Orthotropic Steel Deck Research Articles

Rewelding Residual Stress of Fatigue Crack at U-Rib-to-Deck of an Orthotropic Steel Deck

The orthotropic steel deck is a prevalent stiffening girder structure utilized in long-span cable-stayed bridges and suspension bridges. Nonetheless, the issue of fatigue cracking has persisted in in-service orthotropic steel decks, significantly impacting the longevity of bridges. This study examines the analysis of the distribution of residual stress during the rewelding process of a fatigue crack at the U-rib-to-deck-plate joint of an orthotropic steel bridge deck. Additionally, the impact of the initial welding and the stiffness of the boundary constraint on the residual stress field during rewelding is discussed. The findings indicate that the removal of the fatigue crack prior to rewelding alleviates the transverse residual stress caused by the initial welding. After undergoing the rewelding procedure, both the transverse residual stress and the longitudinal residual stress exhibited a significant stress peak. More precisely, the transverse tensile stress underwent a rise from 21 MPa to 385 MPa, while the longitudinal tensile stress experienced an increase from 345 MPa to 525 MPa. Furthermore, the range of tensile stress within the longitudinal residual distribution expanded by 88%. Moreover, the stress redistribution during the rewelding of the local fatigue crack varied depending on the constraints imposed on the steel bridge deck. Notably, the transverse residual stress increases by 40.6% when compared to the absence of constraints. The findings of this research offer valuable insights for the implementation of rewelding repair techniques on steel bridge decks, emphasizing the significance of considering the effects of residual stresses induced during the rewelding process.

The Maintenance Effect of Diaphragm-to-Rib Fatigue Cracks in Orthotropic Steel Deck via Steel Plate Reinforcement

To investigate the maintenance effect of diaphragm-to-rib fatigue cracks via steel plate reinforcement, finite element models of different-shaped steel plates were established. Stress intensity factors at the crack tip before and after reinforcement were obtained, and the variations in stresses were studied. Polygonal steel plate reinforcements were then carried out on a real bridge based on the finite element calculation results. The changes in stress amplitudes and fatigue damage degrees at the crack tip were analyzed via the rain-flow counting method and Miner’s linear damage accumulating theory. The results show that both the polygonal steel plate and the rectangular steel plate could effectively eliminate the stress concentration and restrain the propagation of cracks. The stresses in other parts of the arc notch increased after reinforcement and polygonal steel plates had less influence. After the reinforcement in a real bridge, the cycle number of high stress amplitudes at the crack tip decreased significantly. The fatigue damage degree of the repaired part reduced by 70.1%, which verified the maintenance effect via polygonal steel plate reinforcement on diaphragm-to-rib fatigue cracks.

Thermostatic shrinkage effect monitoring and analysis of novel Post-Combination Steel-UHPC composite decks

Combining Ultra-High-Performance Concrete(UHPC) layers to orthotropic steel decks through connectors has been increasingly applied to improve the latter’s fatigue resistance. However, a low water-binder ratio resulting in rapid and large UHPC shrinkage becomes a challenge since the constraint of connectors may cause shrinkage-induced stress and even cracks. To this end, a novel post-combination steel-UHPC composite deck was proposed to induce a low shrinkage constraint effect. It mainly refers to a relatively free shrinkage process due to absence of interlayer connectors in the early construction period. Particularly, 3 full-scale segmental steel-UHPC composite decks were prepared for 120 days shrinkage effect monitoring in a constant 18.5℃ space. Meanwhile, simulation and parametric analysis with shrinkage and damage plasticity constitutions were also conducted. The monitoring results showed that the shrinkage-induced UHPC strain in a post-combination specimen was 43% larger than a normal specimen, while the strain on a steel deck and rib became 60% and 79% lower. It tells an obvious lower-shrinkage constraint feature. Moreover, the lower shrinkage constraint of post-combination also resulted in a nearly 15% larger reinforcement compressive strain. Furthermore, the parametric analysis showed a detailed relationship between the low shrinkage constraint extent and the shrinkage-induced effect. Finally, a simplified theoretical shrinkage effect evaluation method was proposed. The research results provide fundamental knowledge for the shrinkage mechanism understanding of such a novel post-combination operation.

