Journal of Bridge Engineering

The current paper provides a comprehensive review of experimental studies on corrosion-damaged reinforced concrete (RC) components and the ability of current state-of-the-art numerical models to predict the residual capacity of these corroded RC components. The experimental studies on corroded RC components are classified into five different categories: (1) beams in flexure, (2) beams in shear, (3) columns under pure axial compression, (4) circular columns in flexure, and (5) rectangular columns in flexure. For each group, a summary of all previous research is provided. Through regression analyses, the experimental results of each aforementioned group were used to examine the adverse effect of corrosion on ductility and flexural, shear, and axial capacity loss of the corroded RC components. Finally, the observed results of the previous experimental studies were compared with the predicted values using the state-of-the-art numerical models currently available in the literature. The summarized experimental results showed that corrosion has much more adverse impact on ductility of the RC columns than strength. However, the effect of corrosion on ductility and strength reduction of RC beams was the same. Moreover, results of cross-sectional moment-curvature analyses using the state-of-the-art corrosion damage models showed a good correlation between the predicted residual flexural capacity and observed experimental results. Finally, the existing shortcomings in the literature and open issues to be addressed in future research are discussed, and some recommendations are provided.

Steel twin box-girder bridges are considered an attractive option in most of the world because of their basic design, simple form, and ease of construction. Despite their advantages, they are considered fracture critical, and as such, there is an additional mandate for the in-depth inspection of these bridges. This causes their inspection cost to be approximately two to five times greater than that of bridges with non-fracture-critical members. The required additional inspection in the United States is mainly driven by rare historical events of bridge collapse. In these events, the bridges were, however, not steel twin box-girder bridges. In addition, the mandated additional inspection does not reflect the inherent level of redundancy in most bridges. Therefore, it is important to quantify the potential for fracture and the level of redundancy in steel two-girder bridges to minimize their inspection cost. Recognizing the inherently large scatter in fatigue performance, the evaluation of crack propagation and the potential for fracture should be performed in a probabilistic manner using detailed models that represent accurate behavior of the bridge. In this study, a detailed numerical finite-element model of a steel twin tub-girder bridge was developed, and crack-growth analysis, potential for fracture of its main tubs, and its overall redundancy were evaluated. The crack-growth analysis was performed using multimode elastic fracture mechanics while accounting for uncertainties in the random variables associated with crack propagation and fracture. The results of the crack-growth analysis were utilized to develop fragility functions that specify inspection intervals versus probability of failure, where failure is characterized by dynamic crack growth. The analysis conducted to quantify the potential for fracture shows distinct possible failure modes that vary from brittle fracture to ductile fracture. The extreme loading case shows that the bridge overall is not at risk of collapse. It is important to note that this conclusion cannot be generalized for all tub-girder bridges because the level of redundancy is expected to vary between bridges depending on many factors, such as girder geometries, plate thickness, and fabrication, among others. The presented approach and the results provide a systematic method for evaluating fracture-critical bridges.

Heavy trucks, such as tractor–semitrailers weighing up to 360 kN, represent a serious collision hazard for unprotected bridge piers. Current specifications recommend designing a bridge pier vulnerable to vehicular impacts for a static force of 2,670 kN applied on the pier at a specified height. However, the impact load delivered by a heavy truck is dynamic and not applied at a single height during the crash process. High-fidelity computational simulation is used to gain insight into how force is delivered to a bridge pier during a crash. The impact force time histories generated during a collision are simplified into a series of triangular pulse functions applied at various heights. Key parameters defining the pulse models are truck weight, approach speed, and pier size. The values of these parameters are derived from numerical regression based on the simulation results. By comparing pier damage modes and deformation profiles, the proposed pulse model is demonstrated to be able to accurately represent the truck impact demands. We have proposed a capacity design philosophy to mitigate the effects of shear failure. We revealed that piers designed according to the proposed philosophy are less likely to fail in shear compared with regular piers. We asserted that together, the simple pulse model and proposed capacity design approach can serve as a basis for future performance-based design provisions for bridge piers subjected to heavy truck impact.

