Journal of Bridge Engineering

In the past several decades, the inverted-T bent caps (ITBCs) have been frequently used as an innovative type of bridge superstructure worldwide. In some specimens, the bent caps have to be skewed to meet the landscaping requirements. However, the traditional design of ITBC simply flares the transverse shear reinforcements out in skewed ITBCs, which brings significant inconvenience. In order to reduce the construction cost, an alternative skew arrangement with all the reinforcement arranged in parallel throughout the bent cap is recently adopted by Texas Department of Transportation (TxDOT). To investigate the feasibility of this technique, the shear reinforcement arrangement, as well as three other major parametric variations: shear reinforcement spacing, skew angle, and loading position, are studied regarding their effects on the behavior of skewed ITBCs. A total of 17 numerical models are simulated, among which three specimens are verified and validated by experimental results. The same modeling scheme and material parameters are applied to the remaining specimens. The analytical results indicate that the load–displacement curves of ITBCs are not notably changed by the proposed skew reinforcement arrangement, while the reinforcement spacing affects the ultimate capacity and ductility to a limited extent. The increase of the skew angle significantly affects the performance and failure modes. Meanwhile, a modified practical equation for the edge extension length of skewed ITBCs is proposed based on the parametric analysis of varying loading positions.

This study addresses the effects of vertical motion on the nonlinear flutter response of a double-deck truss girder based on section model wind tunnel tests. Six dynamic systems with the same bridge deck section were tested under various wind angles of attack. The nonlinear flutter characteristics under different cases were fully captured. The potential effect of vertical motion on coupled nonlinear flutter was investigated by conducting an additional single-degree-of-freedom wind tunnel test. The aeroelastic mechanism concerning the vertical motion that affects the nonlinear flutter performance is revealed by qualitatively estimating the contribution of coupled aerodynamic damping to the total damping. Results showed that vertical motion introduces noticeable negative damping to the system thus increases vibration amplitude and reduced onset wind speed at lower wind angles of attack, while the vertical motion will be less important at large wind angles of attack since its contribution to the total damping is relatively small. Finally, a preliminary method is proposed to identify nonlinear aerodynamic damping, which helps to understand the participation of vertical motion on coupled nonlinear flutter and to interpret the amplitude dependence of nonlinear flutter.

Ultrahigh-performance concrete (UHPC) offers significant potential to address a variety of needs in bridge design, construction, and performance enhancement. Bridge owners have shown willingness to embrace novel solutions that could address specific challenges related to the cost, speed of construction, durability, and service life of their projects. There are hundreds of bridges worldwide that, largely in the past decade, have utilized UHPC. These applications range from minor field-cast closures to precast segments for long-span bridges to kilometer-long bridge deck overlays on a signature structure. The objective of this paper is to promote the application of this class of cementitious material in bridge engineering by presenting the progress that has been made in different regions of the world in the past two decades. Today, UHPC is being widely used in Malaysia to design and construct many bridges of different types and spans as they build out their roadway network. In South Korea, the unique characteristics of UHPC are being utilized to advance the state-of-the-art in long-span bridges. The French were early adopters and pioneers in building a strong foundation for using UHPC in a variety of bridge applications. In Switzerland, UHPC is employed to address major bridge rehabilitation needs. The United States bridge sector has embraced UHPC for a variety of field-cast connections. Current research and development efforts are promoting the use of UHPC in major rehabilitation projects and construction of primary bridge components. The adoption of UHPC solutions into the bridge sector is progressing rapidly because of the unique opportunities provided by the strength and durability of the material. It is expected that additional innovations and refinements of solutions will occur as knowledge of the material proliferates.

A numerical approach based on potential theory and the boundary element method (BEM) to study the interaction between surface waves and a flexible bridge pier will be developed. The conventional hydrodynamic approach in naval architecture for floating rigid structures will be extended to consider the hydroelastic problem of a deformable bridge pier with arbitrary cross sections. The Euler–Bernoulli beam constitutive model will be incorporated into the hydrodynamic equations to fully couple the motions of fluid and structure and the deformable boundary condition of the pier surface will be expressed in a fashion of structural mode superposition. The numerical results are validated against analytical solutions and a flexible bridge pier with an elliptical section is used as a study case. Based on the proposed approach, the structural responses of base shear force, moment, and pier top displacement subjected to regular and stochastic waves will be investigated. The wave runup, as well as the distribution of wave field, will be characterized. The effect of selected modes and water depth on the responses will be carefully examined. The results show that the interaction effect has an overall influence on both the structural responses and wave fields. The interaction effect might remarkably increase the stochastic responses of base shear force, moment, and pier top displacement, as well as the wave runup, on the pier surface. The increasing water depth dramatically enhances the interaction effect. The proposed approach reaches good convergence by employing the first five structural modes.

Typical design and installation methods for corrugated steel culverts involve consideration of a minimum burial depth and most current North American design codes consider failure only due to excessive circumferential force in the conduit walls (i.e., hoop thrust). However, recent studies have shown that the bending moment is often the more dominant behavior for corrugated steel culverts at shallow cover. To address this issue, an elliptical corrugated steel culvert was tested under simulated vehicle loading at depths ranging from 0.1 to 1.2 m. The results show that, under a wheel pair load, a peak negative bending moment, and thrust, force is consistently developed at the crown with positive bending moments adjacent to the crown and near the shoulders. When the flexural and circumferential force results are extrapolated to the yield point and compared, the bending moment values are up to five times larger than the yield limit while thrust values are only 60% of the limit. The test results suggest that bending moments should be considered during the design and installation of corrugated steel culverts at shallow cover.

