Orthotropic Deck Research Articles

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.

Fatigue verification of orthotropic bridge decks with the hot‐spot method – Background to TS 1993‐1‐901

AbstractThe design of orthotropic bridge decks (OBD) is driven by fatigue. The Eurocode on fatigue of steel structures – prEN 1993‐1‐9:2023 – provides fatigue resistance (S‐N) curves for relevant details in OBD. These curves are to be used with the far field (nominal) stress. However, due to the complex geometry and loading of OBD, the nominal stress is not well defined for many details. In addition, cracks have been found in practice in OBD at locations for which S‐N curves are not provided. In order to overcome these issues, experimental and numerical studies are carried out on the use of local stresses (hot‐spot stresses where possible) for the fatigue design of OBD. The different stress extraction method also implies the use of different S‐N curves. A large number of fatigue tests carried out in the past have been re‐evaluated to determine the hot‐spot stress S‐N curves. Additional fatigue tests have been carried out for details lacking data. The study has resulted in a guideline to design OBD for fatigue with the hot‐spot stress method. This guideline, TS 1993‐1‐901:2023, will be published as a Technical Specification (TS) to the standard prEN 1993‐1‐9:2023.This paper provides a short background to the newly created TS. It demonstrates the derivation of S‐N curves based on available tests for a number of details. It highlights fatigue relevant details that are missing in prEN 1993‐1‐9:2023 and that are added to TS 1993‐1‐901. It explains how to evaluate cracks starting from the root of the weld, for which the hot‐spot stress method is traditionally not applicable. Finally, the paper demonstrates how the method can be applied in the fatigue design, including the application of the load in finite element models.

Generic method of local thickening in shell element FEM models for orthotropic bridge decks

AbstractThis paper presents a method of estimating the hot‐spot stress in orthotropic bridge decks (OBD) using a shell Finite Element (FE) model, in which local thickening is applied around the welded. The dimensions of the area of local thickening are a function of the weld throat thickness and the plate thickness. A comparison of this method with 3D solid element FE models is presented for various fatigue sensitive details. The comparison is carried out for OBD with trapezoidal stiffeners, both with continuous stiffeners through crossbeams and with stiffeners welded in between crossbeams. It is concluded that the accuracy of estimating the hot‐spot stress with a shell element model using local thickening is significantly higher as compared to a conventional shell element model without thickening. The method of local thickening is adopted in the new prTS 1993‐1‐901. This paper functions as the background to this technical specification.

Innovative orthotropic deck strengthening design for the Suurhoff lifting bridge

AbstractFrom 2018, a significant amount of deck plate cracks have been discovered on the movable part of the Suurhoff bridge. These cracks reduce the strength of the bridge and might lead to unplanned hindrance and costly repairs. Renovation of the ortho‐tropic steel deck was chosen instead of frequent inspections and repairs or replacing the structure from a risk and cost perspective.The innovative strengthening scheme consists of the addition of a steel plate which is connected to the top of the existing deck plate by a combination of preloaded‐injection bolts and epoxy. The strengthening steel plate reduces the stress in the existing deck plate thereby improving the fatigue performance. The new and old steel work compositely due to the combined effect of bolts and epoxy resulting in a relatively light‐weight strengthening scheme. The design followed a risk‐based approach in which Arup closely collaborated with Rijkswaterstaat, contractors and research institutions to finish the full design and implementation in less than a year. The design objective is to provide at least 15 years additional fatigue life for the existing deck.The design was developed with the help of a combined numerical and experimental campaign. The novelty of the strengthening scheme and the use of different materials required experimental validation on small and large scale. The extensive validation resulted in sufficient confidence for the Rijkswaterstaat to implement this innovative scheme on an important bridge in The Netherlands. This scheme is especially beneficial from a weight and construction time perspective and therefore suitable for further implementation on other bridges.

