LUHPC-CBD has equivalent flexural capacity and improved ductility compared to the OS-UHPC-CBD. This study found the proposed OS-LUHPC-CBD to be a promising solution for application in long-span bridges with an 8.4% lighter weight and a 6.8% lower cost, and with the same ease of construction as OS-UHPC-CBDs. A finite element model with a strong correlation was developed and validated through the experimental results. Based on this, a parametric study was undertaken on the effect of the key geometric design parameters on the flexural capacity of the OS-LUHPC-CBD. Full article

Localized diaphragm (transversal plate) deformation and buckling were identified at the arc notch region during structural inspections of an operational steel bridge. To evaluate the potential structural consequences, alterations in the fatigue performance and stress characteristics induced by this deformation were systematically investigated through in situ monitoring combined with numerical simulation. It was demonstrated that the global load-transfer mechanism of the orthotropic steel deck (OSD) system remained minimally compromised. While within the localized deformation zone, the stress magnitudes at the diaphragm-to-U-rib (DU) welds were observed to be significantly amplified, and the stress concentration zones were found to be relocated to geometrically depressed regions. Based on the deformation-stage mechanical responses, the strategic employment of residual compressive stress generated through controlled hammer peening was proposed for counteracting stress escalation at DU welds recently caused by diaphragm buckling, whereas steel plate reinforcement strategies were recommended for mitigating progressive deformation development. Full article

Rib–deck (RD) welded joints in orthotropic steel bridge decks are prone to different fatigue crack mechanisms. Standard fatigue design methods are inadequate for some of these mechanisms under multiaxial non-proportional loading conditions. This study presents a framework to assess fatigue damage at RD welded joints, considering the different crack mechanisms based on the equivalent structural stress method and its extension to multiaxial non-proportional fatigue, which is the path-dependent maximum stress range (PDMR) cycle counting algorithm. The method is validated for uniaxial loading by using experimental data from the literature. Additionally, non-proportional fatigue damage at RD welded joints of a suspension bridge girder is investigated under simulated random traffic loading. The analyses reveal the limitations of the nominal stress approach to account for complex stress field variations. The PDMR method, more suited to capture the stress path dependency of non-proportional fatigue damage than the hot spot and critical plane-based methods, predicts higher fatigue damage. A comprehensive fatigue test campaign of full-scale RD welded joints is necessary to better understand their fatigue behaviour under multiaxial loading. Until more experimental data are available, the PDMR method is recommended for fatigue verifications of welded RD joints as it yields safer predictions. Full article

The residual stresses at U-rib joints have a significant adverse impact on the structure. Therefore, it is necessary to conduct research and analysis on their residual stresses. Based on experimental testing and thermal elastic-plastic finite element analysis (FEA), this study investigates the residual stress (RS) of a U-rib joint using gas metal arc welding in an orthotropic steel bridge deck (OSBD). X-ray diffraction (XRD) was adopted to measure the RS of the U-rib welds, and the measurement results were utilized to verify the FEA. The effects of the weld root gap, weld penetration, and weld groove angle on the RS of U-rib welds were investigated by using FEA. The weld root gap had minor effect on the RS of the U-rib welds. With an increase in weld penetration, the peak values of the transverse tensile RS at both the deck plate and the U-rib weld toes increased. Additionally, an enlargement of the groove angle also resulted in a notable increase in the transverse tensile RS peak at the deck plate weld toe. Full article

Due to prolonged heavy traffic, the Wuhan Changfeng Bridge has experienced extensive cracking in its main girder structure. Of the bridge’s 60 crossbeams, 51 (85%) have developed cracks, while the deck pavement over the steel beams has accumulated a total of 648.8 m of transverse cracks. Additionally, two T-beams exhibit structural vertical cracks of 0.3 mm at the mid-span, exceeding the maximum allowable width of 0.2 mm. This recurrent pavement damage not only compromises driving safety and comfort but also increases maintenance costs. To address these issues, this paper proposes a systematic upgrade plan for the bridge deck system. The plan involves welding additional high transverse beams onto the existing steel transverse beams, removing the original deck slab and replacing it entirely with an orthotropic steel deck. Additionally, two new steel longitudinal beams will be installed. The original simply supported concrete longitudinal beams in the deck will be transformed into an integrally connected continuous steel structure deck system. Using Midas/Civil finite element software, 3D models of Changfeng Bridge, pre and post renovation, were created to analyze the overall dynamic characteristics under five loading scenarios. The ambient vibration test and vehicle field test were conducted to measure the bridge’s natural frequency and impact factor, verifying the dynamic performance and driving comfort of the bridge after the upgrade. The results indicate that the retrofitted bridge experienced a 19.9% increase in overall stiffness. The dynamic performance of the bridge structure was significantly enhanced, and the most notable improvement was observed in dynamic stress, which decreased by 19.4% to 76.9%. Additionally, the steel deck reduced the bridge’s dead load, and the driving comfort on the bridge deck improved. Full article