Fatigue improvement of rib‐to‐deck welded joints using adhesively bonded steel patches ‐ LEFM‐based parametric study

AbstractRib‐to‐deck welded joints in orthotropic steel decks of bridges are prone to develop fatigue cracks. Repairing such cracks allows for prolonging the life of the infrastructure, provided that structural safety is guaranteed. Among others, the repair technique of adhesively bonded steel patches is relatively simple and inexpensive. Moreover, it has the advantage that the original structure is not altered, e.g. as in the case of crack stop holes. This technique has been used in other details like the diaphragm of steel bridges. However, limited information is available when applied to rib‐to‐deck joints, which are the most common joint type in orthotropic steel decks. This study proposes two repair schemes using adhesively bonded steel patches for the rib‐to‐deck joints. A 3‐D finite element model which takes account of the crack size is established. Based on linear elastic fracture mechanics (LEFM), a parametric study is performed to investigate the effect of patch geometry and adhesive thickness on the performance of repair schemes.

Fatigue performance evaluation of stiffener‐to‐deck plate weld in orthotropic steel decks based on generative adversarial network

AbstractThe stiffener‐to‐deck plate welds are one of the weak areas of orthotropic steel decks (OSDs). Accurate evaluation of fatigue performance of stiffener‐to‐deck plate welds is important for the design and service of OSDs. Traditional fatigue performance evaluation method of stiffener‐to‐deck plate welds based on S‐N curves requires a large amount of experimental data as support. However, fatigue tests are time‐consuming and costly‐approach. In this paper, generative adversarial network (GAN) was used to augment hot spot stress range data and fatigue life of rib‐to‐deck welded joints based on a small amount of test data. Then, the least‐squares regression was used to fit S‐N curves base on original data and generated data. The fitted S‐N curves were compared with experimental curve. Compared with the S‐N curve fitted by a small amount of original data, the S‐N curve fitted by generated data is closer to the experimental result, which indicates that the fatigue data generated by GAN has the potential to be an effective tool in the fatigue performance evaluation of fatigue critical details.

Orthotropic composite slabs for road bridges

AbstractLarge increases in traffic loads led to extensive fatigue damages to existing orthotropic steel deck slabs of road bridges. Reinforced concrete bridges and conventional composite bridges are less susceptible to fatigue but considerably heavier. The ortho‐composite slab is a lightweight and robust alternative construction method, which retains the advantages of the previously mentioned construction methods, but eliminates their disadvantages. Within the framework of the AiF‐FOSTA research project P1265 [1], the construction of the bridge deck was developed using dowel strips as composite elements with high load‐bearing capacity and fatigue resistance. The principle of area composite with loading of the dowel strips in longitudinal and transverse direction was used. Extensive experimental and structural mechanics studies were conducted, particularly investigating the load‐bearing capacity and fatigue strength of the ortho‐composite slab under local load application. The following article describes the load‐bearing structure of the ortho‐composite slab and the motivation for the research project P1265. It gives an overview of the experimental investigations carried out. Finally, the article presents pilot projects that were carried out to apply the construction method. In further articles on Eurosteel, the experimental investigations and structural‐mechanical calculations are described in more detail (see [2] and [3]).

Experimental determination of the fatigue behavior of dowel strips in ortho‐composite slabs for road bridges

AbstractIn contrast to reinforced concrete and conventional composite bridges, the orthotropic steel deck slab offers a high load‐bearing capacity combined with a low dead weight. It is therefore ideally suited for slender and long‐span structures. However, the notch sharpness in the details and drastically increased traffic loads led to extensive fatigue damage and, as a consequence, often to premature repair or replacement work. With the ortho‐composite slab a lightweight and robust construction is currently being developed as an alternative. It combines the significant advantages of a low dead weight, long service life and economical production. The construction consists of a modified orthotropic stiffened steel plate and a thin, single‐layer reinforced in‐situ concrete. Composite dowel strips (CDS) with a clothoid shape are provided as shear connectors. In this paper, the experimental test program will be introduced. It comprises static push‐out tests on CDS in longitudinal and transverse directions as well as static and cyclic beam and segment tests. The focus lies on the test set‐ups, sample preparations, measurement concepts and the results of the so‐called beam tests. The investigations presented here were carried out as part of the AiF‐FOSTA research project P1265 [1].

