Orthotropic Steel Bridge Research Articles

Residual stress measurement at the weld root of rib-to-deck welded joints in orthotropic steel bridge decks using the contour method

This paper presents a comprehensive study on measuring residual stress (RS) distribution at the weld root of rib-to-deck joints using the contour method (CM). Two different cutting techniques were performed at the weld root to examine their influence on the distribution of mapped RS. A fully automated data processing code was developed to prepare and treat the raw measured displacements where the smoothed displacements were printed out as constraints normal to the cut surface. Linear elastic calculations were carried out to map RS distribution across the cut surface. Different boundary conditions (BCs) cases were also studied to examine their influence on the resulting energy as well as RS distribution. The results provide full 2D maps of RS distribution across the cut surface. The results reveal compressive RS is induced at the weld root for the two cutting techniques. It is also noticed that the applied cutting techniques influence the distribution of mapped RS. Further, the examined BCs cases show a small influence on the resulting energy while they have a negligible impact on the general distribution of mapped RS. Moreover, 2D stress maps were prepared by means of the plane strain condition to provide a general image of RS distribution, especially at the weld root. The results obtained by the plane strain condition give a good understanding of the induced RS distribution at the weld root for the two cutting techniques.

Fatigue strength of transverse attachment steel joints with single-sided arc weld using low transformation temperature welding consumable

This study investigated the applicability of low transformation temperature (LTT) arc welding consumables to improve fatigue strength against weld root failure. Transverse attachment joints formed by single-sided welding, similar to rib-to-deck connections in orthotropic steel bridge decks, were fabricated using an LTT welding consumable and conventional welding consumable. Fatigue tests were performed with out-of-plane bending loads using a vibration-type fatigue testing machine. The test results indicated that higher fatigue strength can be achieved in the joint with an LTT consumable compared with a conventional one. In addition, residual stresses around the weld bead were clarified by X-ray diffraction measurements and finite element analyses. The results revealed that the LTT consumable weld metal can reduce residual stress around the weld and also introduce compressive residual stress to the weld root, which can contribute to improved fatigue strength.

Study of the Strain Response of Asphalt Pavements on Orthotropic Steel Bridge Decks through Field Testing and Numerical Simulation

Abstract A composite structural system consisting of an orthotropic steel bridge deck, waterproof prime, binding course, and wearing surface is complicated. To simplify the analysis of such systems, general elastic and continuous structure theory is applied to the asphalt pavement on steel bridge decks to determine the magnitude of the strain. Large differences in mechanical results have been previously obtained in assessments of steel bridge deck pavements. Few studies have focused on the mechanical state and time-dependent response of a realistic steel bridge deck wearing surface because of the difficulty of measuring the strain of the pavement on a steel deck of a long-span bridge that is in service. This study performed static and dynamic loading tests on an actual long-span steel bridge and analyzed the characteristics of the time-dependent strain response of the bridge deck wearing surface. The results demonstrate that the asphalt wearing surface exhibited significant loading time and rate-dependent characteristics under both static and dynamic loading conditions. The test analysis results also revealed that the axle load, vehicle speed, and longitudinal slope of the bridge had significant effects on the mechanical responses of the bridge deck wearing surface. Based on a comparison between the finite element numerical simulation results and the measurements obtained from testing the actual bridge, the magnitudes of the mechanical strain responses of the wearing surface on a steel bridge deck under the dynamic wheel load of a vehicle were analyzed assuming that the wearing surface is elastic and that the elastic modulus can be determined from a four-point bending test. However, the cumulative effect of plastic deformation must be considered when analyzing the fatigue damage of a permanent wearing surface.

