Orthotropic Steel Bridge Decks Research Articles

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.

Thermal and mechanical properties of natural fibrous nanoclay reinforced epoxy asphalt adhesives

Epoxy asphalt adhesive (EAA) has been widely used as strong waterproof-bonding layers for the orthotropic steel bridge decks in China. This research employs attapulgite (ATT), one kind of natural fibrous nanoclays, as the nanofiller to reinforce EAA. The crystalline structure, rheological property, thermal stability, mechanical properties and morphology of EAA/ATT composites were investigated by X-ray diffraction (XRD), Brookfield rotational viscometer, thermogravimetric analyzer (TGA), universal test machine and scanning electron microscopy (SEM). Results showed the existence of ATT did not change the noncrystalline structure of the EAA. ATT had a significant decrement effect on the rotational viscosity of EAA. Moreover, the viscosity of EAA/ATT composites decreased with the increasing content of ATT at a specific cure time. The addition of ATT improved thermal stability of the neat EAA. In addition, the incorporation of ATT increased the tensile and adhesive properties of the neat EAA. The tensile strength, toughness, Young's modulus and adhesive strength of EAA/ATT composites increased with the increase of ATT loadings.

Studies on Design Parameter and Fatigue Performance of a New Type of Orthotropic Steel Bridge Deck

The rib-to-deck and the rib-to-diaphragm details are the weak position of fatigue problem of conventional orthotropic steel bridge decks (OBDs). To improve the fatigue performance at such fatigue details, a new type of OBDs structure with semi-open longitudinal ribs was proposed. This new structure can not only realize full penetration welding between the deck and longitudinal rib, but also reduce the stiffness difference between the longitudinal rib and the diaphragm. The structural parameters of the new structure were analyzed, and the reasonable values of each structural detail of the new bridge deck were given. The lateral and longitudinal stress influence lines of different structural details in the new and conventional steel bridge deck were comparatively studied. And the results show that the stress on the deck of the rib-to-deck in this new type of OBDs is larger, but full penetration welding can effectively improve the welding quality of the rib-to-deck joint, thus ameliorate the eccentric force of the single fillet welds. The change in longitudinal ribs weakened the stress concentration at the rib-to-deck, and improved its fatigue properties.

Fatigue Reliability Evaluation of Orthotropic Steel Bridge Decks Based on Site-Specific Weigh-in-Motion Measurements

The fast-growing traffic loads may become a safety hazard for existing bridges especially in developing countries. One of the problems induced by heavy traffic loads is the fatigue damage accumulation of the welded joints in steel bridge decks. This study utilized a stochastic traffic flow model and a novel computational framework for estimating fatigue reliability of orthotropic steel bridge decks using site-specific traffic data. The stochastic traffic flow is demonstrated as an effective approach for converting the probabilistic characteristics of the site-specific traffic data into the fatigue stress spectrum modeling of steel bridge decks. In addition, the traffic growth and control measures can be considered in the stochastic traffic flow for lifetime fatigue reliability estimation of the bridge deck. The proposed computational framework involves a meta-model approximated by neural networks that can greatly reduce the computational effort. Orthotropic steel bridge decks in a long-span suspension bridge is chosen as prototype to illustrate the effective of the stochastic traffic flow model and the computational framework. Numerical results show the following conclusions: firstly, the efficiency and accuracy of the framework is associated with the number of training samples, where approximately 180 training samples is essential for training the 6-types of meta-models; secondly, a annual growth rate of the vehicle weight of 0.5% leads to the fatigue reliability index of the bridge in the 100th year decrease from 5.94 to 0.92. The numerical result may provide a theoretical basis for how to control overloaded trucks for ensuring the bridge safety.

