Journal of Bridge Engineering

Galloping vibrations have been identified as potentially problematic for dry stay cables. Three key issues play a major role in the assessment of the structural damping required to prevent galloping of dry stay cables using a quasi-steady approach: the complex inclined-flow aerodynamics, deviation of the geometry of the high-density polyethylene (HDPE) stay cover with respect to that of a perfectly circular cylinder, and choice of a proper stability criterion. In this paper, the mean aerodynamic force coefficients of a real HDPE plain cable cover measured in a wind tunnel are presented. These were obtained by varying wind speed, yaw angle, and angle of attack, and they represent a complete set of aerodynamic data. Cable irregularities (surface roughness, section distortion, and axis curvature) were quantified and correlated to the measured aerodynamics. The experimental aerodynamic coefficients were used to predict instability using different quasi-steady models from the literature on a reference case. Finally, the different exciting and dissipating mechanisms deriving from the application of one- and two-degree-of-freedom (DOF) stability models, together with the corresponding different response predictions, are discussed in detail. It is shown that cable irregularities and detuning direction exert strong influences on aerodynamic stability and that instability is mainly due to critical Reynolds number effects. Moreover, a comparison of the results shows that the use of multi-DOF models is not justified in this case because one-DOF models prove sufficiently accurate to predict the amount of structural damping required to prevent galloping instability.

Since its completion in 1976, Osstrupen Bridge in Norway has sagged about 250 mm beyond its original precamber at the midspan hinge. Since the general state of the bridge is good, a solution was sought for raising the girder back to its target configuration while also strengthening it. It was determined to add an internal arch composed of two parallel tubes, hidden in the box and continuous at the center. The tubes are jacked at both ends and the uplifting forces are transferred to the girder through interconnections composed of trusses, which also prevent the tubes from buckling. Two alternative materials were considered for the tubes: high-strength steel and carbon fiber reinforced polymer (CFRP). The paper presents the mechanical response of the two types of coupled systems during jacking operations, under service loads, and when subjected to temperature variations. CFRP has the advantages of a low weight and a low coefficient of thermal expansion, giving a somewhat higher uplift and stress relief to the girder, as well as lower deflection due to ambient temperature variations. Both choices of material were shown to work well and to possess sufficient buckling resistance. For the bridge, a nearly full recovery of the sag at the hinge can be expected, with the extra weight of a new wearing course being accounted for. After rehabilitation, the bridge will carry heavier vehicles than it was originally designed for.

In cable-stayed bridges, cable anchorages are subject to significant forces in the structure and carry a heavy stress concentration. The structural features and cable-force transfer pathway of four typical cable-girder anchorages in cable-stayed bridges with steel girders were introduced. Finite-element analysis (FEA) and a full-scale specimen test were performed to investigate the mechanical behavior of tensile-plate anchorages. Stress distribution and stress concentration of tensile-plate anchorages were obtained by combining the results of the FEA and experiments. The effect of design parameters on the mechanical behavior of tensile-plate anchorages was also investigated by the FEA. Test results confirmed that the anchorage is designed reasonably and reliably with a large safety margin. According to the parametric studies, fillet radius significantly affects the stress field of the local fillet zone. Also, the welding tensile plate with extended web shows the best work performance for tensile-plate anchorages.

The strut-and-tie model (STM) has been adopted as a preferred methodology for the design of disturbed regions of structural concrete; however, the service behavior of structural concrete, especially with regard to cracking, cannot be predicted well by a STM, which is based on the lower-bound theorem of plasticity. To address this issue, this paper presents the development of an advanced elastic-to-plastic STM (EPSTM) to capture the full elastic and inelastic responses of a deep beam. The principle of stationary complementary energy was introduced into the STM to satisfy the compatibility and generate the adaptive EPSTM at each load step. The proposed EPSTM provides a consistent analysis of the behavior of a deep beam, including the average strain of struts and ties, load-deformation response, and the maximum crack width. Through comparisons of model outputs with test results, the proposed model was verified to be sufficiently accurate.

