Journal of Bridge Engineering

Ever increasingly, corrosion-induced steel bridge deterioration, particularly near or at the welded joints, has led to a huge economic burden in the United States. There is, however, no sufficient information about weldment corrosion in steel bridges, which has hindered the application of appropriate corrosion mitigation. This study is to better understand corrosion behavior of steel bridge welds. Investigation of weldment corrosion of commonly used bridge steels, the low-carbon iron steel, and weathering steel, was performed using four electrochemical tests under simulated corrosive environments. Two coating systems, organic zinc-rich three-coat system and one-coat calcium sulfonate alkyd (CSA), were deposited to the samples to determine their performance at weldment. Results revealed that bridge welds exhibit higher corrosion initiation over base metals, regardless of types of steel or coating. In addition, the weathering steel shows the higher resistance to corrosion initiation (twice as high) in welded area as compared to the low-carbon iron steel. Moreover, the protective coating can effectively delay the corrosion initiation at the welds, thus enhancing the corrosion resistance of bridge welds.

Seismic performance of bridge structures supported by extended pile-shafts principally depends on the curvature demand in critical regions of the pile below ground level. The equivalent fixed-based cantilever model is commonly used to assess the local curvature ductility demand of a yielding pile-shaft at any inelastic displacement level. In this approach, adequate prior knowledge of several parameters, including depth-of-fixity, plastic-hinge depth, and equivalent plastic-hinge length, is essential for proper estimation of ductility capacity. The present study aims to propose analytical formulations by using concepts of the strain wedge method based on nonlinear behavior of the soil-pile system to assess the key parameters of the equivalent cantilever model. The ability of the developed model in assessing the curvature ductility demand of the bridge system is validated against several published full-scale tests on RC shafts in clay and sand.

This paper presents the experimental and analytical results of a new composite girder that consists of a steel girder and hybrid fiber–reinforced concrete (HFRC) slab. First, six push-out tests were performed, and the test results were used to verify the interface behaviors of two composite girders. Then, the composite behavior between the steel girder and HFRC slab was investigated under sagging moment. It was found that the composite girder with HFRC slab exhibited a much greater ductility and a slightly smaller ultimate moment capacity, and the probability of cracking was also significantly reduced compared with the normal concrete (NC) slab. Finally, equations introducing the reinforcement indexes to determine the capacity, degree of shear connector, and effective moment of inertia of the steel–HFRC composite girders with partial interaction were proposed. It was found that the analytical results of the equations had a fairly good agreement with experimental results.

Precast concrete segmental bridge columns (PCSBCs) have developed rapidly in recent years. To study the effect of shear on the carrying capacity of the joints in PCSBCs, four conventionally reinforced concrete segmental bridge columns (CRCSBCs) and three totally prestressed concrete segmental bridge columns (TPCSBCs) with different aspect ratios were subjected to monotonic loading for failure. During the test, initiation and development of failure cracks, failure processes and modes, relative slide along the joint plane, strains of stirrups, longitudinal steels, and prestressing tendons were recorded. The results showed that the failure crack always concentrated in the joint plane in PCSBCs, and stirrups near the joint contributed little to resist the shear force at the joint section. Subsequently, the peak carrying capacity of the joint was attained with uncracked concrete subjected to combined normal and shear stresses that resulted in the interaction of axial load, shear, and bending moment at the joint plane in PCSBCs. Based on the simplified failure modes proposed in this paper, both a general and a simplified method were proposed to calculate the axial–shear–flexure interaction resistance of the joints in PCSBCs.

