Journal of Bridge Engineering

Because variations associated with the strut-and-tie model (STM) in the design of pier caps could lead to over-reinforcement of steel rebars, special attention should be paid to using STMs for reasonable rebar arrangements. Here, static loading tests were conducted on three scaled-model specimens of bridge pier caps to investigate the efficient arrangement of steel reinforcement in the bridge pier cap design. To determine the effect of the loading condition on the pier cap behavior, T-type pier caps with two or four support bearings were tested under realistic boundary conditions, using three hydraulic actuators. The tested load–resistance capacities were compared with the STM predictions. The study revealed that the arrangement of vertical ties in the STM along the shear critical section in the column’s vicinity could induce excessive vertical shear reinforcement. The experimental results showed that all specimens designed using the STM with no unnecessary vertical ties exhibited flexure failure without any sudden shear failure. The effect of load distribution on the pier cap behavior was evaluated using different numbers of support bearings.

The heavy rainfall that occurred in western Japan in July 2018 caused massive and widespread damage to social infrastructures and lifelines. Certain cases that can be used to specifically and quantitatively analyze the damage situation and the cause of the damaged bridge groups are valuable for overcoming structural and complex engineering problems. Such cases can be used to identify the causes of the failure and the analysis progress, and they will help improve the design elements and construction method of bridges in the future. They could also yield such measures as washing out of the bridge at the time of flood. In this study, we conducted a field survey of the washed out Misasa railway bridge, and we evaluated the conditions that caused the failure based on hydrological, hydraulic, and structural analyses at the time of the flood, based on a field survey of the affected bridge. These analyses will help obtain design elements for small and medium bridge structures and countermeasures in the future. We focus on the collapse issue of the 1st Misasa Railway Bridge, wherein the collapse trigger of structural stability can be evaluated through its collapse mechanism. The structural analysis reveals the flood hydrodynamic force on the bridge girder during the flood that caused the collapse. In particular, when the hydrodynamic force of the water flow acts on the bridge girder part, the flood hydrodynamic force that led to the collapse of the bridge is estimated from the engineering point of view of structural stability. Based on the failure processes and conditions revealed by the analyses, we identified design elements that can help increase the resistivity of bridge structures on small rivers against floods with effective methods.

Seismic safety assessment of reinforced concrete box girder bridges has received considerable attention as they are increasingly popular in modern highway systems. However, the detailed seismic assessment of box girder bridges requires a consideration of the material nonlinearity and uncertainty in geometry, material properties, and loading. This paper presents the development of metamodels for selected seismic response parameters of a box girder bridge considering the uncertain input variables using high-dimensional model representation, a relatively new nonstatistical metamodel-based approach. The seismic responses at the sampling points of high-dimensional model representation are evaluated through detailed finite-element analysis. The developed metamodels are further utilized to generate seismic fragility curves that are found to be much simpler than traditional fragility analysis. The results from this approach are found to agree with that of other popular response surface methods (using Central Composite Design and Box Behnken Design) with significantly fewer simulations. High-dimensional model representation (HDMR) provides a failure metamodel that includes all related random variables, but at the same time significantly reduces the computational effort of fragility analyses.

This paper examines the seismic performance of a bridge–helical pile foundation based on the seismic fragility analysis, considering the element fragility of a coupled bridge–soil–foundation system. Nonlinear time history analyses were conducted using a finite-element modeling scheme that was validated using the results of large-scale shaking table tests of soil–piles–structure systems involving both liquefiable and nonliquefiable soils. Incremental dynamic analysis was conducted to generate the fragility curves for a two-span bridge supported on helical piles in nonliquefiable and liquefiable sites considering a suite of ground motions. The damage limit states were defined to describe the capacity of the bridge components. In total, 440 nonlinear time-history analyses were performed to evaluate the seismic demand of the helical piles and the bridge-reinforced concrete pier components, and the results were used to establish their fragility curves. The results revealed that the helical piles were the most fragile component in the nonliquefiable and liquefiable tests. The liquefiable soil could decrease the seismic demand on the column lateral deformation and increase the demand dispersion. On the other hand, the reinforced concrete pier exhibited a large drift response in the nonliquefiable soil, causing it to be more vulnerable to seismic hazards than in the case of liquefiable soil.

On July 7, 2020, the Taiyangbu Bridge crossing the Changjiang River was hit by a barge loaded with sand, resulting in the collapse of the main span. Such side collisions are seldomly investigated in previous studies. To this end, high-fidelity physics-based finite-element (FE) models are developed in this study to reproduce the barge side collision accident of the Taiyangbu Bridge and scrutinize the causes of its collapse. The collapse process of the Taiyangbu Bridge obtained from the high-resolution FE simulations is consistent with that observed from the video data. The FE results indicate that the collapse of the Taiyangbu Bridge is attributed to the flexural failure of the pile foundation in the longitudinal bridge direction, which agrees with the field investigation. In addition, side collisions are demonstrated to be the most unfavorable scenario in comparison with head-on collisions and oblique collisions. Based on the vessel–bridge interaction analysis, a simplified model with two degrees of freedom (2-DOF) is proposed to efficiently predict the vessel-side-collision-induced responses. Compared with the force-based design method used in current design codes and the energy-based method, which may result in an unsafe and inadequate design, the proposed 2-DOF method is more suitable for the side collision analysis.

