Journal of Bridge Engineering

In this study, an analytical model is proposed to predict the flexural fatigue behavior of reinforced concrete (RC) beams strengthened with externally bonded (EB) fiber-reinforced polymer (FRP) laminates due to FRP debonding. The proposed model is capable of predicting the bond stress of EB FRP-concrete interface, flexural fatigue behavior, tensile strain of EB FRP, and beam deflection while considering bond heterogeneity due to different levels of fatigue damage. A trilinear bond-slip relation is adopted to represent the hardening, softening, and residual phase of the FRP-concrete bond stress. The fatigue bond degradation is characterized by a strain-dependent relation using available test data and incorporated into a one-dimensional mesh with appropriate boundary conditions to obtain the closed-form solution. To validate the proposed model, test results from several existing studies are compared with reasonable correlation. The parametric study shows that higher concrete compressive strength and axial stiffness of FRP with larger diameter steel rebar could be beneficial.

This paper focuses on probabilistic seismic loss estimation of bridges. The results provide several crucial insights on the distribution of seismic repair costs and the reasoning behind their nature—the distribution of seismic repair costs follows a multimodal distribution. Additionally, Gaussian mixture models (GMMs) are proposed to appropriately model the total repair costs in closed form. Furthermore, this study demonstrates that the multimodal distributions for repair costs can be efficiently predicted using neural networks (NNs). To study the repair costs of bridges, this study simulated the responses of 696 bridges, with varying geometry and design parameters, subjected to a suite of synthetic ground motions. Next, uncertainties in component capacities, repair actions, and costs of repair actions were propagated through Monte Carlo simulations (MCS) with 10,000 samples for each bridge. Additionally, for repair-cost estimation, this study also considered the correlation in damage states within all elements of the same component type and among elements belonging to different component types. Studies in the literature usually neglect these correlations and use maximum component damage estimates to assess the repair costs, overestimating the repair costs. The resulting multimodal distributions of repair costs are attributed to uncertainty in repair actions and differences in damage states of elements belonging to the same component types, such as columns, bearings, and abutments. The NN models, along with GMMs, used to predict the multimodal distribution of total repair costs are demonstrated for six cases of study bridges; the predictions are observed to be in good agreement with the actual distributions, underscoring the viability of the proposed strategy to support seismic loss estimation for bridges in seismic zones.

Overturning collapse has been regarded as one of the most critical failure modes for single-column-pier bridges in current practices. To reveal the entire overturning process, a meticulous three-dimensional (3D) simulation of bridges with superstructures, bearings, and piers, considering geometric and material nonlinearities, was first established. Multiple load patterns were applied, including the practical eccentric truckloads that lead to overturning incidents and the conventional checking loads that are defined in the bridge design specifications. Second, four sequential limit stages of the overturning process were defined to precisely describe the structural behaviors under different mechanical conditions before the final collapse. A safety indicator was further proposed to quantify the possibility of overturning with respect to different limit stages. Using such a safety indicator in a case study, the ability of bridges to resist overturning was assessed and compared to results from the specifications and field observations. By doing this, the drawbacks of specifications in checking the safety of single-column-pier bridges were demonstrated. A parametric study was finally conducted to investigate the influence of different single-column-pier bridge arrangements on the overturning behaviors. It can be concluded that the specification-based methods greatly overrate the safety level of single-column-pier bridges, whereas the safety indicator provides more reasonable results as well as multiple-sublevel safety warnings up to the final collapse. Additional findings and suggestions for a better design or maintenance of single-column-pier bridges in curved-girder cases were also discussed.