Fatigue behaviour of orthotropic steel bridge decks with inner bulkheads

Tests on a full-scale orthotropic steel deck (OSD) specimen were conducted to investigate the effects of inner bulkheads set inside the U-ribs on the static and fatigue behaviours of the OSD. The total length and width of the OSD specimen are 5 m and 2.24 m, respectively. It contains three longitudinal floorbeams and four transversal U-ribs. U-ribs with and without inner bulkheads are symmetrically arranged in the cross section of the specimen. Finite element (FE) analyses on the OSD specimen model and sub-models were conducted to further study the effects of the inner bulkhead design and different bulkhead shapes. Results of the test and corresponding FE analysis of the specimen showed that inner bulkheads can be used to improve the fatigue life of the OSD. Meanwhile, fatigue cracking in the rib-to-bulkhead details was introduced by installing the inner bulkhead. Results of the FE analysis of the sub-models showed that the distance from the bottom edge of the inner bulkhead to the tip of the floorbeam cutout affects the stress state of the rib-to-floorbeam connection weld significantly. Additionally, the bulkhead shape affects the hot spot stress of the weld toe of the rib-to-floorbeam connection weld significantly. Thus, proper bulkhead shape should be determined by considering the specific stress distribution of the rib-to-floorbeam connection area.

Virtual Monitoring of orthotropic steel deck using bridge weigh-in-motion algorithm: Case study

This article outlines a Virtual Monitoring approach for fatigue life assessment of orthotropic steel deck bridges. Bridge weigh-in-motion was used to calculate traffic loads which were then used to calculate “virtual” strains. Some of these strains were checked through long-term monitoring of dynamic strain data. Field tests, incorporating calibration with pre-weighed trucks and monitoring the response to regular traffic, were conducted at Fochen Bridge, which has an orthotropic steel deck and is located in Foshan City, China. In the calibration tests, a 45-t 3-axle truck ran repeatedly across Lane 2, the middle lane in a 3-lane carriageway. The results show that using an influence surface to weigh vehicles can improve the accuracy of the weights and, by inference, of remaining service life calculations. The most fatigue-prone position was found to be at the cutout in the diaphragms. Results show that many vehicles are overweight—the maximum gross vehicle weight recorded was 148 t, nearly 3.6 times heavier than the fatigue design truck.

Bridge vehicle load model on different grades of roads in China based on Weigh-in-Motion (WIM) data

Bridge vehicle load is an important parameter that is relevant to the construction and maintenance stages of a bridge. In recent years, a large number of orthotropic steel deck bridges have been built in China, and it is urgent to establish a fatigue load model that reflects the actual traffic conditions of the bridges. This study has investigated the variation of vehicles over time on four grades of road (expressway, first-class highway, second-class highway and urban main road) according to the weight-in-motion (WIM) data. Subsequently, the statistical model was established in terms of speed, axle weight, and gross weight of vehicle (GVW) acting on the four grades of road. Finally, a fatigue load model of vehicles on the four grades of road was established based on a two-stage method. The results show that (1) the speed of vehicle on the four grades of road obeys the unimodal distribution; (2) the GVW of two- and three-axle vehicles on the four grades of road belongs to the t-distribution and the log-normal distribution, respectively; (3) the GVW of four- and five-axle vehicles on expressways is a finite mixed distribution, whereas the GVW of four- and five-axle vehicles on the remain three grades of road obeys the log-logistic and log-normal distribution respectively; (4) the GVW of six- and above axle vehicles on expressways and second-class highways obeys a finite mixed distribution with two variables, whereas that on first-class and urban main roads obeys the log-normal distribution; (5) the axle weight of standard fatigue vehicles differs remarkably on different grades of roads, which is difficult to describe the fatigue damage in a uniform standard fatigue vehicle.

Creep Compliance and Relaxation Moduli of PmB 25 A and PmB 45 A Gußasphalts at Different Temperatures

AbstractPmB 25 A and PmB 45 A Gusasphalts (poured asphalts) are commonly used to pave orthotropic steel bridge deck surfaces, especially in Germany, because they are light, stiff, and easily applie...

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.

Research on three dimensional detection system of fatigue cracks of steel box girder

The fatigue cracks are inevitably existed in steel bridges after they are working for a fairly short time because of the environmental pollution, overloading vehicles and larger numbers of automobiles. How to efficiently detect the fatigue cracks, especially the initial fatigue cracks, become one of the most important question to be solved for the steel box girder. The static and fatigue tests of the orthotropic steel bridge deck models were carried out in this research paper, which presented the fatigue damage developing laws, compared the test results with homogeneous test results in existing documents. Three dimensional micro detection scheme of fatigue cracks in steel box girder with three dimensional detection system is studied. Through the data from the testing design, the important characteristic width and length of the fatigue crack can be achieved, which can be used for the grasping of the mechanism of the steel box girder.

