Orthotropic Bridge Decks Research Articles

Fatigue crack propagation simulation of orthotropic bridge deck based on extended finite element method

Orthotropic Steel Decks (OSDs) are widely used in various types of steel bridges due to its benefits of light weight, high load bearing capacity and speedy construction. However, fatigue remains as the predominant problem for OSDs. Many researchers have investigated fatigue issues of welded joints through experiments but is not a cost-effective solution. Therefore, it is necessary to combine experimental data with numerical approaches. Fracture mechanics approach has already shown its reliability and can be used to model and analyze fatigue crack propagation. In this paper, a numerical simulation is performed to predict the fatigue crack propagation using extended finite element method (XFEM). Two numerical models were considered namely CT-specimen and OSD, to evaluate the modelling efficiency. To verify the simulation, the results were compared with the experimental data. In predicting the fatigue crack propagation rate using two-dimensional CT-specimen, numerical results provided a good agreement with a maximum difference of 0.03% in the slope (m) and 1.48% in the intercept (C) of the power law equation. Furthermore, a simulation was performed on three-dimensional OSD structure to predict the fatigue crack growth.

Analysis of Fatigue Crack Propagation on Orthotropic Bridge Deck Based on Extended Finite Element Method

Due to stress concentration as well as welding residual stress, fracture due to vehicle fatigue loads is easy to occur in the weld and its adjacent position of long-span bridge, especially at the toe of weld between the U-rib and orthotropic steel bridge deck. In order to investigate the fatigue crack propagation mechanism of the toe of weld in long-span bridge, a multi-scale finite element model including the whole bridge, local components, the welding details and cracks was established firstly. And then, based on birth and death element technology, the welding heat and structural coupling process simulation was carried out in order to investigate the effect of welding residual stress on fatigue performance. Finally, based on the extended finite element method, the static analysis and the dynamic crack propagation analysis for the semi-elliptical crack in the established multi-scale finite element model were conducted. The welding process shows that the peak value of residual tensile stress in weld zone between the U-rib and top deck could reach the material yield strength, while the regions far away from the weld are in the state of compression. A 32ton standard fatigue vehicle specified in British Standard BS5400 was applied for the fatigue crack static analysis. The results show that when the vehicle is acting on different lanes, the fatigue crack initiating from the toe of weld between U-rib and top deck is mainly under compression in most cases. Only in several cases the fatigue crack is in the state of tension, however, the tensile stress required by the fatigue crack propagation has not be reached. Under the 50ton vehicle, the fatigue stress only at the toe of weld of U-rib can meet the requirements of the fatigue crack propagation. The dynamic analysis on fatigue crack reveals that the crack in the toe of weld of U-rib is in tensile stress state, and the fatigue crack is the mixed mode crack of Mode I, II and III. When the residual stress field was introduced, the stress state at the region where fatigue crack initiates will change and the angle of fatigue crack propagation will increase. The crack at the toes of weld of top deck under the 32ton and 50ton fatigue vehicles is mainly under compression. When the residual stress field was introduced, the crack will be subjected to be a tensile state. It will become mixed mode crack of Mode I, II and III and be dominated by Mode I.

Orthotropic Analysis of Steel Deck–Girder–Rib Systems Subjected to Transverse Load

As one of the advanced modern techniques, orthotropic steel decks are widely used in bridge engineering. Because of its structural complexity, theoretical analysis of mechanical performances of the orthotropic steel bridge deck is very difficult. Therefore, in the past 50 years, a series of experiments and finite element analysis have been used to obtain the information. A steel deck–girder–rib bridge system subjected to the transverse load is investigated in this paper. The bridge deck is laid on four simply-supported girders at the four edges and is reinforced by ribs in longitudinal direction. The longitudinally stiffened deck is idealized as an orthotropic plate. The equivalent material properties in the longitudinal and breadth directions of the orthotropic plate are evaluated using micro-mechanics of composite material by treating the ribs as reinforcing fiber-beams. Governing equations for the deck–girder–rib bridge systems are established and are solved using Ritz method. The analytical solutions are substantiated by comparing with the classic solutions of an isotropic deck with fixed ends and with the finite element predictions. The analytical approach presented in this paper eliminates the very intricate and arduous kinematics study among deck–girder–rib and allows the bridge engineer to fast and convenient estimate the deformation in an orthotropic bridge deck.