Agricultural or farm vehicles with various configurations and weights are frequently driven over timber bridges on secondary roadways in the United States. Lateral live-load distribution factors (LLDFs) for these bridges loaded with farm vehicles are not well known. Further, the effects associated with farm vehicles have not been considered in the current AASHTO specifications that solely provide codified formulas to calculate LLDFs of timber girders. To estimate the timber-girder LLDFs more explicitly, three multispan timber-girder bridges in Iowa were selected, and LLDFs for each of girder were determined on the basis of various methods, including codified processing, field testing, simulation, and statistical analysis. For field LLDFs, the bridges subjected to four farm vehicles were tested and a roadway semitruck was used as a reference for determining roadway-vehicle load characteristics. As part of analytical LLDF investigation, analytical models of the bridges were generated and calibrated with field data using finite-element analysis (FEA) software. To consider the effects of farm vehicles with vastly different features, configurations of approximately 121 different farm vehicles were gathered and used as applied loads in the FEA models to determine analytical LLDFs per bridge. The analytical LLDFs were used to create LLDF limits for each bridge in a statistical manner. The resulting LLDFs were compared to those determined from the codified formulas, showing that the AASHTO LLDFs were, in specific cases, insufficiently conservative for the bridges studied.

Steady traffic growth may pose a safety hazard to in-service bridges, especially long-span bridges subjected to the simultaneous presence of multiple heavy-duty trucks. This study presents a methodology for evaluating the statistical extrapolation of traffic-load effects on long-span bridges. As part of the contributions advancing the state of the art, this study addresses several challenging issues, including traffic growth, and the resulting dynamic impact, and actual traffic patterns. The nonstationarity of the traffic-load effects due to traffic growth is considered in a series system compounded by several interval traffic models. The dynamic impacts of traffic loads were simulated by a traffic-bridge-coupled vibration system, and the statistical characteristics were captured using a level-crossing model. The actual traffic pattern was simulated by stochastic traffic flows on the basis of the statistics of the weigh-in-motion measurements of a highway bridge. Two numerical examples show the ability of the interval-traffic-growth model to capture the nonstationarity of the growing traffic loads. In addition, a case study of a long-span suspension bridge shows the effectiveness of implementing the proposed methodology for the statistical extrapolation of the maximum deflection. The numerical results of the case study also reveal that the degradation of road-roughness conditions leads to more level crossings but also results in a slight increase in the extrapolation of the deflection. However, traffic growth results in rapid increases in both the extrapolated deflection and the probability of exceedance of the deflection limit.

A new precast segmental bridge pier system using modular construction methodology is proposed in this study. The proposed system contains multiple segmental layers with several small precast modular RC segments for each layer. The connections between the precast segments in the upper and lower segmental layers are hybrid connections containing shear keys, unbounded prestressing tendons, and bonded bar reinforcements. The bonded bar reinforcements running continuously between segments can provide strength and energy dissipation capability, and prestress force in the unbounded tendons can provide recentering force as the joints between the segments are open. In particular, each precast segment of each segmental layer is connected with at least two neighboring precast segments of the neighboring segmental layer by mortise-and-tenon joints to provide interlocking bonds between segments in the horizontal direction. To investigate the seismic performance of this proposed system, two large-scale column specimens with different connection details were constructed and tested. From the experimental results and construction practices of the developed system, the seismic resistance and constructability of the proposed column were confirmed to be satisfactory. Furthermore, to establish a proper analysis procedure for such a bridge column system, two finite-element models using two different commercial software packages were also developed for each specimen, and both were shown to be appropriate and effective in capturing the seismic behavior of the proposed system.

In this study, the live-load moment-distribution factors (LLMDFs) were evaluated for an adjacent precast prestressed concrete box beam bridge. The bridge used a new shear key configuration, which was grouted with ultrahigh performance concrete (UHPC) and contained noncontact lap-splice dowel bars. The bridge did not contain transverse tie rods, transverse posttensioning, intermediate diaphragms, or a composite deck. As newly developed shear key connections, the LLMDFs are not addressed in the current professional bridge design specifications. Therefore, the LLMDFs were evaluated using static truck load testing. A three-dimensional finite-element model was created and validated by using field results. After validation, the truck load designed by professional bridge standards was applied to the model, and the LLMDFs were evaluated. The results indicate that LLMDFs based on the professional bridge design specifications were conservative compared with the field results. Furthermore, the predicted LLMDFs by means of the professional bridge design specifications were also conservative when the finite-element model was loaded with a truck designed by these specifications and assuming full connectivity for the beams to act as a unit.

