Orthotropic Bridge Decks Research Articles

Multi-crack propagation analysis of double-side welded rib-to-deck joint in orthotropic steel decks

Rib-to-deck welded joints are among the most susceptible to fatigue in orthotropic bridge decks (OSDs). Prior research has primarily examined the stress intensity factor (SIF) and propagation morphology of a solitary fracture at these joints, allocating limited attention to the investigation of the propagation of multiple cracks. This paper presents a methodology for simulating and computing the weld toe magnification factor and the SIF of semi-elliptical surface cracks in innovative double-sided welded rib-to-deck (DWRTD) joints. The intention was to simplify the calculation of the SIF for this fatigue detail. The SIF obtained from the calculation model in combination with a multiple crack coalescence approach resulted in a series of fatigue life prediction models of multiple co-planar semi-elliptical cracks. Compared with the results of fatigue tests on the DWRTD joints, the calculated fatigue life and propagation morphology of multiple cracks from the model showed good agreement. Finally, the parameters were analysed to investigate the effects of crack number, bridge deck thickness, residual stress, and penetration rate. Compared to a single crack, multiple cracks reduced the service life of the bridge deck by approximately 30%. When the bridge deck thickness increases from 12 mm to 20 mm, the nominal stress amplitude near the weld ∆σ decreases by 2.2 times, resulting in a 7-fold increase in crack propagation time. Compared to penetration rate and residual stress, ∆σ is the most crucial factor affecting fatigue propagation life. Therefore, it is suggested to increase the thickness of the bridge deck during design.

Numerical study of full penetration single- and double-sided U-rib welding in orthotropic bridge decks

Under the repeated action of residual stress and wheel load caused by welding, fatigue cracks easily occur on the top plate-U rib welding of an orthotropic bridge deck (OBD). These affect the service life. To study the influence of different full-penetration welding methods on the residual stress and fatigue of OBD, this study compared the residual stress, welding deformation, and fatigue performance of full-penetration single- and double-sided welding through finite element analysis. The welding temperature and residual stress fields were simulated based on Goldak's double ellipsoid heat source model using the thermal elastic-plastic method. The numerical results were verified using measured data from relevant literature, and the two were in good agreement. The results showed that the longitudinal residual stress of the double-sided welded U-rib was larger than that of the single-sided welded U-rib, primarily in the compressive stress range, and the maximum deviation reached 99.44 MPa. The longitudinal displacement of single-sided welding along the weld direction was 0.060 mm lesser than that of double-sided welding, and the maximum vertical displacement perpendicular to the weld direction was 2.457 mm lesser than that of double-sided welding. For the same frequency of fatigue load (wheel load), the fatigue strength of single-sided welding was larger than that of double-sided welding, and the fatigue life increased by 29.7%. In this study, analysis models of the full-penetration single-sided and full-penetration double-sided welding were established, which could provide a reference for structural fatigue assessment using the two full-penetration welding techniques under the influence of residual stress.

Fatigue behaviour of root crack in stiffener-to-deck plate weld at crossbeam of orthotropic bridge decks

Steel Orthotropic Bridge Decks (OBDs) are widely used in long-span and movable bridges. Fatigue resistance analysis plays an important role in the design or assessment of OBDs. One possible fatigue failure is the crack initiating from the weld root of stiffener-to-deck plate connections at crossbeams. A full-scale experimental investigation in this study using a 20 mm thick deck plate with a dimension of 9.4 m × 5.1 m, including three crossbeams, represents the modern designed OBDs. The experiments show an arrest of crack propagation with a final crack depth of approximately 75% of the deck plate thickness. On the contrary, through thickness cracks develop in deck plates of 10 or 12 mm. Hot spot stress based fatigue detail categories (DC) using various failure criteria derived from the tests. Analysis with the effective notch stress shows that the DC has low sensitivity to the amount of weld penetration. The results of analyses with the eXtended Finite Element Method (XFEM), employed to analyse the fatigue crack propagation path and crack arrest, are in line with the experimental study.

Prediction accuracy of fatigue-relevant load effects in an orthotropic deck

The accuracy of stress estimates in Orthotropic Bridge Decks (OBD) may be negatively impacted by the complex load transfer and asphalt properties. Yet, accurate stress estimates are crucial for optimal fatigue verifications. A field measurement and modelling study has been conducted to evaluate the accuracy of finite element (FE) models. The level of detail of the FE model resembled engineering practice. Measurements comprised of strains caused by normal flowing traffic and by single vehicles with known load. The study gave insight into the distribution of the transverse vehicle location, dynamic vehicle–bridge deck interaction, and the asphalt influence. Comparing with international guidelines, the prediction error of FE models of OBDs is on the edge of acceptable.

