Journal of Bridge Engineering

More than 40% of the bridges in mountainous areas of Southwest China are constructed with piers having a height of over 40 m. Such piers are characterized by large structural flexibility and distributed mass. To investigate the effects of higher modes on the seismic performance of this class of bridges, shake table tests on two 1/7-scale, tall-pier models were conducted at Tongji University, Shanghai. This paper describes the design, instrumentation, and loading protocols for the tests and discusses and compares the results. Due to the higher-mode effects, the curvature at the pier base and displacement at the pier top of were found to be weakly correlated, indicating that displacement is not a reliable damage measure for tall piers. Moreover, results indicated that the contribution of higher modes can lead to the formation of an additional plastic region at midheight in the piers. However, current seismic design code guidelines are for short to medium-height piers, where the midheight region of piers is assumed to respond elastically; code guidelines are not provided for tall piers. This paper explores the effect of higher modes on the seismic performance of bridges with tall piers and suggests two methods to improve the seismic performance: (1) eliminating the midheight plastic response by including more longitudinal steel, and (2) using more confinement in the midheight region to improve pier ductility and prevent shear failure.

The mechanical stiffness and damping coefficients of a spring-suspended deck section model in still air are conventionally assumed to be constants and can be extracted through free decay vibrations. The extracted stiffness and damping coefficients, indeed, include both mechanical and aerodynamic components. In this study, the vertical and torsional single-degree-of-freedom (SDOF) free decay vibration tests of two typical bridge deck section models were carried out in still air to study the nonlinear vibration characteristics of the sections. SDOF motion equations of the section models were developed on the basis of the equivalent linearization theory. A system identification procedure was developed to extract the amplitude-dependent frequency and damping ratio from the measured acceleration responses. The efficacy of the equivalent linearization and the identification accuracies of the mechanical and aerodynamic parameters were verified by an example. The mechanical parameters (stiffness and damping ratio) and aerodynamic parameters [added mass (or moment of inertia), and damping ratio] of the spring-suspended systems were extracted separately. The aerodynamic damping was found to be the major damping source for the spring-suspended system. The influences of the initial condition, mass (or moment of inertia), vibration frequency, and amplitude on the mechanical and aerodynamic parameters and nonlinearities were thoroughly investigated. The aerodynamic parameters were more sensitive to the vibration amplitude than were the mechanical parameters. The conclusions advance a better understanding of the nonlinear vibration characteristics of bridge deck section models in still air.

Rib-to-deck joints of orthotropic steel decks (OSDs) in steel bridges are susceptible to longitudinal fatigue cracking, which often results in considerable repair costs as well as traffic interruption. To mitigate such cracking, a strengthening method using externally bonded fiber-reinforced polymer (FRP) angles was investigated. Seven OSD specimens were tested and subjected to pure bending to evaluate the effectiveness of the strengthening. The influences of different FRP materials, adhesives, and angle dimensions on the fatigue lives of rib-to-deck fatigue details were experimentally studied. It is demonstrated that the proposed method can significantly reduce the hot-spot stress ranges in the vicinity of welded details and elongate their fatigue lives. Ductile adhesive with higher strength and angles with longer legs would help improve the fatigue performance by delaying the occurrence of debonding between angles and OSD specimens. It is also observed that carbon FRP angles are more effective than glass FRP ones, due to their higher elastic modulus. Besides, FRP angles with stiffeners can further increase the fatigue life of the details due to the additional stiffness, if debonding could be avoided or delayed. Finally, numerical analysis validated the beneficial effect of different FRP-based strengthening measures on the stress intensity factors at crack tips. This study provided a reference to the design and application of externally bonded FRP angles in the strengthening of weld details in OSDs.

Since the September 11, 2001, attack in New York, the number and intensity of terrorist activities around the world have attracted our attention toward infrastructure systems. Also, unintentional explosions resulting from fuel oil (gas) and fireworks in transit can lead to the interruption of the highway system. In addition, crucial bridges in a local war are main targets for hostile forces because they convey military supplies. Bridge piers are main axial bearing components and readily suffer damage under blast loading, so damage modes of bridges in different cases and explosive damage assessments should be studied to provide design advice for protection against explosion. In this paper, numerical models of reinforced concrete (RC) piers are built and verified by the explosion experimental acceleration data and the theoretical ultimate bearing capacity. Based on the verified model, different damage modes of RC piers in three noncontact explosive cases are investigated, in which the locations of explosive centers are at the bottom, the midheight, and the top of the pier. RC piers always experience flexural failure in these cases. The residual bearing capacities of piers before collapse are also studied, and the relations between trinitrotoluene (TNT) mass and residual bearing capacity are fitted by a cubic polynomial, resulting in a downward trend. From damage index and polynomial, the damage extent after blasting can be evaluated.

