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A new experimental investigation approach of a moving vehicle device is proposed to investigate the aerodynamic characteristics of moving vehicles on bridges under crosswinds. The new moving vehicle device, which can adjust the incoming wind directions and wind attack angles, consists of a vehicle, bridge segment, and motion system etc. The motion system includes a linear module propelled by a servo motor and it can realize bidirectional motions and rapid acceleration and deceleration. The five-component coefficients of the moving vehicle model were tested with the force balance equipment, and the sensitivity of some parameters on the aerodynamic characteristics of moving vehicles is studied. The results show that the proposed moving vehicle device can provide a rather smooth guideway. The measured time histories of aerodynamic force and moment are stable after filtering and the identified aerodynamic characteristics of moving vehicles have a good consistency over different wind speeds.

Vehicle ride comfort issues for the drivers are related to not only individual satisfaction of driving experience, but also driving safety and long-term health of the drivers. A new methodology of ride comfort analysis is presented for typical vehicles driven on long-span bridges considering realistic traffic and environmental loads such as wind excitations. Built on the simulation framework developed previously by the writers, complex interactions among the long-span bridge, all the vehicles in the traffic flow and wind excitations are appropriately modeled. Vehicle ride comfort condition is evaluated by extending the advanced procedures as currently recommended in the ISO 2631-1 standard to the scenarios of multiple vehicles in the stochastic traffic flow, including obtaining the whole-body vibration response, frequency weighting the original response and determining the Overall Vibration Total Value (OVTV). The proposed methodology is then applied to a prototype long-span cable-stayed bridge and traffic system to demonstrate the proposed ride comfort evaluation methodology. The study starts with the baseline scenario when the vehicles are driven on the rigid road without considering the interactions with the supporting structure and wind excitations, followed by the scenarios of vehicles driven on the bridge. The influences of dynamic interactions, presence of other vehicles and wind excitations on the ride comfort are also numerically evaluated.

Accidents, such as deflections, side slips, and even rolls, can easily occur when road vehicles moving on the bridge deck at high speed are subjected to sudden changes owing to strong crosswinds. Wind barriers are an effective way to ensure the driving safety of vehicles on the bridge but with potential negative influences on the aerodynamic performance. Therefore, it is critical to evaluate the shielding effect of wind barriers on road vehicles by assessing the overall impact on the vehicle–bridge system. To optimize the wind-barrier scheme, a series of wind tunnel tests is conducted to evaluate the effects of barrier parameters on the aerodynamic characteristics of the wind-vehicle-bridge system. In this study, the aerodynamic force coefficients of the wind–vehicle–bridge system installed with wind barriers with four different heights and three ventilation ratios were investigated. With wind barriers installed on the bridge deck, dynamic responses of the wind–vehicle–bridge system were simulated with the proposed prediction procedures as those used in an earlier study. Results show that wind barriers on the bridge deck have significant influences on the aerodynamic force coefficients of the bridge, especially on the side-force coefficients, and on the dynamic responses of the wind–vehicle–bridge system. Additionally, the increase of the barrier height and the decrease of the barrier ventilation ratio considerably increase and decrease the lateral and torsional displacements of the bridge and the vehicles, respectively, but with only minor influence on the vertical displacements of both bridges and vehicles. Therefore, it is necessary to include the wind barrier in both experimental and numerical simulations of the wind-road vehicle-bridge system to explore the effect of different barrier parameters on the wind-vehicle-bridge system.

High-sided vehicles often experience considerable single-vehicle accident risks under crosswinds. Long-span cable-supported bridges are usually flexible, wind-sensitive and support considerable amount of vehicles on a daily basis. When vehicles are driven through a long-span bridge, the complex dynamic interactions among wind, vehicles and the bridge significantly affect not only the safety of the bridge members, but also passing vehicles. Therefore, realistic modeling of the bridge–traffic system by characterizing these critical coupling effects becomes essential for rationally assessing traffic safety of passing traffic through a long-span bridge. In most existing studies about traffic safety study on bridges, vehicle safety was assessed for only one single vehicle or uniformly distributed vehicles at a constant driving speed. It is known that the traffic flow on a long-span bridge is typically stochastic and vehicle speeds vary following some traffic rules. Based on the stochastic traffic flow simulation, two new analytical frameworks, one using mode superposition and the other using the finite element (FE) formulation, were proposed recently for the bridge–stochastic traffic system. By considering the full-coupling effects among all the vehicles of the traffic flow, bridge and wind, the dynamic response of each individual vehicle of the stochastic traffic can be accurately obtained for the first time. Built based on the recent advances made by the authors, an integrated dynamic interaction and safety assessment model of the fully-coupled bridge–traffic system is further developed without considering vehicle aerodynamic interference and shielding effects. Traffic safety of vehicles in the stochastic traffic through the prototype long-span cable-stayed bridge is investigated as a demonstration.