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.

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.

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.

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

Fatigue assessment and crack propagation of floorbeam cutout in orthotropic bridge decks

Based on the fatigue cracking of floorbeam cutout in a bridge, the field testing under random traffic flows was firstly conducted to investigate the fatigue crack initiation, and then a multi-scale numerical model, based on extended finite element method (XFEM), was established to reveal the propagation mechanism of crack growth. It was found that floorbeam cutout exhibits a complex three-dimensional deformation state under wheel loads, leading to an I-II-III mixed crack growth mode. The crack propagation direction is normal to the free edge of floorbeam cutout, which is the crack propagation direction at initiation. Increasing floorbeam thickness can facilitate preventing the crack propagation of floorbeam cutout.

Vehicle Load Identification on Orthotropic Steel Box Beam Bridge Based on the Strain Response Area

With the development of the economy and the rapid increase in traffic volume, an overload phenomenon often occurs. This paper studied a vehicle load identification technique based on orthotropic bridge deck stress monitoring data. The strain responses on the lower edge of multiple U-ribs were collected under vehicles crossed the deck. Firstly, an index based on the cross-correlation function of strain response between different measurement points on the same U-rib was used to evaluate vehicle speed. Secondly, a cosine similarity index was proposed to locate the transverse position of the vehicle. Finally, the unknown vehicle load was identified on the basis of a calibrated strain response area matrix. The effectiveness and anti-noise performance of the proposed method were verified using numerical simulation. An experimental model was designed and some strain gauges were installed to measure the strain response, and the test was carried out to further verify the algorithm’s performance. Numerical and experimental results show that the proposed method could effectively identify the vehicle load with good anti-noise performance. Moreover, a calibration space was provided to guide practical engineering applications. The proposed method does not damage bridge decks, does not affect traffic, and is economical.

Impedance-based damage assessment of steel-ECC composite deck using piezoelectric transducers

The excellent crack and fatigue resistance of Engineering Cementitious Composites (ECC) materials makes it promising to be used in orthotropic bridge deck system. However, overloading and fatigue load might cause structural damage and, consequently, structural performance degradation. In this work, the piezoelectric lead-zirconate-titanate (PZT) transducers are used to identify the structural damage of the steel-ECC composite deck by implementing both experimental test and numerical simulation. Two steel-ECC composite deck are prepared and four-point bending loading tests are performed on the two specimens to introduce several damage scenarios by gradually increasing the load. The impedance output signals of the piezoelectric sensors are measured under different damage scenarios, and the damage index are extracted to identify the structural damage. A finite element model of the steel-ECC composite deck is established, and the impedance signals with different damage scenarios are calculated and used to assess the structural damages. According to the experimental test and numerical simulation, the impedance-based technology performs to be an effective way to identify the structural damage of the steel-ECC composite deck.

Fatigue assessment of U-rib full penetration welded joints based on local methods

Experimental and numerical methods were used to carry out fatigue assessment of double-sided full penetration U-rib welded joints with different deck thicknesses in Orthotropic Bridge Decks (OBD). The local stress field analysis was conducted by the finite element method. S-N curves for different thicknesses can be obtained based on fatigue test results. The Nominal Stress (NS) method, the Effective Notch Stress (ENS) method, and the Theory of Critical Distances (TCD) were applied to estimate the fatigue life. The feasibility of these three approaches was validated by fatigue test results. The results show that two types of fatigue crack initiation sites (inner and outer weld toes) and typical smooth and rough regions are found. The maximum principal stress decreases by about 30% when the deck thickness increasing from 14 mm to 18 mm, while the fatigue life increases by 6–11 times for different stress ranges. The stress concentration factors (SCFs) for U ribs with 14 mm, 16 mm, and 18 mm deck thicknesses are 2.71, 3.16, and 3.15, respectively. Double-sided U ribs welded joints with thicker decks have better fatigue performance. All predicted results using the NS method and the ENS method are greater than the FAT71 and FAT225 fatigue curves, respectively. The Point Method (PM) and Line Method (LM) in the form of TCD are found to be successful in predicting the fatigue life and recommended to fatigue assessment for double-sided welded U-ribs.

