Abstract: The stochastic responses of highway bridges to spatial variation of ground motions (SVGM) are analysed in this paper. A model of spatially varying ground motions is used to investigate the relative importance of the incoherency effect, the wave passage effect and the site effects on the stochastic dynamic response of an asymmetrical R.C box girder highway bridge with variable inertia. In this study, the incoherency effect is investigated using two widely used models while the wave-passage effect is incorporated using various wave velocities. Then, the random vibration theory is applied to study the effect of the non-uniform seismic excitations on the bridge structure. The bridge response is evaluated in terms of the mean values of the maximum displacements and the bending moments. Analyses of both stationary and transient response are performed. The results show that the stochastic dynamic responses related to site effects are mostly much greater than those calculated using uniform, delayed and incoherent seismic excitation assumptions. As a result, analytical models used for the stochastic dynamic analysis of long span highway bridges should take into account all the SVGM components, particularly the site-response effects.

Abstract: Impact factor is amplification factor of vertical dynamic effect produced by vehicles. It is a main parameter of bridge design and an important index of dynamic load effect evaluation. In order to study the influence of structure and excitation factors on the impact factor of highway bridges, and then obtain the real impact factor of the continuous beam arch composite bridge, taking a three-span arch bridge made with continuous composite concrete filled steel tube beams as an example, considering the vehicle-bridge coupling vibration effect, the spatial beam element model of the bridge and the half vehicle model with the three-axis are established by using ANSYS. The impact factor of different parts of the main beam and different responses affected by the deck surface roughness, the vehicle speed and the number of vehicles are analyzed. The binary regression formula of impact factor is obtained by taking the vehicle speed and the roughness of bridge deck as independent variables. Finally, the formula is verified by the measured data of two bridges with similar fundamental frequencies. The results show that the impact factor calculated by the current code is generally small for the bridge structure with complex structure and relatively low frequency, such as arch bridge made with continuous composite concrete filled steel tube beams. The impact factor is most affected by the roughness of bridge deck. When the roughness of bridge deck reaches grade B or above, the impact factor exceeds the specification value, and the maximum impact factor can reach 5.42 times of the specification value. For the main beam, the impact factors of different external excitation, different responses and different parts are not the same, and some impact factors exceed the specification value. The regression formula of impact factor given can be used to estimate the impact factor of main beams of similar structures.

Abstract: The scope of this effort is to evaluate the performance of a link slab transversely connecting press-brake-formed tub girders (PBFTG). Modular PBFTGs were developed by a technical working group within the Steel Market Development Institute’s (a business unit of the American Iron and Steel Institute) Short Span Steel Bridge Alliance, led by the current authors. This working group consists of stakeholders in the steel bridge industry, including mills, fabricators, service centers, industry trade organizations, universities, and bridge owners. A full-scale link slab transversely joining two PBFTGs was fatigue loaded simulating a 75-year fatigue life in a rural environment. Strain and deflection data was recorded and compared throughout the fatigue life to determine the link slab’s effectiveness. Results of this effort show the link slab detail performs adequately throughout its fatigue life.

Abstract: This study investigated the relationship between “rust color distribution ratio,” “corrosion surface shape,” and “fatigue strength” of high-strength galvanized steel wires used in cable supported bridges. The study utilized a digital image color analysis system to classify the rust color distribution rate and categorize corrosion levels based on the distribution ratio. The relationship between cross-sectional loss rate and corrosion depth tendency was visually and quantitatively comprehended from the categorized corrosion levels. The study found that fatigue and tensile strengths of the specimens from the corrosion levels set in this study were equivalent to or higher than those of new wires. However, the possibility of variations due to the small number of specimens or insufficient corrosion progress cannot be ruled out.

