Journal of Bridge Engineering

Existing nonlinear optimization-based algorithms for estimating Markov transition probability matrix (TPM) in bridge deterioration modeling sometimes fail to find optimum TPM values, and hence lead to invalid future condition prediction. In this study, a Metropolis-Hasting algorithm (MHA)-based Markov chain Monte Carlo (MCMC) simulation technique is proposed to overcome this limitation and calibrate the state-based Markov deterioration models (SBMDM) of railway bridge components. Factors contributing to rail bridge deterioration were identified; inspection data for 1,000 Australian railway bridges over 15 years were reviewed and filtered. The TPMs corresponding to a typical bridge element were estimated using the proposed MCMC simulation method and two other existing methods, namely, regression-based nonlinear optimization (RNO) and Bayesian maximum likelihood (BML). Network-level condition state prediction results obtained from these three approaches were validated using statistical hypothesis tests with a test data set, and performance was compared. Results show that the MCMC-based deterioration model performs better than the other two methods in terms of network-level condition prediction accuracy and capture of model uncertainties.

To study the effects of ground motion spatial variations on curved bridges, this paper presents a shake-table test for a $1/10\text{-scale}$ typical curved bridge under spatial ground motions, including wave passage effect, local site effect, and ground motion multidimensionality. The experimental results show that both wave passage and local site effects have significant influence on seismic responses of curved bridges. Wave passage effect on curved bridges is attributed primarily to the higher asymmetric modes and pseudostatic displacements induced by asynchronous excitations, whereas local site effect is more obvious for structures with fundamental frequencies close to the predominant frequencies of the sites. Compared with straight bridges, the curvature radius causes curved bridges to be more sensitive to ground motion spatial variations, especially the local site effect. Therefore, curved bridges may be damaged more seriously than straight bridges during the same earthquake. Furthermore, seismic responses of irregular curved bridges are more sensitive to ground motion multidimensionality than are those of straight bridges. In this experiment, the effects of bridge abutments and nonuniform sites along the bridge were not considered.

Precast concrete segmental bridges with dry joints have the advantages of rapid construction speed and low cost. The shear strength and shear behavior of dry joints with castellated keys in precast concrete segmental bridges are still debatable. In this paper, full-scale dry joints with castellated keys were tested under different confining stress levels. The main parameters for tests were the number of keys, the confining stress, the depth in key geometry, and the distance between two keys. For comparison purposes, flat joints, monolithic joints, and joints with steel fibers were also tested. The shear behavior, shear capacity, and crack pattern of the joints were investigated as well. Two crack modes for the single-keyed joints are explicitly proposed. The phenomenon of sequential failure of multikeyed dry joints from the inferior key to the superior one was observed in the tests and verified by finite-element simulation. The experimental results obtained in these tests were compared with the design provisions. A shear failure mechanism of sequential failure for multikeyed dry joints is presented to explain the differences between the test results and the formula used. Based on the new explanation and test results, a reduced coefficient of 0.7 is recommended for the shear strength of three-keyed dry joints. Pending more test data, this conclusion could be extended to the shear strength of multikeyed dry joints to improve the formula.

A method for the shape finding of a specific type of self-anchored suspension bridge whose main cable is three-dimensionally curved is proposed in this study. The method, referred to as the coordinate iteration method (CIM), is developed from the force equilibrium features of the rational arch axis for suspension cables modeled by truss-cable elements. By establishing the linear iterative equations in terms of unknown coordinates and updating the relation matrices iteratively, a trial profile of the three-dimensional cable-only system easily and stably converges to the target system. The CIM is then extended to the shape finding of the total bridge system with the aid of a specific numerical model proposed in this study referred to as the indiscrimination coordinate rod model (ICRM). This model is used to simulate the core deformation effects of the total bridge. The detailed procedure undertaken to establish a finite-element model of the equilibrium system for the finished dead load state based on CIM and ICRM is also presented. The precision and efficiency of the method are demonstrated through actual numerical examples.

