Coupling Vibration Of Wind-Road Vihicle-Bridge System And Its Program Design

A Wind-Road Vehicle-Bridge (WVB) system is regarded as an integrated mechanical system consisted of nature wind, road vehicles and bridge with coordinate interaction. Due to fluid-solid interaction between wind and bridge, solid contact between vehicles and bridge and stochastic wind excitation on vehicles and bridge, time-varying coupling vibration exists in the WVB system. Using a relatively reasonable dynamic analysis model, a framework for performing dynamic analysis of the coupled WVB system is built by the means of numerical method.Firstly, a new approach for the finite element simulation of foundation stiffness with the 3-Orthogonal-Beams model is presented, avoiding the disadvantages of several reported methods. According to this approach, foundation stiffness is represented by the structure of 3 orthogonal beams with a common node. The element stiffness can be determined by the structural typical equations for each beam, thus the structural stiffness of the common node equals to that of foundation. The present model, as a simplified, practical but precise method, can simulate foundation stiffness matrix including the principal terms and the cross terms. It is worthy of widely application.Secondly, combined flutter and buffeting analysis in the time domain for bridge is realized with the wind induced static force and time domain buffeting and self-exited force being combined as unified wind loads on the bridge. Wind loads nonlinear problem induced by attack angle is further considered, which makes possible to conduct a relative comprehensive flutter and buffeting analysis in the time domain method for bridge.Thirdly, road vehicles are idealized as a spring-damper-mass model with 13 DOF for dynamic analysis. Based on this model, movement equations of road vehicles are derived. A safety analysis model for road vehicles is established, increasing the rationality of wind induced roll and sideslip accidents of vehicles. In the proposed evaluation criteria of vehicle accidents, forces considering peak factor between wheels and bridge deck is considered to be more reasonable for evaluation of vehicles accidents. In this thesis, terms of equivalent forces and sideslip resistance are introduced for safety analysis of road vehicles.Finally, improved framework for analysis of coupling vibration of wind-road vehicle-bridge system is established. According to the framework, a WVB system analysis computer program, named WVBroad (Wind-Vehicle-Bridge for Roadway), is developed based on object-oriented programming method. Then, a high-pier & long-span continuous rigid frame bridge and a single pylon cable-stayed bridge with hybrid beam are taken as case study, to investigate coupling vibration of vehicle-bridge system in vertical plan and three dimensions, respectively. Various cases are explored to consider many issues aiming to investigate the dynamic impact factor of bridge, reveal the characteristics of the coupling vehicle-bridge system vibration, and analyze the safety problems of vehicles under the cross wind.Vehicle-bridge system vibration analysis for the continuous rigid frame bridge shows: the dynamic effects of vehicles for the bridge are mainly accounted for period impact owing to wheels involved; with the increase of road surface roughness, the response of bridge and vehicles increases, and the response of vehicles mainly depend on the roughness, due to large bridge deck stiffness; the impact factor for the bridge is affected considerably by the regular motion of vehicles and dynamic characteristics of the bridge structures.Wind-vehicle-bridge system vibration analysis for the single python cable-stayed bridge shows:wind static loads acting on vehicles can notably increase the lateral response of bridge, especially in the case that many vehicles are involved; under the cross wind, the vertical buffeting response of the bridge is notable, as the bridge deck section has relatively streamlined shape, and thus the aerodynamic lift force plays an important role in the aerodynamic effects; but the lateral buffeting response of vehicles appears notable, because the lateral force may play a major role for vehicles due to its blunt shape.Using the proposed accident analysis model of road vehicles, the effects of road surface roughness, vehicle speed and road surface condition (dry, wet, snowy or icy) on the safety of vehicles running on the bridge deck are investigated, respectively. Then accident critical speed of vehicles is calculated, and traffic speed limit criteria are further proposed.