Abstract: The application of Fiber Reinforced Polymer (FRP) materials in concrete structures has been rising due to their several advantages, including lightweight, high tensile strength, ease of installation, and corrosion resistance. They have been mostly implemented for strengthening and repairing existing structures in the form of an externally bonded system, i.e., sheet, jacket, near surface mounted. Furthermore, they have been recently utilized as internal reinforcement of concrete elements in the form of strands, bars, tendons, etc. Although higher durability and performance are associated with the FRP material in some aspects compared to steel, concerns remain regarding damages and defects in this material, many of which are related to their unique features. Importantly, debonding of FRP materials from a concrete surface or within a concrete element has always been an issue resulting in the premature failure of the structure. To this end, concrete elements strengthened or reinforced with FRP materials has to be inspected periodically to detect potential issues and hence prevent any premature failures. This study first determines all possible or potential damages and anomalies attributed to FRP reinforced/strengthened concrete (FRP-RSC) elements. It then investigates Non-Destructive Testing (NDT) methods that can be applicable to the inspection of FRP-RSC elements from a literature survey of past studies, applications, and research projects. Furthermore, this study evaluates the ability of two of the most commonly used NDT methods, Ground Penetrating Radar (GPR) and Phased Array Ultrasonic (PAU), in detecting FRP bars/strands embedded in concrete elements. GPR and PAU tests were performed on two slab specimens reinforced with GFRP (Glass-FRP) bars, the most commonly used FRP bar, with variations in their depth, size and configuration, and a slab specimen with different types of available FRP reinforcements. The results of this study propose the most applicable methods for detecting FRP and their damage/defects in FRP-RSC elements. This study further investigates the feasibility of two new methods for improving the detectability of embedded FRP bars. By providing the inspection community with more clarity in the application of NDT to FRP, this study offers means for verifying the performance and, therefore, help the proliferation of FRP materials in concrete structures.

Abstract: Wind stability and design loads of long-span bridges are assessed applying experimental and theoretical methods. The commonly used approach entails the extraction of fundamental aerodynamic data of key structural elements such as the deck, towers, and cables, either experimentally or numerically, and the application of theoretical models for evaluation of structural responses to turbulent winds. This phenomenon called buffeting is extremely complex and, to date, there is no closed-form theoretical model to reproduce how the wind converts to structural responses and loads which the bridge must resist. The objective of this paper is to explore the base of the problem, namely the transformation of wind gusts to actual loads, and the response estimations. The time domain response approach has been adopted for solution of the generalized equations of motion allowing the exploration of details in the performance of various theoretical interpretations. Starting from the classic quasi-static linear model, theoretical simplifications are removed toward a more complete model of buffeting loads. Non-linear and aerodynamic coupling effects on response predictions are examined specifically aiming at improved buffeting load representations within the framework of the currently available experimental data. A new concept called stack state-space analysis has been introduced for the response solution to wind buffeting. Aerodynamic and structural data of Pierre-Laporte Bridge in Québec City, and the IABSE Working Group 10, long-span bridge validation example, are utilized as representative cases in this study. Avenues for further experimental and numerical validations of the presented new solution approach are suggested toward more accurate predictions of wind response and design loads of long-span bridges.

Abstract: BIM intelligent modeling is used to analyze the safety of the construction scene of prestressed concrete continuous girder bridge, so as to realize the safety management of the bridge construction scene and improve the construction efficiency. The construction safety analysis system is used to analyze the binding data of construction safety, and the data is combined with the self-applicable equilibrium control and the game equilibrium control to build the construction scene safety objective function model. On this basis, combined with the control constraints of the whole life cycle, the statistical analysis regression model is used to build the scene safety analysis model based on BIM. The whole life cycle safety intelligent analysis of the construction scene is realized, and the improved particle swarm optimization algorithm is used to solve the model by adaptive differential evolution, so as to shorten the calculation time of the model. The experimental results show that the safety management performance of the proposed method is high, and the safety management evaluation grade is 285. The identification accuracy of main beam stress change is high. Under the conditions of unbalanced load, combination of unbalanced load and prestress, combination of wind load and prestress and unbalanced load, the safety analysis of upper edge stress and lower edge stress of main beam can be effectively completed, and the construction safety of prestressed concrete continuous beam bridge can be realized.

Abstract: Rail-structure interaction (RSI) analysis and vehicle-track-structure-interaction (VTSI) analysis are often required during bridge design. For example, the California High-Speed Train Project requires RSI analysis for final design of all structures, as well as VTSI analysis, with the level of interaction to be modeled determined by the complexity of a structure. The goal of RSI analysis is to ensure that superstructure deformations and rail stresses are within acceptable limits. VTSI analysis is a dynamic analysis that takes into account influence of actual trainsets. VTSI Level 1 analysis includes train loads as a series of moving loads. This analysis allows evaluation of dynamic impact effects from trainsets and vertical accelerations of the deck. For complex high-speed railway bridges, VTSI Level 2 might be required, accounting for full dynamic interaction between the trainset and the bridge. To represent this interaction, the trainset is modeled as a multibody system consisting of rigid bodies, springs, and dashpots. The interaction between wheels and rails is accounted for through kinematic constraints and Lagrange multipliers. This paper presents modeling, RSI, and VTSI analyses of a railway bridge in the LARSA 4D software package. The track and superstructure are modeled in an expedited way using a macro that generates the track, approach, and bridge geometries. Fasteners are modeled as hysteretic springs and automatically positioned along the curved geometry of the track using a LARSA 4D’s bridge path coordinate system definition. RSI analysis is performed accounting for temperature differentials between rails and the deck, vertical train loads, acceleration and braking forces. Break in the rail is introduced using stage construction analysis, followed by progressive collapse analysis (with adapting increments and arc-length control) or nonlinear dynamic analysis. Finally, VTSI Level 1 and 2 analyses are performed and the results are compared. Car body accelerations are compared to limit values to ensure passenger comfort.