Propagation behaviour of deck-through type cracks in existing orthotropic steel deck bridges

Propagation behaviour of deck-through type cracks in existing orthotropic steel deck bridges

Interlaminar thermal effect analysis of steel bridge deck pavement during gussasphalt mixture paving

ABSTRACTIn this research, the effect of high-temperature asphalt concrete paving on the interlaminar shear behaviour between the steel bridge deck pavement (SBDP) and the orthotropic steel bridge deck (OSBD) is the main objective. A thermal field model of steel box-girder was established based on the transient thermal field theory, and the element deletion method was used to simulate the dynamic paving process of gussasphalt mixture (GAM). The thermal field model was validated by the field monitoring data of Taizhou Yangtze River Highway Bridge in China, and the temperature variations in OSBD during the paving was summarised. Applying the most unfavourable temperature load during GAM paving to the steel box-girder mechanical model, the interlaminar shear stress distribution was calculated, and combined with the shear strength variation of waterproof bonding material during GAM paving, the interlaminar thermal effect of SBDP was evaluated. Results show that the thermal field of steel bridge presents temporal and spatial variation characteristic. The interlaminar shear stress during GAM paving in the low-temperature season is much larger than that in the high-temperature season, but the interlaminar thermal effect is more severe in the high-temperature construction season due to the more inferior shear performance of waterproof bonding material.

Experimental Study on Fatigue Resistance of Rib-to-Deck Joint in Orthotropic Steel Bridge Deck

Experimental Study on Fatigue Resistance of Rib-to-Deck Joint in Orthotropic Steel Bridge Deck

Temperature Behavior and Stability Analysis of Orthotropic Steel Bridge Deck during Gussasphalt Pavement Paving

Temperature Behavior and Stability Analysis of Orthotropic Steel Bridge Deck during Gussasphalt Pavement Paving

09.16: Edge clamping effect on the fatigue resistance of an orthotropic steel bridge deck

ABSTRACTOrthotropic steel decks are an excellent solution for long span bridges, except if the spreading of wheel loads through the pavement is poor. In the latter case they are heavily sensitive to fatigue cracking. The most critical locations of fatigue cracks are the connection of longitudinal stiffeners to the deck plate and the cutouts and cope‐holes in the webs of the transverse stiffeners. OSD with variable depth are seldom used, since the idea contradicts with one of the main assets to limit the bridge deck depth. However, in few cases variable depth may be meaningful as in the case of a railway bridge across river Dyle, recently built in Mechelen (Belgium). This 50 m span bridge consists of 2 lateral stubs of 1.55 m diameter connected by the OSD. The tubes are slightly bent to foster arch thrust action and rotated towards the bridge axis. In addition, the arch springs are encased in the concrete abutment. Due to this arrangement, the crossbeams are partially clamped in the lateral tubes of high torsion stiffness. The effect of the end clamping of crossbeams reduces the tension in the lower part of the crossbeam web, also near the outer cope holes, where the largest stress concentrations occur and fatigue resistance is the lowest. The reduction of the magnitude of these stress concentrations is significant and depends on the crossbeam span. However, the effect disappears if the crossbeam web is higher, thus confirming it is due to bending tension of the crossbeams. In addition, the influence length of crossbeams has been verified in the case of river Dyle bridge and complies well with Eurocode.

Probabilistic Modeling of Fatigue Damage in Orthotropic Steel Bridge Decks under Stochastic Traffic Loadings

Fatigue truck models with deterministic parameters were developed int a stochastic vehicle flow model. A response surface method was used to approximate the function between vehicle axle weight and equivalent fatigue stresses with few training data to solve the time-consuming problem of bridge finite element analysis under traffic flow loads. A probabilistic fatigue damage modeling method was presented and applied to the rib-to-deck details of steel box girder bridges. Finally, the fatigue damage model was applied to the reliability assessment of steel box girder bridges, and influences of traffic flow parameters on structural fatigue reliability were studied. Numerical results indicate that the higher occupancy rate of heavy vehicle flow in a slow lane than in a fast lane mainly explains the decrease in the fatigue reliability of corresponding rib-to-deck details. The increase in vehicle axle weight causes a rapid decrease in the fatigue reliability index of steel box girders. The fatigue reliability index of rib-to-deck detail in the slow lane decreases from 3.42 to 0.72 when the annual linear growth factor ranges from 0 to 1%. The stochastic fatigue vehicle flow model and the probabilistic model for fatigue damage exhibit considerable potential in the probability assessment of bridge fatigue damage.