Navier’s 1823 Memoire (C. L. Navier. 1823. Rapport à Monsieur Becquey, Conseiller d’État, Directeur Général des Ponts et Chaussées et des Mines; et mémoire sur les ponts suspendus. Paris: L’Imprimerie Royale) is the seminal analytical study on displacements, stiffness, and vibration of suspension bridges. Navier derived a linearized formula for the vertical displacement at midspan of an unstiffened cable caused by a small change in cable length or span length. He predicted the vertical displacement caused by a concentrated midspan load on a cable with a dominant, uniformly distributed load on its horizontal projection. He thus quantified the geometric stiffness of a cable with a large axial force. Navier also examined the effects of different bearings on displacements of multispan suspension cables subject to unequal vertical loads on adjacent spans. To assess the accuracy of Navier’s quantitative results and to provide insights on structural behavior, geometrically nonlinear models were defined and solved. Navier’s analyses of the vibration of cables and the later contributions of Edward Routh, Hans Reissner, and David Steinman were assessed by geometrically nonlinear OpenSees models of unstiffened and deck-stiffened suspension cables. The influence of Navier’s work on the designs of Charles Ellet and John Roebling was revealed.

This study investigated the fractal and multifractal characteristics of crack patterns observed in prestressed concrete girders. In particular, it focused on cracks that form in the end regions of prestressed girders during the fabrication phase and attributed to prestress transfer operations (i.e., end-region cracks), and shear cracks that form due to subsequent structural (i.e., mechanical) loading. Synthetic crack patterns and experimental data collected during the fabrication and bending test of two large-scale girder specimens were used in this study. The results supported one of the key contributions of the study, which is using fractal analysis to quantify the extent of cracking that develops in prestressed concrete members. Another contribution of the study is that both fractal and multifractal analyses can be used to identify the development of different cracking mechanisms.

A single enlarged shaft foundation is often used to support bridge columns. In some conditions, it is constructed with a permanent steel casing, which is typically ignored in calculating the structural resistance of the shaft. This study investigated the contribution of this steel casing to the structural resistance and seismic response of single shaft foundations. The composite action between the steel casing and the interior reinforced concrete shaft was investigated. A series of six cyclic large-scale tests were conducted on cantilevering shafts of 50.8- and 76.2-cm diameters with heights of 5.2 and 7.6 m, respectively, with reinforced concrete columns at their top. Different interface conditions were applied to the specimens, which included the natural bond, grease, bentonite slurry, and use of shear mechanisms. In addition to the different interface conditions, the effects of the diameter-to-thickness ratio (D:t) and applied axial load were also considered. The composite behavior of the tested specimens and the plastic hinge development under large deformations were investigated and compared to results from plastic moment calculations.

In the last decades, the long-term structural health monitoring of civil structures has been mainly performed using two approaches: model based and data based. The former approach tries to identify damage by relating the monitoring data to the prediction of numerical (e.g., finite-element) models of the structure. The latter approach is data driven, where measured data from a given state condition are compared to the baseline or reference condition. A challenge in both approaches is to make the distinction between the changes of the structural response caused by damage and environmental or operational variability. This issue was tackled here using a hybrid technique that integrates model- and data-based approaches into structural health monitoring. Data recorded in situ under normal conditions were combined with data obtained from finite-element simulations of more extreme environmental and operational scenarios and input into the training process of machine-learning algorithms for damage detection. The addition of simulated data enabled a sharper classification of damage by avoiding false positives induced by wide environmental and operational variability. The procedure was applied to the Z-24 Bridge, for which 1 year of continuous monitoring data were available.

Modern advances in steel production have resulted in materials with increased fracture resistance. Material characterization studies have quantified fracture behavior, while large-scale experimental tests have demonstrated large critical crack lengths. Early testing focused on demonstrating the extreme potential of high-toughness materials. Recently, a test program utilizing large-scale specimens aimed to identify the toughness level appropriate for steel bridge design of structures traditionally classified as fracture critical. The work resulted in the concept of an integrated fracture control plan (FCP), combining the intent of the original AASHTO FCP from 1978 with modern advances in steel production, analysis, and understanding of fracture mechanics. An integrated FCP prevents fracture through a series of interrelated components, which influence each other in a rational and quantifiable way. The project was comprised of material characterization, full-scale fracture testing of steel bridge components, three-dimensional finite-element analysis (FEA), and an analytical parametric study. Large-scale flexure test results, which included both traditional and high-toughness materials, are presented. Results suggest historical large-scale fracture testing practices may result in critical crack lengths larger than would be expected in service due to the generation of high compressive residual stresses at the crack tip after unsuccessful fracture attempts on a given specimen. Further, fracture toughness demands calculated using FEA compared well with material characterization testing. Results indicated that fracture toughness values indirectly obtained from large-scale experiments should be calculated using FEA. Ultimately, the high-toughness steels tested demonstrated greatly improved fracture performance. High-toughness material, examined at a Charpy V-notch (CVN) impact energy of 170 J (125 ft-lbf), exhibited a 285% increase in critical fracture toughness as compared with a material with over twice the impact resistance of the current specification.

