Journal of Bridge Engineering

This paper introduces a new strategy for the accelerated fabrication and erection of steel bridges: a modular joint. The modular joint is a prefabricated, nodal connector composed of a weldment/built-up section of webs and flanges that includes a starter segment for each connecting member. It joins standard rolled wide flange sections through bolted splice connections in double shear. Flanges and webs are connected independently, forming a moment-resisting connection. This provides flexural stiffness for truss-like or beam-like behavior and provides the potential for the structure to tolerate member loss. The flange splice plates connecting the joint and any member can be bent to varying angles to achieve a variable depth geometry. This is a “kit-of-parts” approach, where members are standard sections and the prefabricated modular joint can be repeated throughout a single structure and also used for many structures. Although this approach retains all the advantages of modular construction (e.g., prefabrication, mass production, rapid erection, and reusability), it overcomes the prime deficiency of the existing technologies that a fixed panel size limits the span length. This paper investigates this approach through (1) developing a methodology to achieve rational constant- and variable-depth bridge forms, (2) performing structural optimization for minimum self-weight while meeting structural performance demands and transportability criteria, and (3) demonstrating the promise of this approach through detailed finite element numerical analyses.

This paper presented a new retrofit system for strengthening the stringer-to-floor-beam double-angle connections in a 92-year-old riveted railway bridge in Switzerland, using prestressed carbon fiber-reinforced polymer (CFRP) rods. The strengthening system transmitted the forces purely through friction, with minimum interference with bridge traffic. The system consisted of two components: a newly developed mechanical wedge-barrel anchor to hold the prestressed CFRP rod and a clamping system attaching the stringer flange. The strengthening system reduced the out-of-plane deformation of the connections, resulting in a reduction in the distortion-induced stresses in the connections. The short-term bridge measurements showed that the application of a total prestressing force of 100 kN reduced the dominant mean stress in the connection hotspot by 47% (from 22.9 to 10.9 MPa) under the passage of passenger trains, whereas the stress range remained unchanged. Using the modified Wöhler curve method (MWCM) as a critical plane-based multiaxial fatigue model, the strengthening system was observed to reduce the multiaxial mean stress parameter by 30% under the passenger train loads. The long-term monitoring of the strengthening system, using a wireless sensor network (WSN) system, indicated no prestress loss in the CFRP rods during the seven-month period since its installation.

Externally prestressed steel–concrete composite (EPSCC) beams in their deformed configuration are characterized by changes in the effective depth of external tendons. However, little information is available on this second-order effect and parameters that are closely related to it, such as the deviator spacing and load type, have never been analyzed. This study will describe an in-depth investigation of the second-order effect in EPSCC beams. By applying an experimentally validated model, numerical simulations will be performed to assess the effect of the ratio of deviator spacing to span length (S_d/L) and load type on the behavior of EPSCC beams. The results show that the second-order effect was negligible for S_d/L <0.25. The ultimate load decreases linearly with an increasing S_d/L from 0.25 to 1. An increase in S_d/L resulted in a decrease in ultimate tendon stress increment. Compared with two-point or uniform loading, one-point loading at midspan led to substantially lower ultimate tendon stress and deflection, and therefore, a lower second-order effect. An equation that considers the second-order effect will be proposed to estimate the ultimate tendon stress in EPSCC beams. The proposed equation showed a good correlation with the numerical simulations.

Coastal reinforced concrete (RC) bridges have the potential to be subjected to tsunami hazards within their service life. On the other hand, the time-dependent chloride-induced corrosion will degrade the performance of the bridges. Few efforts have been made to investigate the life-cycle performance of deteriorating RC bridges subjected to tsunami hazards. In this paper, the time-dependent collapse fragility analysis is conducted to investigate the life-cycle performance of deteriorating RC bridges subjected to tsunami hazards. With corrosion modeling, the time-dependent deterioration of material properties as well as shear capacity deterioration of the columns are considered. Uncertainties from materials are accounted for in developing numerical bridge models. Nonlinear tsunami pushover analysis is used to investigate the bridge damage under tsunami loading. Tsunami collapse failure curves are constructed assuming a lognormal distribution, and the time-dependent tsunami collapse fragility curves can be efficiently calculated with the quadratic model for the median and standard deviation of tsunami intensity, that is, flow velocity. Time-dependent collapse fragility analysis is conducted for a three-span, two-column bent RC bridge. Results indicate that the bridge columns can fail in shear for low inundation depth flow and high corrosion levels. Collapse failure probability of the bridge increases with the flow depth and a clear jump of collapse failure probability for inundation depth from below to above the deck can be observed. The collapse failure probability also increases over time due to corrosion effects.