In recent years, fatigue cracking in orthotropic steel bridge deck pavements has become a significant concern, so the investigation of the mechanical response of the pavement layer has become a central focus in pavement structure design. This experiment subjected a full-scale specimen to a constant amplitude dynamic load of 60 kN to 300 kN over 2 million cycles. Throughout the testing, a circulating water bath elevated the temperature of the pavement layer from 15 °C to 50 °C. Key locations were monitored for strain and deflection data, facilitating an investigation into the mechanical response of the epoxy asphalt pavement system under the effects of temperature and load. The results indicate that the maximum transverse strain at the bottom of the steel deck occurs at the U-rib weld aligned with the load center, reaching 190% of the initial loading strain. Meanwhile, the maximum transverse strain on the pavement surface is observed at the U-rib weld adjacent to the loaded area, measuring 167% of the initial strain. The maximum longitudinal strain is lower than the maximum transverse strain. In the load zone, the longitudinal strain between the U-ribs exceeds that at the U-rib weld. Both transverse strain and relative deflection increase as the load intensifies. The relationship between transverse strain and applied load is characterized by an exponential function, while deflection exhibits a cubic relationship with the applied load. Elevated temperatures also contribute to increased transverse strains at both the bottom of the steel deck and the pavement surface, following an exponential trend. Relative deflection is primarily influenced by the applied load and remains relatively unaffected by temperature variations. When accounting for the coupling of load and temperature, the maximum transverse strains at both the bottom of the steel deck and the pavement surface can be modeled as an exponential function of the independent variables: load and temperature. Full article

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

Orthotropic steel decks (OSDs) are commonly used in the construction of bridges due to their load-bearing capabilities. However, they are prone to fatigue damage over time due to the cyclic loads from vehicles. Therefore, the early structural health monitoring of fatigue damage in OSDs is crucial for ensuring bridge safety. Moreover, Lamb waves, as elastic waves propagating in OSD plate-like structures, are characterized by their long propagation distances and minimal attenuation. This paper introduces a method of emitting high-energy ultrasonic waves onto the OSD surface to capture the nonlinear Lamb waves formed, thereby calculating the nonlinear parameters. These parameters are then correlated with the fatigue damage endured, forming a damage index (DI) for monitoring the fatigue life of OSDs. Experimental results indicate that as fatigue damage increases, the nonlinear parameters exhibit a significant initial increase followed by a decrease. The behavior is distinct from the characteristic parameters of linear ultrasound (velocity and energy), which also exhibit changes but to a relatively smaller extent. The proposed DI and fatigue life based on nonlinear parameters can be fitted with a Gaussian curve, with the R-squared value of the fitting curve being close to 1. Additionally, this paper discusses the influence of rib welds within the OSDs on the DI, whereby as fatigue damage increases, it enlarges the value of the nonlinear parameters without altering their trend. The proposed method provides a more effective approach for monitoring early fatigue damage in OSDs. Full article

