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Pre-stressed concrete hybrid guideways are often used in the high-speed maglev transit system. The long-wave deviations of the stator plane based on the initial pre-camber could be possibly caused by temperature and concrete creep. When the high-speed maglev train moves over the guideways system, significant vehicular vibration could be triggered by the long-wave deviations. In the present study, the influence of the long-wave deviations on the dynamic characteristics of high-speed maglev train is investigated. First, the vertical analysis model of the coupled maglev train-guideway system is presented, and the loading model of long wave deviations of the stator plane is determined. Then, the effect of several key parameters, that is, initial pre-camber, the long wave deviations levels, train speeds, and the bridge span, on the dynamic response of maglev train-guideway system is evaluated. The results show that the initial pre-camber will improve the driving safety index and riding comfort level, especially for the middle vehicle of the high-speed maglev train. The results also indicate that the existence of long-wave deviation on the stator plane could deteriorate the driving safety and comfort level of the vehicle. Meanwhile, higher train speed and long-wave deviations levels as well as larger bridge span result in larger vehicle dynamic response. [ABSTRACT FROM AUTHOR]

It is inevitably to encounter overtaking events as vehicles pass through long-span bridges under crosswinds. The effects of the aerodynamic interference on the dynamic responses of the overtaking vehicles should be taken into account in the analysis of the driving safety of vehicles under crosswinds. The time-varying aerodynamic coefficients of the overtaking vehicles are obtained by scale model wind tunnel tests. A vehicle dynamic model is established for the analysis of the dynamic responses of articulated lorry. Based on the coupling vibration framework of the wind-vehicle-bridge system, an improved dynamic analysis system is constructed to solve the transient aerodynamic responses of the overtaking vehicle. It investigates the effects of the overtaking events on the driving safety of vehicles on bridge deck under crosswinds. The results show that the interference aerodynamic forces produced during the overtaking process have significant influences on the dynamic responses of vehicles. The maximum load transfer ratio and side-slip factor of vehicles in consideration of the effects of overtaking event are much greater than the case taking no account of the interference aerodynamic forces. Although the overtaking event do not play a decisive role in the driving safety of vehicles crossing the bridge, it is necessary to consider the combined adverse effects of the overtaking event and crosswinds on the safety of vehicles. [ABSTRACT FROM AUTHOR]

To investigate the stochastic characteristics of vehicle-bridge (VB) system under crosswind, an efficient method which combines AutoRegressive Moving Average with eXogenous inputs (ARMAX) model, high-order differencing (HOD) and important sample was proposed in this paper. First, the wind turbulence spectra relative to a moving vehicle and equivalent static gust load method were adopted to simplify the turbulent wind field of VB system, and a wind-vehicle-bridge (WVB) model was established and verified. Then, an analysis framework for WVB system based on ARMAX model was proposed, and HOD method and important sample were used to improve the prediction performance of the surrogate model. Prediction accuracy and calculation efficiency of proposed AMRAX model were verified and compared by Monte Carlo simulation (MCS). Finally, the impacts of vehicle speed and wind velocity on the stochastic characteristics of train response were discussed. Results indicate that the HOD method has significantly improved the prediction performance of ARMAX model for lateral response of trains, and the train responses predicted by ARMAX model based on HOD and important sample show perfect agreement with target results. Compared with MCS, the calculation efficiencies of proposed ARMAX model are improved by about two orders of magnitude. The extreme values of the train response with different vehicle speed and wind velocity gradually obey right skewness distribution, especially the lateral acceleration. [ABSTRACT FROM AUTHOR]

The present article proposes a novel framework for analyzing the dynamic responses of suspended monorail vehicles running over curved bridges under crosswinds. In this model, the curved bridge model is established with the finite element method and vehicles are simulated as a multibody system. Subsequently, a wind model is proposed with the wind tunnel test, spectral representation method, and yaw wind-decomposition method, taking into account the effects of the angle between the wind and vehicle changes when vehicles pass through the curved bridge. Finally, a suspended monorail curved bridge is analyzed to demonstrate the effect of the wind model on the vibration of the system. The results show that wind direction has a great effect on the lateral dynamic response of curved bridges, the lateral force of guiding tire, and the vertical force of running tire. The influence of crosswind on the dynamic response of the vehicle decreases with the increase of running time of vehicle on curved bridges. [ABSTRACT FROM AUTHOR]