Current seismic design procedures such as Caltrans Seismic Design Criteria (2013, 2019) are continuously evolving to develop methodologies for conducting seismic analysis to achieve more accurate estimations of the demands corresponding to target hazard levels. The most widely used conventional procedure to conduct seismic demand analysis is to scale recorded or simulated ground motions to achieve the intensity measure (IM) associated with the target hazard level. The scaled ground motions are then used to conduct the nonlinear time-history analysis (NLTHA) of the bridge models, and the obtained response values are then utilized to design the bridge structure. This study systematically shows how to make use of site-based synthetic ground motions for assessing the seismic demands of Caltrans ordinary bridges in the context of performance-based design. Within this framework, catalogs of synthetic ground motions representing a time-span of 100,000 years for seven sites in Southern California are generated; the ground motions are then used to conduct NLTHA of four Caltrans standard ordinary bridge structures (denoted as A, B, C, and F). Using the results of the analyses, statistical methods of Hypothesis T-Test and KL-Divergence are applied to obtain the optimal number of ground motions and ground motion intercept angles that can statistically replicate the results of simulated ground motions that naturally possess the IM of the target hazard level. Scaling relations are provided that convert engineering demand parameters (EDP) associated with IM for a target hazard level with EDPs directly representing the target hazard level.

In a chloride-containing environment, steel bridges that use carbon steel can become corroded and require periodical inspection, repainting, and replacement to maintain an acceptable level of safety and serviceability during their service life. In recent years, several new bridges in the United States have adopted corrosion-resistant steels (i.e., ASTM A1010). Although corrosion-resistant steel can result in a substantial reduction in maintenance costs, its production cost is much higher than carbon steel. From a life-cycle cost perspective, the circumstances under which corrosion-resistant steel is economically advantageous remain unclear. The life-cycle costs that account for the uncertainties associated with traffic loads, including resistance, corrosion propagation, and maintenance activities further complicate this problem. The objective of this paper is to investigate the acceptance of corrosion-resistant steel in the design of steel girder bridges based on expected utility theory (EUT). The methodology developed will be exemplified on a steel girder bridge. Two types of utility functions will be used to characterize the preference of decision makers under uncertain conditions. The analysis results indicate that A1010 is the preferred solution for bridges in aggressive environments, or with severe failure consequences, or both, when the discount rate is low.

The main design principles for girders in cable-supported bridges have not changed significantly over the past 60 years, and are limited in further development. The design concept suffers from substantial fatigue issues, and will be challenged by self-weight in future very-long bridges with main spans beyond 2 km. In this work, truss topology optimization, including global and local stability, is applied in a conceptual study of new weight-reduced designs for girders in cable-supported bridges. The methods are based on finite-element limit analysis and convex optimization. A single section of a continuous girder, subject to local and global loads, is optimized to minimize weight while fulfilling constraints on stresses as well as global and local stability. The optimized designs, significantly different in layout from the conventional, show initial weight savings of up to $45\text{\%}$ compared with the present design. Further parameter studies indicate potential weight savings of up to $54\text{\%}$.

External post-tensioned tendons in concrete segmental bridges have had strand corrosion failures due to grouting deficiencies such as voids or bleed water. Nondestructive assessment of the grout condition is thus often needed, preferably by a cross-section imaging method. Here, a magnetic sensing approach to image the position of the steel strand bundle is combined with an electric impedance method to evaluate the condition of the grout space. Both are embodied in a device that images the tendon’s cross section. The magnetic sensor travels around the circumference of the tendon and measures the force of attraction to the steel strands from which an image of the strand pattern inside the tendon is created. Simultaneously, a traveling plate rotates around the tendon, and variations of the electric impedance between the plate and strands identify grout deficiencies. The impedance and strand position data create a complete color-coded image of the tendon cross-section flagging grout deficiencies. The approach was validated by experiments with tendon specimens with known deficiencies and under field conditions. The method is rapid, economical, easy to replicate, with a small and safe device not requiring specialized operator training.

Large-scale connecting segments can provide reasonable load transition in hybrid girders, and have been broadly used in long-span cable-stayed bridges. However, the large volume of concrete in connecting segments bears a high cracking risk at an early age in the life of the concrete. In this study, field measurement and numerical simulation were performed on a large-scale connecting segment with early-age concrete to investigate its thermomechanical coupling behavior. Based on the thermal behavior modeling, mechanical behavior modeling was subsequently carried out by considering the comprehensive effects of temperature history and actual age on the development of the hardening concrete’s mechanical properties. Both measurement and simulation show that the peak temperature can reach about 90°C, which is far beyond expectation, and high cracking risks exist in the external surfaces of concrete in the monitored connecting segment. To reduce the cracking risk, methods of multilayer pouring and cooling pipes were then adopted to quantitatively evaluate the anti-cracking effects. Results show that embedding cooling pipes in the thick concrete slabs can significantly lower the peak temperature, further reducing the cracking risk of the concrete.