Bulb versus Trough

AbstractWith the increasing traffic intensity and traffic loads, it can be questioned whether the application of orthotropic steel decks with troughs as longitudinal stiffeners is still the best solution. Possibly, the use of bulb profiles as longitudinal stiffeners could offer a better solution. Bulb profiles were commonly used till the late sixties but are no longer applied due to high manufacturing costs. However, new welding techniques have become available nowadays, which could possibly eliminate this disadvantage. In this study, a comparison is made between an orthotropic deck with troughs and with bulb profiles. For both deck types, an optimized design is made with respect to fatigue, after which both designs are compared with respect to weight, costs, production, maintenance, and inspection. Surprising outcome is that the bulb deck can be more favorable on certain aspects compared to the more recent trough deck.

Effect of ultrasonic impact treatment on welding residual stress and fatigue resistance of doubly-welded rib-to-deck joints in OSD

Innovative doubly-welded rib-to-deck joints (DRJ) have been developed to enhance the fatigue life of orthotropic steel decks (OSD) used in steel bridges. However, the welding process and welding residual stress (WRS) distribution of DRJ are more complicated than those of conventional single-side welded rib-to-deck joints. To release WRS and improve the fatigue resistance of DRJ, ultrasonic impact treatment (UIT) and fatigue tests were performed in this study. The effect of the UIT process on the WRS distribution and fatigue resistance of the DRJ was investigated. Furthermore, the welding processes of the DRJ and UIT were simulated using the finite element method and validated against the relevant measurements. Subsequently, they were used to investigate the effect of the UIT process on the WRS distribution and represent the mechanism of fatigue failure of the DRJ. Compared with the as-welded specimens without UIT, the fatigue strength of the DRJ increased by more than 60%, and the UIT process altered the dominant fatigue failure mode of the DRJ. The fatigue crack, caused by a UIT-induced fold defect, tends to initiate at the bottom of the impact pit. Owing to the UIT process, the adverse tensile WRS in the weld toe is eliminated, and beneficial compressive residual stress is introduced, leading to an improvement in the fatigue strength of the DRJ.

Fatigue Performance of Rib-to-Deck Double-Sided Weld Joint of Orthotropic Steel Deck on Plate Girder Railway Bridges

This research work presents the stress behavior of rib-deck weld joints in Orthotropic Steel Deck (OSD) railway bridges. It is essential to determine the most vulnerable load mode of the wheels for fatigue failure of OSD bridges and to improve the fatigue resistance of the welded rib-deck connection. Fatigue performance largely depends on the weld stress. Double-sided welds for rib-deck welds improve fatigue performance. The fatigue behavior of the rib-deck double-sided weld joint has been compared with the single-sided one. This study used Abaqus software to create the global shell model and the solid submodel of the OSD. The results of the structural stress-based finite element analysis indicated that when the center line of the front axle pair of a locomotive coincides with the center line of the midspan of the bridge, the most severe loading condition occurs. The rib near the main girder experiences the maximum structural stress in the weld toe of the rib-deck joint. Moreover, the rib-deck double-sided weld joints have 43.7% less structural stress compared to single-sided weld joints at the root of the weld, and this improves the performance during fatigue of OSDs.