In this study, a novel acceleration-based vehicle identification method is employed within a hybrid bridge weigh-in-motion (BWIM) system in which the traditional strain-based BWIM system is augmented with an array of accelerometers. The implementation of such a system is discussed through a full-scale case study arterial highway bridge in the province of New Brunswick, Canada. The accuracy of the proposed vehicle identification method was studied in detail using an extensive set of field study data. To achieve this, a systematic evaluation of existing methods for velocity estimation and axle identification was conducted, evaluating the effects of vehicle direction, lane position, vehicle velocity, and vehicle configuration. The methods were compared based on the sensor signal characteristics, the velocity estimation techniques, axles detection methods, and the effects on gross vehicle weight (GVW) calculation. From this study, it was found that the proposed hybrid system resulted in more accurate velocity estimation, axle identification, and ultimately better GVW estimation.

Stay cables are vital load-bearing components of cable-stayed bridges that are prone to corrosion and fatigue. Damaged or deteriorated cables can endanger the safety of bridges. In this paper, a performance alarming method for stay cables based on a frequency–deformation relationship (FDR) model is proposed. First, the FDR model, which represents a normal relationship between the frequency and the deformation of a certain intact cable, was established according to the stress–strain relationship of the cable. Second, the performance alarming for a stay cable was realized by constructing a mean value control chart for the estimation error of the baseline FDR model, followed by an implementation procedure for the early warning method. Last, the long-term monitoring data of a large-span bridge are utilized to validate the effectiveness of the performance alarming method. The results demonstrate that the modeling and prediction capabilities of the proposed FDR model are satisfactory and that the performance alarming for stay cables can be carried out effectively by the proposed method.

Drive-by health monitoring (DBHM) is an indirect structural health monitoring (SHM) strategy developed to reduce costs associated with traditional SHM systems on a variety of bridge structures. Experimental studies have successfully demonstrated DBHM’s bridge system identification capabilities; however, there exists a noticeable lack of full-scale experiments validating the methodology’s feasibility on highway bridges shorter than 18.28 m. Furthermore, few studies have used existing operational modal analysis (OMA) techniques, as the DBHM methodology violates fundamental OMA assumptions. This study addresses these research gaps by experimentally investigating the feasibility of employing OMA techniques in DBHM to identify the modal properties of a 9.14 m bridge span. Multiple OMA techniques were employed to identify their strengths and weaknesses under the DBHM framework. Results demonstrated that histograms constructed of frequencies identified across multiple tests were necessary to consistently identify bridge frequencies and that a tradeoff exists between vehicle mass and the speed at which bridge frequencies can be identified; this tradeoff also has an effect on the vehicle-on-bridge occupation time and the resolution of bridge frequencies. No single OMA technique was found to yield the best system identification capabilities in all test conditions; rather a combination of techniques is recommended, where the continuous identification of frequencies across multiple methods provides a means of reliably distinguishing between real and spurious frequencies and helps with accurately labeling vehicle and bridge frequencies.

This study revisits the modeling of buffeting forces on bridge decks and establishes the relationship between one- and two-wavenumber admittances, and between the spanwise coherence functions of turbulence and buffeting forces. The two-wavenumber admittance of the lift of a thin, flat plate section caused by vertical turbulence is then used to investigate the three-dimensionality effect of turbulence on integrated buffeting lift of a finite length. To investigate the characteristics of two-wavenumber admittance of bridge deck sections, synchronous pressure distributions of a streamlined bridge deck are measured and characterized in a wind tunnel at three different turbulent flows and several angles of attack. The means and standard deviations of surface pressure coefficients and integrated drag, lift and moment coefficients, the power spectra, spanwise correlation, and coherence of turbulence and buffeting forces are analyzed, from which the two-wavenumber admittances of drag, lift, and moments are determined. The effects of integral length scale and intensity of turbulence and angle of attack on static force coefficients and admittances are characterized. Finally, the three-dimensionality effect of turbulence on integrated buffeting forces and responses of long span bridges are investigated using the measured two-wavenumber admittances. The results of this study highlight the importance of appropriate simulation of large-scale turbulence in wind tunnel for characterizing static force coefficients and admittances of bridge deck sections, and for estimation of buffeting responses of long-span bridges.

This study explores the use of refined analysis methods to potentially increase load ratings of concrete T-beam bridges by obtaining a decrease in live-load distribution factors. The studied T-beam bridges are vulnerable to posting under consideration of the new federal regulations and when using conventional, simplified equations for load distribution factors. Finite-element models for a total of 25 in-service bridges were developed and analyzed under different vehicle loadings, including special hauling vehicles (SHVs). The effect of transverse positioning of the vehicle load on the computation of the distribution factors was also considered. The moment and shear effects in each girder were extracted and the distribution factors for the interior and exterior girders of the selected bridges were computed. These distribution factors were compared with those obtained from the AASHTO code-specified equations. The results were used to develop regression models to predict the percent change in distribution factors if a refined analysis is implemented. Furthermore, a support vector machine (SVM) is used to identify the governing truck type based on geometrical properties of bridges. Results indicate that moment distribution factors obtained from refined analysis will likely improve rating factors for SHVs, while the shear distribution factors will likely be larger.