Fatigue Performance Evaluation for an Orthotropic Steel Bridge Deck Based on Field Hotspot Stress Measurements

Abstract This study has introduced a method for fatigue performance evaluation of steel orthotropic bridge decks based on filed measurements for hotspot stress. The long-term stress of the orthotropic bridge deck of Jinchang Road Canal Bridge in Hangzhou, China, was observed by sensors. The fatigue damage and fatigue reliability of the bridge deck were analyzed and evaluated according to the stress. The results show that: (a) the fatigue life of the bridge deck is larger than the design value, indicating that the design of the orthotropic bridge deck is reasonable; (b) the fatigue loads acting at three hotspots can be described by normal distribution; and (c) for the current traffic volume, the fatigue reliability index of the three hotspots is greater than two in the design period. The fatigue reliability index of the three hotspots decreases significantly with the increase of traffic flow, at which time the fatigue damage becomes considerable.

Fatigue Performance of Different Rib-To-Deck Connections Using Traction Structural Stress Method

The fatigue performance of an orthotropic steel bridge deck is significantly influenced by the type of the rib-to-deck connection considering the crossbeam. Fatigue fracture of the weld seam at the rib-to-deck connection has been a serious problem in such decks. In this paper, numerical models are developed for the orthotropic steel bridge decks and are analyzed for the fatigue behavior. The traction structural stress method is proven to be more accurate and effective in predicting the fatigue life. Fatigue behavior of three typical rib-to-deck connections are obtained by using traction structural stress method and by considering the effect of crossbeams. Compared to the bridge deck with weld seam of a large root, the fatigue performance of the deck with single-sided weld seam is much better with lower equivalent structural stress. The results indicate that the weld seam size should be strictly controlled for better fatigue resistance. The fatigue performance of the bridge deck with double-sided seam is significantly better than that of the bridge deck with single-sided weld seam. An increase in the thickness of the inner weld seam in the rib-to-deck connection optimizes the distribution of the equivalent structural stress and shifts the fatigue failure location from the weld root of the outer weld seam to the weld toe of the inner weld seam thus demonstrating the effect of the crossbeam. The trends of equivalent structural stress with geometric parameters of the weld seam in the rib-to-deck connection are obtained in this study. The fatigue behavior of the components and the equivalent structural stress are significantly influenced by the bridge deck thickness.

Fatigue Property and Improvement of a Rounded Welding Region between the Diaphragm Plate and Closed Rib of an Orthotropic Steel Bridge Deck

By means of finite element modeling (FEM) and fatigue experiments, we study the fatigue performance of the rounded welding region between the diaphragm plate and closed rib of orthotropic steel bridge deck in this work. A local sub-model of the rounded welding region from the orthotropic steel bridge deck was developed to analyze the stress distributions. Based on the analysis results we designed the fatigue specimen for the fatigue test of this detailed structure. The fatigue experimental results revealed that the crack initiates from the weld toe of the rounded welding region and the stress concentration at the rounded welding region is the main mechanism of fatigue crack initiation. In addition, we propose three improvements to reduce the stress concentration of the rounded welding region, and the local structure optimization scheme of the diaphragm–rib weld can effectively improve the fatigue resistance of the detailed weld structure.

Fatigue stress analysis of orthotropic steel bridge decks in Xinghai Bay Cross-sea Bridge

Fatigue stress analysis of orthotropic steel bridge decks in Xinghai Bay Cross-sea Bridge

Evaluation of epoxy asphalt rubber with silane coupling agent used as tack coat for seasonally frozen orthotropic steel bridge decks

To improve the durability of tack coat applied to orthotropic steel bridge decks against freeze-thaw cycle in seasonally frozen regions, an epoxy asphalt (EA) tack coat modified by silane coupling agent surface-treated rubber particles (ARP) is proposed. In comparison with epoxy asphalt and epoxy asphalt rubber (EAR), the performance of ARP modified epoxy asphalt (EAAR) and EAAR tack coat were evaluated by conducting an experimental program in the laboratory. The properties of studied tack coat binders were first evaluated by viscosity, direct tensile and bending beam rheometer tests. Furthermore, the steel-asphalt interface performance including pull-off, shear and freeze-thaw damage resistance were evaluated as well. Results show that the incorporation of ARP can improve the mechanical properties and freeze-thaw damage resistance of EAAR, but it had shown a negative effect on the allowable construction time. When EAAR tack coat was used, the low temperature pull-off and shear strength can be improved to approximately 1.2 times that of EA tack coat, and the average interface fracture energy of the EAAR tack coat was about twice higher than EA tack coat. Moreover, EAAR tack coat had shown higher freeze-thaw damage resistance than EA tack coat, regardless of the higher nominal seepage pressure ratio, higher shear strength ratio and lower freeze-thaw damage ratio at the same freeze-thaw cycle periods. All the above findings indicate that the EAAR is of great potential to be applied as tack coat for seasonally frozen orthotropic steel bridge decks.