Because fatigue damage considerably reduces the service life of steel bridges, maintenance for fatigue damage should be performed properly. For the effective maintenance of fatigue damage, it is important to monitor traffic loads over long periods of time because fatigue damage is caused by repeated high stresses due to the weight of traveling vehicles. This study verified the long-term effectiveness of a portable weigh-in-motion (pBWIM) system through 1-year field measurements conducted on an actual in-service bridge. The pBWIM consists only of microelectromechanical systems (MEMS) accelerometers and MEMS inertial measurement units (IMUs), which are ideal for field measurements because they can be easily attached and detached using a magnetic jig. Furthermore, because MEMS accelerometers and MEMS IMUs are low-power-consumption devices, they are suitable for long-term field measurements. Field measurements were performed using a test truck in winter, summer, and autumn. The results indicate that regardless of the ambient temperature, the pBWIM system can estimate gross vehicle weights (GVWs) within an error of ±10.6% over a 1-year period compared with static weights measured using a truck weighing scale. Furthermore, it is found to be important to determine the dependence of the influence line on ambient temperature to estimate GVWs with high accuracy.

A performance-based design (PBD) framework, suited for incorporation into design codes, is proposed for bridge piers subject to truck impact. Pier performance was judged as a function of shear distortion and plastic rotation at key locations along the pier. Calibrated pulse models were used to compute the demand imposed by a single-unit truck or a tractor-semitrailer colliding with a concrete bridge pier. Capacity design concepts, similar to those in earthquake engineering, were also incorporated into the proposed performance-based approach to mitigate collapse by minimizing shear distortion of piers impacted by trucks. Based on the computational data, the argument is made that adopting the proposed PBD theory for impact-resistant pier design can allow bridge designers to meet predetermined performance objectives for given vehicular impact scenarios.

The life expectancy of bridge bearings is not well understood or predicted, and bearing replacement is primarily determined through field inspection and engineering judgement. An improved estimate of the time line for bearing replacement would aid in maintenance scheduling and budgets. As a first step in determining the age for replacement, the annual and lifetime cyclic demands must be estimated. The bearing displacements are largely caused by temperature fluctuation, seismic events, and traffic cycles. In this study, a probabilistic framework is presented to quantify the annual cyclic displacement demands on a bearing from these diverse loadings using an idealized archetypal continuous concrete girder bridge. The likelihood of an occurrence per annum of cycles of increasing amplitudes is presented. In addition, the mean and cycle periods, which are related to the loading scenario, and cycle amplitude are discussed, and a suggested loading protocol is presented. Three locations across Canada are considered (Quebec City, Toronto, and Vancouver) to investigate the influence of location on the bearing demands. The annual expected demands can be used for future work on fatigue testing of bearings to better relate to replacement schedule projections for bridge bearings.

In this research, a low-damage seismic design technology has been proposed for accelerated bridge construction (ABC). ABC low damage aims to minimize, and potentially eliminate, damage in a precast bridge during an earthquake. The low-damage design uses dissipative controlled rocking (DCR) connections between the precast elements in a bridge substructure. A DCR connection replaces the traditional plastic hinge at the column-to-footing or column-to-cap beam locations. DCR combines unbonded post-tensioning and externally attached metallic dissipaters to provide self-centering and energy absorption capabilities for the bridge, respectively. In this research, a half-scale precast bent was tested under quasi-static cyclic loading to validate the concept of low-damage design. The performance of the bent was compared against an equivalent bent with emulative cast-in-place connections. Results from testing suggested high performance of the low-damage bent. Following many cycles of large drift ratios, there was no damage or residual displacement in the bent. Findings from this research were implemented in the Wigram-Magdala Link Bridge in Christchurch, New Zealand, in July 2016. The bridge remained intact during the Kaikoura Earthquake on November 14, 2016.