Built-Up Closed-Rib Steel Orthotropic Bridge Decks

A new built-up closed-rib section is proposed that may improve the installation, performance, and durability of orthotropic steel bridge decks. The rib is composed of two partial or whole standard hot-rolled steel sections which are connected by a steel plate. The concept is used to design a built-up closed-rib replacement for the Benjamin Franklin Bridge deck. In addition, section performance was compared with the actual bulb section as well as a typical trapezoidal section through finite element simulations. The analyses indicate that the built-up section has smaller stress concentration values as compared with the other sections, and hence, improved fatigue resistance is expected. Finally, it is concluded that the built-up rib has potential to be considered in future orthotropic steel deck designs.

A criterion for fatigue failure mode evaluation of U-rib to deck joints

In this study, a numerical analysis model was established, on basis of the traction structural stress method, for fatigue failure mode prediction of orthotropic bridge deck (OBD) under symmetric three-point bending conditions. The structural stress-based criterion was validated by comparison with a collection of 64 test results. Fatigue failure modes are found to hinge on a dimensionless normalized constraint distance l/lcr that is related to specimen geometric dimensions and supporting arrangements. OBD specimens in symmetric three-point bending fatigue tests fail at toe-U-rib and external toe-deck as the actual constraint distance l is lower and higher than the critical constraint distance lcr where fatigue failure mode changed. The prediction power of the evaluation criterion is not affected by the fatigue load patch width in fatigue tests, U-rib profile shape, or weld penetrations.

Modeling of fatigue failure mode in U‐rib to deck joints in orthotropic bridge structures

AbstractVarious fatigue failure modes (i.e., cracking position and orientation with respect to a weld) can develop in welded rib to deck connections in orthotropic bridge deck structures. After demonstrating its effectiveness in correlating fatigue test data covering different failure modes, the master S‐N curve method was then adopted in this study for determining the critical failure mode in welded U‐rib to deck connections. These include considerations of additional failure modes potentially present in double‐sided welds between U‐rib and deck versus the traditional single‐sided weld design. The effects of weld penetrations and test loading conditions on failure mode development have been quantitatively established by means of the master S‐N curve method.

Analysis of fatigue test conditions for reproducing weld toe cracking into U-rib wall in orthotropic bridge decks

In this study, the fatigue test conditions for reproducing weld toe cracking into U-rib wall in orthotropic bridge decks (OBD) are investigated by both experimental and numerical methods. The traction structural stress method is shown effective for evaluating this fatigue failure mode (referred to as “toe-U rib” hereafter) and its associated test conditions. Experimental validations were then performed in this study, in which toe-U rib failure mode was consistently observed. It is found that the toe-U rib failure mode and its fatigue capability are not impacted by typical variations in weld penetration in both single-sided and double-sided welds.

A Study of Fatigue Crack Propagation Paths at U-Rib Welds in Orthotropic Bridge Decks using a Phased-Array Imaging Technique

In this paper, the fatigue failure mode of single- and double-sided welded joints in orthotropic bridge decks is innovatively investigated with the phased-array imaging technique for verifying the fatigue failure path defined using the traction structural stress method. The full-scale fatigue specimen tests are conducted, and the fatigue depth and length are imaged and sized for the completeness of fatigue crack propagation law. It can be concluded that the fatigue failure mode of single- and double-sided welded joints is proven to be the thickness-through mode, which is consistent with the fatigue failure path defined in the traction structural stress method. The analysis method for calculating the main characters is first proposed, and the fatigue crack propagation law of the crack length and depth in the through-thickness mode is determined for completeness.

An experimental investigation into fatigue behaviors of single- and double-sided U rib welds in orthotropic bridge decks

In this study, the fatigue resistance properties of single- and double-sided welded joints in OBD are investigated using the traction structural stress method by conducting experimental and numerical investigations. Full-scale fatigue specimen tests are conducted to analyze the fatigue property validations and failure modes, considering the effects of length scale, residual stress relaxation, angular misalignment corrections, and stress ratio. Double-sided welded joints have been found to fail at the interior weld toe with the propagation direction of deck thickness, and the prediction results will be more accurate considering the effect factors of angular misalignments and stress ratio. The specific united master S-N curve for the fatigue performance prediction of single- and double-sided welded joints in OBDs is recommended with the combination of fatigue test data.