Welding Process Influence on Welding Deformation of Orthotropic Steel Bridge Slab

Orthotropic bridge deck is the main structural form of steel box girder bridge deck. Due to the dense U-rib weld and complex structure, it is easy to produce large deformation during welding. At present, the determination of the amount of deformation is mainly based on the empirical value and the trial and error method. It is of great significance for welding deformation control to study the influence of welding process on welding deformation of orthotropic bridge deck and clarify the influence of welding parameters and welding sequence. Based on Marc software, the finite element thermoelastic analysis method is used to simulate the post-weld residual deformation of orthotropic bridge deck. The influence of welding parameters and welding sequence on welding deformation is analyzed, and the sensitive parameters affecting welding deformation are determined. The optimal combination of welding parameters was developed, and the reasonable sequence of U-rib welding was established, which laid a foundation for welding deformation control of orthotropic bridge deck.

A Whole-Range S–N Curve for Fatigue Assessment of Steel Orthotropic Bridge Decks

The fatigue assessment of orthotropic bridge decks under routine traffic loading is a significant task to ensure the serviceability and safety of steel bridges. The sequential law computes fatigue damages using whole-range [Formula: see text]–[Formula: see text] curves and sequential stress histories and has been proven to provide more realistic results than Miner’s rule under variable amplitude loading. In this paper, a whole-range [Formula: see text]–[Formula: see text] curve covering the very low-cycle region, the low-cycle region, the finite life region, the high-cycle region, and the very high-cycle region is proposed for the sequential law to evaluate the fatigue performance of steel orthotropic bridge decks. The mathematical model of the whole-range [Formula: see text]–[Formula: see text] curve is first deduced based on the partially known [Formula: see text]–[Formula: see text] curve recommended in steel bridge design codes. The properties of the whole-range [Formula: see text]–[Formula: see text] curve are then explained from the geometrical point of view in the double logarithm coordinates system. Finally, rib-to-deck joints in steel orthotropic bridge decks are used as a case study. Fatigue test data are used to validate the proposed model. The whole-range [Formula: see text]–[Formula: see text] curve, with a 97.5% survival limit, is established for fatigue assessment of rib-to-deck joints in real bridges. The results show that the proposed whole-range [Formula: see text]–[Formula: see text] curve allows a good fit of experimental data and excellent agreement with code [Formula: see text]–[Formula: see text] curves in the finite life region and provides an effective extrapolation from the finite life region to the whole range of cycle numbers.

Influence of the welding process on the residual welding stresses in an orthotropic steel bridge deck

An orthotropic steel bridge deck consists out of a number of longitudinal and transverse stiffeners. These stiffeners are welded to the deck plate which cause residual stresses to be present near the vicinity of this connection. In addition, the welding operation causes multiple fatigue problems across the bridge deck which lead to the formation of fatigue cracks. For an accurate fatigue design of an orthotropic bridge deck, the residual stresses should also be taken into account to determine the effect of these stresses with respect to the load-induced stresses. Tensile residual stresses should be avoided since they tend to open fatigue cracks which results in a shorter fatigue life. The welding of the longitudinal stiffener to the bridge deck plate is simulated with finite element modelling. The effect of the size of the tack welds, the welding current and the welding speed on the residual stresses is determined. These different welding sequences are modelled in order to minimize tensile residual stresses near the weld connection. The welding configuration which leads to smaller tensile residual stresses will result in an orthotropic steel bridge deck with a longer fatigue lifetime.

Fatigue Assessment of Full-Scale Retrofitted Orthotropic Bridge Decks

Full-scale fatigue tests were performed on two retrofitted orthotropic bridge decks (OBDs). The retrofitting systems consist of adding a second steel plate on the top of the existing deck. The aim is to reduce the stresses at the fatigue-sensitive details and therefore extend the fatigue life of the OBD by stiffening the existing deck plate. Two retrofitting systems were studied. The bonded system consists of bonding a second steel plate to the existing deck by vacuum infusing a thin adhesive layer (2 mm) between the two steel plates. The sandwich system consists of bonding the second steel plate through a thick polyurethane core (15 mm). The aim of the study was to assess the fatigue performance of both retrofittings. No fatigue damage was detected in the retrofitting layers during fatigue tests after three million cycles of wheel load. The stresses close to the deck-plate-to-stiffener welds decreased by at least 55% when using the bonded steel plates system and 45% when using the sandwich steel plates system. Both systems proved to have sufficient fatigue life to withstand traffic wheel loads running on orthotropic bridge decks and help extend the fatigue life of the existing OBD.