Abstract: In order to clarify the influence of water on the natural vibration of bridge with complex piers, based on a continuous beam with 4-column pier, the numerical analysis model is established. Single column circular pier is taken to discuss the range of waters. Then the influences of water on the natural vibration are analyzed. The research shows that waters reduce the natural frequency. When waters area width is less than 10 m, the natural frequency of the pier decreases. And the first-order longitudinal bending frequency is reduced by 3.36%. When waters area width is more than 10 m, the vibration frequencies tend to be stable gradually. Therefore, the waters 10 m can be regarded as an infinite boundary. The natural frequencies of single column pier and 4-column pier decrease with the increase of water depth. When the water depth is less than 10 m, the changes of natural frequency of the first four orders of single column pier are relatively small, and the changes of 5–10 order natural frequency are large. The maximum effect of the first ten orders is 14.84%. The natural vibration frequency of the bridge decreases gradually with the increase of water depth. The maximum effect of the first five orders is 3.33%.

Abstract: EDITORIAL

Abstract: Aiming at the anti-collision performance of SS-grade concrete guardrail of Chinese highway bridges, the nonlinear dynamic simulation of collision is carried out. On this basis, aiming at the defects of rigid guardrail, a rigid and flexible composite double-layer guardrail is proposed, and its anti-collision performance is evaluated. The vehicle factor analysis shows that the energy absorbed by the guardrail system, crash force, guardrail damage and reinforcement stress range increase with the increase of vehicle speed and impact angle. The effect of concrete grade on improving the anti-collision performance of guardrails is limited. It is not that the higher the strength grade, the better the effect. Compared with concrete guardrail, the vehicle deformation energy of double-layer guardrail system is only 59.1% of that of concrete guardrail system. This shows that the deformation of the vehicle is more serious when the vehicle hits the concrete guardrail, and the damage to the driver and passenger is greater, while the double-layer guardrail can improve the safety of the driver and passenger. The crash force of double-layer guardrail is reduced, so the impact suffered by passengers is reduced and the double-layer guardrail has good buffering effect.

Abstract: This study investigates the effect of superstructure configuration on the optimum design of slab on Precast I (PCI) girder bridges. For this purpose, more than 20,000 bridge cases of varying superstructure configurations are considered to investigate the effects of various superstructure parameters such as girder spacing, span length, slab thickness and girder types on the optimum design of slab on PCI girder bridges. PCI girders are designed conforming to the AASHTO LRFD for flexure using stress limits at the service limit state, then checked at ultimate for flexure and shear using factored loads at the strength limit state. A modified harmony search optimization algorithm is used to obtain optimum bridge design parameters using standard AASHTO PCI girders according to these AASHTO LRFD requirements. Those girders are designed taking into consideration geometrical constraints, stress constraints and constraints related to the conformity of the design with the AASHTO LRFD code. Various sensitivity analysis are performed to investigate the effect of different geometrical factors on the design of the girders, and easy-to-use design aids were developed. The outcomes of this study may facilitate the bridge engineers to choose optimum design parameters such as girder types and spacing as well as number strands for a certain span length before the design of slab on PCI girder bridges.

Abstract: How to quickly and accurately identify the bridge rubber bearing deterioration plays an important role in ensuring the bridge structure and road safety. This paper selects the common rubber bearings of domestic bridges as the research object, and proposes an improved YOLOv4-based bridge rubber bearing deterioration detection algorithm to address the reasons for the difficulty in detecting bridge rubber bearing deterioration due to large scale variations and small sample data sets. An image dataset (named HRBD) with annotations is constructed from real inspection scenarios, and the data is expanded by image processing means such as rotation, translation and brightness transformation, so that this dataset has sufficient data complexity and solves the problem of overfitting due to insufficient samples for network training. The anchor applicable to this dataset was regained by the K-means++ clustering algorithm, and then the CA module was inserted into the YOLOv4 backbone network for more accurate anchor localization. The improved YOLOv4 network was used for migration learning to train the dataset, and finally the trained network model was used for detection on the test set. The experimental results show that the improved YOLOv4 bridge rubber bearing deterioration detection and identification network can effectively identify and locate bridge rubber bearings and their deterioration types (crack damage, shear deformation, bearing void).