A CNN-based lamb wave processing model for field monitoring of fatigue cracks in orthotropic steel bridge decks

Orthotropic steel bridge decks (OSDs) are prone to fatigue cracking under vehicle cyclic loads, and hence, fatigue crack monitoring is important, especially for the identification of crack growth. To achieve the intelligent monitoring of fatigue cracks in OSDs, Lamb wave technology equipped with machine learning algorithms was proposed in this study. A convolutional neural network (CNN) model with three functional layers was constructed, where a convolution layer was used to eliminate ambient noise disruption from wave feature data, a feature pooling layer to enhance wave features, and a full connection layer to identify crack dimension. The optimal time and frequency parameters of the feature pooling layer were determined based on numerical simulation data and, therefore, could be applied in general situations. In comparisons through field monitoring with continuous wavelet transform (CWT) and continuous Fourier transform (CFT) algorithms, the wave features obtained by the CNN model are more regularized and less fluctuant. The fatigue crack length identification errors of the CNN model are within 1 mm, which are smaller than those of the other algorithms. The CNN model obtains the highest accuracy rates under various loss thresholds. The proposed model also demonstrates superior identification accuracy in comparison to other existing methods. Consequently, when combined with Lamb wave technology, the model can therefore be suitable to applied in the fatigue crack monitoring of real OSDs.

Design and Optimization of the Bi-Directional U-Ribbed Stiffening Plate–Concrete Composite Bridge Deck Structure

The steel–concrete composite structure is widely used in civil engineering for large-span bridges. Orthotropic steel bridge decks (OSDs) have particularly gained popularity due to their excellent mechanical performance. To address cracking issues in OSDs and concrete in negative moment regions, a novel bi-directional U-ribbed stiffening plate (BUSP)–concrete composite bridge deck is proposed. By using finite element analysis, the mechanical performance is evaluated based on maximum tensile stress and vertical displacement of concrete overlays. Results show that the BUSP–concrete deck outperformed conventional flat decks. It is also found that increasing the height, thickness, and opening width of U-ribs reduced tensile stress and maximum displacement. Adjusting height had the most significant effect on displacement while opening width affected tensile stress the most. Considering material usage, optimizing height is proved to be more effective than adjusting thickness and opening width. Decreasing spacing parameters improved performance but added complexity and reduced construction convenience. These findings will guide the design and optimization of steel–concrete composite bridge deck structures.

Experimental and numerical study on cracked steel bridge diaphragm reinforced with bonding Fe-SMA plate

This study proposes a novel iron-based shape memory alloy (Fe-SMA) plate covered crack-stop hole method for repairing fatigue cracks at the arc-shaped cutout of the transverse diaphragm on the orthotropic steel bridge deck (OSD), which aims to reduce stress levels and increase the stiffness of the cracking part, in order to alleviate the stress concentration problem at the edge of the crack-stop hole. Firstly, a static tensile loading test on specimens strengthened by the proposed method was conducted. Results revealed that the edge stress of the crack-stop hole repaired by Fe-SMA plates with thicknesses of 1.75 mm activated at 150 °C, 2 mm activated at 200 °C, 2 mm activated at 150 °C, and 1.75 mm unactivated was reduced by 83.93%, 88.45%, 81.84%, and 66.76%, respectively, compared with those repaired only by the crack-stop hole method. Then, numerical simulations were carried out to analyze the geometric parameters and activation temperatures of the Fe-SMA plate, with the prestress of Fe-SMA simulated by an equivalent temperature method that had been validated through an activation test. Results showed that with the thickness of the Fe-SMA plate increasing from 1 mm to 3 mm, the stress concentration factor K of the hole edge decreased from 2.5 to 0.5. In practical application, it is recommended to use 2 mm-thick Fe-SMA plates, with a width just exceeding the crack-stop hole by approximately 10 mm to completely cover the cracking part and the hole. Further analysis indicates that the recommended activation length is 50–100 mm. Moreover, the repair effect is positively correlated with the activation temperature of Fe-SMA plates, indicating that higher activation temperatures can be used to improve repair efficiency within the acceptable temperature range.

Lightweight design method of orthotropic steel bridge deck with U-ribs based on multi-objective optimization

This paper proposed a lightweight design method for orthotropic steel bridge deck U-ribs. Firstly, the U-rib is analyzed in static structural properties. An analytic hierarchy model was constructed to maximize the stiffness for multi-objective topology optimization. Secondly, a parametric reconfiguration model of the topologically optimized U-rib was established. Finally, static tests are carried out and the performance of the 3D printing scale model was tested. The test results show that the method is effective. Weight of the original model with U-rib is 99.8 kg, and the weight of its optimized model is 76.8 kg. The method achieved a weight reduction of 23% for the U-ribs, and the stiffness still met the permitted conditions. The orthotropic steel bridge deck composed of the optimized U-ribs effectively reduced the weight by 150 kg on the basis of basically unchanged stiffness. The method provides an important reference for the lightweight transformation of assembled bridge structures.