Ensuring serviceability is central to the design of pedestrian bridges (PBs); hence, their design is often governed by the serviceability limit state (SLS) under pedestrian loads. A reliability-based evaluation of various design codes and standards (collectively called guidelines), namely, ISO 10137, Eurocode 5, the British National Annex, and SÉTRA, has demonstrated a need to calibrate these guidelines for a higher reliability level to achieve a sufficient and uniform reliability index across different PBs for both the design and rare traffic loading events. This paper discusses the process and the results of calibration of these SLS design provisions for PBs. To achieve sufficiency for both design and rare events, an iterative process is introduced to estimate the desired reliability index. To achieve economic designs after the calibration process, comfort limits depending on both the frequency of traffic and the bridge class based on their routes, uses, and locations are applied during the estimation of desired reliability index and the corresponding design partial factors. This study is limited to truss-type metal PBs. A general observation from the calibration results is that the partial factors for a given reliability index are consistent across different bridge classes and guidelines, as a result of the approach adopted in this exercise. It is possible to achieve a sufficient and uniform reliability index across all bridge classes under both design and rare loading events while ensuring economic designs using frequency and class-based comfort limits. Although the desired reliability index is the same for all of the guidelines for sufficiency during the design loading event, there is significant inconsistency observed for the rare loading events. To achieve the same desired reliability index (i.e., uniformity) across guidelines, it is recommended to calibrate using the maximum desired reliability index estimated across all the guidelines for a particular event. The estimated desired reliability indices and the partial factors are sensitive to the coefficient of variation (COV) of the acceleration limit used for the SLS check.

Weld residual stresses (WRSs) in orthotropic steel decks (OSDs) contribute prominently to fatigue damage. WRSs relax during the accumulation of fatigue damage. However, their effects are ignored in conventional methods of fatigue damage evaluation. This paper presents the first evaluation approach to fatigue damage that considers of the relaxation of WRSs. WRSs were analyzed using a thermomechanical analysis that took into account the relaxation of WRS. An elastic–plastic fatigue damage model was developed using continuum damage mechanics. The proposed model of fatigue damage was experimentally validated using fatigue tests on U-rib weld connection specimens under different cyclic loading conditions. The test results indicated the feasibility of the elastic–plastic fatigue damage model for predicting WRSs and fatigue damage in OSDs. Ignoring the effects of WRSs may result in the overestimation of fatigue life, resulting in structural designs that are not conservative enough.

A full-scale steel fiber reinforced concrete (SFRC) bridge deck was tested to investigate the behavior under two-way action. The deck was designed to reduce the amount of traditional reinforcing bars in a design controlled by service-limit criteria. The SFRC is intended to reduce the strains in the steel at service limits. Loads were applied to simulate the single and tandem loads in the continuous spans of the bridge deck and a single tandem load in the overhang. A companion test program tested slab strips to establish the one-way flexural response with and without reinforcing bars. One-way strength was used in a yield-line analysis to predict the experimental capacity of the specimens. Theoretical capacities were significantly less than the experimental strength for interior loads where significant multiple-cracking effects were observed from the SFRC. In the overhang where membrane action and load redistribution were not possible, yield-line analysis predicted the experimental capacity.

Structural modal parameters are greatly sensitive to ambient temperatures. Therefore, false identification of damages may arise in vibration-based health monitoring. In this paper, the dynamic properties of long-span suspension bridges are described according to fine temperature effect analysis and thermoeigenvalue theory. Heat transfer between a structure and the surroundings is related to solar radiation, wind speed, atmospheric environment, and thermal properties of the water surface. Temperature variations in cables and nonuniform surface transfer coefficients for the pylon were obtained through multiscale modeling and the computational fluid dynamics (CFD) method, respectively. Then, natural frequencies of the fine model were compared with those from the three-dimensional (3D) beam–shell element model and measurement data from other bridges. Finally, on the basis of the fine temperature distribution, the effect of temperature variations, temperature gradient, material properties, and pavement on the structural dynamic properties were quantified and compared for different seasons. Consistent with other research on various types of bridges, an overall decrease in modal frequency was observed with increasing temperature; however, for long-span suspension bridges, the time-varying dynamic properties were mainly caused by a thermal stress stiffening effect. Furthermore, removal of asphalt pavement caused higher average temperatures of the girder, which resulted in lower natural frequencies. The novelty of this work relates to the accurate description of the temperature field and the refined mechanical representation of time-varying thermodynamic properties for cable-suspended structures.

This study shows how integrating fiber optic sensor (FOS) networks into bridges during the construction stage can be used to quantify preservice performance. Details of the installation of a large FOS network on a new steel–concrete composite railway bridge in the United Kingdom are presented. An overview of the FOS technology, installation techniques, and monitoring program is also presented, and the monitoring results from several construction stages are discussed. A finite-element (FE) model was developed and a phased analysis was carried out to simulate strain development in the bridge during consecutive construction stages. The response of the self-sensing bridge to the time-dependent properties of the concrete deck was evaluated by comparing FOS measurements to predicted results according to several model code formulations implemented in the FE model. The preservice strain distribution due to dead loading is typically assumed to act uniformly along the bridge length; however, the monitoring results revealed that the distribution was highly variable as a result of the complex interactions between gravity loading, bridge geometry, time-dependent concrete properties, and temperature effects. Moment utilization of the main girders and composite beams, during preservice conditions, was assessed and found to be between 19.3 and 24.9% of the respective design cross-section capacities. Quantifying preservice performance via integrated sensing also provided a critical baseline for the bridge, which enables future data-driven condition assessments.

