Experimental study on fatigue behaviour of orthotropic steel decks under traffic loads

Fatigue performance evaluation for composite OSD using UHPC under dynamic vehicle loading

<p>Orthotropic steel decks in long-span steel bridges are susceptible to fatigue cracking, especially subsurface root-deck cracks. These cracks, hard to detect visually, can cause significant damage if unnoticed. Therefore, the early detection of these subsurface cracks is crucial in preventing further deterioration and ensuring the long-term sustainability of the bridge. In this study, a novel approach for the detection of subsurface cracks in orthotropic steel decks, utilizing new signal processing techniques based on eddy current technology (ECT), as well as optimizing the configuration of the ECT probes, is proposed. Through numerical analysis, response signals obtained from subsurface crack detection using ECT in frequency domains are extracted and analyzed with the proposed method to develop advanced feature extraction techniques that enhance sensitivity and improve the depth of subsurface crack detection. Additionally, various coil-based eddy current probes are examined to identify the most suitable probe configuration that offers robust performance in detecting subsurface cracks. The findings from this study contribute to the advancement of more effective strategies for subsurface crack detection in orthotropic steel decks by integrating advanced eddy current techniques, feature extraction methods, and optimized hardware configurations.</p>

Fatigue cracking of rib-to-deck conventional single-sided welded joints is a prevalent issue in orthotropic steel decks (OSDs), significantly impacting their structural integrity and durability. Rib-to-deck innovative double-sided welded joints have the potential to enhance the fatigue resistance of OSD. However, Welding Residual Stresses (WRS) significantly influence the fatigue life of these joints, mandating its consideration in fatigue assessments. This study introduces a novel approach for assessing the fatigue reliability of rib-to-deck double-sided welded joints in OSDs, accounting for the effects of traffic vehicle loading and WRS. Initially, a comprehensive fatigue damage equation for welded joints of OSDs was formulated, integrating WRS and dynamic vehicle loads, utilizing fracture mechanics theory. Subsequently, a measurement-based random traffic model was utilized to derive the vehicle-induced stress spectra at the welded joints. The effects of deck thickness, fatigue crack depth and fatigue crack aspect ratio on the stress intensity factor (SIF) of the crack at the weld toe were analyzed. These three variables were considered as feature vectors for the construction of a polynomial model of the shape functions, which was utilized to calculate the SIF. Finally, the fatigue reliability of the rib-to-deck double-sided welded joints in OSDs subject to traffic vehicle loading considering the WRS was estimated using Monte Carlo simulation. The influence of traffic volume growth on fatigue reliability was discussed. This research underscores the critical role of WRS in the fatigue performance of welded joints in OSDs and offers an innovative framework for assessing the fatigue reliability of steel bridge welds.

The orthotropic steel deck is widely used in long-span steel bridges due to its simplicity and efficiency. The welded joint of the U-rib to e deck panel area is extremely sensitive to fatigue cracks. In this study, an orthotropic steel deck with an arc-shape stiffener was proposed that aimed to alleviate the fatigue cracks and enhance the fatigue resistance in long-span steel bridges. Based on the Mingzhu Bay steel bridge, the proposed steel deck FE model was first established. Then, the moving vehicle load was applied to investigate the impact of the arc-shape stiffener on the fatigue stress amplitude and distribution. The Miner fatigue cumulative damage theory was employed to evaluate the fatigue life of the orthotropic steel deck with arc-shaped stiffener, and comparative analyses were carried out. Finally, the results show the maximum stress of the orthotropic steel deck with an arc-shaped stiffener is reduced by 15%, and the fatigue life is improved by 40% compared with the OSD.

When exposed to static and dynamic traffic loading, road pavements can exhibit degradation and permanent surface deformation. This study examined the impact of dynamic loading on the layers of a flexible pavement. This study used two types of geotextile (woven and non-woven) as reinforcements. Two cases were investigated; the first one by placing the reinforcement within the wearing layer, and the other one by placing it between the wearing and base layers. The road layers experienced a harmonic dynamic load with an amplitude of 1.5 tons and a frequency of 0.25 Hz. The measurement of strain in the layers of the road was carried out using a strain gauge sensor. The results indicated that when geotextile was placed between the wearing and base layers, it provided a better reinforcement with a reduction of 74.8% in strain using woven geotextile. Keywords: Geotextile reinforcement, Flexible pavement, Sliding between layers, Strain, Strain gauge sensor, Dynamic load.