Staged bridge deck construction is the practice whereby a portion of a bridge is left open to traffic while the closed portion is constructed, repaired, replaced, or widened. Traffic-induced deflections and vibrations during staged construction may affect the integrity of the longitudinal construction joint between the deck stages and the bond between reinforcing steel and concrete in this area. In this investigation, two test specimens were constructed using a simulated staged bridge deck construction process. To simulate traffic, the specimens were subjected to different magnitudes of differential deflections during curing of the second-stage concrete. Once the concrete achieved its specified compressive strength, the specimens were tested to failure to evaluate the integrity of the longitudinal construction joint and the bond between concrete and lap-spliced steel reinforcement in the construction joint region. Immediate damage caused by the induced differential displacements was minimal; only a single hairline crack was observed in each specimen at the location of maximum negative moment. When subjected to a flexural strength test, both specimens failed in flexure–compression at the end of the spliced reinforcement after substantial inelastic deformations had taken place. Additionally, strain data indicated that even when subjected to differential displacements during curing, the concrete–steel bond was capable of developing the actual yield strength of the reinforcing bars (558 MPa or 81 ksi).

Probabilistic damage control application (PDCA), an implementation of performance-based earthquake engineering (PBEE), is a stochastic process to identify the possible distribution of modern bridge responses when subjected to various seismic events. The PDCA procedure adopts reliability analysis principles based on nonlinear time history analyses (NTHAs). This paper presents the PDCA study of conducting more than 4,000 NTHAs with ground motions scaled using three different methods at 10 bridge locations to confirm the distribution of the statistical parameters associated with various site characteristics and scaling methods. Findings from the study along with supplementary parametric studies are discussed in this paper. Details from one of the locations are presented as an example to demonstrate how to compute the probability of exceeding each damage state (DS) given an earthquake and the combined probabilities. Lastly, this paper introduces a total probability-based method to estimate the probability of exceeding a DS within a bridge lifespan.

The forthcoming editions of the American and Canadian design codes will include complete sections with provisions on designing nonprestressed-concrete compression members (columns, piles, and piers) reinforced with fiber-reinforced polymer (FRP) bars subjected to combined axial and flexural load. This article presents the results of a research program investigating the use of newly developed sand-coated basalt-FRP (BFRP) bars and ties in axial–flexural members made with high-strength concrete (HSC). Eight full-scale concrete columns 400 × 400 mm in cross section and 2,000 mm in height were constructed and tested. The test variables were eccentricity-to-depth ratio and reinforcement type (BFRP and steel bars and ties). The test results indicate that the specimens reinforced with BFRP bars and ties under different levels of eccentricity behaved similarly to their steel-reinforced counterparts. An analytical study was conducted to predict the axial–flexural capacity. A parametric study was introduced to examine the effect of increasing the reinforcement ratio and concrete strength. Moreover, the effective flexural stiffness was estimated and plotted at different load levels and compared with design-equation results. The findings of this investigation can be considered as a fundamental step toward developing code provisions for the use of BFRP bars and ties as internal reinforcement in bridge pier and pile applications.

The study investigates the seismic response of the Azzone Visconti Bridge, which is a fourteenth century stone arch bridge crossing the Adda River in northern Italy. Based on previous extensive three-dimensional (3D) geometric surveys and mechanical characterization of both the soil constituting the riverbed and the masonry constituting the piers, a detailed 3D finite-element (FE) model was built. On-site ambient vibration tests have allowed dynamic characterization of the bridge. A preliminary sensitivity analysis on soil–structure interaction (SSI) parameters pointed out the key role of this boundary condition in the fitting of the mode shapes and their frequencies. Fully nonlinear dynamic analysis including the SSI have highlighted the safety levels for the structure and for the foundations.

The presence of truck platoons on our nation’s highways is an inevitability. This research study aims to explore the potential effects of this paradigm shift in our transportation system as it relates to existing and future bridge infrastructure. Platooning provides substantial improvement in fuel efficiency by allowing trucks to operate closely spaced together. Not surprisingly, these conditions may violate the fundamental assumptions that underlie our past and current design codes, which were created without any knowledge of platooning. The purpose of this study is to identify potential conditions to which these fundamental assumptions may not be adequate. To address this question, a series of analytical studies were conducted, focused on steel multigirder bridges. A single girder was analyzed in various configurations for a wide range of span lengths. Each configuration was analyzed under past and current design specifications along with numerous truck platoon arrangements. The results indicate that the current design specification performs well. The exception is longer span structures carrying closely spaced truck platoons. In these cases, live-load positive bending moment and shear force demands can be substantially greater. The historic design standard does not perform well overall. Based on these results, recommendations for identifying structures with increased live-load demands are provided, as well as the future research required to account for platooning in new design.