Analysis of Fatigue Performance of U-Rib to Deck Connections in Orthotropic Steel Bridge Structures

The stress condition of the transverse rib, bridge deck, and crossbeam in orthotropic steel bridge decks (OSBD) is complicated. Existing fatigue test specimens and the fatigue performance of components in OSBD differ significantly. In this paper, the numerical analysis method using traction structural stress is validated by the comparison with fatigue test results. The evaluation results of the fatigue behavior using the traction structural stress method are proven to be accurate. The comparative results give the fatigue performance of various types of typical test specimens in terms of the equivalent structural stress and initiation locations.

Analytical study on local stress of the weld of vertical stiffener on orthotropic steel bridge

Analytical study on local stress of the weld of vertical stiffener on orthotropic steel bridge

Performance Evaluation of Long-Span Suspension Bridge Pavement Based on Long-Term Maintenance Data

Based on the long-term maintenance data, the performance and service lives of several orthotropic steel bridge deck (OSBD) pavement materials in long-span suspension bridges were studied and evaluated. According to the results, the pavement service life was found to have a strong relationship with traffic volume, so limiting overload of vehicles is an effective means to ensure the performance and prolong the pavement service life. Gussasphalt (GA) and ordinary road pavement asphalt mixtures cannot meet the requirement of OSBD pavement in suspension bridges, and cold-mixed resin-asphalt concretes are expensive and their application effects were not excellent enough. High-resilience polymer and rubber-modified asphalt concrete can be used as an alternative material in the maintenance of OSBD pavement because of their acceptable service life and proper cost. Epoxy asphalt concretes (EAC) were found to be the most successful materials in suspension bridge OSBD pavements. One kind of EAC, named Kindai Bridge Epoxy Pavement (KD-BEP), was confirmed to be more suitable for the maintenance of long-span suspension bridges’ OSBD pavement because of its simpler construction process, shorter curing period, and more stable quality.

Fatigue behavior of orthotropic bridge decks with two types of cutout geometry based on field monitoring and FEM analysis

This paper provides comparative results on stress behavior and fatigue performance of two types of cutout geometry on orthotropic bridge decks based on simultaneous field monitoring and finite-element method (FEM) analysis. The two types of cutout are incorporated in two closely spaced diaphragms with distance of 6 m and at the same transverse location on a real bridge, allowing simultaneous stress measurement under random traffic flows. The research was conducted on the Pingsheng Bridge in Southern China, a self-anchored suspension bridge with a main span of 350 m and a steel box girder with orthotropic steel bridge decks (OSBD). Results of the study reveal that the two types of cutout geometry present high stress response and severe stress concentration at the floorbeam (FB) cutout, and that the excessively large stress at the original FB cutout contributes greatly to the early cracks of this detail. Compared to the original cutout geometry, the new cutout geometry with large radius increases the stress level at the FB cutout, resulting in a further low fatigue life at this detail. Meanwhile, the new cutout geometry also deteriorates the fatigue resistance at the rib-to-floorbeam (RF) weld connection, particularly at the detail of rib wall at cutout, where the stress level is significantly increased and its fatigue life becomes substantially lower than the design life of 100 years. In addition, the new cutout geometry only slightly improves the out-of-plane distortion under direct wheel loading, and the in-plane stress still dominates the total stress at the FB cutout. Since the new cutout geometry weakens the FB web, the total stress at FB cutout will increase due to the increased in-plane stress. The research also finds that if the free edge of cutout did not satisfy the fabrication requirement per the AASHTO LRFD, category B is suggested for fatigue evaluation at the FB cutout, which is confirmed by the observed fatigue life of the original FB cutout on the real bridge. It is concluded that the new cutout geometry lowers the fatigue resistance both at the FB cutout and at the RF weld connection, hence it will no longer be recommended to retrofit the present bridge in the future.