This paper investigated a novel hybrid precast pier system that utilized ultrahigh-performance concrete (UHPC). The pier combines features of emulative and nonemulative (of cast-in-place construction) systems to balance self-centering and energy dissipation under seismic loading and uses UHPC to maintain that balance with low damage. An analytical model was used to study piers with varying UHPC mixes, properties of which were determined through material testing. Two large-scale pier specimens with UHPC and with varying confinement reinforcement grades were tested under quasi-static cyclic lateral loading. The test results demonstrated that the selected UHPC mix enabled the balance between bending and rocking. The rocking-induced cracking was not prevented by UHPC but was alleviated with a steel case. When the rocking-induced damage was prevented, more than 40% of the total displacement was caused by rocking at smaller drift ratios (<0.5%), enabling self-centering. At larger drift ratios (>4.5%), approximately 80% of the displacement was from bending, enabling energy dissipation. Replacing normal-strength steel with high-strength steel confinement did not improve the flexural capacity or ductility of UHPC.

The dynamic properties of bridges can be affected not only through damage but also from ambient uncertainty. False-positive or negative alarms may be raised if environmental effects are not considered in the detection algorithm. This article presents a two-step data-driven approach that can incorporate temperature effects in vibration-based damage detection and localization, provided the temperature is also measured. To detect the occurrence of damage, prediction errors of an autoassociative neural network (AANN) framework are first employed as a temperature-invariant novelty index (NI). Further, for damage localization, NIs associated with each of the damage cases, are classified using a radial basis function neural network (RBFNN). The proposed algorithm is numerically tested on a multispan bridge structure involving measurement uncertainties. The performance of the RBFNN classifier is further assessed using different classifier performance metrics. The possibility of positive and negative false alarms raised by the proposed algorithm and its sensitivity to measurement noise contamination is also investigated. It is observed that the proposed data-based approach can efficiently isolate a fault, even in the presence of temperature variation.

Shape and size design of twin-box decks involves managing a number of highly sensitive deck features, including aerodynamic, stiffness, and mass properties, which leads to important and complex changes in the aeroelastic and structural performance of the bridge. This design problem is addressed in this study by recasting it as an aero-structural optimization problem. A generic short gap twin-box bridge is optimized considering 164 shape and size design variables and 2,753 design constraints. The proposed methodology obtains sustainable and economical optimum designs by minimizing the required amount of material to build the bridge, while meeting the performance and safety requirements in the structural and flutter design constraints. Furthermore, parametric studies provide very valuable information to better understand the role of different design variables on flutter. It has been found that the gap size plays an important role in managing the flutter requirements in the design process.

The performance of large diameter corrugated steel culverts/pipes under varying cover depth up to deep burial has previously not been investigated in a laboratory setting due to limitations associated with the application of overburden pressures. Using the new deep burial simulator at Queen’s University, it is now possible to test flexible pipes up to 3 m in diameter up to a simulated burial depth of approximately 17 m. In this study, a 2-m diameter corrugated steel pipe (CSP) culvert was instrumented with displacement transducers, strain gauges, and distributed fiber optic strain sensors and was tested under increasing overburden pressure up to a total of 358 kPa (equivalent to a depth of 17.9 m of soil with a unit weight of 20 kN/m³). The diameter change values along the length of the culvert were within 10% of each other, suggesting that the simulator produces approximately uniform loading. The Canadian bridge design code produced thrust estimates within 10% of the measured response but did not predict the development of localized plastic hinges seen in the experiment.