Numerical Simulation on Crack–Inclusion Interaction for Rib-to-Deck Welded Joints in Orthotropic Steel Deck

Weld defects such as porosity, inclusion, burn-through, and lack of penetration are difficult to detect and control effectively in an orthotropic steel deck (OSD), which will be a fatigue crack initiation site and lead to several fatigue cracking. The crack growth behavior in defective welded joints is different from that of defect-free joints. This study investigates crack–inclusion interaction for rib-to-deck welded joints in OSDs based on numerical simulation and linear elastic fracture mechanics (LEFM). A refined finite element model of a half U-rib with cracks and inclusions was established by using the FRANC3D-ABAQUS interactive technology. The full processes of the crack–inclusion interaction from approaching and penetrating were accurately simulated. Critical parameters, including the stress intensity factor (SIF), the shape factor, the growth rate, and the growth direction were analyzed. The stiff and soft inclusions amplify and shield the SIF of cracks when the crack grows to the local area of inclusions. During the entire process of crack growth, the soft and stiff inclusion accelerate and inhibit the crack growth, respectively. The stiff inclusion will lead to asymmetric growth of the crack shape, where the portion of the crack away from the inclusions has a higher growth rate. The soft and stiff inclusions will attract and repel the direction of crack growth at the proximal point, respectively.

Fatigue properties of OSD in large cantilever cable-stayed bridge on highway-railway layer

To enhance the understanding of fatigue issues in orthotropic steel deck (OSD) bridges with cantilevered steel-box girders on highway–railway layers and ensure the fatigue life of similar bridges, this study focused on the OSD fatigue characteristics of the Jinhai Bridge, the world's widest dual-use–cable-stayed bridge for road and railway transport. The fatigue-stress distribution characteristics and variation rules were investigated using a full-scale fatigue test model. Four U-ribs were subjected to four million loading test cycles, and the OSD fatigue performance was evaluated using the nominal stress method. The results indicated that the stress-influence range of the crossbeam U-rib in a large cantilever steel box girder was approximately nine U-ribs wide and three crossbeams long, significantly exceeding that of a conventional closed-box steel girder. The stress difference in the crossbeam opening bottom-edge detail in the box girder with and without a cantilever was 85.4%. Along the transverse bridge, the most unfavorable stress amplitude difference among similar fatigue details in different regions reached 57%. After 4 million cycles, the crack length was 90 mm. The fatigue cracks had a minimal effect on the overall deformation performance of the model. Combining the traffic volume statistical data and damage accumulation, the estimated fatigue life of the crossbeam opening detail was 103.55 years. According to JTG-D64–2015, this satisfies the recommended fatigue design life requirement of 100 years for the crossbeam opening details of large cantilever steel box girders. However, the economic development trends and increasing traffic volumes necessitate further research.

Experimental study on flexural and interfacial shear properties of the steel-UHPC glued composite deck

This paper proposes a Steel-UHPC Glued Composite Deck (SUGCD) to mitigate the fatigue cracking of orthotropic steel deck and improve the destructible paving layer of bridge, respectively. A series of flexural tests are conducted on 20 SUGCDs and shear tests are performed on 20 push-out specimens, respectively. The objective is to examine the effects of various interface treatment methods, reinforcement ratios, and types of epoxy adhesive on the flexural and shear properties of the composite decks. Additionally, the characteristic strength of the UHPC layer is calculated by the section conversion method. The results demonstrate that the elastic phase of SUGCD under hogging moment depends on the material properties of UHPC and the interface properties of the composite deck, respectively. The maximum difference of the cracking load of UHPC layer is 150.2% for various interface treatment methods. The composite deck has a higher elastic limit and cracking load under sagging moment than the hogging moment. The interface remains intact when the composite deck reaches its yielding strength, indicating that the interface has sufficient bonding strength. Finally, the cast-in-situ push-out specimens exhibit the optimal interfacial performance with ZR14 epoxy adhesive and 3–5 mm bauxites, and the prefabricated push-out specimens with ZR14 epoxy adhesive demonstrate the best interfacial performance, respectively. Therefore, the proposed steel-UHPC glued composite decks may meet the requirement in practical engineering.