To ensure the safety and normal working performance of both road vehicles and the bridge, it is important to study the dynamic interaction between the bridge, road vehicles, and wind loads. The wind–vehicle–bridge dynamic analysis has been extensively developed in the past decades. Recent studies highlighted the importance of predicting the dynamic responses of the vehicle–bridge system by considering the aerodynamic interference between the bridge and vehicles. However, the aerodynamic forces on vehicles in the previous studies were either calculated from the empirical formulae built on the work of vehicles running on roadway or obtained from wind-tunnel tests, which did not consider the interaction of the aerodynamic forces between the road vehicles and the bridge. Based on the wind tunnel tests, first, the aerodynamic force coefficients of the vehicle are fitted considering the aerodynamic interference between vehicles and the bridge, and a more effective and accurate approach to estimate the performance of vehicles and the bridge is provided in this study. Then, the application of the proposed methodology on the Jiangshun Bridge in China is presented as a numerical example. Effects of the coherence of the buffeting forces of the bridge and the aerodynamic parameters of the vehicle and the bridge on the dynamic performance of both the bridge and the vehicles are discussed. It is found that the coherence of buffeting forces of the bridge has obvious effects on the dynamic responses of the bridge and the vehicle, which should be considered in the analysis of the coupled vibration of wind–vehicle–bridge system. The aerodynamic parameters of the bridge have significant effects on the dynamic responses of the bridge, but slight impacts on the dynamic responses of the vehicle. Meanwhile, the aerodynamic parameters of the vehicle have essentially no impact on the responses of the bridge and have a great impact on the responses of the vehicle.

A reliability analysis method is proposed in this paper through a combination of the advantages of the response surface method (RSM), finite element method (FEM), first-order reliability method (FORM) and the importance sampling updating method. The method is especially applicable for the reliability evaluation of complex structures of which the limit state surfaces are not known explicitly. After the accuracy and efficiency of the method are demonstrated through numerical examples, the method is used to estimate the flutter reliability of a suspension bridge. The uncertainties such as material properties, geometric parameters, structural damping ratio, flutter derivatives and extreme wind velocity at the bridge site are considered. The example suspension bridge is the Jiang Yin Bridge with a main span length of 1385 m built in China. The results show that the proposed method based on an empirical formula in which the limit state function is explicitly represented as a function of variables overestimates the flutter reliability of suspension bridges. The actual flutter reliability should be more accurately analyzed using the proposed method based on the deterministic finite element method in which the limit state function is implicitly represented as a function of variables. Finally, the most influential random variables on flutter reliability of suspension bridges are identified by using a sensitivity analysis.

Currently, there are very few systematic analyses of vehicle performance on bridges in windy environments. There are thus no scientific data to support bridge management in this regard, such as when to close traffic on bridges. This paper presents a framework of vehicle accident analysis model on long-span bridges in windy environments. In the accompanying paper, a three-dimensional analysis of the coupled bridge–vehicle–wind system is developed. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers. Dynamic interaction analysis is then conducted on the vehicle–bridge system to predict the “global” bridge and vehicle dynamic responses without considering accident occurrences. The results of the global bridge–vehicle vibrations serve as the basis for the present accident analysis of the “local” vehicle vibrations. With the global vibrations as inputs of the accident model, the lateral response, yaw response of the vehicle, and the reaction forces of each individual wheel are obtained and the stability condition of the vehicles are analyzed. The vehicle accidents on long-span bridges are then identified with given accident criteria. The developed framework can be used in not only analyzing the vehicle performance on highways and on bridges, but also in predicting useful information for emergency preparedness agencies in developing evacuation plans.

This paper presents a framework of dynamic analysis of coupled three-dimensional vehicle-bridge system under strong winds. A general formulation of this system is introduced to simulate a series of vehicles consisting of different numbers and different types of vehicles running on bridges under hurricane-induced strong winds. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers, considering wind and road roughness loads. With this vehicle-bridge model, coupled dynamic analysis of vehicles running on bridges is conducted with a numerical example. Effects of driving speeds on the dynamic performance of the vehicles as well as the bridge are discussed. It is found that the driving speeds mainly affect the vehicle's vertical relative response while they have insignificant effect on the rolling response of vehicles. Vehicle's absolute response is dominated by the bridge response when wind speed is high, while it is dominated by road roughness when the wind speed is low. Detailed accident analysis of vehicles on bridges under strong winds will be reported in an accompanying paper.

A study on buffeting control of the Yangpu Bridge using a multiple tuned mass damper (MTMD) system is performed in this paper. The MTMD system consists of a set of TMDs which are attached to the center region of the bridge's main span and are symmetrical about the center of the main span as well as about the central line along the bridge span. It is found that the control efficiency of the MTMD system is sensitive to its frequency characteristics, namely, the central frequency ratio and the frequency bandwidth ratio. On the other hand, the damping ratio of the TMDs has less significant effects on the control efficiency. A total of seven MTMD systems with different mass ratios are designed. Each one of these seven MTMD systems can be used for the buffeting control of the Yangpu Bridge, depending on the required control efficiency and the available budget.