Journal of Bridge Engineering

To enhance the normal service adaptability and seismic resistance performance of isolation continuous bridges, a superelastic-sliding lead rubber bearing (SSLRB) isolation system was developed by incorporating shape memory alloy (SMA) wires with sliding-LRB. A parametric design method was proposed to design the SMA wires in the SSLRB system for the optimum performance of bridges in terms of suppressing the displacement response and in the meantime limiting the increment of the force response in piers. A parametric investigation was performed to obtain the SMA parameters as a critical part of designing the SSLRB system. The seismic responses of bridges isolated by SSLRBs were investigated and compared with those of the same bridges with the conventional sliding-LRBs. The efficiency of the SSLRB system was further demonstrated by conducting a case study. Results verified the effectiveness of the suggested method for optimizing the parameters of SMA wires and the SSLRB system for response control. The displacement responses (e.g., residual displacement) can be effectively mitigated, and in the meantime the seismic demand of the piers can be suppressed. This study demonstrates that the proposed SSLRB isolation system can maintain stable re-centering performance against near-fault earthquakes.

Distortion-induced fatigue cracking is a primary maintenance and structural safety concern in steel bridges built prior to the 1980s in the United States. Manual, hands-on inspections are currently the primary method departments of transportation and other bridge owners use to identify and quantify fatigue cracks. To improve the efficacy of fatigue crack inspections, previous research has proposed and examined numerous fatigue crack detection approaches, including both user-implemented technology and structural health monitoring methods. However, these approaches typically require human presence and active participation at the location of interest or prolonged mechanical contact and continuous monitoring of the structure. This limits the effectiveness and flexibility of these approaches for inspecting a large number of fatigue-susceptible regions found on steel bridges. Recently, vision-based sensing technologies have been explored for applications related to damage detection and health assessment in civil infrastructure, as they offer the benefits of being low cost, noncontact, and deployable without human presence at the specific region of interest. This paper presents a digital image correlation-based methodology developed from in-plane compact fracture specimens for the detection and quantification of fatigue cracks. The effectiveness of the proposed methodology is further evaluated through experimental tests of a fatigue crack on a large-scale steel girder-to-cross-frame connection, similar to the out-of-plane fatigue cracks commonly found on steel highway bridges. Results indicate that the digital image correlation methodology can adequately characterize fatigue cracks, both in-plane and out-of-plane, in terms of crack length. This quantification from a noncontact inspection technology has the potential to lead to future automation of steel highway bridge fatigue inspections.

Ultrahigh-performance concrete (UHPC) is increasingly recognized as being a better material in girders, and a composite prestressed UHPC-normal concrete (NC) girder is a better choice to be used for strengthening existing members and precast concrete constructions. In this study, 10 composite girders and 1 pure NC girder were fabricated and tested to investigate the effect of UHPC heights, prestress levels, and NC compressive strengths on the flexural properties of composite girders. The test results show that increasing the prestress level and UHPC height both delayed the formation and propagation of cracks. Compared with the pure NC girder, the mean crack spacing of composite girders decreased, and the number of cracks was considerably higher for the incorporation of UHPC. Adding UHPC into girders can considerably increase the stiffness and ductility of members. An analytical model based on the finite strip method was developed by considering the constitutive models of materials. The agreement between the predicted results and the experimental data is sufficient, indicating that the analytical model is suitable for analyzing composite girders. Additionally, the influencing factors of composite UHPC-NC girders were comprehensively investigated using the theoretical model. Finally, the reasonable range of the UHPC height is determined by the analytical results. The experimental results revealed the flexural behavior of large-scale composite prestressed UHPC-NC girders, including the failure modes, the load–deflection relationship, the concrete strain, and the crack pattern. The analytical model provides a powerful tool for the prediction of flexural behavior of composite girders, which would be helpful for the design analysis of composite girders.

Bridge damage and failure due to the effects of hurricane-generated storm surge is well documented. Over the past ten to fifteen years, research efforts have been undertaken to improve understanding of storm surge effects on bridges and explore how best to mitigate these effects. This paper documents development and assessment of a finite element analysis framework named AMBUSH that calculates forces applied to bridges subjected to storm surge loading. AMBUSH was shown to be capable of calculating reaction forces for a Biloxi Bay Bridge span for 14 storm events representing 5 storm categories. Simulation results compared favorably to American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications that were released relatively soon after Hurricane Katrina. Deviations of AMBUSH could be applied to other bridge or structural engineering problems with manageable reconfiguration.

Design for slender high-strength concrete (HSC) bridge compression members (columns, piers, and piles) reinforced with glass fiber-reinforced polymer (GFRP) has yet to be addressed in the relevant American and Canadian codes and guidelines. Including such provisions undoubtedly requires a comprehensive assessment of the structural performance of such members, as well as a definition for the slenderness limit below which second-order responses can be discarded. Consequently, full-scale slender GFRP-HSC columns with a concrete compressive strength of 80 MPa and measuring 2,500 mm in height and 305 mm in diameter were prepared and tested at four eccentricity levels (0%, 16%, 33%, and 66% of the column size). The influence of HSC on the behavior of slender GFRP-HSC columns was also assessed with respect to reference normal-strength concrete (NSC) counterparts. Moreover, the effect of two different longitudinal GFRP-reinforcement ratios (3.28% and 4.66%) on the performance of the test specimens was investigated. The test results herein indicate the ability of HSC and GFRP reinforcement to improve column strength and to maintain stability at various loading stages. An analytical second-order model was then developed to extend the research program to include a wide range of parametric studies. The developed model was validated against the test results for 47 FRP-HSC columns selected from the current study and the literature. Lastly, the applicability of the current slenderness limit to HSC columns was verified and a modified slenderness limit was proposed to account for HSC columns with compressive strengths up to 125 MPa.