This paper introduces a new type of bridge structure: the prefabricated composite box girder with corrugated steel webs, which features use of a composite upper flange and a prestressed tubular bottom flange filled with concrete. To understand the flexural behavior of this new structure, a static experiment was conducted on a 32-m-span tested girder with simply supported boundaries to investigate the deflection, strains, and bending capacity of it. Meanwhile, the tested girder and two hypothetical reference girders were theoretically analyzed according to elementary beam theory to obtain further insight into the flexural failure mechanism and the effectiveness of the different components. The experimental and theoretical results fit well, revealing that the bottom flange dominated the flexural capacity and the tested girder had sufficient bending resistances to meet the requirements specified in bridge design codes. A simplified equation for bending capacity was also proposed. The findings from this research may provide a reference for the application of this type of bridge structure.

Many state agencies are investigating the use of unmanned aerial systems (UASs) for bridge inspections. Some agencies are receiving pressure from consultants and their own administrations to implement UAS inspections with limited knowledge of their efficacy. This paper studies the feasibility of using UASs for fatigue crack detection in bridges with fracture critical members (FCMs) through real-time and postflight visual inspection. The effects of surface illumination on the maximum crack-to-camera (MCC) distance at which a fatigue crack can be detected were investigated in the laboratory. Mock field inspections evaluated the achievable crack-to-platform (ACP) distance in Global Positioning System (GPS)-denied and windy environments to determine whether known cracks can be identified at achievable standoff distances. Finally, two FCM inspections demonstrated the field performance of UASs in identifying fatigue cracks. Results highlight the importance of camera specifications and surface illumination in determining the required standoff distance of crack detection. Furthermore, the results demonstrate the difficulties in obtaining clear images with unstable UASs in GPS-denied or windy environments. Nevertheless, the best performing platform tested in this study exhibited a performance comparable to an average of 30 human inspectors at a fatigue crack identification training structure. The limited results presented here proved the feasibility of using UASs for fatigue crack detection in FCM inspections of steel bridges and highlighted the shortcomings of UASs for this type of hands-on inspection.

In this paper, a continuum model for a three-span suspension bridge with a floating girder is newly proposed to investigate its static and dynamic behaviors. This model can consider the extensibility of hangers and thus vertical differential motions between a main cable and a girder. Coupled differential equations for the vertical displacements of the main cable and the girder subjected to external loads are derived. The equations of motion are obtained in matrix form by utilizing the Galerkin method with the shape functions for the main cable and the floating girder. A numerical example is used to verify the continuum model against a finite element model. Verification results prove that the continuum model can accurately determine the static and dynamic responses of a suspension bridge with a floating girder subjected to static distributed loads on the girder, temperature changes in the main cable and hangers, and moving loads on the girder. The continuum model can determine nonzero displacements of the girder at its intersection with the towers. The displacements of the girder at this intersection are much smaller than those at its center because the motion of the girder at this intersection is largely restrained by the tower top. The results also show that the main cable and the girder have clearly different accelerations around the towers because the main cable is vertically restrained by the tower tops, whereas the girder is not restrained at the intersection.

This paper focuses on evaluating the effectiveness of an unmanned aerial vehicle (UAV) as a supplementary bridge damage quantification tool. For this study, a glued-laminated timber arch bridge in South Dakota was selected, and an UAV was utilized for the bridge damage quantification. A recommended four-stage UAV-enabled bridge damage quantification protocol involving image quality assessment and image-based damage quantification was developed. A field application using the UAV to measure crack lengths, thicknesses, and rust stain areas of the selected bridge was conducted following the recommended protocol. The image quality parameters, including sharpness and entropy, were used to determine the quality of the UAV-captured images. Pixel- and photogrammetry-based measurements using the high-quality images were obtained to quantify the bridge damage, and the damage was compared to that from actual field measurements. Once the damage information was gathered, the UAV image–based damage level classification was established based on the damage levels defined by current standards. The findings confirmed the accuracy of the recommended protocol, with results within 3.5, 7.9, and 14.9% difference for crack length, thickness, and rust stain area, respectively, when compared with the field measurements.

