Journal of Bridge Engineering

In this paper, a numerical wave-loading model using the dynamic-mesh updating technique is combined with a nonlinear finite-element (FE) model to investigate the behavior of costal bridge superstructures under solitary waves. The numerical model has been tested by comparing it with laboratory experiments performed at Oregon State University. It is proven that the proposed model is reliable for predicting the bridge–wave interaction. Full-scale numerical experiments are then conducted to discuss the effect of vertical flexibility on connection forces. In this study, a typical value of horizontal restraint has been assigned to each bridge deck, and the vertical flexibility is introduced by allowing the bridge deck to rotate about the onshore side. The results show that a higher extent of deck rotation movement is accompanied with larger horizontal resultant forces. Also, the pattern of vertical resultant is significantly influenced, whereas the peak value does not change much. Moreover, the general characteristics of the relationship between the vertical resultant force and the overturning moment are discussed in detail for a vertically fixed deck, and they are represented by interaction diagrams. The direction of the overturning moment is distinguished. The significance of a negative overturning moment is revealed. At the end of the paper, an empirical model for predicting the interaction diagrams is proposed and tested.

Truck weight regulations maintain controls on the actual truck-load characteristics and can further affect the serviceability of constructed infrastructures. To investigate the truck weight regulations of small- to medium-span bridges, a reliability-based analysis method was first established. Second, the truck-load characteristics were investigated based on long-term weigh-in-motion (WIM) data, and the typical truck types were extracted. Third, the threshold values of the truck-load effect corresponding with different target reliability indices (TRIs) and coefficients of variance (COVs) were obtained based on the established analysis method. Finally, the weight limit of each truck type was derived by inverse calculation with a self-developed software program. The influences of TRI and COV on the weight limit are discussed according to the analysis results. Some recommendations are provided for the optimization of Chinese truck weight regulations and U.S. bridge formulas.

In this study, the influence length of wire damage and wire-to-wire interaction in helically wired strands were investigated both experimentally and numerically. Greased seven-wire steel strands (2 long and 11 short specimens) were tested, each with one outer wire damaged locally. Prior to fracture, the difference in strains between the damaged and intact wires was negligible at 1.2 m (2 ft) away from the damage location. Sudden fracture in the outer wire with 90% area reduction caused only slight or negligible dynamic effect. The influence length (IL, in feet) of the wire fracture can be empirically determined from the applied load (T > 0.5 kips) by $\mathrm{I}\mathrm{L}=1.62T-0.7$. Calibrated with test results, the interaction among greased wires can be simulated by isotropic Coulomb friction with a coefficient of friction of 0.005. In an intact strand, axial stress in the core wire was found to be approximately 1.5 times that in any outer wire. As a result of the nonaxisymmetric section at the location of fracture, axial stress increased significantly in the two outer wires in direct contact with the fractured wire and changed slightly in the remaining wires.

Because complex cable systems are widely used in engineering practice, the issues related to parameter identification of complex cable systems are becoming increasingly important. In this study, a universal characteristic frequency equation, considering boundary conditions, various lateral forces, and multiple factors pertaining to cables simultaneously, was established for a class of cable systems installed with intermediate lateral components. The optimization model corresponding to the equation was established to transform the root-finding problem of the complicated transcendental equation into a relatively simple parameter identification and optimization problem. Thereafter, a parameter identification scheme for complicated cable systems was proposed using the particle swarm optimization algorithm. Through experimental tests using a full-scale cable–damper system, a detailed multistep, multiparameter identification program was presented for complex cable systems. The experimental results, achieved effectively using the proposed method, indicate a significant reduction in parameter identification errors and improvement in identification quality.