The piled raft foundations are widely used in infrastructure built on soft soil to reduce the settlement and enhance the bearing capacity. However, these foundations pose a potential risk of failure, if dynamic traffic loading and ground conditions are not adequately accounted in the construction phase. The ground conditions are complex because of frequent groundwater fluctuations. The drawdown of the water table profoundly influences the settlement and load sharing capacity of piled raft foundation. Further, the dynamic loading can also pose a potential risk to these foundations. In this paper, the two-dimensional finite element method (FEM) is employed to analyze the impact of water drawdown and dynamic loading on the stability of piled raft. The seismic response of piled raft is also discussed. The stresses and deformations occurring in and around the raft structure are evaluated. The results demonstrate that water drawdown has a significant effect on the stability and seismic response of piled raft. Various foundation improvement methods are assessed, such as the use of geotextile and increasing thickness of the pile cap, which aids of limiting the settlement.

Since the first application of steel orthotropic deck in bridges, engineers have shown great interest in the popularization of steel decks, based on their various advantages like light-weight, high capacity and so on. However, because of their complex configurations, repeated loading, and stress concentration, many details of steel orthotropic bridge decks are fatigue-sensitive. Recently, considerable increase in traffic volume and wheel loads has caused a number of fatigue cracks in steel orthotropic bridge decks in China. For example, bridge engineers have detected thousands of fatigue cracks in steel orthotropic deck on the main box girder of Humen Bridge only ten years after opening to traffic, which is the first modern suspension bridge with the main span of 888 meters in China. So the bridge owners pay more attention to evaluate the locations of fatigue damages. In current paper, the standard section of the real bridge deck was simulated and a kind of typical fatigue cracks was selected to analyze their fatigue life using S-N curve, the fatigue damage analysis was carried out on the longitudinal ribs to deck plate connections. The fatigue damage analysis results were consistent with the observations from real bridge decks.

Fatigue cracking is a common issue in steel orthotropic bridge decks subjected to long-term dynamic loading. When repairs are required, especially by welding, it is typically necessary to close the bridge to traffic to ensure proper weld quality. However, bridge closures can lead to significant societal and economic impacts, including traffic congestion, long detours, increased emissions, and loss of time. Therefore, the ability to carry out repair welding without full traffic closure is of considerable interest for infrastructure operators and public authorities. The first essential step in enabling such in-service repair is to assess the dynamic behaviour of existing fatigue cracks under traffic loads. Specifically, it is crucial to monitor the crack flank movements to determine whether they remain within acceptable limits during ongoing traffic, thereby permitting welding without compromising the repair quality. This paper presents the development and deployment of a specialized monitoring system designed to measure crack flank displacements in real time. Crack flank movement amplitudes and frequency responses were recorded and analysed. Measured data were compared with results from similar monitoring campaigns conducted in other countries.

Most research conducted so far has primarily focused on pile-supported gravel embankments. The ability of solidified soil used as an embankment filling material has been verified, and a clear view on the performance of solidified soil embankments on piled foundations is rather limited. The three-dimensional unit cell models of pile-supported embankments are conducted to investigate the performance of solidified soil embankments in comparison to gravel embankments under static and dynamic loads. Then, a systematic parametric analysis is performed to investigate the effects of various factors, including the cohesion and friction of solidified soil, the velocity and wheel load of vehicles, the pile spacing, the height of embankments. The results show that, compared with the results of gravel embankments, the heights of the outer soil arch plane in solidified soil embankments reduces under static and dynamic loads, and the piles bear more load. In addition, the total settlements of solidified soil embankments decrease with increasing cohesions, and there is an economical cohesion of 25 kPa. The vehicle wheel load, pile spacing, and the height of embankment significantly influence the load transfer mechanism and total settlement of solidified soil embankment, while the friction angles and velocities have little effect on the total settlements and vertical stress. The relationship between the soil arch height and various parameters in solidified soil embankments is established by multiple regression analysis. This investigation highlights the advantage of solidified soil in reducing total settlement and provides an insightful understanding of the load transfer mechanism of solidified soil embankment on piled foundation.

