Journal of Bridge Engineering

Precast concrete segmental beams (PCSBs) with external tendons have become more and more popular all over the world for achieving the advantage of rapid construction. This paper focuses on the effects of shear span-depth ratios, joint types (monolithic, dry, and epoxy), joint number, and joint location on the shear behavior of PCSBs with external tendons. A total of 14 specimens with external tendons were fabricated and tested, which included three monolithic specimens, six segmental specimens with dry joints, and five segmental specimens with epoxy joints. The crack propagation, failure mode, deflection, and stresses of prestressing strands were recorded. It was found that joint location plays an important role in the shear strength of PCSBs with dry joints when compared with monolithic specimens. The failure processes and failure modes of PCSBs were independent of joint types. The experimental results also revealed that the joint number had an effect on the deflection and stress of external tendons. Specifically, the shear behavior of PCSBs with dry joints had no evident difference from that with epoxy joints. The strength of beams with external tendons was predicted using the strut-and-tie model. AASHTO and Chinese codes conservatively predicted the shear strength of PCSBs with external tendons when the shear span-depth ratio was less than 2.5. The actual prestressing force in external tendons can accurately predict the ultimate strength of beams with external tendons at different shear span ratios.

This numerical study aimed to develop probabilistic seismic demand models for RC bridge columns, vulnerable to failure due to lack of flexural ductility, that have been retrofitted using a newly emerging active confinement technique. The new technique involved the application of thermally prestressed spirals made of a shape memory alloy (SMA) at the plastic hinge region of the columns. Columns with different fundamental time periods were chosen, and retrofitting schemes corresponding to three confinement levels were explored. The performance of the retrofitted columns under ground motion records was assessed using four demand measures (DMs)—maximum drift, residual drift, energy-based concrete damage index, and low cycle fatigue based steel damage index The suitability of eight intensity measures (IMs) for the development of probabilistic demand models to predict the DMs was explored. The final demand models, developed using IMs that predicted the DMs with least dispersion, were presented and compared to understand the effect of lateral active confinement. The results indicated that increasing the confinement reduced the damage in concrete substantially, whereas the damage associated with low-cycle fatigue of steel was also reduced. Higher levels of active confinement were also seen to be effective in reducing the residual drifts of long-period columns.

Composite deck systems composed of a steel deck and a reactive powder–concrete (RPC) layer are widely used in long-span bridges because of their satisfactory crack resistance and fatigue resilience. However, durability problems usually appear at the interface between the wet joint and the precast RPC layer. In the present study, a dovetail-shaped RPC wet joint is proposed to improve crack resistance. An experimental study was conducted to describe the mechanical behavior of the dovetail-shaped RPC wet joint under a negative moment, including crack development, strain distribution, and load–deflection response. A finite-element model validated with the experimental results was built in a finite-element program for supplementary parametric analysis. The reinforcement ratio and the inclined angle of the dovetail-shaped area were quantitatively investigated. Design parameters are recommended according to the parametric analysis.

Bridges with hybrid sliding-rocking (HSR) columns offer an attractive alternative for accelerated construction in seismic regions. HSR columns include internal unbonded post-tensioning, end rocking joints, and intermediate sliding joints over the column length. As such, HSR columns introduce new design variables, such as the number and distribution of sliding joints, the coefficient of friction at the sliding joints, and the joint-sliding amplitude, compared to conventional cast-in-place systems. Force-based seismic design methodologies are difficult to apply because of the lack of response modification factors—R-factors—accounting for the various combinations of these design variables and the corresponding nonlinear responses. To address this challenge, this paper introduces a capacity spectrum seismic design (CSSD) methodology for bridges with HSR columns that holistically accounts for all design variables and directly utilizes the resulting nonlinear system properties. A key component of the proposed CSSD methodology is the development of a simplified model for the monotonic and cyclic quasi-static pushover analysis of HSR columns. The simplified analysis model was validated through experimental data, and was further used to explore the effect of major design variables on the response of HSR columns. Furthermore, this paper explores the existence of multiple performance points (i.e., multiple solutions) predicted by the capacity spectrum method for given ground motions and provides a tracking algorithm to identify them. The proposed CSSD methodology was validated through both experimental data and computational studies. The simplified analysis model was capable of capturing the fundamental response mechanisms of HSR columns. The proposed CSSD methodology provided reasonably accurate predictions of peak displacements and base shear. Larger discrepancies were observed in the comparisons with experimental data (by overpredicting the response by 25%) due to the existing damage to the test specimen from prior testing, which could not be accurately captured by the simplified model, and because the simplified model does not account for variations of the vertical load due to vertical excitation.

