Journal of Bridge Engineering

This paper presents a hydrodynamic experiment that examines the wave forces acting on the superstructure of coastal highway bridges to gain insight into the mechanical characteristics of the wave forces caused by the combination of storm surges and huge waves. The experiment is unique in that the specimen is a full bridge model, including its superstructure, substructure, and neighboring segments. After introducing the experimental setup and test program, this study analyzes the quasi-static and slamming components of the vertical wave force, the horizontal wave force of the superstructure in different clearances, wave heights, and wave periods. The test results are subsequently compared with two theoretical models suggested by Douglass and AASHTO guidelines to provide the experimental validation of those models. By comparing the test results and the existing models, a number of observations and discussions are produced to improve the accuracy of those theoretical models further.

The use of precast concrete elements in the construction of highway bridges has been a common practice in the United States since the 1950s. These bridges have generally performed well during the initial years after construction, but recent failures in Pennsylvania and Indiana have aroused a nationwide alarm to investigate the causes of failure and find solutions to repair these bridges or develop designs for new replacement bridges. It was found that the stressed and nonstressed embedded reinforcements were severely corroded owing to the ingress of chloride ions in the bridge deck through the surface cracks occurring within the closure pours (shear key) and at the interface of the joints between the precast elements and the closure pours. This paper addresses the corrosion activity of embedded steel bars within the closure pours. The experimental investigation consisted of two types of samples: uncracked and cracked slabs, containing regular precast concrete with different closure pours, namely, Quikrete with polyvinyl acetate (PVA) fibers, Ductal with PVA (polyvinyl alcohol) fibers, and Ductal with steel fibers. These specimens were exposed to 3% NaCl solution for the duration of 2 weeks in alternate cycles of wet and dry periods to accelerate the corrosion process. Electrochemical measurements along with the visual inspection revealed active corrosion at the interface of two materials, closure pour and precast concrete, regardless of the materials used in closure pours. This indicates that the bonding at the interface is not strong enough to prevent chloride penetration. Severe corrosion of reinforcing bars observed in cracked and uncracked specimens with the Ductal with PVA fibers as their closure pours, indicating rapid chloride transport through the PVA fibers.

Nonlinear finite-element (NLFE) calculations were used to compare and optimize the load transfer and failure mode of precast and cast-in-place bridge barriers subjected to transverse loads on bridge deck overhangs. The NLFE calculations were validated by successfully simulating the behavior of concrete barriers anchored to bridge deck overhangs and submitted to static transverse loading. The behaviors of three different barrier configurations—a normal concrete cast-in-place barrier, high-performance fiber-reinforced concrete (HPFRC) precast barriers, and HPFRC precast barriers with barrier-to-barrier connections—anchored to slab overhangs were accurately simulated with NLFE models. The validated models were then used to investigate the impact of the fiber orientation in the HPFRC precast barriers, the effect of the precast barrier length, the eccentric load application, and the utilization of a HPFRC slab overhang. The fiber orientation of the HPFRC precast barriers was shown to be well oriented to resist the applied overturning moment. The adequate performance of 4-m-long precast barrier modules commonly used in actual industrial projects was confirmed, although the reduced load-carrying capacity of a smaller 2-m-long precast barrier with shear keys also surpasses the design requirements. The precast barrier length was as critical to the structural performance as an eccentrically applied load. The HPFRC slab allowed the reduction of crack spacing and crack-opening widths and increased the rigidity and load-carrying capacity of the bridge deck overhang.

Repair has become a viable option for restoring the use of earthquake-damaged RC elements, even those that have been severely damaged. To select and design an appropriate repair system for damaged RC bridge columns, it is important that results from previous studies are known. This paper presents a comprehensive summary and review of techniques to repair earthquake-damaged RC bridge columns, as well as numerical methods for analyzing the response of repaired columns. Repair of columns with and without fractured longitudinal reinforcing bars is discussed. Studies are reviewed in terms of the apparent damage, repair technique, and performance of the repair. Advantages and disadvantages associated with each repair technique are discussed.

