Journal of Bridge Engineering

Two different experimental approaches for the evaluation of a bridge deck’s stationary aerodynamic forces are studied in this paper: both wind tunnel measurement of global force and pressure distribution are evaluated on deck sectional models. Advantages and drawbacks of these different approaches are discussed using the results obtained on a simple deck section, specifically chosen to compare the selected methods. Two-dimensional computational fluid dynamics (CFD) simulations have been performed to provide an insight into the differences of the aerodynamic forces measured with the two methods. Specifically, the effect of shear stresses, measurement discretization, and axial correlation of pressures are addressed. In CFD analysis, several turbulence models are tested and discussed using Reynolds-averaged Navier-Stokes (RANS) equations.

The objective evaluation of the capacity of a bridge to carry self-weight and traffic loads after an earthquake is essential for a safe and timely reopening of the bridge; this performance goal gains in importance with the recognition of the economic losses caused by the reduced traffic capacity of the transportation systems of a region affected by an earthquake. An analytical model of a bridge column was developed, calibrated, and validated to facilitate the quantitative evaluation of the remaining traffic-load capacity of a typical California highway overpass bridge after an earthquake. The bridge-column model was developed using a fiber cross section, force-based beam-column element with distributed plasticity. The model was calibrated using the data from a series of bidirectional quasi-static tests and validated using the data from hybrid simulations of the bridge earthquake response. It was found that the postpeak degrading slope of the confined-concrete core has a significant influence on the accuracy of the axial-load capacity of damaged columns.

The often-reported premature failures of expansion joints of long-span steel bridges call for a better understanding of their performance in service conditions. This paper presents the long-term monitoring and analysis of displacements of expansion joints, with emphasis on the influence of viscous dampers that were installed to mitigate seismic responses of the bridges. Data from the three long-span steel bridges in China—the Sutong Bridge, the Runyang Suspension Bridge, and the Jiangyin Bridge—are compared. Decomposition of displacement signals in various frequency bands reveals that temperature-induced movements contribute to only a small portion of the total cumulative displacements. Because of the small but rapid movements caused by vehicle/wind loads, the cumulative displacements of long-span steel bridges may far exceed those caused by temperature changes. According to the monitoring data, the existence of viscous dampers may reduce the vehicle/wind-induced displacements but have no significant influence on the temperature-induced movements. Finite-element analyses are conducted to further validate the influence of viscous dampers on displacements of expansion joints.

A fast algorithm for determining the installation force of parallel strand cables is proposed in this paper. Because cable-stayed bridges are flexible structures, the algorithm must consider the sag effect of cable stays as well as the prestressing loss caused by displacements of the deck and the pylon when erecting stay cables with a strand-by-strand method. Based on the principle of the isotension method for parallel strand cables, two basic problems involved in the stretching process and the corresponding numerical computing method are fully demonstrated in this paper. To consider the nonlinearity of cables, catenary theory is used for determining the cable shape and cable forces during the entire loading process. According to said method, a corresponding calculation program was compiled, followed by an additional error analysis. Case studies are provided to compare the results calculated by the program with data measured from an ongoing road-rail cable-stayed bridge and from other calculation methods. The results confirm that this computing method can ensure both efficiency and accuracy and is equally applicable to the problem of cable replacement.

A lightweight, low-profile ultrahigh-performance concrete (UHPC) deck system reinforced with high-strength steel (HSS) has been proposed by the authors as an alternative to open grid steel deck. The system consists of a thin slab with primary ribs spanning between girders and shallower secondary ribs, parallel to the girders, connecting the primary ribs together. Earlier studies have shown the constructability of the deck. This paper presents system development of the deck, its connections to girders and adjacent deck panels, its response to repeated loading, and its lateral distribution of live loads. The deck-to-girder connection was made as cast-in-place UHPC around welded shear connectors and was designed to resist the shear from braking forces and the uplift from wind loads. The deck-to-deck connection was made as tongue and groove to transfer the load from one panel to the other as vehicles move on the bridge. The experiments presented in this paper confirm the feasibility of the proposed deck because the panels and their connections successfully endured 2 million cycles of repeated loading with a residual strength of at least 47% higher than the target load. Further studies are needed (1) to optimize the design by further decreasing the weight of the deck, (2) to assess the effectiveness of the UHPC as wearing surface, and (3) to monitor field performance of the deck under ambient traffic and designated truck load.

Long and torsionally slender H-shaped cross sections, often used as tension members in truss bridges, can exhibit wind-induced torsional motions. These motions have produced high-cycle fatigue damage for some bridges. There is limited information available to evaluate the torsional response on the fatigue performance of the members and connections. An in-service bridge with a documented history of wind-induced torsional motions in the verticals was instrumented to capture the wind speed and direction that induced torsional motions in the verticals. Sensors also captured the rotation angle amplitudes and numbers of cycles. Laboratory tests were conducted on a full-size replica of a vertical-and-chord connection to establish the relationship between rotation and normal stresses in the cross section from warping restraint at the connection locations. Analytical methods were shown to accurately predict the rotations and warping stresses along the member length. Applying the experimental and analytical results, the stress ranges were determined for the field-measured torsional responses, and the fatigue potential was evaluated. The results showed the measured stress ranges are near the constant amplitude fatigue limit, but the large cycle counts and frequency of events in the historical wind record that could produce torsional response indicate the need for continued monitoring and a long-term mitigation strategy.

A frequency-response function–based parameter-estimation method was used for finite-element (FE) model calibration of a full-scale bridge using measured dynamic test data. Dynamic tests were performed on the bridge to obtain measured frequency-response functions. Data quality was ensured by comparing measured data with the FE model and removing erroneous data. A coherence data selector was developed to remove the noise-contaminated portions of the measured frequency-response functions. An unrefined FE model was created using design information for the geometry and structural parameters. This model was improved to a refined model by using concrete cylinder property data, as-built drawing geometry, and the addition of components that participate in the dynamic response of the bridge. Simulations were performed using the model to ensure both observability and identifiability of structural parameters. The model of the bridge was then calibrated successfully using measured frequency-response functions. An increase in the negative bending region concrete-deck rigidity was found during the calibration and verified by increased reinforcement in that area. Examining the second norm of the residual between the different models and the measured data resulted in an improvement from the unrefined to the calibrated FE model. The proposed method proved to be robust in the presence of modeling and measurement errors and computationally efficient for use with full-scale structures.

This paper describes a statistical approach to estimating an appropriate inspection interval for highway bridges based on historical condition data collected from 20 years of routine inspections. Condition ratings of 4,270 bridges with concrete, steel, and prestressed-concrete superstructures were analyzed in this study to determine the time-in-condition rating (TICR) for superstructure components. The Anderson-Darling test was used to assess five conventional distributions to determine goodness of fit for describing the distribution of the TICR probabilistically. The test results revealed that the Weibull distribution was the best fit for the TICR for superstructure components. Parameters of the Weibull distribution were estimated for concrete, steel, and prestressed concrete in different condition ratings and used to define probability-density functions (PDFs), which were then used to determine the likelihood of a bridge deteriorating from a good condition to a poor condition over some time period. These data can be used for rational decision making regarding the appropriate inspection interval for bridges of a given type based on quantitative historical analysis of data. This study is beneficial because of the simplicity of the models developed and their accessibility for practicing engineers.