Analysis of fatigue behavior of welded joints in orthotropic bridge deck using traction structural stress

In this study, the fatigue behavior of welded joints in an orthotropic steel bridge is simulated and analyzed. The traction structural stress method is proven to be more accurate and effective, and the predicted results agree well with the test results compared to traditional assessment methods, including the nominal stress, hot-spot stress, and effective notch stress methods. The traction structural stress concentration factor curves of welded joints under cyclic tensile and bending moment loading are obtained. The accuracy and validity of finite-element simulation methods for welded joints in orthotropic steel bridge are verified by comparing simulation results with full-scale tests results. Equivalent nominal stresses predicted by the master S–N curve method based on traction structural stress results agree well with the fatigue test results with small standard deviation. The fatigue behavior of orthotropic steel bridge analysis specifications Eurocode3 and GB50017 is combined with the traction structural stress method using unified traction structural stress concentration factor curves. This approach provides practical guidance for the fatigue behavior design of orthotropic steel bridges.

Remaining Fatigue Life Prediction of Welded Details in an Orthotropic Steel Bridge Deck

AbstractOrthotropic steel decks have been applied after World War II to long-span bridges due to several advantages, such as light weight, high strength, rapid construction, durability, and life-cy...

Fatigue Cracking Resistance of Engineered Cementitious Composites (ECC) under Working Condition of Orthotropic Steel Bridge Decks Pavement

In order to investigate the fatigue cracking resistance of engineered cementitious composites (ECC) used in in total life pavement, the semi-circular bending (SCB) test and improved three-point bending fatigue test (ITBF) were utilized in this study. The digital image correlation (DIC) method was also utilized to track the surface strain fields of specimens during the SCB test. X-ray computed tomography (CT) and digital image processing (DIP) technologies were applied to measure the internal-crack distribution of the ITBF specimen. The results of the SCB test showed that the fatigue cracking damage process of ECC can be divided into three stages and that the cracking stable propagating stages occupied the main part, which indicates that ECC has excellent ductility and toughness and could work very well with existing cracks. The ITBF results showed that the fatigue cracking resistance of ECC was better than epoxy asphalt concrete (EAC). In addition, the internal-crack distribution along the depth direction of the ITBF specimen could be presented well by the image pixel statistical (IPS) method based on CT scanning of image slices. It could be found that multiple cracks propagate simultaneously in ECC, instead of a single crack, under the OSBD pavement working condition.

RESEARCH ON PROPAGATION CHARACTERISTICS AND REINFORCEMENT METHOD OF PENETRATING CRACK AT RIB-TO-DIAPHRAGM WELDED JOINTS IN STEEL BRIDGE DECK

The rib-to-diaphragm welded joints in the deck of an orthotropic steel bridge is most prone to fatigue cracking. A FE model was established and fracture mechanics was used to study the reinforcement effect of angle steel reinforcement methods on the penetrating crack at fatigue vulnerable details. Based on the finite element model corresponding to a full-foot segment fatigue test model, a penetrating fatigue model was established for the cracks in rib-to-diaphragm welded joints, and the reinforcement effect was evaluated on two reinforcement techniques:bolted angle steel and the bolted steel plate beside a longitudinal rib. The results indicate that:the fatigue cracks at the welded joint in the rib-to-diaphragm of a steel bridge deck expand into a certain length and will develop into penetrating cracks, the deformation of the crack surface under stress conditions is complicated, the fatigue crack propagation characteristics of the inner and outer side of longitudinal ribs are not the same, and as the crack propagation progresses, the cracking mode of the crack tip will be dominated by composite cracking. The existing research results show that:the bolted angle steel reinforcement method can well inhibit the longitudinal rib and diaphragm connection details of the vulnerable part with the fatigue crack type I cracking. Therefore, the short crack propagation can be well suppressed. However, the reinforcement effect on penetrating fatigue cracks extended in a composite type in this detail is not as good as the short crack that have not penetrated the web; the reinforcement method of the half U rib steel plates bolted to the outside of longitudinal ribs can effectively reduce the equivalent stress intensity factor of penetrating fatigue cracks, and stay below the crack propagation threshold after reinforcement. It shows that the reinforcement method has a good reinforcement effect on penetrating fatigue cracks.