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.

Aluminium Bridges under Fire Conditions: Structural Behaviour

Due to a number of advantages, aluminium is used in the attachment units of mullion and transom systems for decorative panels and translucent fillings, as well as for bridge structures. Despite its advantages, aluminium has a low melting point and does not have fire resistance performances required by regulatory documents under fire conditions. Therefore, this article is aimed at studying the behaviour of aluminium structures under high temperatures. To achieve this objective, we have analysed the aluminium structures most commonly used in construction—the attachment units of mullion and transom systems, with different protections against fire, columns and orthotropic decks used in bridge construction. In order to assess the behaviour of selected structures under fire conditions, we have developed methods for studying temperature distributions in structures in detail. Using the developed methods, tests have been carried out. Based on the received experimental data, we analysed the behaviour of aluminium structures in fire conditions and developed measures to increase the fire resistance of aluminium structures. Such measures include using hollow profiles to ensure air exchange with the cold sections of the structure, applying dedicated cooling agents to cool the structure and removing heat to the atmosphere and thermal barriers so as to protect aluminium structures. We found that fire resistance measures enhance the fire resistance of aluminium attachment units of mullion and transom systems by 1.5 times. The use of hollow air-permeable profiles and cooling agents in orthotropic decks increases fire resistance by 3 times by removing heat from the structures. The fire resistance rating of hollow profile aluminium columns is 1.5 times higher than that of structures without air-permeable profiles. The obtained results can be used as the most effective basis for the design of aluminium structures. The principles of increasing fire resistance given in this article are applicable to other types of structures, and can also be used with other methods of fire protection. Increasing the fire resistance of aluminium structures enables the expansion of the scope of their applications.

Fatigue resistance of rib to deck, crossbeam to deck and deck to deck welds in orthotropic decks using structural stress

This study derives the fatigue resistance of welded details in orthotropic decks using structural stress (hot-spot stress where possible) based on tests described in literature and tests by the authors. The data are supported with linear elastic fracture mechanics simulations. Details covered are the rib to deck weld, the crossbeam to deck weld and the deck butt weld. High fatigue resistances are found, caused by favourable loading modes (bending and compression) and reduced driving force with the growth of cracks. The technical specification TS 1993-1-901, part of the new generation of Eurocodes, is based on the results of this study.

Potential of Ultra-High-Performance Concrete (UHPC) for Refurbishment of Bridges

In many countries, the bridge infrastructure suffers from damaged bridges that need to be rehabilitated or replaced. This means that the state or the institutions responsible for this must make extensive investments. Are there other ways to address the problems caused by the damaging effects of de-icing agents, by fatigue due to high vehicle loads and frequencies on the load side or by lack of fatigue strength of, for example, orthotropic bridge decks? Yes, UHPC surface courses can be used as a protective barrier against aggressive substances such as chlorides. They can also be load-bearing and contribute to improved bearing capacity while providing durability. In addition, a single layer can replace the foundation of multiple layers required for sealing and trafficability. The following article shows the potential of such UHPC layers for improving existing bridges, be they concrete or steel bridges.

Stochastic Propagation of Fatigue Cracks in Welded Joints of Steel Bridge Decks under Simulated Traffic Loading.