00.06: Advances and development needs in the structural design of steel box girders for major bridges

ABSTRACTMajor cable‐supported bridges with a span exceeding 600m would not normally be feasible without a steel box girder to carry the traffic load. These box girders generally comprise a structural steel deck plate stiffened longitudinally by open or closed ribs and transversely by diaphragms. The stiffened deck plate supports the local wheel load and distributes it to the diaphragms from where it is transferred into the box girder. The stiffening ribs also increase the total cross‐sectional steel area and thereby contribute to the overall bending capacity of the box girder and finally, the stiffeners increase the resistance of the plate to buckling.This type of deck structure is generally called an “orthotropic bridge deck” due to the orthogonal nature of the stiffened deck plate and was first developed and utilised in 1950. The orthotropic steel deck is considerably lighter than a concrete slab in a composite girder and therefore makes longer span bridges possible, by reducing the self‐weight forces that would otherwise dominate. The self‐weight of the girder is a key driver in major bridge designs since it must be carried by all other bridge components, such as cables, towers, anchorages and foundations. The orthotropic steel girder is usually a fully closed box girder with all stiffening ribs placed inside the girder giving a smooth outer surface that is easy to paint and maintain. The interior of the closed box is often dehumidified without being painted giving an environmentally‐friendly fabrication that is safe to operate and maintain.However, the orthotropic steel deck is highly prone to fatigue meaning that the number of passing lorries, their axle/wheel configuration and total vehicle weight have a significant impact on the bridge deck design and fatigue life. The orthotropic deck therefore has higher fabrication costs when compared to conventional steel structures due to the high‐quality steel manufacturing and welding procedures that are necessary to achieve the required fatigue performance.The overall layout of an orthotropic bridge deck is basically unchanged since the 1960s, however the detailing has been refined considerably to a level where it is now seems difficult to improve it much further. However, the introduction of new materials e.g. sandwich steel deck structures in combination with new welding or gluing techniques could push box girder designs to new heights.

09.04: Fatigue behaviour of the closed rib to deck and crossbeam joint in a newly designed orthotropic bridge deck

ABSTRACTOrthotropic decks are widely used in large span and movable steel bridges and the design is dominated by fatigue resistance. Closed rib to deck welded joints in the orthotropic decks are sensitive to fatigue loads and a number of fatigue cracks are reported in bridge inspections. For the design of new bridge decks, thicker deck plates are proposed for reducing stresses in fatigue sensitive locations like the conjunction of the deck plate, rib and crossbeam. Compared to the joints in span, the variation of stress at the crossbeam is larger due to the high stress concentration near the weld root. In this study, fatigue tests are carried out on a full‐scale orthotropic deck segment to study the initiation and propagation of fatigue cracks in the deck plate. Trapezoidal stiffeners are welded to a 20 mm thick deck plate and different welding methods are used in manufacturing the specimen. Various load levels are applied on the deck plate by hydraulic jacks. The strain gauges are attached both at the top and bottom of the deck plate in the vicinity of the expected crack paths. The strain history and distribution of strain ranges at the characteristic sections are analysed. An ultrasonic method, time‐of‐flight diffraction, is used to inspect the sizes of the cracks after testing. Comparison of the number of cycles that corresponds to a crack propagation is given in the hot spot S‐N curve figure. With a failure criterion of 10% strain range deviation, the fatigue strength scatter of the 20 mm thick deck plate is similar to that of the 12 mm deck.