Bridges consisting of full-depth precast concrete deck panels connected to steel girders are an increasingly popular option for accelerated bridge replacement. In designing the shear connectors for this bridge type, fatigue is often the governing failure mode. Typically, design provisions developed for cast-in-place deck systems are used. To date, only limited efforts have been undertaken to assess these provisions for precast applications. Most of the data has been obtained from push tests under constant-amplitude loading conditions. Against this background, this article presents measured strain, fatigue life, and autopsy results for 12 composite beam specimens (6 with precast concrete slabs) subjected to a variable-amplitude loading history until multiple stud failures were observed. The results indicate that shear studs in beams with precast slabs exhibit a fatigue performance at least on par with those in beams with cast-in-place slabs. In addition to yielding valuable fatigue data, the test results provide evidence of the effects of redundancy and the value of beam tests, rather than push tests, for assessing and designing shear connectors.

Prior to the 2013 Interim Revisions of the AASHTO LRFD Bridge Design Specifications [AASHTO (2013). Interim Revisions to AASHTO LRFD Bridge Design Specifications, 6th Ed., Washington, DC], the value of reinforcing steel yield strength used in design did not exceed 517 MPa (75 ksi). NCHRP Project 12-77 was initiated to evaluate the AASHTO specifications with respect to the use of high-strength reinforcing steel and other grades of reinforcing steel having no discernible yield plateau. Among the objectives of this project was the investigation of high-strength steel as transverse reinforcement in flexural members and as shear-friction reinforcement. This research led to a number of recommendations that were subsequently incorporated into the 2013 interim revisions of the specifications allowing reinforcing steel yield strengths up to 690 MPa (100 ksi) in many instances. This paper provides the background for the 2013 interim revisions related to the impacts of using high-strength reinforcement on shear strength and web cracking in girders, and on cold construction joint interfaces. The research shows that the use of standard sectional design methods is acceptable for shear reinforcement having yield strengths up to 690 MPa (100 ksi). However, a maximum design yield strength of 414 MPa (60 ksi) must be maintained when calculating shear-friction capacity regardless of the reinforcing steel used.

To evaluate the residual service performance of corroded high-tensile steel wires, a batch of in situ wires that had served for 13 years in the hangers of an arch bridge was investigated. Four types of corroded wires were derived from the in situ wires by placing them in the indoor environment for 1.5 years (Type A) or treating them in an alternate dry–wet environment for 0.25–1.5 years (Types B, C, and D). The mechanical properties of the corroded wires were investigated with tensile and fatigue tests, and the fracture characteristics were observed. Fatigue tests on Type A wires with different stress ranges were conducted, and the stress intensity factor range ΔK_p at the bottom of crack-initiation pits was analyzed. According to the S-N curve for Type A wires, the crack-propagation characteristics of steel wires were investigated. The linear elastic fracture mechanics (LEFM) approach was used to predict the residual life of corroded wires in two systems of arch bridges. The tests show that the ultimate strain of corroded wires decreased with an increase in degree of corrosion. The fatigue properties of wires were found to degrade significantly at the early corrosion stage, and the degradation rate slowed down with further development of corrosion. The correlation between the fatigue life and the stress intensity factor range ΔK_p at the bottom of corrosion pits shows that larger pitting size tended to have shorter life under the same stress range, and fatigue cracks were difficult to initiate at the corrosion pits below the fatigue threshold. The crack-growth parameters of the Paris law identified from the S-N curve of Type A wires were m = 2.87, C = 8 × 10 ⁻¹² under the stress ratio R = 0.5. The residual life predicted by LEFM shows that in a dry environment, corroded wires with an initial pitting depth of 0.6 mm can serve for more than 30 years in arch–beam combination-system bridges, whereas they can only serve for 5 years in floating-system arch bridges.

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.

