The Dynamic Analysis Of Long-span Suspension Bridge Subjected To Wind And Vehicle

Due to their smaller stiffness, long-span suspension bridges will create largeinternal force and deformation under the action of wind and vehicle loads. So thedynamic analysis of long-span suspension bridges is of great significance to thedesign and maintenance of bridges.Taking the Aizhai large bridge as an example, we established thethree-dimensional finite element analysis model, analyzed the dynamic response ofthe long-span bridge under the action of wind and vehicle loads. The main contentsare as followings:1. The four common bridge deck pavement irregularities in our country aresimulated in the time domain and the harmonic superposition method is used tosimulate the wind speed field around the bridge.2. The following conclusions are obtained by analyzing the dynamic response ofthe bridge under the action of only vehicles:1) With the increment of road grade, the vibration trends of vertical displacementand acceleration time history curves change, and the values of the maximumdisplacements and accelerations increase, and the multiples of the increments areequal.2) With the increment of vehicle speed, the vibration trends of verticaldisplacement and acceleration time history curves change, and the values of themaximum displacements and accelerations increase, but the multipleof accelerationincrement is larger than that of displacement.3) With the increment of vehicle weight, the vibration trends ofverticaldisplacement and acceleration time history curves have no difference, meanwhile thedynamic responses of bridge increase linear.4) The lateral dynamic responses result mainly from the unbalanced forces onboth sides of the bridge, the more the unbalance is, the larger the dynamic responses are.3. Through a simply supported beam model and a half vehicle model, theinfluences of initial vehicle vibration on the dynamic responses of the bridge areanalyzed, meanwhile,the problems caused by the vehicle nonuniform motion arestudied.The following conclusions are obtained:1) Compared with no initial vibration, the vehicle with a certain initial vibrationcan lead to larger dynamic responses of the bridge during a period of time after thevehicle goes into the bridge, as the vehicle continues to move ahead, this effect willfade away.2) The dynamic responses of the bridge have no large change when the vehicleruns with varying speed. In the actual calculation,the influence of the speed variationof the vehicles on the dynamic responses of the bridgecan be ignored.4. The responses of the bridge under wind loads or both wind and vehicle loadsare analyzed respectively. Thefollowing conclusions are obtained:1)The responses of the bridge increase with the wind velocity.2)The stress time-history curve of both the windward and leeward braceschanges contrarily. What’s more, the stress peak of leeward braces is larger than thatof windward braces under the same wind velocity.3)The transverse vibration is mainly caused by wind loads, while the verticalvibration is mainly caused by vehicle loads.4) The bridge deviates to one side,under the action of static wind loads, besides,it fluctuatesunder the action of dynamic wind loads. Both the deviation andfluctuationwill increase with the increment of wind velocity.