In order to cover the complexity of coding and extend the generality on the road vehicle-bridge iteration, a process to solve vehiclebridge interaction considering varied vehicle speed based on a convenient combination of Matlab Simulink and ANSYS is presented. In this way, the road vehicle is modeled in state space and the corresponding motion equations are solved using Simulink. The finite element model for the bridge is established and solved using ANSYS. The so-called inter-history iteration method is adopted to realize the interaction between the vehicle model and the bridge model. Different from typical method of road vehicle-bridge interaction in the vertical direction, a detailed longitudinal force model is set up to take into account the effects of varied vehicle speed. In the force model, acceleration and braking of the road vehicle are treated differently according to their mechanical nature. In the case studies based on a simply supported beam, the dynamic performance of the road vehicle and the bridge under varied vehicle speeds is calculated and discussed. The vertical acceleration characteristics of the midpoint of beam under varied vehicle speed can be grouped into two periods. The first one is affected by the load transform between the wheels, and the other one depends on the speed amplitude. Sudden change of the vertical acceleration of the beam and the longitudinal reaction force are observed as the wheels move on or off the bridge, and the bridge performs different dynamic responses during acceleration and braking.

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Moving on a bridge, a road vehicle will experience a gusty crosswind caused by the shielding effects of the bridge tower. The corresponding driving safety is affected by several uncertain factors. In this study, a closed-loop driver-vehicle-crosswind (DVC) model is established to obtain the dynamic responses of the vehicle under given driving conditions. The nonlinear tire cornering force, the real driver behavior and the vehicle aerodynamic loads considering the wind shielding effects of the bridge tower can be taken into account. Based on the support vector classifier approach, a probability-based procedure is established to assess the driving risk of a road vehicle passing by a bridge tower under crosswind. A typical two-axle road vehicle passing by a bridge tower is studied as a numerical case. The dynamic responses of the vehicle and driver reaction under two given driving conditions are analyzed by solving the DVC numerical model firstly. Then, the probabilitybased model is used to assess the driving risk of the vehicle under different driving conditions; the effects of vehicle speed, wind velocity and friction coefficient of road surface on the driving risk are investigated.

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As a vehicle moves on roads, a complex vibration system of the running vehicle is formed under the collective excitations of random crosswinds and road surface roughness, together with the artificial handing by the drivers. Several numerical models in deterministic way to assess the safety of running road vehicles under crosswinds were proposed. Actually, the natural wind is a random process in time domain due to turbulence, and the surface roughness of a road is also a random process but in spatial domain. The nature of a running vehicle therefore is an extension of dynamic reliability excited by random processes. This study tries to explore the dynamic reliability of a road vehicle subjected to turbulent crosswinds. Based on a nonlinear vibration system, the dynamic responses of a road vehicle are simulated to obtain the dynamic reliability. Monte Carlo Simulation with Latin Hypercube Sampling is then applied on the possible random variables including the vehicle weight, road friction coefficient, and driver parameter to look at their effects. Finally, a distribution model of the dynamic reliability and a corresponding index for the wind-induced vehicle accident considering these random processes and variables is proposed and employed to evaluate the safety of the running vehicle.