This paper develops a simplified method to quantify the effects of liquefaction-induced lateral spreading on bridge responses, expressed as the response modification factor of the column drift ratio under seismic shaking. Using the newly developed global dynamic p-y analysis procedure, nonlinear time history responses were obtained for a benchmark bridge–foundation–soil system when it was subjected to a suite of input motions under seismic shaking (nonliquefaction) and lateral spreading (liquefaction) cases. Under seismic shaking, the column drift correlated well with the peak acceleration of the nonliquefied input motion at the ground surface in addition to the dynamic characteristics of the bridge. Under lateral spreading, and due to its largely static loading nature, the column drift was related linear logarithmically to the crust layer energy content imposed on the pile foundation at bridge piers, which was a function of the cumulative absolute velocity of nonliquefied ground motion at the surface, and lateral resistances and geometric parameters of soil layers. By normalizing the column drift under the lateral spreading to that under the seismic shaking, a closed-form expression was derived for the response modification factor. Additional multipliers were identified in the proposed formula to account for different bridge designs, foundations, and soil conditions. The proposed method was validated against the simulation results for eight randomly selected bridge cases. It was demonstrated that the method can effectively estimate the column drift due to lateral spreading, which takes into account of dynamic characteristics of bridges, soil and foundation parameters, as well as ground motion variations.

Slender bridges, often built in harsh coastal environments, may experience dynamic loadings from strong winds and high waves. Busy traffic is expected during normal operating conditions and during evacuation events before extreme weather or emergency-related conditions. Understanding the dynamics of the complex vehicle-bridge-wind-wave (VBWW) system is critical to the safety of both vehicles and bridges. For the present study, an analytical model was developed to evaluate the dynamic performance of the coupled VBWW system. First, the bridge was discretized using the FEM, and vehicles were modeled as mass-spring-damper systems to build the equations for the dynamic equilibrium. Then, the time histories of the wind and wave around the bridge site were simulated as stochastic random processes and generated using the spectral representation method. The dynamic system integrated the conventional buffeting analysis for the wind–bridge interaction, the quasi-static analysis for the wind–vehicle interaction, and the dynamic interaction between the moving vehicles and the bridge according to the geometric and mechanical relationships between the vehicle tires and the bridge deck. In addition, the interaction between the wave and bridge group-pile foundation was included in the system using the Morrison equation. Finally, for demonstration purposes, the dynamic responses of a coastal slender cable-stayed bridge under different vehicle-, wind-, and wave-loading scenarios were analyzed. The case study results indicated that the lateral vibration of the prototype bridge can increase by 13.6–82.4% for different components of the bridge under different lateral incident wave scenarios with varied wave heights and frequencies. The coupled VBWW results also indicated that wind load was the predominant dynamic response of both the vehicle and bridge with slight loading effects from the waves.

Clustering stud shear connectors with a narrow spacing to form the group studs is useful for concrete slab prefabrication in steel-concrete composite bridges; however, the group studs fatigue design has not been specified in detail so far because the related tests and results are not enough. In this case, 13 corresponding cyclic push-out tests were executed. The test results showed that the stud root fracture and the nearby concrete damage were the main fatigue failure modes. Arranging studs in a group made the cyclic stud stiffness degradation and the slip creep develop faster, thus lowering the stud fatigue life. Moreover, the group stud fatigue lives as well as some other related literature results were compared with the S-N curves of AASHTO, Eurocode, and Japan Society of Civil Engineers (JSCE) codes, which are mainly for one single stud. In general, the evaluations based on the Eurocode and AASHTO were relatively conservative. The JSCE evaluation may have less safety redundancy compared with the other two specification-based estimations. Furthermore, a parametric analysis was executed for understanding the mechanism of the group arrangement effect on the stud fatigue behavior. The severer fatigue damage accumulation and uneven distribution among the studs in a group were considered to be the main unfavorable factors in the fatigue behavior.