This article presents the observed cyclic responses of three types of metal hysteretic, axial dissipative devices (typically used with dissipative controlled rocking bridge piers) under varying degrees of corrosion. Dissipative controlled rocking bridge piers employ a combination of unbonded posttensioning tendons and external replaceable dissipaters. Unbonded posttensioning provides the ability to self-center, and dissipaters absorb seismic energy. The quality and properties of dissipaters decrease over time as a result of corrosion, which needs to be considered for capacity evaluations. The effects of chloride-induced corrosion on the hysteretic and cyclic response of these dissipaters were studied experimentally. To save time, the dissipaters, having equal length and cross-sectional area in the reduced area, were corroded using an accelerated corrosion technique called the impressed current method at a corrosion rate of 800 $\mathrm{\mu }\mathrm{A}/{\mathrm{c}\mathrm{m}}^2$. Cyclic (tensile-compression) tests for 36 dissipaters in total were conducted under three levels of corrosion and two different deformation rates. This investigation has resulted in clear quantification of the relationship between the degree of corrosion and both cyclic and hysteretic properties of the dissipaters studied.

Adjacent box-girder bridges are a popular choice for short- to intermediate-span bridges in several states because they are easy, quick to build, and cost-effective. Although longitudinal shear keys filled with grout between the girders and transverse posttensioning (TPT) ties ensure a monolithic behavior for the bridge, the durability of longitudinal shear keys still concerns researchers and engineers. Ultrahigh-performance concrete (UHPC) has been adopted as a new grout material for connections between bridge components. However, there is not yet any guidance or specification on the design of UHPC shear key configuration for adjacent box-girder bridge connections. The aim of this study was to use experimental results and finite-element (FE) modeling of direct shear, flexural, and direct tension tests to optimize a UHPC shear key configuration. These models were calibrated and validated with laboratory experimental results previously published by the authors. The models, along with different shear key configurations, were used to investigate the load transfer through previously proposed connections. After comparing the simulated shear keys in terms of the maximum load capacity, the optimized shear key shape (Type OPT) was designed to obtain a desired balance between economy and strength effects. The results demonstrated the contribution of the shear key configuration to the joint strength, and suggest that Type OPT shear key significantly increased load transfer, resulting in an enhanced serviceability. Therefore, use of Type OPT shear keys in a bridge may reduce the number of transverse shear reinforcement bars required, which in turn would improve the constructability of the bridge and reduce material and construction costs.

This article addresses a time-domain method for the postflutter analysis of long-span suspension bridges. The energy input properties of indicial functions (IFs) were first analyzed, and based on the findings, the concept of multistage IFs was brought forward to describe the nonlinear aeroelastic properties of bridge decks. The application of the multistage IFs to the nonlinear postflutter analysis entails resolution of two basic issues: smooth switching between groups of IFs and the integration of the mean wind loads. To avoid nonphysical transient responses that result from the abrupt involvement of a group of IFs, a strategy was developed that shows that groups of IFs participate in the aeroelasticity simulation simultaneously and independently; however, in this strategy, only two appropriate groups of IFs were engaged in denoting the aeroelasticity. To avoid double counting of the mean wind loads and to reflect the nonlinear properties of the loads correctly, separation of the pseudosteady effects from the aerodynamic loads denoted by IFs is suggested. The numerical example presented in this paper indicates that multistage IFs can be applied successfully to describe amplitude-dependent nonlinear aeroelastic effects and to conduct a time-domain postflutter analysis.

Super long-span bridges offer great convenience, but, because of their high decks, they also suffer from traffic safety problems related to strong winds. In this paper, large eddy simulation and dynamic mesh techniques for computational fluid dynamics are used to explore the aerodynamic forces acting on vehicles travelling on bridges and the mechanism of the aerodynamic interference between two vehicles during the processes of overtaking (from the same direction) and approaching (from opposite directions). The results indicate that during overtaking or approaching, the lateral aerodynamic interference between moving vehicles in a crosswind exhibits several characteristics that are fundamentally different from those of the interference between static vehicles. In the area behind a moving vehicle, a pressure cavity (a low-pressure zone) exerts a suction effect on the crosswind, which causes the crosswind in this region to change direction. This suction effect will markedly influence the aerodynamic force on another vehicle travelling in an adjacent lane in a crosswind, even when the latter vehicle is not directly sheltered by the former. The ratio of the velocities of the overtaking and overtaken vehicles exerts a significant influence on the aerodynamic forces that act on vehicles in a crosswind, and the transverse interval exerts a significant influence on the aerodynamic forces on both the windward and leeward vehicles. These lateral aerodynamic interferences cause vibrations of the vehicle and oscillations of the vehicle’s contact forces with the bridge deck or road, which threaten its driving safety and comfort in a crosswind.