This study numerically investigated the shear behavior of novel composite shear connectors, which consisted of grouped head studs embedded in high-strength concrete-filled (HSC-filled) shear pockets. The shear pockets were prefabricated and retained open in the precast concrete slab. The finite-element (FE) models were established and verified with the full-scale test results. The validated FE models were further used for parametric studies. In this study, the shear strength of grouped head stud shear connectors almost linearly increased with the stud diameter and infilling concrete strength. However, the stud height had little effect on the shear strength. Increasing the stud spacing and slab thickness could not enhance the shear capacity of composite shear connectors. In addition, the precast method of the shear pocket also had no reduction in the shear strength. Finally, the parametric analysis results were compared with the current design codes. It was observed that those specifications almost had conservative predictions on the shear strength of grouped head studs because the interaction between the concrete crushing and head stud fracture was not considered. A more accurate analytical equation was proposed to predict the head stud shear capacity. The average values of predicted/tested results for all specimens were varied from 0.949 to 1.022, which indicated that the equation could accurately evaluate the shear strength of grouped head studs in high-strength concrete.

Precast concrete columns have been widely used in bridge constructions. Most studies regarding precast columns focused on seismic instead of static behaviors. To investigate the cracking mechanism and failure modes of the columns with column-to-footing connections using grouted splice sleeves, four full-scale sliced specimens, two precast columns with different axial loads, and two monolithic columns with different cover thicknesses were designed and constructed based on their prototypes. These specimens were subjected to monotonic loading for failure. Experimental results showed significant differences between the precast and monolithic columns. The first crack of the precast column appeared in the joint section. The cracking load of the precast column was 10% less than that of the monolithic column. Nevertheless, the tensile strains of longitudinal bars in the precast column were approximately three times as large as that in the monolithic column. Strain and deformation concentrations occurred near the joint section. When the peak load was attained, the joint section became the failure section, and the lateral load was primarily balanced by the shear stresses in uncracked concrete. Based on the cracking mechanism and failure mode obtained from experiments, practical methods were proposed to calculate the cracking moment and bearing capacity of the joint section in precast columns and the difference between the calculated and measured results was less than 2% and 7%, respectively.

Inspired by the structural system and the construction technique of self-anchored suspension bridges and earth-anchored suspension bridges, a new type of suspension bridge, named hybrid anchored suspension bridge, was investigated in this paper. Additional anchorages, connected with the main girder by anchor cables, could provide a feasible solution for optimizing structural efficiency and constructability. To comprehend the static behavior of this innovative structural system, both the static equilibrium differential equations and compatibility equations were established on the basis of deflection theory. Meanwhile, a simple approximate solution method and a general procedure used for the preliminary static analysis were expounded. Finally, the results of a numerical example were used to verify the accuracy of the proposed method by comparing it with the nonlinear finite-element method. Collectively, it has been shown that the hybrid anchored suspension bridge, as a hybrid structural system of earth-anchored and self-anchored suspension bridge, can be regarded as an improvement to the industry of modern suspension bridge.

Stress monitoring is always a challenging task in bridge structural health monitoring (SHM) since the measured pointwise stress is not enough for fully reflecting structural conditions. Therefore, a novel hybrid modeling technique was proposed in this paper, which calculates stress distribution with the aid of finite-element (FE) submodels from limited measured data. However, unlike common FE analyses, the requirement of complete input information is avoided by an FE model-based partial least-squares regression (FEM-PLSR) method. First, the regression equations among the FE model, unknown structural input, and output were set up, into which measured displacements, rotations, and strains were fused simultaneously. By solving the regression equations, the boundary conditions of the FE submodel can be precisely estimated. Then, the stress distribution can be calculated through FE analyses under the assumption of known local vehicular loads. Numerical simulations of a continuous steel box girder bridge were carried out for verification. Corresponding results indicated that the accuracy of the calculated stress distributions was competitive to the widely used multiscale FE model, even if the structural input information outside the submodel was not directly measured. Furthermore, the proposed method was also proved insensitive to random measurement errors. Finally, a large-scale experiment was designed to validate the accuracy of the hybrid model under three loading conditions. The strain distribution over both space and time accorded well with the measurement. Thus, the present hybrid modeling offered a novel way to obtain unmeasured structural responses, revealing great potential in the field of bridge SHM.