Fatigue assessment of longitudinal rib-to-crossbeam welded joints in orthotropic steel bridge decks

Fatigue cracks at rib-to-crossbeam welded joints in orthotropic steel decks (OSDs) accelerate degradation of steel bridges. This research aims to investigate fatigue cracking characteristics of rib-to-crossbeam welded joints, and assess the fatigue strength of the welded joints through fatigue testing and finite element analysis. Nine large-scale specimens were tested under static and fatigue loading to explore the failure mode, fatigue life, and failure process. The fatigue test results were compared with the fatigue strength values recommended in different design specifications. Based on the hot spot stress and notch stress approaches, SN curves for rib-to-crossbeam welded joints were derived and compared with the existing fatigue test data. The results indicate that fatigue cracks that initiate from the weld end at the weld toe controls the fatigue resistance of the rib-to-crossbeam welded joints. A statistical analysis was performed to study the probability distribution of the fatigue strength.

Research on Fatigue Strength for Weld Structure Details of Deck with U-rib and Diaphragm in Orthotropic Steel Bridge Deck

The orthotropic steel bridge deck weld structure would easily cause fatigue cracking under the repeated action of vehicle load. This paper took the steel box girder in a bridge as a research object, researched the mechanical properties of the steel plate and the microstructure of the welded joint, then designed the fatigue specimens of the deck plate and did the fatigue test. The Δσ-N curves and stress amplitudes of the weld details of the deck plate with U-rib and diaphragm under different probabilities of survival were obtained. After extended the Δσ-N curves to the long life range, the fatigue damage calculation equation of the detail was proposed, and the cut-off limit under the 50% and 97.7% probability of survival were 81.50 MPa and 53.11 MPa, respectively. Based on the actual vehicle load spectrum and simplified finite element model of the steel box girder section, the stress amplitude of the details of the weld joint was calculated. The calculation result shows that the maximum stress amplitude of the concerned point was 38.29 MPa, less than the cut-off limit. It means that the fatigue strength of the details of the weld joint meet the requirement of the fatigue design.

Long-Term In Situ Performance Investigation of Orthotropic Steel Bridge Deck Strengthened by SPS and RPC Solutions

Long-Term In Situ Performance Investigation of Orthotropic Steel Bridge Deck Strengthened by SPS and RPC Solutions

Traction structural stress analysis of fatigue behaviors of rib-to-deck joints in orthotropic bridge deck

In this study, a traction stress method is adopted for analyzing some of the unique fatigue behaviors observed in a series of recent experimental studies on rib-to-deck joints in orthotropic steel bridge decks. It is found that the traction-based structural stress definition is not only effective for describing the relevant stress state responsible for each of the four fatigue failure modes, but also mesh-insensitive in finite element computation. The latter attribute is essential for achieving a reliable evaluation of the most likely failure mode possible out of four typical failure modes for a given joint design (including exact weld dimensions) under specified loading conditions. As such, effective means of avoiding undesirable failure mode, e.g., Type 4 (i.e., weld root cracking), can be examined, e.g., by increasing either weld fillet size and/or weld penetration. Furthermore, the rib-to-deck joint fatigue test data investigated in this study are shown falling within the scatter band of the traction stress based master S-N curve adopted by ASME Div Code since 2007, implying that data transferability exists among these three sets of test data obtained independently by different laboratories.