A research program investigated the application of high-early-strength self-consolidating concrete (SCC) for precast, prestressed bridge girders. The SCC and conventional concrete (CC) in mixtures had a target 16-h release strength of 34 MPa (5,000 psi). Testing was performed to evaluate the flexural response and bond performance of the girders. This included assessing and comparing camber and deflection, moment-curvature, cracking moment, nominal moment, and crack development of prestressed bridge girders containing SCC and CC. In addition, river gravel and limestone aggregate were used to evaluate the impact of aggregate type on the mechanical properties and bond performance in the full-scale testing of both SCC and CC girders. Early-age characteristics, material properties, and field observations are also documented. Test results indicate that the flexural capacity and bond performance of the SCC girders are similar to those of the companion CC girders. Also, AASHTO equations for the nominal moment were found to be appropriate for SCC girder-deck systems similar to those tested in this study. The AASHTO expressions used were found to be appropriate for estimating the cracking moment for the river gravel SCC girder-deck system, but they slightly overestimated the cracking moment for the limestone SCC girder-deck system.

Physical protection systems typically are used to reduce vessel impact loads to nondestructive levels or redirect vessels away from bridge piers. An efficient physical protection system is critical for the safe operation of bridges and vessels. A new fender system, referred to as a floating fiber-reinforced plastic (FRP), can meet the design needs to protect both bridge piers and vessels. In addition, the floating FRP fender system, which is composed of FRP box modules filled with rows of FRP tubes, offers high-performance energy dissipation capabilities, modular construction, and easy replacement benefits. This paper focuses on a performance evaluation of this new fender system, used in a prestressed concrete bridge, by using a nonlinear explicit dynamic finite-element analysis program. The study included a vessel collision analysis with material properties calibrated by experimental data. The authors concluded that this new fender system has excellent energy-absorbing capabilities, significantly reduces collision forces, and increases collision duration imposed on the bridge pier and colliding vessel. Therefore, the new protection system is worthy of consideration for locations where a vessel-bridge collision is a concern.

Overloaded trucks, including some extra heavy trucks, often cause serious threats to bridges, such as deterioration, fatigue damage, or even collapse. Compared with the standard traffic design loads in design specifications, the actual characteristics of overloaded trucks, such as truck weight and types, are very difficult to predict or define. These characteristics are not specific only to the location. Rather, they depend on the economy, regulations, and law enforcement, and also vary over time as a result of uncertainties at a given location. In the current study, long-term traffic monitoring data are statistically studied to identify the key characteristics of extra heavy trucks, such as vehicle type, lane distribution, speed, axle weight, axle distance, and the variation of flow rate over time. All of the trucks from the traffic monitoring data are classified into 17 typical vehicle types, in which a total of 1,319 extra heavy truck scenarios are extracted from the traffic monitoring data. To study bridge performance under extra heavy trucks, advanced bridge/traffic interaction analysis software is developed and used to analyze the selected traffic scenarios. The bridge response and the dynamic amplification factors (DAFs) for a typical medium-span highway bridge are numerically investigated. Finally, these DAFs and bridge responses are compared with those as specified in both the AASHTO LRFD bridge design specifications and Chinese codes.

There has been a rapid development of high-speed rail in Spain. Many bridges have been constructed to carry these lines. The relevant Spanish design codes require static and dynamic testing of these structures for acceptance of the design and construction before opening for service; such testing is considered too costly in some other countries. This paper presents the concept, practice, and results of such testing for 119 precast and posttensioned concrete girder bridges. Their static and dynamic properties and responses to loads have implications for their structural safety, serviceability, and possibly durability. Inaccurate models used in design for static and dynamic parameters (such as stiffness, first natural frequency, and damping ratio) may result in incorrect responses and possibly unsafe structures; therefore, in situ testing is required. The test results of these structures also lead to an empirical relation between the first natural frequency and span length and a range of damping ratios for these types of structures, which can be useful for bridge engineers, particularly at a preliminary design stage of similar structures.