21.02: Strengthening of orthotropic steel decks using UHPC: UHPC‐concrete instead of asphalt layer for additional at least 50 years in service

ABSTRACTOrthotropic steel bridge decks for slender and long spanned girder bridges were frequently built in the 60ties and 70ties of the last century in Europe. In the design of such bridge decks only the ultimate load carrying capacity was considered, without fatigue aspects. Due to the dramatic increase of heavy traffic in the European road network, sometimes the calculated remaining fatigue life is exhausted, after only 50 years of service life.In the paper the relevant results of a research project are presented, with the challenging aim to increase the service life of such orthotropic bridge decks to at least 50 years after strengthening. The research activities were based on a very slender orthotropic deck, with a slenderness of elr/tdp = 36 for the deck plate. Two significant details for fatigue of such a representative bridge deck have been analysed. Detail D1 represents the welded connection of the longitudinal rib to the deck plate and Detail D2 is the welded connection of the longitudinal rib to the cross girder. Extensive numerical studies were done for the strengthening solution with an UHPC‐concrete layer. First the present remaining service life was calculated using a finite element model of the steel deck. The beneficial effect of the asphalt layer is considered by an increased wheel contact area. The current fatigue load model FLM‐4 from the Eurocode with 5 lorry types and 3 different axle types was executed and the gross weight of each lorry type was adapted to weigh in motion measurements at an Austrian highway bridge. For determining the stress reduction factors in the details D1 and D2 after strengthening the finite element model had to be extended with the UHPC‐concrete layer. The concrete cracking was conservatively considered with an effective Young modulus Ec,eff = Ec/4. For both details at least 50 years in service can be guaranteed with an UHPC‐pavement that has a thickness of 80mm. Based on these studies full scale tests on an orthotropic deck specimen were done, including overload effects (increased axle loads) and severe temperature effects (simulation of a cold rain event on a very hot summer day) to stimulate concrete cracking. The full scale tests together with the numerical studies showed very good results with regard to the remaining fatigue life. Therefore in the near future a prototype application on an Austrian highway bridge is intended.

Accurate Dynamic Responses Analysis of Orthotropic Steel Decks Using a Novel Multiscale Time-Varying Boundary Approximation Method

An accurate evaluation of the dynamic responses on critical components of orthotropic bridge decks is of significance for identifying structural damage and predicting the fatigue life of long-span cable-stayed bridges. However, the traditional finite element (FE) methods are computationally cost-prohibitive for this application. In response, a new multiscale time-varying analysis method based on the dynamic balance equations and FE strategies is proposed and derived theoretically in this paper. Unlike most existing methods, the dynamic responses of this refined model is easily solved through repeated iterations, using the dynamic responses of a large-scale model as the boundary conditions. To validate the effectiveness of the method, a simply supported steel plate beam was used in a field test that demonstrated good correlation between the analytical dynamic responses and the experimental ones. To further validate this method, a case study involving a whole segment model of the Pingtan Bridge orthotropic bridge deck was established and the complex junction area between the plate and longitudinal ribs was modeled using two refinement processes. For comparison, a sufficiently refined model was also developed using ANSYS software based on the traditional FE methods. This study attempted to provide a new high-efficiency analysis framework for accurate analysis of local vibration problems. Under relatively small and easily manageable calculation conditions at each cross-scale processing level, the proposed method meets not only the requirements of global design for actual engineering applications, but also supports further in depth analysis.

An experimental and numerical study on the behavior of a continuous orthotropic bridge deck with sandwich construction

The buckling of steel-polyurethane sandwich bridge deck is studied via experiment and nonlinear numerical calculations, the authors first analyzed the stress distribution of key points of a three-span continuous bridge deck with sandwich structure in the state of buckling. and then analyzed the influence of the changes of several size parameters on the buckling modes and the critical loads. The results show that when the sandwich bridge deck is compressed, the closer to the middle section in mid-span, the greater the longitudinal compressive stress on the steel faceplate, but the smaller the longitudinal compressive stress on the bottom of the stiffening ribs. The longitudinal stresses on the steel faceplate and the bottom of the longitudinal stiffeners are unevenly transversely distributed near the ends of the applied force, but the stresses are gradually uniform near the midspan section. When this kind of sandwich bridge deck is designed, its thickness should be selected first, and then adjust the spacing of the longitudinal stiffening ribs in order to reduce workload and save material.