Stochastic traffic flow, as a type of repeated load, can cause serious high-cycle fatigue damage to bridges. In addition, the rough simulation of stochastic traffic flow and inappropriate analysis method of fatigue stresses cause the fatigue evaluation results to deviate from reality. To overcome this challenge, a probabilistic fatigue valuation method is proposed based on an elaborate simulation of the stochastic traffic flow and field-measured strain influence line. By selecting vehicle load features affecting the bridge structural fatigue as clustering parameters, the two-step clustering (TSC) method is applied to distinguish the different traffic states with the clustering numbers to be determined objectively. On this basis, the elaborate stochastic traffic flow is simulated by random sampling of vehicle feature probabilistic models for each traffic state. Subsequently, the bridge strain influence line, which is identified through synchronous monitoring of strain and vehicle positions, is loaded by the simulated traffic loads to obtain the stress history instead of the traditional finite-element model (FEM). Finally, the structural fatigue life can be probabilistically predicted through a Monte Carlo simulation. The proposed method was verified to be effective through a case study of a long-span suspension bridge. It can be concluded that distinguishing the different traffic states can improve the rationality of stochastic vehicle load simulation, and a more reasonable prediction of the vehicle-induced bridge fatigue damage can be obtained through the influence line loaded by stochastic vehicle loads.

With the development trend of accelerated bridge construction, the precast ultra-high-performance concrete (UHPC) segmental bridge might be increasingly used due to the advantages of lightweight superstructure and advanced structural performance. However, there is still lack of study on the UHPC keyed epoxy joint, especially in terms of theoretical aspects. In this study, a theoretical model was developed to predict the shear capacity of UHPC large-keyed epoxy joints. In the proposed model, the shear capacity of joint was determined as the superposition of the shear contributions of the flat part and the keyed part. For the flat part, the shear strength mainly depends on the bond shear performance at the joint interface, which could be determined though test results of flat epoxy joints. To obtain the shear strength of the keyed part, the failure envelopes for UHPC were determined based on Mohr–Coulomb shear failure criterion, and the theory of Mohr’s circle was adopted. Then, the direct shear test was performed on 15 UHPC large-keyed epoxy joint specimens and four flat epoxy joint specimens to obtain their failure modes and shear resistance for verification. In addition to the test data in this study, test results of related existing studies were also utilized to validate the proposed theoretical model. Furthermore, the AASHTO equation and the existing formulas for epoxy joint were also used for comparison. Results indicated that the proposed model performed well in both the accuracy and the variation degree.

Practical Applications

With the development trend of accelerated bridge construction (ABC), the precast ultra-high-performance concrete (UHPC) segmental bridge might be increasingly used due to the advantages of lightweight superstructure and advanced structural performance. The shear performance of joint between precast segments is of great importance since fibers and reinforcements are discontinuous at the joint. This paper presents a theoretical model for predicting the shear capacity of UHPC large-keyed epoxy joints in precast UHPC segmental bridges. In this model, the shear capacity of UHPC large-keyed epoxy joints is assumed to be contributed by the flat part and the keyed part, and the shear strength of the keyed part is determined based on Mohr–Coulomb shear failure criterion and the theory of Mohr’s circle. This theoretical model has been validated by the test data of UHPC keyed epoxy joint specimens obtained from this study and other existing studies, indicating that it performs well in both accuracy and variation degree. It should be noted that this model is limited to the UHPC large-keyed or single-keyed epoxy joint while it is not applicable to the multikeyed joint. This study will contribute to establish the equation for determining the shear capacity of UHPC precast segmental bridges in the design.

The stringer connections of a historical “Model 1936” Swiss military bridge are investigated through a full-scale field-testing program, with the aim of clarifying modeling uncertainties and enabling a standard fatigue analysis for practicing engineers. Due to global bending, axial tension forces arise in the bridge’s stringers, which were not considered in original dimensioning. In contrast to historical steel bridges with typical riveted connections, Fritz Stüssi designed the “Model 1936” military bridge with custom bolts and nuts. Unlike rivets, these custom bolts and nuts can accommodate prestressing and enhance connection stiffness and thereby encourage potential fatigue problems. Field tests with strain measurements along the stringer beams themselves were used to determine bending moment profiles and connection stiffness parameters, and to calibrate a static model of the bridge. Following the nominal stress method with a standard load model, a basic finite-element analysis indicates that the stress range in the bridge’s stringer connections lies within the prescribed fatigue limits from standards. The implementation of a five-year periodic inspection plan further ensures the bridge’s safe use and long-term integrity.