The flow field around a horizontally oscillating bridge pier during earthquakes is characterized by a high Reynolds number and a small Keulegan-Carpenter number. This study aimed at the fluid forces exerted on a circular bridge pier in quiescent water during earthquakes. By scaling the hydrodynamic equations, it is analytically shown that the inertial force dominates the drag force. This characteristic is further demonstrated by performing numerical simulations. A given earthquake is first decomposed into a series of equivalent harmonic components. Then, the hydrodynamic forces are computed in the numerical code. The numerical results confirm that the inertial force dominates the drag force, and the inertial coefficient is essentially equal to 1 for all conditions examined for the monochromatic and two-frequency oscillations as well as the actual earthquakes. This confirmation is crucial, because the dominance of inertial force means that the resultant force can be predicted with the linear superposition of decomposed frequency components, owing to the inertial force being linear in the fluid-flow acceleration.

Modular or panelized bridges, comprised of stacked rectangular panels forming girder-type bridges, are the most widely used approach for rapidly erectable bridging. Limitations of these systems, however, include inefficient material distribution of both panels and lateral bracing. This research addresses this challenge by implementing structural optimization for the conceptual design of modular bridges, including module topology and spatial orientation optimization. This contribution generalizes an existing formulation for optimizing modular trusses to include (1) reusability of modules among multiple structures and (2) practical considerations in design, such as multiple types of modules, multiple load cases, the capability to compute the displacements in an elastic design formulation, and limitation on stresses. This methodology is demonstrated for the conceptual design of single- and double-story simply supported bridges. Further studies find that (1) incorporating module reusability results in a trade-off between constructability and material efficiency and (2) better designs can be obtained by modifying the module configuration. This research culminates in guidelines to assist designers during preliminary design phases.

A monitoring strategy for investigating the long-term longitudinal deflections at the expansion joints of the I-35W St. Anthony Falls Bridge was developed as a means of inferring the integrity of the bearings. During the duration of this study, the deflections were primarily caused by time-dependent behavior, which tends to be highly uncertain, and changes in temperature, which are comparatively predictable. The proposed monitoring strategy uses separate anomaly-detection routines to monitor the expansion joints for quickly developing problems, such as bearing lockup, and slowly developing problems, such as unexpected changes in the rate of time-dependent bearing movement that might be indicative of slow degradation. The quickly developing anomaly-detection routine presented used Bayesian regression to combine the uncertainty in the time-dependent deflection predictions with the scatter of the data to realize coherent bounds for discerning problems that occur instantaneously or over the course of several weeks. The slowly developing anomaly-detection routine used the rates of the measured time-dependent behavior with respect to the Arrhenius-adjusted age to discern deterioration developing over time frames from several months up to several years. These rates were expected to decrease with time according to a power function for a structure with no damage. The system was tested on the collected linear potentiometer data from the I-35W St. Anthony Falls Bridge to investigate the incidence of false positives. Use of model code time-dependent provisions for the two anomaly-detection routines minimized false positives. To test the efficacy of the developed system in identifying true positives, artificial perturbations were introduced to the collected data. These perturbations were intended to mimic probable quickly developing and slowly developing problems that the bridge might encounter. The system successfully identified the introduced quickly developing and slowly developing perturbations unless sensor failure followed by a delayed sensor replacement occurred at approximately the same time as introduction of the perturbation.

Tensions in the hangers of suspension bridges are vital for quality control during their construction and health monitoring and maintenance during service. Hence, accurate and efficient estimation of the tensions in hangers is very important. A novel method for identification of the tensions in hangers is proposed in this paper. Different from other methods, this new method identifies the tensile forces in hangers by only using the measured coordinates of the main cables of the bridge, which is convenient and economical to implement in practice. This method is developed based on form-finding theory and a new catenary element for form-finding of suspension cables established in this paper, which are derived by considering the force equilibrium equation of an infinitesimal segment of suspension cable. The method is applied in a case study for Aizhai Bridge. The results show that, compared with the other methods, the proposed method is accurate and efficient. More importantly, the proposed method can identify the tensions in hangers with shock absorbers in cases in which the vibration-based method does not work. In addition, the proposed method can identify the internal forces in all hangers of the suspension bridge simultaneously.