Durability of glass fiber-reinforced polymer bridge panel based on differential thermal analysis, dynamic mechanical analysis, and differential scanning calorimetry analysis

Modern bridge structures need light decks with long durability and promising technical parameters. Glass fiber-reinforced polymer orthotropic bridge deck creates unconventional possibilities in bridge designing. Parallel identification of glass fiber-reinforced polymer deck panel by differential thermal analysis, spectroscopy analysis, scanning and optical microscope monitoring, dynamic mechanical analysis and differential scanning calorimetry analysis, tensile and flexural tests will be presented in the paper. Differential thermal analysis was carried out for estimation of the physical and chemical transformation of glass fiber. The differential scanning calorimetry experiments were performed in the glass fiber-reinforced polymer–bridge deck material for determining the mass variation and the energy changes suffered by the materials, as a function of temperature and time. Dynamic mechanical analysis was allowed to detect thermal effects based on the changes in the modulus or damping behavior. Tensile and flexural tests allowed the observation of the decomposition process and information about the basic stress parameters of glass fiber-reinforced polymer material used in bridge applications was taken. Aforementioned analyses are necessary to examine the durability description of the composite element.

Using artificial neural networks in the design of orthotropic bridge decks

For orthotropic bridge decks a lot of progress has been made in the development of codes to aid in the design process, in addition to software tools for numerical analysis and design. However, professional software tools will not aid the designer in choosing a preliminary economic layout at the conceptual design stage. Designers would go through iterative, lengthy and expensive procedures to reach the best configuration. The present research provides a methodology to investigate the contingency of using artificial neural networks for conceptual design of orthotropic steel-deck bridge. A neural network model was trained with different combinations of dimensions, and eight types of safety checks were performed on all of them. The resulting network can predict whether the deck is safe or not. It is found that this approach for the selection of orthotropic deck dimensions is a better and cost-effective option compared with international codes or expert opinion.

Properties of Fiber Reinforced High Performance Cement Based Overlays for Orthotropic Bridge Decks

An increasing number of steel orthotropic bridge deck require repair due to fatigue cracking. For the rib to deckplate joint, a possible solution is to reinforce the fatigue prone deck plate by replacing the asphalt wearing surface with a reinforced high strength concrete overlay. However, this process has been proven very difficult to execute and consequently has some issues regarding durability. This paper reports on high performance fiber reinforced cement based overlay solutions with gritted epoxy interlayer for a typical orthotropic deck with inadequate plate dimensions. Material characterization of three mix designs includes determination of compressive and tensile strength, and post crack behavior by CMOD registration from 3PBT. Furthermore, the steel-concrete composite action in the positive and negative bending moment zone is investigated experimentally. The test results give insight into the concrete behavior, the steel-epoxy-concrete interaction, and are used as input for a 3D finite element model of the reinforced deck under fatigue loading. The results indicate that fiber reinforced cement based overlay solutions may be a viable option for orthotropic decks with inadequate deck plate thicknesses

Experimental Study of Asphalt Surfacing Influence on Rib-to-Deck Joints Considering Temperature and Dynamic Effects

AbstractNumerous fatigue cracks have been observed in many orthotropic bridge decks that have been in service for a long time. The cracks around rib-to-deck (RD) joints might affect traffic safety. In most current design specifications, the asphalt surfacing is treated merely as a layer dispersing wheel loads. To investigate critical transversal load cases for RD joints and to assess the influence of temperature and dynamic loads on stresses around RD joints, a full-size orthotropic bridge-deck specimen with asphalt surfacing was subjected to wheel loads under different thermal and dynamic conditions. Experimental results show that the most critical transversal load cases occurred when dual wheels traveled over the RD joint and also around adjacent RD joints. Stresses around RD joints were found to be extremely sensitive to asphalt temperature and dynamic loads. Hence, the asphalt’s temperature, vehicle speeds, and the number of heavy axles of trucks should be considered when evaluating RD joint fatigue life.