The wind-resistant performance of cable-stayed bridges under construction deteriorates sharply as the cantilever length increases, and the arrangement of the temporary pier is an effective measure to improve aerodynamic stability. To investigate the effect of the temporary pier on buffeting response of a long-span three-tower cable-stayed bridge under construction, the nonlinear buffeting analysis and wind tunnel test of aeroelastic model methods are adopted in this paper. The influence of the type and arrangement positions of temporary piers on mean wind response and the nonlinear buffeting response of double-cantilever construction are studied, and the arrangement of the temporary pier is optimized based on the buffeting response. The results show that the reduction rates of the RMS of the torsional moment at the tower bottom and the lateral buffeting displacement at the girder end with the rigid pier are 35.6% and 59.2% compared to those without the temporary pier. Further, the buffeting response will decrease as the distance between the rigid pier and the tower increases in the state. On the contrary, in the double-cantilever construction state before the constraint of temporary piers, the buffeting response will become significant as the distance increases. Therefore, it is necessary to consider the buffeting response under two construction states when optimizing the arrangement position of the temporary pier. [ABSTRACT FROM AUTHOR]

A growing number of long-span bridges are under construction across straits or through valleys, where the wind characteristics are complex and inhomogeneous. The simulation of inhomogeneous random wind velocity fields on such long-span bridges with the spectral representation method will require significant computation resources due to the time-consuming issues associated with the Cholesky decomposition of the power spectrum density matrixes. In order to improve the efficiency of the decomposition, a novel and efficient formulation of the Cholesky decomposition, called "Band-Limited Cholesky decomposition," is proposed and corresponding simulation schemes are suggested. The key idea is to convert the coherence matrixes into band matrixes whose decomposition requires less computational cost and storage. Subsequently, each decomposed coherence matrix is also a band matrix with high sparsity. As the zero-valued elements have no contribution to the simulation calculation, the proposed method is further expedited by limiting the calculation to the non-zero elements only. The proposed methods are data-driven ones, which can be applicable broadly for simulating many complicated large-scale random wind velocity fields, especially for the inhomogeneous ones. Through the data-driven strategies presented in the study, a numerical example involving inhomogeneous random wind velocity field simulation on a long-span bridge is performed. Compared to the traditional spectral representation method, the simulation results are with high accuracy and the entire simulation procedure is about 2.5 times faster by the proposed method for the simulation of one hundred wind velocity processes. [ABSTRACT FROM AUTHOR]

Wind tunnel experiments are used to investigate the aerodynamic interactions between vehicles and wind barriers on a railway bridge. Wind barriers with four different heights (1.72 m, 2.05 m, 2.5 m and 2.95 m, full-scale) and three different porosities (0%, 30% and 40%) are studied to yield the aerodynamic coefficients of the vehicle and the wind barriers. The effects of the wind barriers on the aerodynamic coefficients of the vehicle are analyzed as well as the effects of the vehicle on the aerodynamic coefficients of the wind barriers. Finally, the relationship between the drag forces on the wind barriers and the aerodynamic coefficients of the vehicle are discussed. The results show that the wind barriers can significantly reduce the drag coefficients of the vehicle, but that porous wind barriers increase the lift forces on the vehicle. The windward vehicle will significantly reduce the drag coefficients of the porous wind barriers, but the windward and leeward vehicle will increase the drag coefficients of the solid wind barrier. The overturning moment coefficient is a linear function of the drag forces on the wind barriers if the full-scale height of the wind barriers h≤2.5 m and the overturning moment coefficients Co≥0. [ABSTRACT FROM AUTHOR]