Journal of Bridge Engineering

Three bridges were recently constructed in Missouri using a new type of hybrid composite beam (HCB) incorporated within traditional RC deck systems. These HCBs are comprised of three main subcomponents: a composite shell, compression reinforcement, and tension reinforcement. The compression reinforcement is a self-consolidating concrete (SCC) arch that is tied at the ends by high-strength galvanized steel strands. The compression and tension reinforcements are encapsulated in a glass fiber–reinforced polymer (GFRP) box, and the voids are filled with polyisocyrunate (polyiso) foam. This unique configuration aims to optimize the structural performance of the HCB constituents, hence optimizing the overall performance of the beam. However, because of the novelty of the HCB, its structural behavior is not yet completely understood. Consequently, the finite-element (FE) modeling of this new type of beam is crucial for providing deeper insight into its structural behavior and validating the current design assumptions. It is, therefore, the main goal of this study to examine the accuracy of linear FE analysis (FEA) in predicting the static behavior of the HCB under service loads. This paper explains in detail the FE modeling of the superstructure of one of the recently constructed HCB bridges, using two commercial FEA packages. A field load test that simulates several load cases was applied to the bridge, and the deflections of the HCBs were measured at different locations. A simple analytical procedure that is based on the transformed area method is also used to predict the HCB deflections. The comparison between measured deflections and predicted deflections shows that the FEA can predict the HCB bridge behavior with acceptable accuracy, whereas the theoretical procedure significantly overestimates the beams’ deflections. Finally, the two FE models are used to analyze the behavior of the HCBs.

Current seismic design practice related to integral bridge girder-to-cap beam connections allows little or no lateral seismic load to be distributed beyond the girders immediately adjacent to the column. However, distribution results from several large-scale tests have shown that the distribution of column seismic moment typically engages all the girders. An approach utilizing simple stiffness models to predict distribution in integral bridge structures is presented in detail; distribution predictions based on grillage analyses also are compared. The experimental results and the analytical results from the stiffness and grillage models show that current design methods related to vertical load distribution are sufficiently accurate. However, when applied to the distribution of lateral load, similarly obtained results reveal that current design practice does not appropriately account for the amount of load that is distributed beyond the girders adjacent to the column to the nonadjacent girders. The current practice leads to excessive girder-to-cap connection reinforcement, increased girder depth, unnecessarily high seismic mass, and increased construction cost. Finally, this paper makes recommendations for more appropriate distribution of seismic lateral load in integral bridge superstructures.

Recent problems with grouted posttensioning tendons in U.S. bridges have led to interest in tendons that are not grouted, but rather filled with a pliable corrosion protection system such as grease or wax. The use of a flexible filler material in place of cementitious grout results in an unbonded tendon, which not only affects the structural behavior but also enables the application of new methods for improved monitoring and maintenance. This paper outlines a novel continuous monitoring approach that aims to detect wire breakage in unbonded tendons based on relative strain variation in the anchor head (or wedge plate). The feasibility of the method is investigated using a finite-element model calibrated with experimental data from a seven-strand anchor head. The model is subsequently extended to a 19-strand anchor head to assess the method’s performance on detection, localization, and quantification of tendon damage. The numerical results confirm the correlation between wire breakage and relative strain variation among the monitoring points and illustrate the method’s effectiveness in determining the location and severity of damage.

Analyses of two production-oriented culvert load-rating demand models were performed using live-load test data from three instrumented RC box culverts under four cover soil depths. The demand models were a two-dimensional (2D) structural-frame model and a 2D soil-structure interaction model. As expected, increased sophistication in the soil-structure model compared with the structural-frame model resulted in higher precision and accuracy for predicted moments. The impact of modeling accuracy for sections in a culvert where the demand moments approach zero was deemed practically insignificant. When evaluating model accuracy, it is of first importance that the models predict meaningful load magnitudes. Variations in predicted moment accuracy and precision were not uniform but were a function of the location of the critical section in the culvert structure. Improvements in modeling prediction associated with increased modeling sophistication were seen only when the structural-frame model was very imprecise.