USE OF THE HOLE DRILLING METHOD TO DETERMINE RESIDUAL WELD STRESSES IN BRIDGE CONSTRUCTIONS

Complex welding operations in orthotropic steel bridge decks introduce residual stresses near the weld region. To estimate fatigue failure of this type of bridge deck, tensile residual yield stresses are usually assumed around the weld region. However, to estimate the residual stress distribution near a weld connection more precisely, a test setup is developed. The weld connection of a closed longitudinal trapezoidal stiffener with the deck plate of an orthotropic bridge deck is investigated. The incremental hole-drilling technique is used to measure the residual stresses with strain gauge rosettes. Strain gauge rosettes are positioned on the deck plate and on a longitudinal stiffener of the orthotropic steel deck. A small hole is drilled through the center of the strain gauge rosettes and strains are measured at incremental depths. The residual stresses are calculated and based on these experimental measurements a distribution of the residual stresses is obtained. Compressive residual stresses exist near the longitudinal stiffener-to-deck plate weld. On the deck plate, the compressive residual stresses are equal to 60% of the yield strength while the compressive residual stresses on the stiffener are 42% of the yield strength. There are tensile residual stresses on both sides of the weld region. However, more research is necessary to confirm this distribution since it is contradictory to expected stresses in literature.

Maintenance decision model for steel bridges: a case in the Netherlands

A probabilistic model is developed to investigate the crack growth development in welded details of orthotropic bridge decks. Bridge decks may contain many of these vulnerable details and bridge reliability cannot always be guaranteed upon the attainment of a critical crack. Therefore, insight into the crack growth development is crucial in guaranteeing bridge reliability and scheduling efficient maintenance schemes. The probabilistic nature of the crack growth development model and the dependence of this model on many interdependent random variables result in significant uncertainties regarding model outcome. To reduce some of these uncertainties, the probabilistic model is combined with a monitoring system installed on a part of the bridge. In addition, a Bayesian network is used to determine the dependence structure between the different details (monitored and non-monitored) of the bridge. This dependence structure enables us to make more accurate crack growth predictions for all details of the bridge while monitoring only a limited number of those details and updating the remaining uncertainties.

Fatigue Reliability Assessment of Orthotropic Bridge Decks under Stochastic Truck Loading

A steady traffic growth has posed a threat to the fatigue safety of existing bridges. Uncertainties in traffic flows add to the challenge of an accurate fatigue safety assessment. This article utilizes a stochastic traffic load model to evaluate the fatigue reliability of orthotropic steel bridge decks. The traffic load model is simulated by site-specific weigh-in-motion measurements. A response surface method is presented to solve the time-consuming problem caused by hotspot stress simulations in the finite element model. Applications of the stochastic traffic load model for probabilistic modeling and fatigue reliability assessment are demonstrated in the case study of a steel box-girder bridge. Numerical results indicate that the growth rate of the gross vehicle weight leads to a rapid decrease of the fatigue reliability in comparison to the traffic volume growth. Even though the traffic volume growth is rapid, the control of overloaded trucks in comparison to the traffic volume is an effective way to ensure the fatigue safety of the steel bridges.

Dynamic amplification of a multi-span, continuous orthotropic bridge deck under vehicular movement

The response of a multi-span, continuous orthotropic bridge deck during truck loading is investigated to better understand the dynamic interaction between moving vehicles and highway bridge decks. The present study is based on a recently published, semi-analytical approach for free vibration in which the modal superposition method incorporates intermodal coupling. Herein, the bridge deck is modeled as a jointless, multi-span, orthotropic plate, and the vehicle is modeled as a dynamic, multi-body system. The road surface roughness randomness is modeled as a normal, stationary, random process described by its Power Spectral Density (PSD). The coupled equations of the motion vehicle/bridge deck are solved by Newmark’s method. An iterative process in each time step is performed to find the equilibrium between the bridge deck and vehicle tires using an uncoupled algorithm previously developed by other authors. Two numerical application examples are presented: an isotropic and an orthotropic, three-span bridge deck both crossed by an AASHTO-based vehicle model. In example one, the intermodal coupling affects the dynamic deflection of bridge deck but only slightly. Example two demonstrates that the loading mode and the vehicle speed have a significant influence on the Dynamic Amplification Factor. However, the most important parameter to affect the dynamic vehicle/bridge deck interaction force is the road’s surface roughness, as has been shown for other bridge types under various load conditions.