During the 2011 Great East Japan earthquake, the rollover of a truck crossing the Yokohama Bay cable-stayed bridge was reported. A similar incident was also reported at the viaduct of the Hanshin-Expressway during the 1995 Hanshin (or Kobe) earthquake. Rollover of a vehicle can cause damage to the bridge, injury to the driver, and damage to other vehicles. Moreover, the incident can create hours of blockage of the major traffic line and impede postdisaster relief efforts. Currently, there are very limited studies on the effect of the seismic response on the stability of moving vehicles. This paper presents a general analytical framework for the analysis of the lateral stability of a vehicle crossing a bridge during an earthquake. An equation of motion for a two-axle vehicle under seismic excitation from a bridge girder was developed considering in-plane and out-of-plane vehicle motions and a driver reaction model. Numerical simulations were conducted using three-dimensional finite elements of the Yokohama Bay cable-stayed bridge using ground accelerations recorded during the 2011 Great East Japan earthquake as the inputs. Results of the simulation showed that the significant bridge-deck vibration due to an earthquake reduces the effective normal force on vehicle wheels. To evaluate vehicle stability, two conditions were studied: rollover and lateral-slip stability. Rollover stability defines the critical condition that might lead to a rollover and that is related to zero normal force on the wheels. The lateral-slip stability relates to the lateral force equilibrium between the earthquake-induced lateral force and the slip resistance provided by wheel friction. Case studies and discussions involving different driving responses, such as deceleration, and the driver’s reaction model were provided for both stability conditions.

An increasing number of structures, and in particular pedestrian bridges, experience excessive vibration levels when they are dynamically excited by humans in motion. Although several models have been presented to incorporate the influence of a single pedestrian traversing a flexible structure, there is no commonly accepted method to include the presence of dynamic interactions that results in complex time-varying and coupled dynamics. This paper presents a new coupled model shown to be effective in modeling the coupled dynamics associated with pedestrian–bridge interaction (PBI). Through a series of experiments involving three human subjects walking under different conditions, the model was validated in accordance to its capability to reproduce and replicate the complex vibration patterns observed on a full-scale bridge with a single pedestrian. The results demonstrate that the PBI model provides an effective and reliable approach to simulate human–structure interaction.

Cold reinforcement techniques refer to reinforcement methods that produce no or only low tensile residual stresses in structural details, avoiding new fatigue vulnerable details. To ensure the fatigue safety and extend the fatigue life of steel bridges, cold reinforcement techniques are proposed to stop the fatigue cracking of the critical details of orthotropic steel decks (OSDs) and web gap zones. Cold reinforcement techniques were evaluated by fatigue testing in the laboratory, in situ steel bridge case studies, and numerical fracture mechanics analysis using the extended FEM. Compared with drilling stop-holes, cold bonding of steel plates or bonding and bolting of steel angles have shown to effectively decrease local stresses, increase local rigidity, and extend fatigue lives. For in situ case studies on both a railway and a highway bridge, measured fatigue stress range spectra indicated that the bonding and bolting steel plate methods significantly enhance local rigidity and decrease local stresses. Numerical fracture mechanics results reveal fatigue stresses at the crack tip below the threshold of crack propagation.

The performance of bridges prone to tsunami hazards is critical to the resilience of coastal communities. An important component of resilience is the development of design guidelines, which requires simulating the hydrodynamic loads imparted on bridges by tsunami waves. To support such simulation efforts, data collected from wave flume experiments were used to validate the particle finite-element method (PFEM) implementation in OpenSees, which has been widely used for earthquake engineering simulation of bridges. The numerical results agree well with the experimental data, showing the potential use of OpenSees for determining hydrodynamic loads on engineered structures. Given the wide-ranging earthquake engineering simulation capabilities of OpenSees, these validations form a basis for simulating bridge responses to multihazard earthquake and tsunami scenarios.