The huge axial force in the main girder challenges the design of superspan cable-stayed bridges. To reduce the self-weight of the girder, the conventional orthotropic steel deck (OSD) system is widely adopted due to its high strength-to-weight ratio, which may generate fatigue problems. In this paper, the optimum combination of different bridge and deck systems was studied by designing a cable-stayed bridge with main span of 1,480 m. Two different bridge systems were investigated: the conventional cable-stayed bridge system and a partial ground-anchored cable-stayed bridge system with crossing stay cables (the new bridge system). Additionally, in each bridge system, three different deck systems were studied: the OSD system, a composite deck system composed of the OSD system and an ultrahigh-performance concrete (UHPC) layer, and an UHPC waffle deck panel system. Finite-element (FE) models of the six plans were developed and analyzed. The static, dynamic, and economic performances of the six plans were compared. Model tests of the composite and UHPC waffle panel systems were performed to ensure the feasibility of the design. Compared to the conventional bridge system, the new bridge system has a much smaller axial force in the main girder, greater longitudinal stiffness, and economic advantages. Under the traffic load, a much lower stress amplitude is developed in the girder with the UHPC waffle deck panel system than in girders with the other two deck systems. Compared to the OSD system, the composite and UHPC waffle panel systems are advantageous in terms of lifecycle cost. Therefore, the combination of the new bridge system and the UHPC waffle deck panel system is recommended as the optimal design plan.

This study numerically examined the seismic performance of a multiple-frame bridge retrofitted with external shape memory alloy (SMA) spirals actively confining the plastic hinges of the bridge piers when subjected to strong main shock–aftershock sequences. A numerical model of the bridge, including abutments and expansion joints, was developed and used in the study. The model accounts for the spread of plasticity along the piers and the constitutive behavior of SMA-confined concrete. A suite of main shock–aftershock records with various characteristics was used in a series of nonlinear dynamic analyses performed on the as-built and retrofitted bridge using different levels of SMA confinement. The seismic performance of the bridge was assessed by monitoring damage states at the local and global levels. The results show that active confinement provided by SMA spirals is quite effective in preventing concrete crushing under strong sequential seismic events and that strength degradation in concrete greatly reduces as the level of confinement increases. SMA confinement can also contribute to reducing fatigue damage in reinforcing bars and residual hinge openings at the bridge joints.

This paper proposes an analytical framework for vibration-based structural health monitoring (SHM) by introducing an energy-based damping evaluation (EBDE). The damage detection by the proposed EBDE was carried out by estimating the contribution of modal damping ratios from different structural elements utilizing experimentally identified modal damping ratios, and estimating modal strain and modal potential energies from an updated finite-element (FE) model of the structure under consideration. Model updating was performed using modal frequencies and mode shapes that are generally not sensitive to local damage. The advantage of using damping as a damage indicator is that the damping change in global modes affected by the local damage can be identified with a small number of sensors. A previous study reported that the studied bridge with damage at the local diagonal member showed a significant increase in the damping of global vibration mode of the structure. The present study utilized the EBDE to identify the cause of the modal damping increase by observing the change in the contribution from different structural elements on the modal damping ratios.

A unique research study was performed on a steel truss bridge over 80 years old that was being taken out of service. The primary objective of the study was to evaluate the accuracy of dead load estimation for an existing truss bridge. The approach taken was to monitor the deconstruction process and identify the locked-in dead load forces within the primary truss members. This novel experiment utilized vibrating-wire strain gauges and distributed data-acquisition equipment to measure the strain release within the examined truss members. Once these measurements were obtained, a comparative study was performed with an independently developed three-dimensional (3D) finite-element model. The comparison quantitatively illustrates the uncertainty of dead load distribution within in-service steel truss bridges. This uncertainty may indicate a wider distribution of dead load than was originally utilized in the derivation of the dead load factors per code standards. The study presented is only from one bridge; however, the findings illustrate a potential misconception about the accuracy of dead load estimates for older in-service truss bridges.

To accelerate bridge construction, U-bar details were proposed to connect the adjacent precast box girders and replace the original welded-loop details in longitudinal joint design. Static loading tests were conducted, and the failure mode, flexural strength, and cracking behavior of the specimens with welded-loop details and U-bar details were compared. The influence of the U-bar longitudinal spacing, the joint concrete strength, and U-bar lap length on joint performance was also considered. The test results show that although the specimen with U-bar details had the same strength as that of specimen with welded-loop details, it cracked earlier and faster, but it still met the code requirement on maximum crack width. Longitudinal spacing of U-bars has a significant influence on joint performance. Interface cracking occurred for all specimens, considering the actual construction sequence. The tested flexural capacities of specimens with U-bar details were compared with theoretical predictions based on two existing strut-and-tie (STM) models, and the accuracy of these two models was evaluated.