Transit agencies own and operate thousands of bridge structures subjected to repetitive train loading. The majority of these bridges were built at the turn of the century and many have exceeded their theoretical fatigue life spans. In New Jersey, the recent increase of the railcar weight limit from 1,170 kN (263,000 lb) to 1,272 kN (286,000 lb) raised concerns for railway bridges that have been in service for more than a century. To prioritize and schedule repairs and rehabilitation events, there is a need to establish refined procedures that would be able to estimate the impact of the increased railcar weight on the remaining life and damage accumulation of bridges. In this paper, three typical railway bridges with various span lengths were selected. Field testing was performed to validate the three-dimensional (3D) finite-element (FE) models of the bridges. A probabilistic approach was developed for fatigue evaluation. For fatigue resistance, a new model was proposed based on previous full-scale fatigue tests. The variance of fatigue resistance increases when the stress range increases based on test results. The new 1,272-kN freight car and its frequency are found to have a significant effect near the supports in terms of remaining fatigue life. Midspan location would not always be the most critical location of the bridge when operating the heavier railcars. An increase of 1,000 freight trains annually will decrease the remaining fatigue life by approximately 2 years. Last, the introduction of heavier railcars will have more significant effects on shorter spans.

Conventionally, in the conceptual seismic design of bridges, absorption of earthquake energy is provided through plastic deformation in the main components of the bridge, such as columns and walls. In recent decades, ductile end-diaphragms have been proposed as one of the passive control systems to reduce the inelastic deformation in the substructure of steel bridges by transferring the majority of seismic energy dissipation to diaphragm inelastic deformations under ground motion in the transverse direction. The proper operation of these systems with stiff substructures has been already demonstrated in several numerical and experimental studies, but the need for separate studies about their design and performance in steel bridges with flexible substructures is quite tangible. In this article, first, the generalized single-degree-of-freedom (SDOF) dimensionless relations of single-span and continuous three-span bridges located on flexible piers are developed. Then, using some assumptions, the relations are extended to the inelastic range. Different forms of ductility imposed on bridges equipped with ductile end-diaphragms, including global, support, diaphragm, and damper ductility, are identified. Moreover, using simplified analyses, a new step-by-step design method is proposed, and the accuracy of the results is verified using nonlinear time-history analyses for some numerical examples. The simultaneous role of the substructure stiffness and deck flexural stiffness and the contribution of girder stiffness in the design and evaluation of ductile diaphragms are examined. Results indicate that increasing flexibility of the substructure may result in superstructure damage like yielding of the girders or impractical required damper components. Although the main focus of this article is on the design of ductile end-diaphragms, because of the subject generality, the concepts can be extended to slab-on-girder steel bridges equipped with other yielding devices.

To explore the seismic performance of RC bridge columns subjected to combined stresses of compression, bending, shear, and torsion, reversed cyclic tests with eight column specimens were performed in the laboratory. Finite-element analysis (FEA) was used to evaluate the strains of the steel bars in columns and to carry out the parametric analysis. It was found that the coupling effect of bending and torsion was significant. Bending hysteresis loops were fuller than torsional hysteresis loops. Different torsion-to-bending ratios resulted in different bending or torsional failure modes. The plastic hinge length increased with an increase in the torsional effect. With an increase of the torsion-to-bending ratio, the flexural capacity was not fully used, but the torsional capacity, torsional stiffness, and torsional energy dissipation increased. With a decrease in column height, the flexural capacity, flexural stiffness, and flexural energy dissipation increased; however, the lateral deformation decreased, and the torsional capacity showed little change. When the longitudinal reinforcement ratio was increased, although the bending performance was enhanced, the torsional performance showed no significant change. An increase in the stirrup ratio improved torsional performance but not bending performance. Strains of longitudinal rebars and stirrups in the plastic hinge area increased greatly after steel yielding. The length of the torsional plastic hinge increased and the position of the plastic hinge moved upward when columns showed the torsional failure mode. The relationship between maximum torque and maximum shear force under different torsion-to-bending ratios is discussed.

