Journal of Bridge Engineering

Life-cycle cost analysis (LCCA) has recognized potential for rationalizing bridge procurement, but its use in this context is far from systematic. The integration of LCCA findings in decisions is often far from robust. Furthermore, although most bridge management systems (BMSs) include databases of relevant information, agencies do not use them effectively to improve future bridge-investment decisions. This paper introduces a comprehensive approach to help agencies exploit their BMSs to procure the most cost-efficient bridge design through fair design-build (D-B) tendering processes. The approach incorporates use of a novel LCCA technique, LCC added-value analysis, that can be conveniently integrated with public agencies' established procurement procedures and maintains contractors' freedoms in D-B processes. The proposed approach allows bridge procurers to establish monetary LCC-efficient benchmarks and embed them in tender documents as core specifications. Hence the lowest LCC bid, rather than the lowest bid in initial investment terms, can be used as the contract award criterion. The Swedish Transport Administration has recently procured several bridges using the approach, thereby gaining considerable cost savings. A case study provides insights into various aspects of bridges’ LCC and illustrates analytical steps that other agencies could apply in bridge procurement. The study shows that the use of D-B processes, together with the lowest LCC bid as the contract award criterion, afford greater opportunities to consider LCC aspects in bridge procurement, rather than relying on traditional contracts and the lowest-bid criterion.

The structural behavior of precast concrete segmental bridges largely depends on the behavior of the joints between segments. The current practice of precast concrete segmental bridges is to use small keys that are usually unreinforced, normally dry, and distributed over the height of the web and the flange of concrete segments. In this study, a numerical analysis model was established based on finite-element code to investigate structural behavior of keyed dry joints under direct shear. The concrete damage plasticity model along with the pseudodamping scheme were incorporated to analyze the system for microcracks and to stabilize the solution, respectively. The numerical model was calibrated by full-scale experimental results described in the literature. It was found that the predicted ultimate load, cracking evolution history, and final crack pattern agreed reasonably well with experimental results. The validated numerical model was then used for parametric study on factors affecting shear behavior of keyed dry joints, in this case confining pressure. The authors found that shear capacity predicted by the AASHTO code equation diverges from that predicted by numerical analysis at high confining pressure, because the contribution of friction in the total shear capacity decreased with an increase in confining pressure. Hence, the authors recommend reducing the friction coefficient used in the AASHTO code equation when high confining pressure is applied. Moreover, the propagation of inclined crack was arrested at high confining pressure owing to the fact that the fracture propagation direction is governed by the criterion of the maximum energy release rate.

The idea of retrofitting web stiffener ends in steel bridge girders susceptible to distortion-induced fatigue using adhesively bonded fiber-reinforced polymer (FRP) angles is introduced in this study. The proposed retrofit method is relatively cheap and easy to use and does not require deck removal or any other severe modification to the steel girder. Fatigue tests were conducted on specimens designed to model the conditions in the region between a web stiffener and a flange in a steel girder bridge. Fatigue life increases on the order of several hundred percent were achieved by implementing the proposed retrofit. The effect of the retrofit on the hot-spot stress in the critical weld detail can be seen in the experimental strain data and in a subsequent finite-element (FE) analysis of the tested specimen geometry. Further research is recommended to assess the performance of the retrofit on full-scale girders and to develop guidelines for fatigue verification and design of the FRP angle and adhesive. However, the presented research shows the potential of the proposed retrofit and the suitability of the hot-spot stress method for predicting its effectiveness.

Ground-penetrating radar (GPR) has been extensively studied in North America as a nondestructive evaluation (NDE) technology for inspection of concrete bridge decks. With current practices, however, GPR has only proven to be an indicator of potential damage. Basically, to obtain the condition map for a concrete bridge deck, one would try to analyze one-time GPR data based mostly on the relative difference between reflection amplitudes at the top rebar layer. With a hypothesis that time-series GPR data can provide better information on bridge deck deterioration progression, this study investigates and proposes a new method to interpret those time-series data sets. Based on a correlation coefficient between A-scans, the proposed methodology was implemented and validated for a bare concrete bridge deck in New Jersey. The map provided by the proposed method clearly shows deterioration progression between the two consecutive scans, whereas the traditional analysis technique using the top rebar amplitude suggests unreasonable improvement of the deck condition over time.

This paper presents the results of an experimental program conducted to evaluate the effects of end region detailing on the capacity and behavior of pretensioned concrete I-girders. The program was conducted using six Florida I-Beam specimens, 1,372 mm (54 in.) in depth, which were load-tested in three-point bending at a shear span/depth of 2.0. Variables in the program included confinement reinforcement configuration, presence/lack of steel bearing plate, strand shielding pattern, and strand layout. Specimen behavior and capacity were found to be significantly affected by end region detailing, especially placement of fully bonded strands. Experimental results were compared with theoretical models for web-shear, bond-shear, and lateral-splitting capacity. By considering multiple models, calculations were able to accurately identify the failure mode of each test specimen.

A novel bridge scour estimation approach that comprises advantages of both empirical and data-driven models is developed here. Results from the new approach are compared with existing approaches. Two field datasets from the literature are used in this study. Support vector machine (SVM), which is a machine-learning algorithm, is used to increase the pool of field data samples. For a comprehensive understanding of bridge-pier-scour modeling, a model evaluation function is suggested using an orthogonal projection method on a model performance plot. A fast nondominated sorting genetic algorithm (NSGA-II) is evaluated on the model performance objective functions to search for Pareto optimal fronts. The proposed formulation is compared with two selected empirical models [Hydraulic Engineering Circular No. 18 (HEC-18) and Froehlich equation] and a recently developed data-driven model (gene expression programming model). Results show that the proposed model improves the estimation of critical scour depth compared with the other models.

Whereas application of sensors that directly detect bridge scour at the foundation may be hindered because of their installation difficulty and vulnerability to floods, the identified scour rarely has been used to assess the bridge performance. This paper presents a new probabilistic approach to assessing the structural integrity of scoured bridges through Bayesian inference based on vibration measurements. The contributions of this paper include (1) introducing a novel application of Bayesian inference for assessing the structural integrity of scoured bridges; (2) parameterizing bridge scour, environmental variation impacts, and their associated uncertainties; (3) integrating the bridge model with the effective sampling algorithm to derive probability distributions of uncertain scour damage and other system properties; and (4) unifying uncertainties of identified scour and the probability of failure of scoured bridges. The proposed approach is illustrated and examined through a numerical study, and its potential for identifying bridge scour and assessing the scoured bridge’s performance reliability is demonstrated based on vibration measurements with environmental variations. The limitation of the presented study and future research directions are also discussed.