Perfobond rib connectors (PBLs) are widely applied to transfer the shear force in steel-concrete composite members. To investigate the mechanical behavior of PBL shear connectors, push-out tests were carried out under static loading, and the effects of end-bearing mode, concrete strength, diameter of holes, thickness of the penetrated plate, number of holes, and diameter of penetrating rebar on the shear capacity and shear stiffness were considered. Moreover, the failure modes of all specimens were analyzed, and the test results were compared with the shear strength obtained from previous models. Because of the discrepancies between the test results and the predictive results, a new method for predicting the shear capacity of the PBL connector was put forward according to the deformation compatibility conditions. In addition, an equation was proposed to evaluate the shear stiffness of the PBL connector based on elastic foundation beam theory, and the load-slip curves of the multihole PBL connector were established on the basis of shear stiffness using the numerical regression analysis method. By comparison, it was found that the results determined by the proposed formulas for evaluating the shear resistance, shear stiffness, and load-slip curves agreed well with the test results, and that these formulas can provide good references for the applications of PBL connectors.

Monitoring the weight of vehicles is essential for policymakers to maintain the condition of bridges. In the group of methods for weighing vehicles, bridge weigh-in-motion (B-WIM) systems are among the most prominent and have several advantages, such as convenience and no interruption to traffic. However, they still have one drawback in that, for most systems, a vehicle’s velocity and wheelbase need to be given in advance. Currently, this problem is usually solved by adding an axle detector, which leads to higher costs. Under such circumstances, this paper presents an alternative B-WIM system to measure a vehicle’s velocity, wheelbase, and axial and gross weight merely based on a single set of long-gauge fiber Bragg grating (FBG) sensors without additional devices. To test the effectiveness of this method under various conditions, a vehicle-bridge interaction (VBI) system simulation was performed based on the result of an indoor experiment. Also, an in situ test on an expressway bridge was performed to initially verify its feasibility. The results showed that this method can achieve its function with good accuracy under various conditions.

Coupling connections and bearing supports have been widely used in high-speed maglev guideways. Accurate identification of their mechanical properties is necessary for guideway design and research. This paper presents an approach to estimate the rotational stiffness of the coupling connection and the vertical stiffness of the bearing support of maglev guideways. First, the dynamic properties of the guideway were identified from the measured data using the operational modal analysis method. Then, a finite-element (FE) model was established to analyze the influence of the stiffnesses on the dynamic performance of the guideway. The practical stiffnesses were estimated by using the presented model-updating method and sensitivity study. The accuracy of this approach was further investigated by a comparison between the predicted and measured guideway responses. Finally, a parametric analysis was conducted to study the effect of the stiffnesses on the dynamic responses of the train-guideway system. The results indicate that the stiffnesses have an important influence on the dynamic responses and considering them in the simulation of the maglev train-guideway system can improve the prediction accuracy. Thus, for the accuracy of the design and research of the maglev guideway, these practical stiffnesses should not be ignored.

High-sided vehicles experience sudden changes in aerodynamic forces when passing through the wake of towers of bridges under crosswind. This may lead, in the worst case, to vehicle rollover or undesired lane changes, thus representing a critical concern for running safety. Computational fluid dynamics (CFD) is used to simulate and investigate the aerodynamic forces acting on a heavy goods vehicle (HGV) during the overtaking maneuver of a bridge tower when the vehicle is passing through the wake of the pylon generated by lateral wind. Dynamic mesh techniques are adopted to simulate the relative velocity between the vehicle and the infrastructure. Such an approach can be used to design lateral shields to be installed on existing infrastructure, reducing the risk of a wind-induced accident involving overturning of the HGV. The validation of the moving mesh strategies is performed comparing numerical and wind tunnel test results in terms of aerodynamic forces and moments acting on a stationary vehicle for different exposure angles.

Adequate prediction of the concrete bridge deck deterioration rate is necessary for maintenance and rehabilitation decisions. The stochastic deterioration of bridge decks can be most accurately modeled with a time-based probabilistic approach. In this work, a semi-Markov time-based model, based on accelerated failure time (AFT) Weibull fitted-parameters, was used to estimate the transition probabilities and sojourn times for the deterioration of concrete bridge decks. Approximately 30 years of in-service performance data for over 22,000 bridges in Pennsylvania were used in the model development. The proposed approach attempts to relate deck deterioration rates to various explanatory factors, such as structural system attributes, average daily traffic (ADT), route type, and environmental conditions. The following factors were found to be statistically significant with respect to the rate of bridge deck deterioration: type of rebar protection, continuous versus simply supported spans, overall bridge deck length, number of spans, bridge location, type of overlay, and whether or not the deck was located on interstate routes. Furthermore, the effects of remediation on bridge deck deterioration and service life were also evaluated and quantified, based on in-service performance data.

A long-term load test of 420 days was performed on three prestressed steel–concrete composite continuous box beams (non-prestressed, partly prestressed, and fully prestressed) to investigate the combined effects of sustained load, shrinkage, creep, and prestressing. Several time-varying parameters, such as deflection, concrete strain, prestressing force, support reaction, and relative slippage between the concrete slab and the steel box beam, were monitored in the test. The long-term performance of the prestressed beams that was developed using a special law increased and decreased the support reactions at the middle and end piers over time, respectively, due to the distinct configuration of prestressed strands (i.e., installation was only at the negative moment area). The growth rate of the deflection of the prestressed beams was slightly greater than that of the deflection of the non-prestressed beam. Moreover, cracking at the negative moment region significantly accelerated the development of the relative slippage of the non-prestressed beam. A calculation model of long-term deflection based on classical theories was proposed to theoretically analyze the measured data and provide valuable insights for future research.