Fatigue performance of cracked diaphragm cutouts in steel bridge reinforced employing CFRP/SMA

Under long-term service conditions, fatigue cracking occurs at the diaphragm arc-shape cutouts in the orthotropic steel deck (OSD) bridges subjected to vehicle-induced vibration and cyclical wheel load. To repair cracks of the diaphragm cutouts, this study proposes two repair methods of the carbon fiber reinforced polymer (CFRP) sheets and shape memory alloys (SMA)/CFRP composite patches on the basis of crack-stop holes. The crack-stop hole eliminates the obvious source of fatigue propagation at the crack tip, but it weakens the section and harms the entirety of the diaphragm. The edge of the crack-stop hole in the cracked section becomes a new stress concentration site and the potential crack initiation point. The CFRP sheets can effectively improve the stiffness and reduce the stress amplitude of the cracked part. Moreover, the SMA/CFRP composite patches can further introduce precompression by activating SMA to reduce the stress level. Relative to the reinforcement by the crack-stop hole only, the fatigue notch factor is reduced by 12.28% and 30.76% after bonding CFRP sheets and SMA/CFRP composite patches, respectively. The fatigue tests show that the bonding of CFRP sheets and SMA/CFRP composite patches can effectively postpone the initiation of fatigue cracks and inhibit crack propagation, so they are ideal repair methods for strengthening fatigue cracks of the diaphragm cutouts in the OSD bridges.

DETERMINATION OF THE RIB-TO-CROSSBEAM STRESSES IN ORTHOTROPIC STEEL DECKS

For long span bridges, the orthotropic steel deck (OSD) is the most popular option for the bridge deck. Normal OSDs consist out of the steel bridge deck, the longitudinal stiffeners (ribs), and the transversal beams. All of the elements are welded together. The welds create geometrical discontinuities that will result in concentrations, which lead to fatigue damage under repetitive loading. In this research, a simplified calculation method for determining the dimensions of OSDs is developed. This method shares the same notion as the Pelikan-Esslinger method, which is using an idealized orthotropic plate. Solving the idealized orthotropic plate, the internal forces of the actual OSD may be acquired. To calculate the distortional stresses, the shear deformation is treated as an independent variable and added to the simplified calculation method. The system of partial differential equations is derived through the equilibrium relationships of the substituting plate. Three rigidity coefficients are required in this method, namely the flexural rigidity coefficient, the torsional rigidity coefficient, and the shear rigidity coefficient. The former two are the same as in the Pelikan-Esslinger method. By performing a frame analysis, the formulas of the shear rigidity coefficient are achieved. Then, a simple local model is proposed for calculating the nominal distortional stress under the weld of the wall of the rib. To summarize, this research shows the possibility of optimizing the prevailing design the rib-to-crossbeam connection. The proposed fatigue life assessment method and simplified calculation method could be adopted in the future.

Performance of Rib-to-deck weld joint of an orthotropic steel deck through structural stress method

Performance of Rib-to-deck weld joint of an orthotropic steel deck through structural stress method

Experimental and numerical study on welding temperature field by double-sided submerged arc welding for orthotropic steel deck

Orthotropic steel deck (OSD) is susceptible to fatigue damage when subjected to repeated traffic loads, and the welding residual stress (WRS) is an important factor contributing to fatigue damage in OSD. WRS is formed by the shrinkage of the welds due to the inhomogeneous temperature field during the welds fabrication process, and thus the study of the welding temperature field is of significance for accurately predicting the WRS. As an emerging welding technology, the double-sided submerged arc welding (DSSAW) technology can generate higher welding temperature and consequently higher welding penetration rate on U rib and deck for welding thicker base metal. However, the DSSAW technology generates more complex welding temperature field compared to the traditional arc welding technology, which has not been evaluated so far. In this study, the finite element model (FEM) of OSD with U rib-to-deck (RTD) welded joints is established to simulate the welding temperature field generated by DSSAW. Moreover, the temperature field in OSD by DSSAW is measured by using the infrared thermal imager (ITI) and the industrial temperature measurement gun (TMG) to verify the FEM simulated temperature results. It is found that large surface temperature gradient and large temperature gradient along the thickness direction would be formed at the weld toe of U rib and deck, which is generally the location where the maximum WRS is distributed and where the fatigue cracks are susceptible in OSD. Compared to the inside welding, the outside welding may generate higher welding temperature, higher temperature gradient, and larger molten pool area, resulting in larger WRS in the OSD. The findings in this study can help to an in-depth understanding of the welding temperature field caused by the new DSSAW technology and support further studies on WRS.