Effect on Stresses of Structural Details of Orthotropic Steel Deck with Thin Surfacing

Although it has the advantage of decreasing the loads on bridge deck when adopting thin surfacing, it is worse for the stress dispersion of vehicle loads, as a result, it is easy to generate local stress concentration of structural details of orthotropic steel deck. To study the stresses of orthotropic steel bridge decks, especially for the structural weld details, which is significant for fatigue durability evaluation. Partial models are created by finite element analyses to analyze the stresses of both normal thickness bridge pavement and thin surfacing under different load locations, and the kinds of material of pavement and the thickness of bridge deck are also considered in the calculations. It’s found that stress amplitude of objective fatigue details of TPO pavement increase up to 28.4% when the models share the same structure dimension, and the thickness of TPO pavement has little impact on the stress amplitude of objective fatigue details which could be ignored, while the influence of the thickness of the TPO pavement is considerable. And the increase of the thickness of bridge deck helps decrease the stress amplitude of objective fatigue details.

Experimental study on fatigue failure of rib-to-deck welded connections in orthotropic steel bridge decks

The rib-to-deck (RD) welded connections are the most sensitive locations to encounter the fatigue failure in orthotropic steel decks (OSDs), and numbers of fatigue cracks arising from these areas have been found in existing OSD bridges. This research focus on the fatigue cracking process, fatigue characteristics as well as failure mechanics of RD connections under cyclic loading. Six full-scale RD welded joints were fabricated, and two load cases of centric and eccentric loading were considered. Static loading was first conducted with aims of measuring elastic strain distributions at potential hot spots. Structural hot spot stresses at weld toes as well as stress concentration factors (SCFs) were linearly extrapolated by using the recorded strains, based on which critical locations were identified. High-cycle repeated loading was subsequently implemented, from which the fatigue crack initiation and propagation process, fatigue failure mode, characteristic fatigue life, as well as degradation of vertical rigidity, were obtained. Four stages of crack propagation were mainly observed, and the remaining fatigue lives after the crack reached the deck edge were short to be neglected. Variations of crack dimensions including the longitudinal length and the depth in the plate thickness were also revealed. Comparison between experimental numbers of cycles and standard S-N formulae indicates that the FAT 100 curve provided in the IIW fatigue recommendation could be conservatively used to estimate the fatigue resistance of such rib-to-deck welded connections composed of 16mm thick deck plates and 80% PJP welds.

Experimental study on the fatigue performance of roof and U-rib welds of orthotropic steel bridge decks

The fatigue performance of a roof-U rib weld on orthotropic steel bridge decks was studied by fatigue experiments on 40 specimens, considering the influences of amplitude, penetration rate, loading position, and steel strength. Influences of different factors on the fatigue life of crack initiation and specimen failure were studied by analysis of crack propagation in the weld and changes in stress amplitude. In addition, nominal stress amplitudes and hot spot stress amplitudes of the welds were compared and the suggested values of fatigue strength were proposed according to the test results. The study shows that increase of penetration rate can decrease the crack propagation rate and extend failure fatigue life. A larger steel strength can increase the fatigue strength of crack initiation. Under the same loading conditions, the fatigue life of crack initiation is about half of the failure fatigue strength. A nominal stress of 70 MPa and a hot spot stress of 75 MPa are recommended for fatigue strength of roof-U rib welds under the manufacturing process investigated here.

Fatigue Performance of Roof and U-Rib Weld of Orthotropic Steel Bridge Deck with Different Penetration Rates

Fatigue Performance of Roof and U-Rib Weld of Orthotropic Steel Bridge Deck with Different Penetration Rates