Gussasphalt concrete (GAC) is increasingly used in long-span steel bridge deck pavements because of its impermeability and compliance. However, the paving temperature of GAC is very high, inducing a significant nonuniform temperature distribution in the bridge during paving, and this has an adverse effect on the serviceability of bridge. In this study, the temperature behavior and stability of orthotropic steel bridge deck (OSBD) during the GAC paving were investigated. First, the temperature distribution of a steel bridge during the GAC paving was studied using field monitoring and numerical simulation. Second, the temperature stress and deformation of the OSBD during GAC paving were calculated. Third, the effect of the temperature deformation of OSBD on pavement unevenness was examined. Last, a submodel and eigenbuckling analysis method was used to evaluate the stability of the U ribs during the GAC paving. The results show that uplift and expanded deformation occur in the steel bridge deck during the GAC paving, and this deformation could cause a nonuniform thickness distribution of pavement. The temperature load during paving could reduce the ultimate bearing capacity of the U ribs in the paving area, and there is a hidden danger of instability in the OSBD during the GAC paving.

Frictional resistance between the main cable and saddle is essential for counterpoising huge unbalanced cable tension in different spans of multispan suspension bridges. Vertical and horizontal friction plates are employed to increase frictional resistance in suspension bridges. In this study, two mechanical models are presented to analyze the frictional resistance between the cable and saddle. Based on the models, analytical formulas of frictional resistance are derived when the saddle is equipped with vertical or horizontal friction plates. The presented analytical methods were validated by finite element models and large-scale model tests. The main components of frictional resistance were found to include friction between the cable and saddle and friction between the cable and friction plates. The effects of vertical and horizontal friction plates on frictional resistance were investigated. The results indicated that the presented mechanical models provide an effective and efficient tool for evaluating the contributions of vertical or horizontal friction plates to frictional resistance. Incorporating vertical or horizontal friction plates significantly increases frictional resistance.

The analytical behavior of concrete-encased concrete-filled steel tubular (CFST) piers under cyclic lateral loading is reported in this paper. A finite-element analysis (FEA) model is developed to investigate the cyclic behavior of such composite piers. Comparisons are made between measured and predicted results on failure modes and load versus displacement relationships. It is found that the proposed FEA model can reproduce the experimental results with reasonable accuracy. Full-range load-displacement relationships, contact stresses between the steel tube and concrete, contact stresses between the restricted region and the outer concrete, and comparisons on different members are analyzed using the verified FEA model. Parametric analysis is conducted to investigate the influence of various parameters on load-displacement (P-Δ) envelope curves. The parameters include the material strength, the steel ratio of inner CFST, the wall thickness to sectional width ratio, the longitudinal reinforcement ratio, and the axial load level. Finally, a simplified hysteretic model for the P-Δ relationship of a concrete-encased CFST pier is proposed.

Laminated elastomeric bridge bearings are commonly employed at bridges as expansion bearings to accommodate thermal displacements. In regions of low to moderate seismicity, these bearings can also be used as fusing components to effectively isolate the superstructure from the substructure during earthquakes. Stiffened angle retainers provide lateral restraint against transverse construction and service demands on a bridge but can also be used as fuses to establish a threshold of maximum inertial force transfer to the substructure. An experimental program has been carried out to evaluate the overall performance and key behavioral characteristics for assemblies of steel-reinforced, laminated elastomeric bridge bearings with stiffened angle retainers subjected to transverse bridge movement. The testing program demonstrated that the retainer-and-bearing assemblies possess significant force capacity, which should be calibrated to maximize the effectiveness of the fuse for protection of the substructure. The experimental configurations exhibited lateral force capacities as much as 100% of the applied vertical load. The structural response of the bearings depended strongly on the bearing type and the base width of the retainer in the direction of the load relative to bearing height. Bearings comprising only a reinforced elastomer block and a thick top plate achieved distinct pre- and postfusing response ranges if the retainer base width was sufficiently large, with a pinched, stiff hysteresis up to a maximum shear strain of 50–100%, followed by a sharp reduction in force capacity after retainer fusing. Elastomer-on-concrete sliding response diminished during initial cycles but stabilized at a consistent sliding friction coefficient. If the retainer base width was not sufficiently large, the behavior was complex, with concrete crushing at the retainer toe and interaction of the retainer heel with the elastomer block. Bearings with a polytetrafluoroethylene (PTFE) sliding layer were fabricated with bottom steel plates, which permitted a more reliable fusing mechanism without the complications of concrete interaction at the retainer toe.

