Journal of Bridge Engineering

Due to structural deterioration, the performance of concrete bridges degrades with time and may result in catastrophic failure events, especially for nonredundant structures. This paper develops a methodology for assessing time-variant reliability and redundancy of multigirder prestressed concrete bridges at material, component, and system levels. Nonlinear analysis was performed to obtain the constitutive relationship of reinforced sections and girder components in which the adverse effects of reinforcement corrosion on structural capacity and ductility are considered. Subsequently, the nonlinear finite-element analysis was conducted to capture the time-dependent probabilistic resistance of the bridge system, considering different failure criteria (e.g., serviceability and ultimate limit states). Given the component- and system-level performance indicator, structural capacity-, reliability- and risk-informed redundancy was assessed. The feasibility and capability of the proposed approach were illustrated using an existing prestressed concrete bridge. The results demonstrate that the integrated damage mechanism between different levels has a significant effect on the structural ultimate capacity, reliability, and redundancy of corroded structures.

Bridge weigh-in-motion (BWIM) systems provide an effective approach to identifying the axle and gross vehicle weights of vehicles as they travel over an instrumented bridge. For the majority of BWIM systems, the vehicle configuration (including axle count and axle spacing) and vehicle speed are prerequisites for identifying the axle and gross weights of vehicles. Existing nothing-on-road (NOR) BWIM systems acquire such data through dedicated sensors, namely, free-of-axle-detector (FAD) sensors, in addition to weighing sensors. These FAD sensors are usually installed on the underside of the bridge deck or girders. This study presents a novel method for identifying the axle spacing and weights of vehicles. It only requires the flexural strain signal recorded from the weighing sensors, leading to both a reduction in the installation cost and broader applications of BWIM systems. The effectiveness and accuracy of the proposed method are demonstrated through numerical simulations. Laboratory experiments based on a scaled vehicle–bridge interaction (VBI) model were also conducted for verification. The results show that the proposed method has good accuracy for axle spacing and axle weight identification.

Bridge modal parameters play an important role in bridge engineering; they can serve as useful indices for many applications, such as numerical mode calibration and updating, and bridge structural health monitoring (SHM). Recently, the indirect monitoring of bridges has been increasingly investigated and developed because it avoids the need for instrumentation on all bridges of a network. The natural frequencies of bridges have been extracted from the dynamic response of a vehicle numerically and in laboratory experiments. This study proposes an algorithm to extract the bridge mode shapes and damping ratio using similar indirect measurements enhanced by the Hilbert transform (HT). The theoretical closed-form equations are derived for a vehicle–bridge interaction (VBI) model in which the vehicle is represented as a moving sprung mass passing over a simply supported beam at a constant low speed. Then, a numerical simulation with a quarter-car model is adopted to verify the proposed algorithm, including case studies on the influence of the vehicle speed and road roughness. In addition, a laboratory test is conducted to further investigate the feasibility of the proposed algorithm.

A shake table experiment of a large-scale, two-span accelerated bridge construction (ABC) bridge model with steel superstructure incorporating six of the more promising ABC connections was conducted on shake tables at the University of Nevada, Reno. The objective was to investigate the seismic performance of the ABC connections integrated into a bridge system and to determine whether ABC bridges can demonstrate adequate load path, integrity, and constructability. The bridge model was subjected to successive bidirectional motions simulating a modified version of the Northridge 1994 earthquake record. Test results showed that the ABC bridge emulated the behavior of cast-in-place bridge columns by undergoing large inelastic deformations in a ductile manner by forming plastic hinges and extensive yielding of the longitudinal bars in the columns. Structural integrity was maintained in all connections through various earthquake levels. Construction procedure of the bridge model ensured the feasibility of handling and connecting different prefabricated members.

Monitoring of bridge displacements is critical for safe and cost-effective railroad operations. One of the essential parameters for determining the serviceability of the bridges is the dynamic displacement of the bridge during train-crossing events. The traditional methods for bridge displacement measurement often utilize linear variable differential transducers (LVDTs). However, irregular terrain, remote and inaccessible locations, and the height of the railroad bridges make implementation of these sensors for displacement measurements inadequate, risky, and time-consuming, and sometimes not possible altogether. In recent years, the use of laser Doppler vibrometers (LDVs) in the field of bridge displacement measurement has drawn attention as an alternative. In these applications, the vibrometer is generally placed on a fixed-point reference close to the bridge. However, it is not always possible to locate a fixed reference perpendicular to the bridge span to measure transverse displacements, especially when the bridge spans over a large opening. Furthermore, LDV sensors require calibration for every unique, different setup and are cumbersome to implement across a variety of different bridges. This paper presents a novel concept for bridge displacement measurement that enables the use of noncontact and reference-free moving vibrometers in the field without the need for calibration. The concept discussed herein proposes a method of compensating for measurement errors due to the angular and linear movement of the vibrometer to obtain accurate transverse displacement measurements of bridges. The results of this study showed that the signal difference between the measured outputs of a moving LDV system and an LVDT was between 10% and 15% peak-to-peak and between 2% and 5% root-mean square (RMS), which are generally considered acceptable levels of accuracy by railroad managers for field applications. An outdoor test was conducted in which an LDV mounted on an unmanned aerial system (UAS) was used to collect displacement measurements of a moving target structure representing a railroad bridge train-crossing event. Researchers conducted three outdoor experiments by collecting LDV and LVDT measurements from the UAS as it was hovering. The results from this outdoor testing showed that the signal difference between the measured dynamic data from the moving LDV and the LVDT was less than 5% (peak) and 10% (RMS). The reference-free dynamic displacement is generally accepted by railroad managers as an important index related to bridge deterioration, so this application can inform railroads in the field of prioritization decisions without the need for installed sensors. The ultimate goal of this research was to validate the applicability of the proposed method by mounting one LDV on a UAS and measuring dynamic bridge displacements with minimal setup and calibration.