No prevailing method is currently available for reducing the seismic response acceleration parameters PGA, S_S, and S₁ from the probabilistic seismic hazard values used for permanent bridge design to levels suitable for temporary bridge design. A method of spectral reduction using spectral reduction factors was proposed to reduce the previously published spectral response acceleration parameters, the peak ground acceleration (PGA), the short-period response acceleration coefficient (S_s), and the long-period response acceleration coefficient (S₁), from the 1,000-year return period used for permanent bridge design to a return period suitable for temporary bridge design. The proposed spectral reduction factors are the ratios of the return period used for the seismic design of a permanent bridge to the return period used for the seismic design of a temporary bridge. Spectral ratios were obtained for each of the three seismic response acceleration coefficients for 100 locations around the United States. The examination of the short- and long-period response acceleration coefficients are presented in this paper. As a result of this examination, two spectral reduction factors for the seismic design of temporary bridges were proposed: one spectral reduction factor, of 2.5, to reduce each PGA, S_S, and S₁ parameter for the western United States, and one spectral reduction factor, of 3.75, to reduce each PGA, S_S, and S₁ parameter for the central and eastern United States.

Flooding and the resultant scour damage to bridges may lead to immense economic losses and significant social and environmental impacts. Currently, bridge management decisions are developed on a bridge-by-bridge basis to prevent bridge failure due to scour, i.e., these decisions are made irrespective of other bridges in the regional transportation network. Because bridge managers are often responsible for the management of several bridge networks, it is essential to develop a framework that considers the bridge performance at the network level to aid making rational bridge management strategies. Furthermore, the economic, social, and environmental impacts dictate the need to develop a sustainability-informed bridge management framework at the network level. The objective of this paper is to develop a sustainability-informed bridge ranking approach for a network of bridges vulnerable to scour using multiattribute utility theory (MAUT) and transportation network analysis. The individual performance of bridges and the impact of bridge failure on the network are systematically integrated into the proposed sustainability assessment methodology. The proposed utility-based approach is applied to an existing highway bridge network located in Camden County, New Jersey. It is shown that the proposed approach can provide an important guideline to bridge managers to prioritize their intervention actions for scour protection/prevention.

Distributed fiber optic strain sensing systems could potentially provide a useful tool for bridge assessment by providing insights into member forces and connection behavior as well as local cross-section changes (e.g., due to deterioration) for steel truss bridges. To investigate the use of distributed fiber optic strain sensing systems, an in-service steel truss bridge that was built in 1902 had a fiber optic sensing system installed at midspan at the top and bottom chord connections. Three load scenarios were used: (a) static loading using a work train, (b) dynamic loading using a work train, and (c) dynamic loading using in-service increasing trains. The static test results indicated that the strains could be used to evaluate behavior in the members, including the presence of bending moments, and the impact of connections such as gusset plates and to locate changes in the member’s cross section. The dynamic load tests indicated that increasing train speed degrades the quality of the strain measurements. However, trends in the data can still be detected and are similar to those observed during static tests, although the detection of localized strain changes was less accurate.

A performance assessment of the Twantay Bridge, Myanmar, which is a suspension bridge that has been damaged by the movement of anchorages due to the soft soil conditions, was conducted based on simple monitoring, spatial measurements by three-dimensional (3D) terrestrial laser scan, and structural analysis with the finite-element method (FEM). Simple monitoring can capture the present progress of main-tower inclinations. This study proposes a method for capturing the overall deformation of bridges based on spatial measurement by 3D terrestrial laser scan. The FEM analysis was able to appropriately reproduce the deformation history of the suspension bridge after the construction, which was caused by movement of the anchorage blocks. Thus, the deformation of the main towers obtained with FEM was found to almost agree with that measured by the 3D terrestrial laser scan. In addition, by giving external loads, ultimate capacities were evaluated. This study clarified that a combination of simple monitoring, spatial measurements by 3D terrestrial laser scan, and structural analyses by FEM is useful for the safety assessment of and maintenance strategy for damaged suspension bridges.