A fundamental understanding of the flutter stabilization of streamlined box girders is of critical importance for ensuring the structural safety of superlong span bridges. This study systematically investigated the flutter characteristics of thin plate sections by performing theoretical analysis in conjunction with wind tunnel tests with the aim of evaluating the flutter mechanism of superlong-span bridges with streamlined box girders. From the results of a two-dimensional, two-degree-of-freedom (2D-2DOF) flutter analysis, it can be seen that with increases in f_torsion/f_heaving, the aerodynamic damping part D of the torsion motion becomes more important and the level of participation level of heaving motion gradually decreases. Thus, the relationship between the structural torsional–heaving frequency ratios (f_torsion/f_heaving) and the critical velocities of flutter can change with changes in the structural frequency ratio in different ways. Furthermore, the method of flutter energy analysis was used to investigate the components of energy input and energy dissipation, and the results show that the components associated with flutter derivatives A₁* and A₂* produce the maximum positive and negative energy inputs, respectively. The maximum energy dissipation has a strong correlation with the mechanical damping force. In addition, the measurements of flow field using particle image velocimetry (PIV) demonstrate that the scale of vortex streets becomes larger with increases in wind velocity, while the bobbing movements of the vortex streets could lead to the flutter instability of thin plates.

Closed-cell foam is used in small movement bridge expansion joints to create a watertight joint. It is popular for new joints and in the rehabilitation of joints because of its low cost, and ease and speed of installation. Some bridge owners, however, have steered away from using this seal because of failures after only a few years of service. The premature failure is potentially linked to compression set of the foam. Compression set is measured using a standard that requires the material to be held compressed for 22 h at 73°F, which is very different from what the foam will experience in-service. In this investigation tests were conducted to study the effect of compression duration, temperature, and recovery duration on the compression set of closed-cell foams. Tests were also conducted to study the effect of compression set on the tensile capacity of the sealed joint. Results show that compression set is dependent on all three of these factors. The values of compression set reported, when tested in accordance with the previously mentioned regulations, are not necessarily appropriate for bridge joint applications. Compression set should be measured by testing under conditions that are more reflective of the actual conditions the materials will experience in-service, when used in a bridge joint. In addition, the tensile capacity of foams that are appropriately bonded to the substrate are as good or better than that reported by manufacturers, even in the presence of compression set of the foam.

In this study, the correlation between the fatigue equivalent stress and the stress cycle was considered using the copula function in the fatigue reliability assessment. In most earlier studies, the variables for the fatigue reliability function were assumed to be independent. However, based on the structural health monitoring (SHM) data in this study, they show that there are correlation properties in part of the variables. Hence, using the traditional method, the calculated fatigue reliability index is not accurate. For this reason, a new calculation method that considers the correlation between the variables was developed. The Gaussian copula was used to solve this problem because of its powerful connect function and concise expression. The study shows that there is a correlation between the fatigue stress and the fatigue stress cycle in the Nan-Xi Yangtze River Bridge. The values of the fatigue reliability index that consider the correlation between the variables are smaller than those calculated by the traditional method.

Monitoring traffic loads is crucial for effective steel bridge maintenance because fatigue damage in steel bridges is caused by the long-term cumulative effect of traffic loads. This article presents a simplified portable bridge weigh-in-motion (spBWIM) system consisting of only accelerometers, which are easy to install because they can be magnetically attached to a painted metal surface without removal of paint. The spBWIM system uses a single accelerometer for all traffic lanes to determine bridge displacement responses attributable to traveling vehicles and two accelerometers for each traffic lane to detect vehicle axles. Field measurements were performed using three different test trucks on an actual in-service bridge to study the effectiveness and accuracy of the proposed spBWIM system. The results show that the spBWIM system can be used to estimate gross vehicle weights (GVWs) to within an error of ±15.3% compared with static weighing using a truck scale. Based on the results, the authors believe that the spBWIM system can potentially be developed into a viable alternative to conventional BWIM systems that use strain gauges.