Structural members that are restrained against motion can develop internal stresses when subjected to changes in temperature. The phenomenon of temperature-induced internal stresses in superstructure members of bridges has prompted the development of codified provisions for determining superstructure temperature load effects. The objective of this study, as a means of assessing the robustness of existing design provisions for a selected bridge case, was to quantify the effect that thermal stresses have on underlying foundation systems, such as intermediate bridge piers in integral abutment bridges. The objective was met by, in part, instrumenting a multispan integral abutment bridge with temperature and bridge response remote-monitoring devices. Data obtained from the remote-monitoring program are made available in graphical form to interested parties via real-time updates on a dedicated website. Simultaneous to the field-monitoring program, a detailed analytical study of the integral abutment bridge was undertaken. Through pairing of in-service field measurements with finite-element analysis of temperature loadings on the selected bridge, the contributions to foundation stresses associated with changes in temperature in the superstructure were quantified. Findings from this study support that available design provisions are capable of leading to conservative bridge foundation designs.

Traffic load plays an important role not only in the design of new bridges but also in the reliability assessment of existing structures. Weigh-in-motion systems are used to collect data to determine traffic loads. In this paper, the potential of hybrid nonparametric Bayesian networks (BNs) is demonstrated for modeling the complex data measured by the weigh-in-motion systems. The quantification process provides insight into the statistical buildup of the traffic load. The BN is shown to be a reliable traffic load model for use in bridge design. The model’s value is shown with applications for prediction of missing data and calculation of extreme loads. A simulation that includes both a dynamic BN and a static component is performed. The model is able to generate the distribution function of section forces, such as bending moments, generated by multiple vehicles in several lanes. The model presented in this paper should serve as a benchmark for further applications.

The absence of tsunami load provisions in coastal infrastructure design has led to unchecked resistance capacity of bridges against one of the most eminent natural hazards on the U.S. west coast. The Spencer Creek Bridge, which was completely rebuilt on the Oregon coast in 2009, is a unique example to demonstrate development and implementation of site-specific tsunami loads during the design stage. Two tsunami models, the Cornell Multigrid Coupled Tsunami model (COMCOT) and the Finite-Volume Wave model (FVWAVE), defined the flow fields from three rupture configurations postulated for a Cascadia earthquake, which has a moment magnitude of 9.0 consistent with the seismic design of the bridge structure. Although both models produce comparable surface elevations at the site, the finite-volume formulation of FVWAVE provides higher flow speed because of its capability to conserve momentum and mass even with formation of tsunami bores. The FVWAVE results define the input to the computational fluid dynamic module of LS-DYNA. The computed time history of the horizontal and vertical loads on the bridge deck, in turn, provide the input to a finite-element model of the bridge structure for capacity comparisons and damage analysis. It is concluded that the earthquake design specifications used for this particular bridge provide more than sufficient strength to resist the maximum tsunami horizontal force. The margin of safety is much smaller for the uplift force, but still remains in an acceptable range.

This paper describes a case study to quantify the behavior of precast, prestressed-concrete bridge girders made with high-strength concrete. As part of the case study, four bridge girders made with 77.2-MPa (11.2-ksi) concrete were salvaged from a decommissioned bridge in Orem, Utah. Each girder was subjected to a flexural cracking test to determine a prestress loss of 22% after approximately 7 years of service life. Once the prestress losses were quantified, a flexural capacity test was performed on one girder. Shear capacity tests were performed at various distances from the support on the remaining three girders. The measured prestress losses and various capacities were compared with estimated values calculated according to procedures in current bridge specifications. The predicted flexural capacity was found to be 7.3% conservative compared with the measured capacity. The measured shear capacities were all within 12% conservative compared with the AASHTO shear procedures. In addition to the physical tests, a nonlinear finite-element analysis was conducted and was found to replicate the experimental behavior, failure mechanism, and magnitude.

Steel bridges that are under severe chloride exposure due to deicing salts or marine environmental effects require frequent maintenance and repair activities to extend their service life and maintain an adequate performance level. In addition to the direct maintenance cost, these maintenance actions may lead to indirect costs associated with traffic delays and environmental effects that can significantly increase the life-cycle cost of the bridge under consideration. The use of more sustainable materials, such as maintenance-free steel, may increase the initial cost of the structure; however, the life-cycle cost, including the maintenance actions during the service life and their associated indirect effects, can be significantly reduced. This paper presents the computational approach and results of an analytical investigation to quantify the life-cycle cost of a steel bridge constructed using conventional painted carbon steel and to compare this cost to that of the same bridge constructed using maintenance-free steel. Indirect environmental, social, and economic impacts of maintenance actions are computed to quantify the sustainability metrics associated with steel bridges during their life cycle. The approach is illustrated using an existing bridge located in Pennsylvania.