Concrete-filled steel tubular (CFST) arch bridges have the advantages of high compressive strength, light self-weight, and convenience in construction, and thus have been widely used in recent years. The current codes or specifications use the equivalent beam–column method to predict the in-plane strength of CFST arches. In this method, the CFST arches are considered under central or eccentric axial compression and are treated similarly to CFST columns. However, different from the CFST columns, the in-plane strength of CFST arches is affected by not only the slenderness ratio but also the rise–span ratio. Especially for the arches with small rise–span ratios, the prebuckling deformation becomes quite nonlinear, leading to a remarkable decrease in in-plane strength. Therefore, it is doubtful if the current method for in-plane strength design of CFST arches can provide correct predictions. In this paper, the elastic buckling and elastic–plastic buckling behaviors of fixed CFST parabolic arches that are subjected to uniform axial compression are investigated. The effect of the rise–span ratio on both the elastic buckling load and the in-plane strength are studied. A new method for the prediction of the in-plane strength of fixed CFST parabolic arches that are subjected to uniform axial compression is developed by considering both the slenderness ratio and the rise–span ratio.

Bridge structures that span navigable waterways are inherently at risk for barge collision incidents and therefore must be designed for impact loading. Current U.S. barge impact analysis procedures consist primarily of static load analysis methods that do not explicitly account for dynamic effects in barge–bridge collisions, and thus are not ideally suited to designing bridge structures to resist barge impacts. Therefore, the development of dynamic-analysis methods for estimating the responses of bridge structures to barge collisions is warranted. Dynamic-analysis procedures that use numerical time-integration techniques are capable of capturing pertinent dynamic effects but often yield voluminous amounts of time-varying results that must be post processed for use in design. In contrast, response-spectrum analysis (RSA) procedures are capable of directly producing maximum response parameters that are most pertinent to structural design. In this paper, an RSA procedure is proposed for use in barge impact analysis of bridges. The efficacy of the procedure is demonstrated for a bridge pier that was included in a series of full-scale impact experiments. The results obtained using the procedure are shown to be conservative when compared with data derived from the full-scale experiments.

Posttensioning has been used successfully to improve the performance of existing bridge structures. High-strength tendons can be used to effectively increase the ultimate capacity of composite beams. The main purpose of this paper is to develop a reliable three-dimensional (3D) finite-element (FE) model to simulate the nonlinear flexural behavior of steel–concrete composite beams strengthened with externally posttensioned tendons. A 3D FE model was used, where the nonlinear material behavior and geometrical analysis based on incremental–iterative load methods were adopted. The effective posttensioning stress was applied as initial strain in the link element used to model the tendons. To verify the accuracy of the developed 3D FE model, comparison between the FE analysis results and previous experimental results is presented. In-depth study has been carried out on the overall behavior of the strengthened beam and the effect of external posttensioning on stiffness, induced stresses, slippage between concrete slab and steel beam, and shear connector moments. The results of the FE model compared well with the experimental results and the FE analysis. Using external posttensioning tendons in the positive moment region for steel–concrete composite beams increased their ultimate capacity by 25%, the stiffness by 33%, and significantly improved the overall response of the bridge structural system.