Climate change has been recognized as a significant threat for transportation infrastructure. The change in temperature profiles and precipitation patterns and the increase in the intensity of weather-related extreme events are among the effects attributed to climate change. Additionally, climate change may also alter the frequency and intensity of flood events, which increases the complexity of assessing the risk of bridge failure due to flood-related failure modes. Flood occurrence generally increases the rate of river bed erosion and may cause the formation of scour holes around bridge piers, leading to an increased risk of bridge failure. Several factors, such as future precipitation, basin parameters, flow direction, and drainage area, affect the streamflow of a river; accordingly, the proper prediction of long-term future flood hazard requires detailed and computationally expensive climate and hydrologic modeling, which can be prohibitive in assessing the life cycle risk of bridges and other transportation structures. This paper addresses these issues by proposing a comprehensive, yet computationally efficient, probabilistic framework for quantifying the risk of bridge failure due to flood events considering climate change. Statistical modeling was employed to draw a relationship between the downscaled climate data adopted from global climate models and the streamflow at a given location. The effects of different global climate models and carbon dioxide emission scenarios on failure risk due to flood hazard were taken into account. The results showed that using traditional assessment approaches that do not properly consider climate change effects can lead to a considerable underestimation or overprediction in the predicted future risk. The approach was applied to an existing bridge in Oklahoma; however, it is equally applicable to bridges and other transportation structures located in various regions in the United States.

In this paper, the solitary wave forces on coastal bridge superstructures with box girders are discussed numerically. Although there are some empirical equations for wave forces on typical bridge superstructures, no relation has yet been proposed for predicting the tsunami-induced forces on box girder superstructures due to the lack of knowledge of wave forces on these kinds of superstructures. In this study, first, a solitary wave model was utilized to represent the tsunami. Then, the Reynolds-averaged Navier-Stokes equations combined with the shear stress transport (SST) k-ω turbulence model were utilized for the wave simulations. Additionally, the horizontal and vertical forces on the bridge superstructures were simulated, taking into account four water depths and five wave heights for each bridge elevation. The effectiveness of the numerical model was proven by a comparison with the experimental measurements. The numerical results showed that the difference in wave forces acting on T-type girders and box girders was significant. Finally, an improved empirical equation was proposed for estimating the tsunami-induced forces on box girder bridges.

Recently, the use of ultrahigh-performance fiber-reinforced-concrete (UHPFRC) closure joints between structural members has increased in accelerated bridge construction (ABC) applications. This paper presents an experimental study to investigate the structural behavior of UHPFRC closure joints between glass-fiber-reinforced-polymer reinforced-concrete (GFRP-RC) bridge-deck slabs. A total of seven full-scale specimens measuring 3,000-mm long × 1,000-mm wide × 225-mm thick were fabricated, comprised of a reference specimen without closure joints and six jointed specimens. The investigated parameters were: (1) the splice lengths (100, 150, and 200 mm with corresponding joint widths of 120, 170, and 220 mm, respectively); and (2) the reinforcement ratio (No. 15 and No. 20 GFRP bars with the same spacing). The specimens were tested up to failure in a cantilever-panel setup under monotonic line loading in which the UHPFRC closure joint was subjected to flexural and shear stresses. The test results are discussed and analyzed in terms of crack pattern, load–deflection response, crack width, GFRP reinforcement, and concrete strains. The test results show that a minimum splice length of 100 mm in 120 mm UHPFRC closure joints yielded adequate strength and performance until failure. The UHPFRC closure joints remained intact without visible cracks and maintained the continuity between the precast slabs.

Accelerated bridge construction (ABC) methods are implemented to reduce mobility impact time. In Michigan, four bridges were replaced using lateral slide, which is one of the ABC methods. The Michigan projects, a large volume of project documentation in the Federal Highway Administration (FHWA) repository, and resources available through state departments of transportation (DOTs) were reviewed and the successes, difficulties, and activities were documented and analyzed. Additionally, instrumentation and monitoring as well as simulations of two slides completed in Michigan were performed. Simulations evaluated structural system response, and investigated the sources and effects of the complications during slides. Based on the experience through all these activities, a detailed step-by-step design procedure is developed and described in this article. The purpose of the article is to provide a structured process to complete, review, and verify the design calculations related to slide activities described in the current AASHTO guidelines. The procedures described in this article, along with the AASHTO specifications, can be used to design and execute repeatable slide implementations.