The fatigue cracking of orthotropic steel bridge decks (OSDs) is a difficult problem that hinders the development of steel structures. The most important reasons for the occurrence of fatigue cracking are steadily growing traffic loads and unavoidable truck overloading. Stochastic traffic loading leads to the random propagation behavior of fatigue cracks, which increases the difficulty of the fatigue life evaluations of OSDs. This study developed a computational framework for the fatigue crack propagation of OSDs under stochastic traffic loads based on traffic data and finite element methods. Stochastic traffic load models were established based on site-specific, weigh-in-motion measurements to simulate fatigue stress spectra of welded joints. The influence of the transverse loading positions of the wheel tracks on the stress intensity factor of the crack tip was investigated. The random propagation paths of the crack under stochastic traffic loads were evaluated. Both ascending and descending load spectra were considered in the traffic loading pattern. The numerical results indicated that the maximum value of KI was 568.18 (MPa·mm1/2) under the most critical transversal condition of the wheel load. However, the maximum value decreased by 66.4% under the condition of transversal moving by 450 mm. In addition, the propagation angle of the crack tip increased from 0.24° to 0.34°-an increase ratio of 42%. Under the three stochastic load spectra and the simulated wheel loading distributions, the crack propagation range was almost limited to within 10 mm. The migration effect was the most obvious under the descending load spectrum. The research results of this study can provide theoretical and technical support for the fatigue and fatigue reliability evaluation of existing steel bridge decks.

Effect of eccentric loading on fatigue cracking mode and characteristics of diaphragm-to-rib welded joints in steel bridge deck

The non-uniformly distributed wheel loads in orthotropic bridge decks will cause its lower components to be eccentrically loaded. By conducting numerical simulation, field measurement and fatigue tests of diaphragm-to-rib welded joints (DU), the crack-growth characteristics under eccentric loading were analyzed and compared with that under symmetric loading, through which the warning crack length for maintenance and an evaluating method for crack-growth rates were proposed. The result demonstrates that the eccentrically loaded side (ES) of DU will crack ahead of non-eccentric side (NES) with a larger growth angle. The crack performs the same three-stage features of fast-slow-rapid growth under eccentric loading with demarcations of 27 mm and 70 mm, which are obviously larger than that under symmetric loading. The weld toe on NES will be particularly prone to fatigue cracking once the crack on ES enters the third rapid-growth stage. The new initiated crack on NES will own the same growth rate as ES. The demarcation 70 mm shall be taken as the warning length for crack maintenance to avoid cracking on the other side. It is appliable to evaluate the crack-growth rate of DU by Paris formula and the maximum stress intensity factor obtained by K I and K II of mixed mode cracks.

Influence of Repair Welding on the Fatigue Behavior of S355J2 T-Joints.

This paper investigated the effect of repair welding on the microstructure, mechanical properties, and high cycle fatigue properties of S355J2 steel T-joints in orthotropic bridge decks. The test results found that the increase in grain size of the coarse, heat-affected zone decreased the hardness of the welded joint by about 30 HV. The tensile strength of the repair-welded joints was reduced by 20 MPa compared to the welded joints. For the high cycle fatigue behavior, the fatigue life of repair-welded joints is lower than that of the welded joints under the same dynamic load. The fracture positions of toe repair-welded joints were all at the weld root, while the fracture positions of the deck repair-welded joints were at the weld toe and weld root, with the same proportion. The fatigue life of toe repair-welded joints is reduced more than that of deck repair-welded joints. The traction structural stress method was used to analyze fatigue data of the welded and repair-welded joints, and the influence of angular misalignment on was considered. The fatigue data with and without AM are all within the ±95% confidence interval of the master S-N curve.

Structural performance of orthotropic Steel-Concrete continuous composite decks with larger U-ribs and PBL shear connectors

This study investigates the structural performance of the OSCCCDs with larger U-ribs and PBL shear connectors. Four OSCCCDs with larger U-ribs and PBL shear connector specimens were fabricated and tested under a static load, in which the experimental parameters were the spacing of the PBL shear connector and the spacing of the holes of the PBL shear connectors. Parametric analysis via finite element models was also carried out to explore the effects of the reinforcement ratio, the thickness of the steel plate, the thickness of the U-ribs, the thickness of the concrete slab, and the hole diameter of the PBL shear connector on the structural performance. It can be concluded from the experimental and numerical results that the OSCCCDs exhibited higher bearing capacity and better ductility. The OSCCCDs exhibited flexure failure at the mid-span and diagonal tension failure at the intermediate supports. The thickness of the U-ribs and the thickness of the concrete slab showed the highest impact on the initial stiffness and ultimate load of the OSCCCDs, followed by the spacing of the PBL shear connectors and the spacing of holes in the PBL shear connectors. The reinforcement ratio, the thickness of the steel plate, and the hole diameter of the PBL shear connector had little influence on the initial stiffness and ultimate load of the OSCCCDs. Finally, a simplified flexural analysis method can be proposed to accurately predict the elastic deflection and ultimate bending moment of the OSCCCDs under the service loads, respectively. The maximum absolute discrepancies of the elastic deflection and ultimate bending moment of the theoretical results are 8.2% and 12.0% by validating against the experimental and numerical results within the investigated ranges of parameters, respectively.