Experimental Investigation on Fatigue Improvement of Orthotropic Steel Bridge Deck Using Steel Fiber Reinforced Concrete

AbstractThe high-performance topping concrete overlay would significantly reduce the fatigue stresses at susceptible details of orthotropic steel deck (OSD) and effectively improve the fatigue performance. Full-scale fatigue tests and numerical simulations were carried out to quantify the effects of steel fiber reinforced concrete (SFRC) topping pavement in reducing the OSD fatigue stresses based on a practical bridge design. Fatigue stress of the OSD critical details was measured from tests and cracking was observed in the SFRC overlay. Both an innovative pre-pump-pulse Brillouin optical time domain analysis (PPP-BOTDA) distributed optical fiber sensor and strain gauges were also used to measure the stress at OSD fatigue-prone details, including the crossbeam cut-out, rib-to-deck weld, rib-to-crossbeam weld and splice of U-rib. The corresponding three-dimensional (3-D) finite element model was then established and verified by the test results, and used to conduct a parametric study to obtain a quantitative expression of fatigue stress reduction factor, in terms of relative elastic modulus and thickness of overlay and steel deck plate. The proposed quantitative model of the fatigue stress reduction effect can guide the cost-effective design of composite bridge deck.

Study on Fatigue Cracking of Diaphragm's Arc Opening of OSD in Steel Bridges by Using Biaxial Stress Method.

Changes in loading position have a significant impact on the stress field of each vulnerable area of an orthotropic steel deck (OSD). The arc opening area of the diaphragm and the connecting area between the U-rib and the diaphragm under the moving load are prone to fatigue cracking. By comparing the stress responses under different methods, the hot spot stress (HSS) method is used as the main stress extraction method in fatigue performance evaluation. The control stress of fatigue cracking was analyzed by comparing the direction of the principal stress field with the crack direction in this experiment. According to the stress amplitude deviation under the biaxial stress state, a set of methods for evaluating the effects of in-plane biaxial fatigue was developed. An improved luffing fatigue assessment S-N curve was applied to analyze the fatigue life of the diaphragm's arc opening area. The results show that when the moving load is exactly above the connection of the deck and the web of the U-rib on one side, it is in the most unfavorable position in the transverse direction, and the diaphragm is mainly under the in-plane stress state. The longitudinal range of the stress influence line of the arc opening is approximately twice the diaphragm spacing. Two to three stress cycles are caused by one fatigue load. Fatigue crack control stress is the principal stress tangential to the arc opening's edge in this area. The normal direction of the principal stress in the model test is roughly consistent with the crack initiation direction. The variation in the stress amplitude deviation in this area is caused by changes in the action position of the moving load. When the moving load is at a certain distance from the involved diaphragm, it is reduced to zero, implying that the in-plane fatigue effect is the greatest in this area.

Experimental study on fatigue behavior of cracked steel plates repaired with adhesively bonded steel patches

Fatigue cracking is prone to occur in orthotropic steel decks (OSDs) due to its complex geometry. To guarantee structural safety and extend the fatigue life of OSDs in steel bridges, the repair technique of adhesively bonded steel patches, which has the advantage of lower cost, easy operation, and not damaging the original structure, is experimentally studied using simplified cracked steel plate specimens. Four repair schemes were considered including bare plate, single-sided patched, double-sided patched, and stop-hole repaired. The failure mode, fatigue crack propagation, and adhesive damage were studied to evaluate the effects of steel patch repair. The morphological analysis was performed to investigate the fatigue fracture characteristics and metal interface performance. The outcomes showed that adhesively bonded steel patches could significantly improve the fatigue life of cracked steel plates and the strengthening was more effective for double-sided patched specimens than single-sided patched specimens. In comparison, the repair effect of the stop-hole method is limited for cracked specimens.