With increases in the span length, the vortex-induced vibration (VIV) in bridges often occurs at modest wind velocities. The tuned mass damper (TMD) is very effective in mitigating the VIV, while robustness is a major concern for the TMD control with a small mass ratio. To improve the robustness, a magnetorheological TMD (MRTMD) instead of the TMD is used to mitigate the VIV with slowly time-varying frequency. A control strategy considering VIV characteristics is proposed for realizing the real-time tuning and mass stroke limitation simultaneously, including the control force design, control command determination, and frequency estimation. Numerical simulations of a long-span continuous bridge subjected to the VIV are presented to validate the feasibility of the control strategy and the superiority of the MRTMD control. Numerical results show that the MRTMD control is more robust against the resonant frequency change than the TMD control, and the maximum mass stroke is less than a preset stroke in both tuned and mistuned cases.

The evolution rule of temperature-induced deflection in main girders is an important index to evaluate the service performance of long-span cable-stayed bridges, which directly reflects the coupling effect between the vertical stiffness of the main girder and the tension of multiple cables. However, temperature-induced deflection is caused by the complex temperature field of the main girder, cable tower and cable, while monitoring data have documented a time-lag effect between the temperature and temperature-induced deflection. Hence, it is difficult to accurately describe and model the behavior of the temperature-induced deflection in a long-span cable-stayed bridge in service. To this end, by utilizing the advantage of long short-term memory (LSTM) network for time series prediction, a digital model in minute scale based on monitoring data and deep learning can be developed to predict temperature-induced deflection, and resolve the low precision caused by the single-point input and time-lag effect. Compared with traditional machine learning algorithm and linear regression, a deep learning LSTM network has the best performance. For the cable-stayed bridge in this paper, the mean absolute error of the LSTM model was even less than 0.5 mm, and with the combined hypothesis test, the early warning accuracy for the abnormal change of temperature-induced deflection could achieve a minimum of 0.3%.

Using low-retraction double-tensioned steel strands vertical prestress system (DTSSVPS) to replace finish rolled rebars (FRR) a vertical prestress system could effectively enhance the vertical prestress efficiency and reduce the occurrence of diagonal cracks on the webs of long-span prestressed concrete (PC) box-girder bridges. This study will conduct a T girder test, short rectangular slab test, double-tensioned anchor (DTA) performance test as well as field tests on two bridges with DTSSVPS to investigate the immediate prestress loss, shear cracking performance of the web, and minimum biting length (d) between the anchor nut and cup. The results showed that the immediate prestress loss using DTSSVPS reduced from 20% to 40% after one tension to approximately 10% after two tensions and the prestress efficiency was much higher than FRR. Therefore, it is recommended that the design retraction value of the DTA was 2 mm. The experimental shear cracking load of the web with DTSSVPS was 1.39−1.45 times the theoretically calculated load. Following unloading, the diagonal cracks on the web were closed and the web worked in the elastic stage. Finally, based on the single-hole DTA performance test, the minimum d between the anchor cup and nut was 10 mm. The design tension force (f) carried by the unit arch length of the thread between the anchor cup and anchor nut was 130 N/mm. A formula is proposed for the design of the minimum d of a multiple hole DTA. In addition, the stress distribution on the surface of the anchor nut was investigated. This study could provide a basis for a wide application of DTSSVPS technology in the future.