In addition to traditional building materials, such as steel and concrete, wood has been gaining increasing prominence in recent years. In the past, the use of wood was limited due to its susceptibility to damage by fungi, insects, and temperature. These shortcomings were gradually eliminated as the quality of wood processing increased and thanks to modern high-quality insulating and protective materials. The return to the utilisation of this natural building material was also supported by the development of new wood-based materials, such as glued laminated wood, and new types of mechanical fasteners, as well as by the introduction of new design methods provided in the Eurocodes. Within this context, this paper focuses on using wood in transport infrastructure, especially as the basic material for footbridges and small road bridges. Combined timber–steel bridges emerge as a very effective type of superstructure in contemporary road bridges and footbridges, especially in areas with natural exposure. Usually, wood is used for the main bridge girders, while steel is preferred for bridge deck elements—stringers and cross-girders. The results of this parametric study offer optimal structural solutions for footbridges with spans of 12.0–24.0 m, reflecting satisfactory static and dynamic footbridge behaviour. Particular attention is paid to a problematic structural detail—the connection between the steel cross-girder and the timber main girder. Firstly, this connection’s characteristics were measured experimentally using nine laboratory samples made of two glued laminated timber blocks, simulating main girders connected with a hot-rolled steel cross-girder. The connection was prepared in three variants, with different heights of the end plates and different numbers of bolts. Subsequently, these characteristics were computed using two numerical FEM models. The first model was created using SCIA Engineer software with a combination of shell and beam finite elements. The second, more sophisticated model was created in the ANSYS software environment using 3D finite elements, allowing us to better take into account the plasticity and orthotropic properties of wood and the points of contact between the individual members. Finally, the experimental results produced by sample testing in the laboratory were compared to the outputs of FEM numerical studies. Full article

Orthotropic steel bridge decks (OSDs) are very popular all over the world because of the low dead load, high stiffness in the longitudinal direction, high strength ratio to weight, and can be used in various types of bridges. The life of these bridges is affected by fatigue cracks in different portions. One of major areas where the fatigue cracks appear in these bridges is rib-to-deck connection. In this research finite element analysis is carried out by using ABAQUS/CAE 2022 software to determine the ways to increase the fatigue life at rib to deck connection in OSDs. In the first part, smaller models are simulated; stress concentration is analyzed and hot spot stress (HSS) is calculated according to International Institute of Welding (IIW) and Det Norske Veritas (DNV) recommendations. In the second part, a parametric analysis is carried out to analyze the effect of weld penetration, thickness of deck, thickness of rib and rib to deck connection type. In the third part, simulation of models similar to the real field is carried out to determine whether the double welded connections are better than single welded connections. Different models are analyzed for different load cases like single wheel load, double wheel load and also the position of the wheels is changed. The boundary conditions are changed to analyze whether the boundary condition has any significant effect on the result obtained. It is found that thicker decks, thinner ribs, and low penetrated welded connections reduce the stress concentrations at rib to deck connections which ultimately increase fatigue life. Among the parameters examined, deck thickness is the most important parameter. It is found that the percentage of stress increase with percentage decrease in deck thickness follows a power relation. The overall fatigue life of double welded connection is excepted to be lower since the stress concentration is maximum at the weld toe at deck on the outer side of the closed stiffener; however, if the cracks initiate on the inner side of closed stiffener, the cracks at the weld root of single welded connection can propagate much rapidly than the cracks initiating on the inner side of the closed stiffener at the weld toe, thereby reducing the fatigue life of the single-welded specimen significantly. Full article

Multiple fatigue cracks are generally present in practical engineering due to the existence of welding; the size and number of cracks of orthotropic steel bridge decks are greatly uncertain. The component failure conditions caused by these cracks may have correlations. Currently, it is still a challenging issue to develop a physical model of multiple fatigue crack propagation in bridge decks and perform a fatigue reliability assessment, which is also the motivation that drives the innovation of this study. A fatigue reliability evaluation method is presented for orthotropic steel bridge decks, considering the coupling effect of multiple cracks and the randomness of vehicle loading. A numerical simulation method for multifatigue crack growth is developed by combining the ABAQUS and FRANC3D programs. The equivalent crack depth under different spacing and depths of collinear cracks is calculated by using numerical simulation and the multicrack equivalent characterization method. The critical damage accumulation function of multiple fatigue cracks is established using linear elastic fracture mechanics. Subsequently, the critical damage accumulation function of multiple fatigue cracks is established based on linear elastic fracture mechanics. In order to solve the time-consuming problem of traditional Monte Carlo method, the iHL-RF method and AK-MCS method are developed for fatigue reliability analysis. The results show that compared with the single-crack model, the fatigue reliability of orthotropic steel deck will be crucially reduced considering the coupling effect of double cracks. The MCS, iHL-RF and AK-MCS methods can effectively solve the fatigue reliability analysis problem. Compared with the MCS method, the reliability calculation time based on AK-MCS method is significantly reduced. The AK-MCS method-based method reduces the time for calculating the reliability of orthotropic steel decks by 50% compared with the iHL-RF method. The reliability analysis of orthotropic steel deck bridge based on AK-MCS method is proved to be efficient and accurate. Full article

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. Full article