Microseismic events commonly occur during the excavation of long wall panels and often cause rock-burst accidents when the roadway is influenced by dynamic loads. In this paper, the Fast Lagrangian Analysis of Continua in 3-Dimensions (FLAC3D) software is used to study the deformation and rock-burst potential of roadways under different dynamic and static loads. The results show that the larger the dynamic load is, the greater the increase in the deformation of the roadway under the same static loading conditions. A roadway under a high static load is more susceptible to deformation and instability when affected by dynamic loads. Under different static loading conditions, the dynamic responses of the roadway abutment stress distribution are different. When the roadway is shallow buried and the dynamic load is small, the stress and elastic energy density of the coal body in the area of the peak abutment stress after the dynamic load are greater than the static calculations. The dynamic load provides energy storage for the coal body in the area of the peak abutment stress. When the roadway is deep, a small dynamic load can still cause the stress in the coal body and the elastic energy density to decrease in the area of the peak abutment stress, and a rock-burst is more likely to occur in a deep mine roadway with a combination of a high static load and a weak dynamic load. When the dynamic load is large, the peak abutment stress decreases greatly after the dynamic loading, and under the same dynamic loading conditions, the greater the depth the roadway is, the greater the elastic energy released by the dynamic load. Control measures are discussed for different dynamic and static load sources of rock-burst accidents. The results provide a reference for the control of rock-burst disasters under dynamic loads.

Multiscale fatigue damage evolution in orthotropic steel deck of cable-stayed bridges

In recent years, the ultra-high performance concrete (UHPC) has been increasingly used to strengthen orthotropic steel decks (OSD) to solve the cracking problems at fatigue-prone details and pavement damage. In this paper, the fatigue life of a cable-stayed orthotropic steel decks bridge under stochastic traffic loads is calculated before and after the orthotropic steel decks strengthened with the ultra-high performance concrete layer. The traffic data of the real bridge for 1 week is first obtained based on the weigh-in-motion system. Then, a stochastic traffic load on the bridge is simulated for its service life by the Monte Carlo method. A fatigue life analysis framework, which includes the traffic load simulation, a refined finite element model, the S-N curve and Miner linear cumulative damage criterion, is proposed for fatigue life prediction of orthotropic steel decks. For the bridge before reinforcement, the predicting results for the fatigue life of three fatigue-prone details, including the scallop cutout, rib-to-diagram and rib-to-deck joint are basically consistent with that of the actual bridge inspection results. After strengthening by ultra-high performance concrete, the fatigue life of the three structural details are increased from 15.87, 13.89, and 32.26 years to more than 100 years, respectively, as compared with the original orthotropic steel decks structure.

To investigate the stress distributions on implant-bone interface and fatigue behaviors of biomimetic titanium implant under static and dynamic loading conditions to provide theoretical basis for a new implant which may effectively transfer the stress to surrounding bones. A 3-D finite element model of a posterior mandible segment with an implant bone was constructed by a CAD (Pro/E Widefire 2.0) software. Two different implant models (a dense implant No.1 and a biomimetic implant No.2) were designed. The stress distributions on bone-implant interface under dynamic and static loading conditions were analyzed by Ansys Workbench 10.0 software, as well as the fatigue behavior of the biomimetic implant. The cervical cortical bones in the 2 implants were all high stress region under the same loading condition. The maximum von Mises stress on the interface and high-stress region in the cancellous bone region, and the maximum stress in the root region of the biomimetic implant were lower than those of the dense implant. The stress on the implant-bone interface decreased from the top to the bottom. The stress in the cervical cortical bone under the dynamic loading was 17.15% higher than that of the static loading. There was no significant difference in maximum stress at the cortical bone region between the dynamic and static loading conditions. The maximum stress of the dense implant in the cancellous bone region was 75.97% higher and that in the root region was 22.46% higher than that of the biomimetic implant. The maximum stress on the implant-bone interface was far less than the yield strength of pure titanium. The stress distribution in the cortical region of the biomimetic implant was 7.85% higher than that of the dense implant, and the maximum stress in the cortical bone was smaller than the yield stress of cortical bone. Within the dynamic loading of 50-300 N, the safety coefficient was all higher than 10, and with the increase of loading pressure, interface stress in the cancellous region increased linearly. Under the loading of 300 N in the axial and 25 N in the lingual 45:, the maximum stress was 11.38 MPa. Biomimetic style implant can effectively transfer the implant-bone interface stress to surrounding bones in the cancellous bone and root region, and the structure with the improved design is safe under normal loading pressure.

The performance of WDM networks using shortest path routing is studied under wavelength continuous (WC) and non‐continuous (NWC) constraints and dynamic traffic loading. Approximate analytical models are presented for the performance studies of such systems. Results of numerical calculations based on these models and simulations are given for different network topologies for the purposes of comparison. These analytical and simulation results are used to study the performance of these WDM networks under dynamic traffic loading. Copyright © 2001 John Wiley & Sons, Ltd.

Inelastic behavior of orthotropic steel deck stiffened by U-shaped stiffeners