Previous seismic events have shown that bridges are more susceptible to severe damage when subjected to near-fault ground motions. Near-fault ground motions usually possess obvious pulse-like features in their velocity time histories. The velocity pulses are further distinguished by either a distinct acceleration pulse (acceleration-pulse) or a succession of high-frequency one-sided acceleration spikes (non-acceleration-pulse). The acceleration-pulse ground motions will probably cause more damage to structures compared with non-acceleration-pulse ground motions. This study will focus on assessing the effects of acceleration-pulse ground motions on the seismic response of a pile-supported bridge at a canyon site. A refined three-dimensional (3D) finite element (FE) model will be developed for the nonlinear time history response analysis of this ground–bridge system, in which enhanced modeling of free field boundary and soil–pile interactions will be considered. To investigate the seismic response of the ground–bridge system, six pairs of acceleration-pulse and non-acceleration-pulse ground motions will be used, and each pair has the same peak ground acceleration (PGA). The seismic response of this ground–bridge system will be subjected to acceleration-pulse and non-acceleration-pulse ground motions and will be fully evaluated considering two aspects. First, the seismic time history responses of the ground–bridge system will be assessed under a single representative acceleration-pulse and non-acceleration-pulse ground motions. Second, the mean of the maximum seismic response of the ground–bridge system under multiple acceleration-pulse and non-acceleration-pulse ground motions will be explored. The results from this study show that compared with the non-acceleration-pulse ground motions, the acceleration-pulse ground motions had a more significant impact on the seismic response of the ground–bridge system. Therefore, special care should be taken on the acceleration-pulse effect of ground motion, because bridge structures are more vulnerable to damage when subjected to acceleration-pulse ground motions.

The vortex-induced vibration (VIV) properties of a π-shaped bridge girder are addressed in this study through wind tunnel tests. Attention is paid to the influence of torsional-bending frequency ratio on the VIV, while the mass-damping property (Scruton number) of the vertical motion remains unchanged. The torsional-bending frequency ratios of the model covered in this study were 0.872, 0.971, 0.988, 1.035, 1.085, and 1.245. The results show that, when the ratio is close to 1.0, the girder exhibits coupled vibration in the vertical and torsional directions. However, the coupling significantly reduces the vortex-induced vertical amplitude, which had been supposed to remain unchanged, owing to a fixed Scruton number. Further, the results indicate that the torsional motion results not only in the transference of a small amount of energy from vertical to torsional vibration, but also in a substantial reduction of the total amount of mechanical energy trapped by the system from the wind field. The energy reduction effects should be understood as a result of the altered flow pattern around the section, which is caused by coupling of the model's degrees of freedom.

For steel bridge girders, several control sections usually exist. If one or more sections fail, then the bridge girder might fail. Therefore, the failure probability analysis of each control section is important for bridge girder safety assessment. To make a reasonable failure probability analysis for bridge girder sections that have structural health monitoring data, first, vine copula models that consider the nonlinear correlation of multiple monitored variables will be established based on the extreme stress data of bridge girder sections, which mean that the extreme stress data fusion will be achieved; second, the vine copula models that consider the nonlinear correlation of failure modes of the multiple monitored points from bridge girder sections that were constructed with the corresponding performance functions, further, by combining the built vine copula models with the first-order second-moment (FOSM) method, the failure probability of the bridge girder section that considers the nonlinear correlation of failure modes at the multiple monitored points will be analyzed; finally, the monitored data of an existing bridge will be provided to illustrate the proposed model and method. The results show that: (1) the C-vine structure-based failure probability of a bridge girder is smaller than the D-vine structure-based failure probability; (2) the obtained bridge girder section failure probability that considered the nonlinear correlation of the failure modes is smaller than when the correlation of the failure modes is not considered. It was illustrated that the obtained C-vine structure-based failure probability was the most reasonable.

A quantitative, rapid screening assessment methodology for masonry arch bridges, with minimal input parameters, is proposed. The developed mechanism-based analysis procedure is validated against a set of available experimental data. Performance levels are then prescribed for bridges falling into proposed subsets based on geometric proportions. A generalized amplification factor (κ) is introduced, which could account for an increase in demand due to a dynamic vehicle–bridge interaction as well as an increase in axle loads. Finally, fragility curves are generated, which gives the probability of collapse for a bridge subset against increasing demand parameter.