Several factors could affect the function of the electromagnet control system when a high-speed maglev train runs over a bridge. To enhance the robustness of the electromagnet control system to the high-speed maglev train running over the bridge, a fuzzy active control rule is introduced into the currently used proportional–integral–derivative (PID) control system. Numerical analyses are then conducted with a high-speed maglev train passing through a series of simply supported beams. The numerical results with the fuzzy PID active control are compared with the maglev train–bridge system with the equivalent linearized electromagnetic forces. The comparative results show that the introduction of the fuzzy PID control system has improved the comfort of the maglev train and that the overall dynamic response of the bridge is reduced. There is an obvious time delay for the maximum dynamic response of the bridge to the high speed of the train.

To ensure the safety of bridges, the comfort of pedestrians and vehicles on bridges, the vortex-induced forces on flat-steel-box girders need to be investigated. The total vortex-induced forces integrated on the surfaces of girders have been studied extensively. This study will be mainly focused on the characteristics of surface distributed vortex-induced force, which can be beneficial to the vortex-induced vibration (VIV) reduction with local aerodynamic optimization. Computational Fluid Dynamics (CFD) method is employed for the simulation of the VIVof a flat-steel-box girder. The simulation results are verified through the comparison with the results of corresponding wind tunnel test. A self-adaptive nonlinear fitting method is proposed to determine the vortex-induced force model. A vortex-induced force contribution factor is defined to account the contribution of the components and the surface location. Based on the surface distributed vortex-induced force analysis, several conclusions are made. The vortex-induced force presents a fairly strong multiple-frequency characteristic, and the high-order terms should be carefully considered. Most energy of the VIV comes from the linear and third-order aerodynamic damping terms. In terms of location, the roof takes most of the aerodynamic damping and the total vortex-induced force. The flow separation around the underside upstream corner, the underside downstream corner and the middle downstream comer lead to large third-order aerodynamic damping term. The flow separation around the underside upstream corner has great contribution to the linear aerodynamic stiffness term.

Simply supported bridges occupy the majority of bridges. Compared with the flexible large span bridges, Dynamic Amplification Factor (DAF) of them is relatively large and attracts lots of studies. However, most of these studies are focused on the simplified condition that a single vehicle passes through a single span bridge. In general, the bridge bears complex traffic flow rather than a single vehicle. The vehicle type and dynamic loads on the bridge are thus dispersed. It is necessary to explore the multi-vehicle effects on the DAF caused by the complex traffic flow. Also, adjacent spans of a multi-span simply supported beam bridge may have continuous dynamic effects on the vehicles. In this regard, the DAF of a simply supported bridge considering the multi-vehicle and multi-span effects are explored numerically based on the coupling dynamic analysis of traffic flow and bridge, which can also consider the acceleration and deceleration of the vehicles. Cellular Automata (CA) method is used to simulate the traffic flow. It is found that the worse the driving condition of the road roughness, the greater the DAF. When road roughness is Class C, the DAF exceeds the values of American and Chinese codes. Under the action of traffic flow, DAF of the first span of the multi-span simply supported beam is larger than that of the span under the single vehicle. Only considering the effect of a single vehicle may underestimate the dynamic impact on the bridge. Sparse traffic flow has a larger DAF than moderate traffic flow and dense traffic flow in the statistic meaning of the multi-span, because the driving speed of sparse traffic flow is closer to the resonant speed of the bridge and the vibration disharmony of multi-vehicles is smaller. The greater the deceleration of the traffic, the greater the dynamic impact on the bridge.

In order to cover the complexity of coding and extend the generality on the road vehicle‐bridge iteration, a process to solve vehicle‐bridge 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.

Threats of wind gusts on the safety of road vehicles have been reported around the world, and extensive studies have been carried out to find the accident speeds of road vehicles under a sudden crosswind. However, most previous studies assume that the angular displacements of the vehicle are small and the mass moments of the vehicle remain unchanged during the overturning of the vehicle, yielding a quasi-linear safety analysis of a road-vehicle under a sudden crosswind. This study aims at a nonlinear safety analysis of a running road vehicle under a sudden crosswind by establishing nonlinear equations of motion of a wind-vehicle system. The assumptions adopted in the previous studies are no longer required, and tires can lose or resume contact with the ground. Wind loads on the vehicle are updated with the consideration of the time-varying attitude of the vehicle. The numerical example shows that the proposed nonlinear analysis procedure is more rational than the currently used approaches for prog...