Fatigue & Fracture of Engineering Materials & Structures Virtual Special Issue: Data science and machine learning for fatigue and fracture assessment

<scp>Fatigue &amp; Fracture of Engineering Materials &amp; Structures Virtual Special Issue</scp>: Data science and machine learning for fatigue and fracture assessment

Tyre contact surface for the fatigue design of orthotropic steel bridge decks

The fatigue life of orthotropic steel bridge decks in road bridges depends on the load effects exerted by heavy lorries. The contact surface of tyres is one of the important variables. Measurements described in the literature demonstrate that the actual tyre contact surfaces of today’s traffic representative for Europe are shorter and slightly wider than the contact surface defined for the load model in the European standard for fatigue loads in bridges — EN 1991-2. This paper derives a new, realistic tyre contact surface to be used with the tyre loads in EN 1991-2, in such a way that the load effects for fatigue are realistically captured and that the required safety level is met.

Fatigue experimental study on full-scale large sectional model of orthotropic steel deck of urban rail bridge

The fatigue problem of orthotropic steel bridge decks of urban rail transit steel bridges has gradually become one of the hot research topics. And it is also a key problem that restricts the further development of rail transit steel bridges. In this paper, the orthotropic steel bridge deck structure of a long-span urban rail transit cable-stayed bridge is studied. Based on the segmental finite element model and full-scale model, the fatigue details of the joint weld between an orthotropic steel bridge deck and U-rib were studied theoretically and experimentally. The theoretical model of the segment is analyzed to obtain the hot spot stress characteristics. On this basis, the full-scale model fatigue test and the fatigue performance evaluation are completed based on the S-N curve. The results show that the fatigue performance of the bridge deck and U-rib joints of the orthotropic steel bridge deck structure model meets the design requirements and has a certain safety reserve. The joint fatigue details of the bridge deck, the U-rib joint weld, and the diaphragm plate are the sensitive areas that are most likely to occur fatigue failure first and need to be paid attention to in the later bridge maintenance and inspection.

Study on Fatigue Behavior of Orthotropic Steel Bridge Deck that Considers Corrosion Effects

As a widely used deck system of long-span bridges, the U rib–diaphragm connection in orthotropic steel bridge deck (OSBD) is prone to fatigue cracking under repeated vehicle loads, and the corrosion medium will accelerate the fatigue cracking. To study the influence of corrosion on the fatigue properties of bridges and the fatigue crack propagation law, the three-dimensional (3D) corrosion morphologies of typical OBSD components under different mass loss rates (w) were obtained by the cellular automata (CA) corrosion model. The, the CA model could reflect the electrochemical metal (Me) corrosion. Then, based on AutoCAD, Rhinoceros, and ABAQUS, the solid model of a U rib–diaphragm connection with surface pits was obtained in ABAQUS. Finally, a multiscale finite-element (FE) model of a long-span bridge with millimeter-scale corrosion pits and cracks was established. The stress intensity factors at crack tips and dynamic fatigue crack propagation at the U rib–diaphragm connection were studied by the extended finite-element method (XFEM), and the difference in fatigue crack propagation life and cumulative energy release rate under different wwere investigated. The results showed that compared with the method of uniform thickness reduction to characterize corrosion effects, the ultimate bearing capacity that was obtained by the CA corrosion model was more consistent with the experimental results. Compared with when the corrosion effects were not considered, when the wof the U rib was 6%, 8%, and 10%, the peak stress intensity factor (KI) of the crack initiation at the weld toe of the U rib increased by 32%, 49%, and 86% and the fatigue growth life of the U rib–diaphragm was reduced by 6.5%, 18.9%, and 50%, respectively. According to the cumulative energy release rate of the crack initiation at the weld toe of the U rib, the crack was a composite crack that was dominated by the opening model crack, supplemented by the in-plane shear model crack and the antiplane shear model crack.