Many bridge deck slabs in Europe are rated insufficient load-carrying capacity in shear and punching according to the Eurocodes. In the past, assessment models have mainly been developed from laboratory studies that simplified real-world conditions. Large-scale or full-scale field experiments are needed to validate more recent improved models. The goal of this study is to calibrate improved models using data obtained from a full-scale bridge deck slab shear test; the objective is to exploit and share our findings and to make recommendations for the planning, design, and implementation of such a complex experiment. Full-scale destructive tests of a 55-year-old reinforced concrete bridge deck slab on prestressed concrete girders were conducted to calibrate a model used to assess existing bridges. Concrete properties were also tested to evaluate the condition of the bridge. Results show that both the load-carrying capacity of the bridge deck slab and the strength of the concrete were much greater than were assumed in design. Finite-element analysis of the parameters governing loading positions and prestress in the girders showed that arch action and boundary condition simplification had important effects on shear distribution.

Early-age unexplained cracking in concrete structures is always a concern, as this signals the occurrence of uncontrolled volumetric changes. A study to investigate the effects of early-age microcracks on the service life of in-service prestressed-concrete girders was conducted. The temporal evolution of the cracks during a two-year period in 13 full-scale prestressed, precast girders was studied. Five of the girders were not subjected to external loads, whereas the remaining eight girders were in-service and under external loads. The results show that during the time frame considered, exposure conditions and the presence of pre-existing cracks had a more significant impact on the growth of microcracking than the effect of external loads, even when a protective coating was applied to the girder surfaces. Furthermore, the study showed that the temporal behavior of cracks can be better understood when both crack width and cracking density are taken into consideration.

Comprehensive bridge design should consider simultaneous actions of wind and temperature. The current load combination method of directly superposing extreme wind and temperature actions ignores the correlation between wind and temperature, resulting in too conservative bridge load estimates, and limiting the further development of the bridge span. Therefore, this paper proposes a method to determine the joint distribution of wind speed, wind direction, and air temperature actions on long-span bridges based on trivariate metaelliptical and Plackett copulas. First, the technique of establishing the trivariate joint distribution via trivariate metaelliptical and Plackett copulas is introduced. Next, the conditional joint distributions of wind speed and air temperature under the specific wind directions are derived from these. Using the concept of conditional bivariate Kendall return period (KRP) proposed in this paper, the conditional KRP isolines of wind speed and air temperature for specific wind directions are constructed. Then, conditional joint estimates of wind speed and air temperature actions for several specific wind directions are obtained using the following principle: the conditional bivariate design return period should be equal to the conditional univariate one. The method feasibility is verified by the case study of the Changtai Yangtze River Bridge in China, which is currently under construction and will be the largest cable-stayed bridge in the world. The results show that the joint actions of wind and temperature on the bridge greatly reduce as compared with the simple superposition of extreme wind and temperature actions specified in the design code. Moreover, a significant contribution of wind direction in the above joint distribution on the large-span bridge load is proved.

The time-varying average and differential temperatures may significantly change the performance of steel truss bridges, which may increase the difficulties for bridge design, construction, and maintenance. Because hundreds of steel members usually have different geometric dimensions, the temperature effect on the steel truss bridge is extremely complicated, and no general formula is available for predicting temperature-induced responses. In this study, the 2-year field monitoring data collected from a 108-m-long steel truss bridge are utilized to investigate the temperature effects on strain responses. In particular, the relationships between temperature-induced stress and standard temperature actions are investigated using correlation analysis and numerical simulation. Accordingly, the simple general formula is provided to capture the relationships between temperature distributions and temperature-induced strains. The accuracy of the proposed formula is verified using the field monitoring data of the box-shaped members and the H-shaped members. The notable vertical temperature gradients are usually observed in box-shaped members, which can generate larger thermal strain responses than H-shaped members. The results of this study could provide a simple and relatively general solution to predict the temperature-induced strain of steel truss bridges. Meanwhile, this conclusion drawn may provide references for the design and maintenance of steel truss bridges.

Several bridges now require widening owing to the continuous development of road transport. However, the standard of traffic load in design specifications has been enhanced. Consequently, old bridges may not meet the safety requirements of current design specifications and, therefore, must be reconstructed or retrofitted. However, the old structures in widened bridges carry fast-lane traffic loads, which are relatively low due to uneven multilane traffic loads. This paper reports a case study conducted on a Chinese highway widening project for comprehensively evaluating the structural safety of multislab widened bridges using code-based deterministic and reliability-based probabilistic approaches. In the deterministic evaluation, previous and current Chinese bridge designs and other national codes were employed. Meanwhile, in the probabilistic assessment, an uneven multilane truckload modeling was implemented based on site-specific traffic data. Subsequently, bridge safety under normal traffic conditions with all lanes open and occasional traffic conditions with lane closure was investigated. The results indicate that most old slabs, especially those closer to medial dividers, are unsafe under the current Chinese design specifications. However, a site-specific assessment under normal traffic conditions indicates that these old slabs possess adequate security reserves, except that the side slab close to the junction requires safety. Further analyses conducted with occasional traffic conditions demonstrated that closing fast lanes does not affect the safety of slabs. Conversely, closing slow lanes significantly affects the safety of inner old slabs, which should be prohibited or addressed with strict weight restrictions. These results can be beneficial for future bridge widening projects.