This paper presents a methodology to predict the pile-head load versus displacement curve, and the associated mobilized stiffness of a pile embedded into sandy soils, on the basis of the soil-pile interaction. The mobilized tensile resistance and displacement of the pile shaft are determined up to failure on the basis of the soil and pile properties, including the soil stress-strain curve. The proposed technique also provides the t-z curves for piles in sandy soils that can be separately used in a combined model for a complete superstructure-substructure solution. A detailed flowchart is presented to describe the proposed methodology that has been compiled through a computer program. A number of comparisons with full-scale load tests at different sites were employed to validate the suggested technique. In addition, a finite-element model has also been developed to compare the results of the presented method with those determined from the finite-element analysis and full-scale load tests results.

The main objective of this study is to comprehensively evaluate the utilization of infrared thermography (IRT) considering different technologies, critical environmental parameters, and uncertainties for bridge deck evaluation. For this purpose, a real bridge was scanned and the results were compared with other nondestructive evaluation (NDE) technologies that were implemented on the same bridge. There are a number of considerations and factors that affect the utilization of IRT, such as thermal contrasts, camera specifications, distance, and utilization speed, and these are evaluated by using three different infrared (IR) cameras with different specifications. These considerations are discussed and results are presented. When compared at fully documented locations with eight concrete cores, a high-end IR camera with cooled detector distinguished sound and delaminated areas accurately. Furthermore, indicated location and shape of delaminations by three IR cameras were compared with other NDE methods from past research, and the results revealed that the cooled camera showed shapes almost identical to other NDE methods including chain drag. It should be noted that these data were collected at a normal driving speed without any lane closures, making it a more practical and faster method than other NDE technologies. It is also presented that the factor most likely to affect high-speed application is integration time of the IR camera.

Deterioration of aging bridges is a serious problem that affects their serviceability and durability. Appropriate repair, strengthening, or replacement work should be performed on aged bridge structures to ensure they remain in good condition. A novel strengthening method using rubber-latex mortar, glass-fiber-reinforced polymer plates, lightweight rapid-hardening concrete, and reinforcement bars is proposed in this article. The strengthening method can be used to strengthen both steel railway bridge superstructures and piers. To confirm the effectiveness of the strengthening method, field tests on a short-span railway bridge and laboratory tests on longitudinal-lateral beam connections and steel piers were performed. Because the structural stiffness of aged steel structures is directly related to the fatigue performance and the seismic behavior of steel piers, the applied load versus displacement and strain responses of the test specimens were of primary interest in the tests. Strain results at key sections were experimentally measured and are reported in this paper. According to the experimental results, the present renovation method can significantly enhance the rigidity and reduce the stress levels in bridge girders, connections, and piers, resulting in the extension of the residual service life of such structures.

The aim of this paper is to reveal the unique dynamic characteristics of the Saint-Bachi suspension pipeline bridge with fluid–structure interaction. With commercial software, a three-dimensional finite-element (FE) model of this bridge is developed to simulate its dynamic properties. The solid and fluid elements are, respectively, applied to model the structural members (pipe girder, cables, and portal frames) of the bridge and the water in the pipe girder. The dry (without fluid) and wet (with fluid) modes of the suspension pipeline bridge are, respectively, calculated and compared. The dry modes are fundamentally the same as those of the ordinary highway suspension bridges. The number of wet modes has been greatly increased due to the interaction between sloshing water and structure. According to the oscillation phases of sloshing fluid and pipe girder, the wet modes can be divided into the in-phase, out-of-phase, and no-sloshing modes. The in-phase and out-of-phase modes represent the synchronous and unsynchronous motions of pipe girder and fluid, respectively. The no-sloshing mode denotes a pure girder bending vibration without water sloshing. The in-phase (synchronous) frequencies are decreased with increased fluid depth. The out-of-phase (unsynchronous) frequencies might be increased or decreased with increased fluid depth. The (local) wet frequencies of pylons and cables may increase with the increment of water depth due to increased tension force of the cables.