The perforated rib shear [Perfobond Leiste in German (PBL)] connector is a type of shear connector used in some steel–concrete composite bridges as a main load-transfer element between the concrete roadway and the supporting steel deck. The shear capacity of PBL connectors is affected by several connection parameters, such as the diameter of the transverse steel reinforcement, the size of the perforated rib hole, and the thickness of the rib plate, and the stress state in the surrounding concrete. In the present study, 33 test specimens were designed, and push-out tests were performed to investigate how these parameters affect the shear capacity of PBL connectors. The test results show that the shear capacity of these connectors increased with an increase in the diameter of the transverse reinforcing bar, an increase in the size of the rib holes, and an increase in thickness of the perforated rib plate. As for the effect of concrete stress state, it was found that the shear capacity of the connectors increased when a transverse compressive stress was present, but it decreased when a transverse tensile stress was present. Using results from these tests, a design equation that takes all of these factors into consideration in determining the shear capacity of PBL connectors is proposed. The proposed equation produces reasonably accurate results when compared with experimentally determined shear capacity for these connectors.

A computationally efficient method is proposed for analyzing train and bridge dynamic interaction responses based on the vector form intrinsic finite-element method. The proposed method does not need to establish a large number of complicated dynamic coupling equations for the train and bridge, in contrast to the traditional finite-element method. A train with multiple cars traveling over a railway bridge with multiple spans was analyzed, and two computational models were considered: two-axle and coach models. The effects of rail irregularity and rail ballast were also considered. In the proposed method, the bridge is modeled as mass particles linked by a series of massless beam elements, and the train is simulated by mass particles. The motions of the mass particles are governed by Newton’s second law, and the central difference scheme is employed to solve the equation of motion for each mass particle. The fictitious reverse-motion procedure is employed to obtain the pure deformations of the massless beam elements, from which the internal forces exerted on the mass particles are evaluated. Assembly of the global stiffness matrix is avoided, and each mass-particle motion is calculated independently, which makes the proposed method easy and efficient. Compared with existing analytical and numerical methods, the proposed method provides simpler modeling of the dynamic interaction between the train and bridge and more efficient computation. Furthermore, the proposed method can yield very accurate results.

A lightweight steel–ultrahigh performance concrete (UHPC) composite deck (LWCD) was developed for alleviating deterioration issues in orthotropic steel decks (OSDs). In recent years, the LWCD has been increasingly applied to steel bridges in China. This paper focuses on the fatigue assessment of the LWCD on the basis of a pilot project on the 310-m cable-stayed Haihe Bridge. A multiscale finite-element (FE) model was built to integrate the global and local responses of the bridge without significantly increasing the computing cost. In the study, a parametric analysis was conducted to reveal the influences of the longitudinal position of the girder segment and the transverse position of the fatigue load on the stresses of the LWCD. In addition, a detailed fatigue assessment was performed that covered the following fatigue-prone details: the rib-to-deck connection and the rib-to-diaphragm connection in the OSD, the headed studs, and the UHPC layer. The analysis results show that for the OSD details, the values of the vehicle-induced stress ranges were significantly reduced when a thin UHPC layer was added, indicating that the fatigue-cracking risks in the details could be basically eliminated. In addition, the results also reveal that both the headed studs and the UHPC layer, generated by the application of the LWCD, can meet the design requirements in terms of fatigue.

With the institution of AASHTO HL-93 loading, calculating the maximum live-load moment on simple spans became more complex than it had been previously. In the past, to find the maximum live-load moment from the HS-20 design truck, the middle axle was offset from midspan by 0.711 m (2 ft 4 in.), and the moment under that axle was the maximum moment on the beam. However, with the combination of the design vehicle and the distributed design lane load, this general approach became obsolete. The purpose of this study was to develop a new generalized approach to determine the location and value of the maximum moment under HL-93 loading on simple spans. This was accomplished by creating moment envelopes and studying their extremum. Subsequently, equations, charts, and tables were developed that describe the location and value of the maximum moment on a beam under HL-93 loading, consisting of design truck or design tandem loading in combination with the design lane load for a simple span of any length.