To address the need for monitoring aging railway bridges, this paper presents a finite-element (FE) model updating approach using time-domain optimization based on in situ measurement of the bridge’s dynamic displacement histories under trainloads. Field tests are performed on a short-span plate girder railway bridge to measure its displacement response to freight trainloads with different speeds using a low-cost remote vision sensor recently developed by the authors’ group. A FE model of the bridge is developed considering train–track–bridge dynamic interactions. Sensitivity analysis is carried out to investigate the intrinsic effects of parameters of the train, track, and bridge subsystems on the dynamic response of the bridge. It is found that the bridge displacement response is primarily sensitive to the stiffness of the bridge, whereas the acceleration response is affected by many other parameters. This justifies that the bridge dynamic displacement is more suited than acceleration for updating the railway bridge stiffness. Consequently, a model updating approach is proposed using the measurement of bridge displacement response to trainloads. This approach is applied to the short-span bridge to first identify the train speed, followed by the bridge stiffness by minimizing the error between the measured and computed displacement time histories. Furthermore, this paper investigates the frequency characteristics from both the measured and computed displacements. The analysis shows that the trainload does not excite the bridge’s natural modes of vibration because the frequency is much lower than the bridge’s natural frequencies. Therefore, it is difficult to use the modal identification-based FE model updating methods based on the dynamic response measurement. This is commonly the case for short-span railway bridges, which tend to have high natural frequencies. The proposed periodic displacement measurement and time-domain FE model updating can be developed into an effective tool for long-term structural health monitoring of short-span railway bridges.

This paper presents an investigation of the influence of vehicle transverse in-lane position on bridge traffic load effects. To analyze the influence, both finite-element analysis and statistical analysis methods are used, and various technical aspects are studied, including statistics of vehicle-transverse-in-lane positions, histogram of stress spectrum, and equivalent stress range. Four sets of vehicle transverse in-lane position data were collected by weigh-in-motion systems installed on highways in different regions of France. These data sets are statistically analyzed to investigate their distribution features and relationship with vehicle types, loading condition, vehicle speed, and lane profile. Two case studies are presented, which investigate the influence of vehicle transverse in-lane position on load effects of different types of bridge deck. The results show that transverse stresses experienced by these two bridge decks are significantly influenced by vehicle transverse position, and fatigue analysis demonstrates that the fatigue damage in terms of equivalent stress range for critical details of an orthotropic steel deck is very sensitive to the transverse-in-lane position of heavy vehicle traffic.

Multispan simply supported bridges with drop spans and steel bearings were commonly constructed in northern India during the 1970s, and little knowledge about their seismic behavior is available in the literature. Because these bridges are part of the existing transportation network, it is important to assess their seismic fragility and suggest possible retrofitting solutions, if required. A four-span model of such a bridge type was analytically investigated for its seismic response. The critical components of such bridges are rocker and roller-cum-rocker steel bearings, and their lateral force–deformation responses were obtained from nonlinear finite-element analyses. Incremental dynamic analyses were performed for the development of fragility curves for failure of the bridge along two horizontal directions. The damage criteria included either failure of bearings due to exceedance of respective displacement limits or dislodgement of the bridge deck due to unseating. It was observed that seismic demands for drop spans were small, and failure of main-span steel bearings was the primary cause for the bridge failure. Retrofitting of the bridge by replacing steel bearings with unanchored elastomeric pads is shown to significantly reduce the fragility of the retrofitted bridge.

Rapid technological advancements and increasing emphasis on sustainability have provided bridge managers with more opportunities and challenges than ever before. This study presents a decision support system developed to optimize the maintenance/repair management of RC bridge superstructures through advanced technology solutions, with the goal of improving structural safety and serviceability while minimizing the lifecycle cost and environmental impact. In the proposed system, a structural performance assessment module is incorporated with information techniques and sensor networks to achieve intelligent real-time perception, a structural failure risk analysis module is provided that is based on stochastic simulation approaches, and a carbon footprint control module is provided that is based on the lifecycle carbon emission track. Three maintenance strategies based on the different principles are compared through the case study of an existing urban bridge. An optimized maintenance/repair plan decision is achieved with the developed system. The results indicate that the maintenance activities consume almost half of the overall lifecycle carbon emissions, and thus the creation of an optimized maintenance plan that considers environmental impacts is of great significance.