Considering the new challenges for high-speed railway bridges, the early warning of abnormal train-induced vibrations is necessary for ensuring the operation safety of both the bridge structures and the trains on the bridge. In this study, an online monitoring system for detecting abnormal train-induced vibration responses is developed, and the Dashengguan Yangtze River Bridge is used for illustration. First, to accurately investigate the influence of different train lanes and the number of carriages on train-induced vibrations, the speed-acceleration (train speed-bridge acceleration) correlations under different loading cases are obtained using an online identification method. Then, a two-stage method for early warning of abnormal train-induced acceleration responses of the bridges is developed using wavelet packet decomposition and interval estimation theory. Finally, the early warning method for identifying abnormal train-induced transverse vibrations is presented. The results show that (1) the train lane and the number of carriages affect the speed-acceleration correlations, and the identification of loading cases is needed for the accurate monitoring of speed-acceleration correlations; (2) by using wavelet packet decomposition, the median line of speed-acceleration correlations can be optimally extracted, and the early warning thresholds for abnormal train-induced acceleration responses can be properly determined using the interval estimation theory compared with the point estimation theory; and (3) the train running parameters of the Dashengguan Yangtze River Bridge are all within safe limits, but the wheel unloading rate and derailment coefficient have reached 60% of the limits due to the train-induced transverse vibrations. The effects of train-induced transverse vibration on the train running stability is worthy of attention.

Bridge agencies seek to apply appropriate rehabilitation or maintenance treatments at the right time. For a specific treatment, improper timing can have significant adverse consequences: Premature application could mean wasteful spending by the agency even if road users and the community enjoy the benefits of a superior bridge condition, and deferred or delayed application can result in higher user or community disbenefits caused by poor condition and consequent reduced asset longevity in the long-term. For short-term decisions regarding the identification of the most cost-effective paint action at a specific time (do nothing, spot paint, overcoat, or recoat), the paper presents a methodology for developing a painting decision tree. For long-term decisions regarding the identification of the most cost-effective schedule over the superstructure lifetime, the paper demonstrates a methodology for developing a long-term schedule of painting activities. An analysis of the state of paint scheduling at a specific highway agency revealed that the current practice of complete recoating every 25 years may not be optimal. Instead, a painting schedule that includes the application of lower-level treatments (spot repairing and overcoating) can yield as much as a 19% reduction in the lifecycle cost and a 31.97% higher cost-effectiveness compared to the current practice.

The use of high-performance materials in bridges is leading to structures that are more susceptible to wind- and traffic-induced vibrations due to the reduction in the weight and the increment of the slenderness in the deck. Bridges can experience considerable vibration due to both moving vehicles and wind actions that affect the comfort of the bridge users and the driving safety. This work explored the driving safety and comfort in a very slender arch bridge under turbulent wind and vehicle actions, as well as the comfort of pedestrians. A fully coupled wind–vehicle–bridge interaction model based on the direct integration of the system of dynamics was developed. In this model, the turbulent crosswind is represented by means of aerodynamic forces acting on the vehicle and the bridge. The vehicle is modeled as a multibody system that interacts with the bridge by means of moving contacts that also simulate road-surface irregularities. A user element is presented with generality and implemented using a general-purpose finite-element software package to incorporate the aeroelastic components of the wind forces, which allows modeling and solving of the wind–vehicle–bridge interaction in the time domain without the need for using the modal superposition technique. An extensive computational analysis program is performed on the basis of a wide range of turbulent crosswind speeds. The results show that bridge vibration is significantly affected by the crosswind in terms of peak acceleration and frequency content when the crosswind intensity is significant. The crosswind has more effect on the ride comfort of the vehicle in the lateral direction and, consequently, on its safety in terms of overturning accidents.

This paper evaluates the fatigue stress and damage accumulation in steel railway bridges using a dynamic coupled train-bridge system model. The system consists of a spatial vehicle model, a three-dimensional (3D) bridge model, and a wheel-rail interaction model including the effects of track irregularities. The proposed approach was validated by comparing the fatigue stresses of an existing steel railway bridge to those obtained from field structural-health-monitoring data. Fatigue evaluation of the critical structural detail in the bridge was performed on the basis of stress data resulting from the proposed approach and two conventional methods (i.e., the static-influence-line method and the moving-load method). In addition, an investigation on the effects of train speed, track irregularities, and lateral vibrations on fatigue damage and remaining service life was performed. The results show that all three considered factors can significantly affect the fatigue behavior of critical members in railway bridges.