Abstract: Over time, owners may face challenges with management of bridges with outdated details. One such detail that is no longer used today is the steel girder shiplap connection. These were originally employed to simplify analysis of continuous girders while also moving joints away from the piers, improving longevity of bridge bearings and substructures. Unfortunately, fatigue issues have appeared in these connections resulting in cracking at critical load-carrying locations. In this project, analysis was performed to investigate connection fatigue and strength and retrofit design verification. Results utilizing non-linear analysis showed that while stresses from ultimate loading could adequately redistribute throughout the web, high stress concentrations were created, exacerbating fatigue. Stress calculations for shiplap web details are not well codified or easily assessed with simple hand calculations, so finite element analysis was utilized. Results showed web fatigue life had been exhausted with more cracking expected at other locations, convincing the owner retrofit was necessary even though the bridge was programmed for replacement.

Abstract: Part of the Netherlands’ busiest highway, the Van Brienenoord Bridge comprises 12 lanes of traffic split across the eastbound bridge built in the 1960 s and the western bridge built in the 1990 s. The Van Brienenoord Bridge complex consisting of two parallel 300 m span steel arch bridges, approach structures and three parallel bascule bridges over the New Meuse. The bridges carry about 230,000 vehicles daily. A strengthening and replacement strategy was developed to reduce road closures to one of the two bridges at a time and reducing this time to weeks instead of months. The strengthening consists of plate stiffeners to the main girders and arches and a new deck. Construction begins in 2025 and will extend the bridge’s useful life to another 100 years. The strengthening instead of replacing is in line with RWS’ commitment to adopting circular economy principles for their infrastructure network.

Abstract: The Bronx-Whitestone Bridge was designed during the 1930s in an era of suspension bridges with decks stiffened by shallow plate girders, many of which were subsequently found to be vulnerable to aerodynamic instabilities such as vortex shedding and flutter. Following the occurrence of mild and benign wind-induced oscillations in the first several years after opening in 1939, the bridge has undergone a series of retrofits, from structural solutions such as stay cables, stiffening trusses, and a steel orthotropic deck, to aerodynamic enhancements such as a tuned mass damper and wind fairings. Wind tunnel studies in 2015 confirmed the improved aerodynamic performance due to the recently installed wind fairing system and stiffer orthotropic deck. A subsequent rehabilitation project gave the opportunity to assess measures to further improve the aerodynamic performance of the bridge. A 3 ft (0.91 m) tall solid screen added on top of the median barrier was found to act as an above-deck vertical baffle plate, disrupting the alternating pattern of vortices, reducing the susceptibility of the bridge to instabilities. This led to the conceptual design of a Median Barrier Extension (MBE) comprised of 3 ft (0.91 m) solid transparent acrylic panels fixed to the top of the existing median barrier posts, supported by a tubular steel frame. To ensure this unique barrier modification met current industry safety standards, the MBE design was iterated through a crash analysis study using non-linear finite element models before the final design proceeded to a full-scale physical crash testing program to MASH Test Level 4. This paper presents the full timeline of this innovative retrofit project, from conception during wind tunnel testing, through to design, crashworthiness studies and final construction in 2020. This project has demonstrated that a vertical extension to a median barrier can act as a simple and cost-effective enhancement to the aerodynamic performance of existing bridges.

Abstract: The minimum flexural reinforcement requirement has been used in the current bridge design specifications to protect the member from brittle failure after the formation of the first flexural cracks. Several variables have been reported to affect this requirement, such as concrete strength, amount of prestressing in the member, and type of cross section. Recently, the Precast/Prestressed Concrete Institute (PCI) developed a new type of beam section (NEXT beam) to accelerate bridge construction and enhance the sustainability of bridges. As a newly developed beam section, no research on the minimum flexural reinforcement has been reported for NEXT beam bridges. This paper aimed to examine the minimum flexural reinforcement requirements in the current AASHTO LRFD Bridge Design Specifications for NEXT beam bridges. A comprehensive parametric study was analytically conducted with various parameters, including bridge section, beam section, concrete strength, and span length. The results from this study showed that the current minimum flexural reinforcement requirements were met for all bridges examined herein; the concrete strength, beam cross section, and span length could affect the levels of safety against brittle failure after first flexural cracks for NEXT beam bridges.