Displacements of railroad bridges under trainloads need to be closely monitored, but conventional displacement sensors have limitations for use in the field. This paper presents a new vision-based sensor system developed for remote measurement of structural dynamic displacements without requiring a specially installed target-marker panel. By implementing a robust object-search algorithm, the displacement can be accurately measured by tracking existing bridge surface features from a remote distance. The accuracy of measured dynamic displacements was first evaluated using a shaking table test. Then field tests were carried out on two railroad bridges subjected to freight trainloads traveling at various speeds. Measurements were taken remotely during the daytime and also at night from different distances with and without a target panel. Through comparison with a conventional contact-type displacement sensor, the high accuracy of the proposed nontarget remote-sensor system was demonstrated in the realistic field environments. From the measured displacement time histories, frequency-domain characteristics associated with the train–bridge systems were further analyzed, confirming the capability of the vision system in measuring high-frequency components. By targeting existing features on a structure without requiring a target panel installed on a fixed location of the structure, the vision sensor system developed in this study provides the flexibility to easily change displacement measurement locations, in addition to other advantages, such as easy setup and no need to access the structure.

The glass cable truss can be used in pedestrian bridges, glass roofs, and glass curtain walls, and its characteristics and components are introduced in this article. Model tests and finite-element analysis (FEA) were conducted to study the static working mechanism of the glass cable truss, and its static performance was compared with that of the single cable and the cross cable truss. The tests and numerical results show that the structural moment is transferred by the chord cables, the shear force is transferred by the glass web plates, and the glass web plates work as a beam when they transfer the concentrated load to the joints of the glass cable truss. Two different materials—namely, the glass web plates and cables—work in a complementary fashion. When subject to a static load, the glass cable truss works elastically and linearly, and the nonlinear deformation appears as a slip of the cable in the clamp apparatus begins. The displacement of the glass cable truss is evenly distributed, and its stiffness is good; therefore, its mechanical performance is better than that of the single cable and the cross cable truss. The fracture of the laminated armored glass could be viewed as a failure of the glass cable truss; however, although the laminated armored glass is broken, the glass cable truss maintains its load-bearing capacity, and the remaining load-bearing capacity can be used as the safety stock.

Effective, economical, and timely repair of RC bridges after a seismic event is crucial. Fiber-reinforced polymer (FRP) composite laminates are one of few options and have several advantages. The paper presents shaking table experimental investigation to evaluate the use of FRP for repairing RC bridge columns with circular cross sections. Two $1/4\text{-scale}$ RC columns were tested in as-built configuration. Both tests had identical geometry and reinforcement details except for the spacing of the transverse bars. One column had closely spaced hoops satisfying code requirements, and the other had larger spacing, representing a shear-critical column. The test specimens were subjected to a series of horizontal and vertical excitations on a shaking table and experienced moderate to high damage. The damaged columns were subsequently repaired with unidirectional FRP composite laminates and subjected to the same set of earthquake excitations. The obtained experimental data showed that the repaired columns achieved higher strength and ductility with lower residual displacements compared with the as-built ones contributing to the resiliency of the bridge system. From this study, it is concluded that the used FRP composite laminates represent a viable solution for the repair of damaged RC bridge columns.

Steel fenders are widely used in China to protect newly constructed bridges from collapse when struck by ships. In fact, steel fenders are more commonly used in China than other types of bridge protection systems. However, few studies have been conducted to verify the performance of these fenders in a collision. To begin this study, a conventional steel fender was investigated using high-resolution finite-element (FE) analyses of ship–bridge–fender collisions. The limitations of the conventional fender were clearly demonstrated. In particular, when a bridge equipped with the steel fender was subjected to a high-energy collision with a vessel, the impact forces and dynamic responses were greater than on those with no fender. Thus, the authors propose a novel fender design composed of steel and concrete to overcome the limitations of the conventional steel fender. In the proposed fender, the panel that comes in direct contact with the errant ship is made of reinforced concrete, and the inner steel members are designed to absorb the impact energy. Detailed FE models were generated to evaluate the performance of the new steel–concrete composite fender under ship-impact loading. Numerical results indicate that the protective performance of the proposed fender is superior to the conventional steel fender.