Vibration energy-harvesting devices are increasingly becoming more efficient and useful. The performance of such devices for energy harvesting from vibrations of civil infrastructure can be theoretically quantified, and energy harvesting under harmonic loadings can be validated experimentally. Experimental validation of such devices for civil infrastructure applications, such as bridges, remains an important but more complex and challenging issue, in part due to the more uncertain nature of the dynamic response of structures under operational conditions and problems with access for such testing. Lack of existing experimental benchmarks is also a major obstacle behind adopting this technology for bridges. This study presents a laboratory-based experimental procedure through which a piezoelectric energy harvester was experimentally verified for rail bridges in their operational condition with trains traversing them. A general experimental arrangement required for validating a piezoelectric cantilever energy-harvesting device is presented, along with the fabrication of a prototype device and detailed experimental setup. A model bridge undergoing loadings from an international train fleet was chosen, and the acceleration response from the bridge was used as the excitation source for the energy-harvesting device. Numerically estimated performances of the energy harvester were validated by experimentation for a range of trains. The method is applicable for validating energy harvesting from arbitrary vibrations of built infrastructure within the laboratory environment without the need of scaling. The device and related experimental procedure will serve as a benchmark for similar unscaled tests within a laboratory environment and can be useful for assessing devices or their applications in monitoring built infrastructure under realistic conditions without the need for deployment on site.

Traffic monitoring, particularly on the gross vehicle weight (GVW) and axle weights (AWs) of heavy trucks, provides valuable information for the design and performance evaluation of bridges. Bridge weigh-in-motion (BWIM) is a recently developed technology that uses the bridge as a scale to estimate vehicle weights. For BWIM systems, the acquisition of vehicle speed and axle spacing (AS) is a prerequisite for accurate identification of the AWs and GVW. Traditionally, axle detectors are placed on the road surface to detect vehicle axles. However, axle detectors are not durable due to their exposure to the traffic. Also, their installation and maintenance also cause disruption to the traffic. For these reasons, the concept of the nothing-on-road (NOR) BWIM is proposed. Most existing NOR BWIM systems require additional sensors for axle detection, which limits their applicability. In this paper, a novel equivalent shear force method (ESF) is proposed to identify vehicle speed and AS by using the flexural strain signal acquired from the weighting sensors. Compared with the existing NOR BWIM systems, the proposed method does not require additional sensors for axle detection, making it desirable for commercial BWIM systems. The effectiveness and accuracy of the proposed method are demonstrated through numerical simulations and validated through an experiment using scaled model tests. Parametric studies are also conducted to investigate the effects of various factors on the accuracy of the proposed method.

This case-study article aims to share the field-test observations of a real-world cable-stayed bridge with the research community of bridge-weigh-in-motion to address the challenges of axle identification. Various structural members of the bridge, including cables, girders, and the deck, were instrumented with strain gauges at different locations to measure the axial, bending, or shear strain responses. Numerous field tests were conducted by running light and heavy vehicles traveling at different speeds, in different traffic directions, and in different lateral locations on the bridge. Because the identification of closely spaced axles is important to ensuring true classification of the vehicles, vehicles with tandem- and tridem-axle configurations were adopted in the field test. The study aimed to identify the sensor arrangement through which the closely spaced axles can be reliably detected regardless of the speed, traveling direction, and lateral location of the vehicle on the bridge. It was found that the axial strains on the cables and bending strains in the girders provided the global response of the structure; hence, they were unable to identify the closely spaced axles. In contrast, it was observed that the longitudinal strains under the deck were able to identify the closely spaced axles, provided they were positioned as closely as possible to the wheel path. Finally, the shear responses at the end of the span were able to identify the closely spaced axles irrespective of the traveling direction and lateral location of the vehicle. In this study, due to the testing limitations, including the short span of the bridge and the presence of a roundabout at one end of the bridge, it was not feasible to maintain a constant speed; therefore, identification of axle weight and axle spacing, which requires a constant-speed assumption, is not discussed.