【摘要】 以嘉绍跨江大桥为工程背景,采用ANSYS有限元软件建模对随机地震动作用下大跨度多塔斜拉桥的结构动力响应进行了数值分析。结果显示,三维一致激励下各跨主梁位移响应规律基本一致,但各塔塔底内力差别较大;各塔塔底内力受该塔塔梁约束条件影响较大;同时各塔间塔梁约束方式对塔底内力存在相互影响。此外分析了行波效应对动力响应的影响,表明不同波速对结构地震响应影响较大,且随视波速变化结构响应存在一定的规律性。更多还原

【Abstract】 This paper establishes a structural model of the Jiashao river-spanning bridge using the ANSYS finite element software,in which the tower and the beam are simulated by beam44.In addition,link8 is used to simulate the cables in the model.Through the solving of the dynamic equation,the results of the model show the dynamic response of the Jiashao bridge.This paper analyzes these responses to study the principles of structural dynamic response of a large-span multitower cable-stayed bridge under a stochastic seismic effect.The results show that,on the whole,the displacement of a beam at each span under three-dimensional uniform excitation has the same response.The horizontal and vertical RMSresponse of a beam’s displacement gradually increases from the base of a tower toward the center of the beam,but the value in each span varies to certain extent.The longitudinal bending moment of the tower,where the height is lower than the place of constraint of the tower-girder,increases linearly with reduction in the height of the tower,but the bending moment of the remainder of the tower decreases with increase in the height of the tower.With respect to the different longitudinal constraints of the tower-girder in the models,the displacement of the main beam in the middle span and the internal forces in the base of the towers show clear differences among the models.Analysis shows that the internal forces in the base of the towers are deeply affected by the constraint conditions of the tower-girder,and that there is interaction between the constraint conditions of the tower-girder and the internal forces in the base of the towers.When each tower is under a longitudinal constraint,the RMSof the vertical displacement of a beam reaches its maximum value.The displacement is intermediate when each tower has vertical dampers(parts of towers have vertical constraints)and the minimum values of displacement are obtained when each tower has only vertical dampers.If a longitudinal tower-girder constraint is set in a tower,the internal forces in the bases of the towers are significantly enhanced as compared to when dampers are used.In addition,in this study,the traveling wave effect on the dynamic response of a large-span multi-tower cable-stayed bridge was analyzed.The results show that the RMSvalue curves of the longitudinal displacement of a beam are similar under different seismic wave velocities.The minimum value is obtained at the location where the longitudinal tower-girder constraint is set,and the displacement gradually increases toward the center span.When the seismic wave velocity is in a lower range of values,the relationship between the velocity and the longitudinal displacement of the main beam is not very obvious,but when the velocity is in a larger range of values,the longitudinal displacement of the main beam increases with increase in velocity.Furthermore,the RMS values of the base of a tower’s moment and shear show the same variation as the displacement of a beam under different velocities.In general,this study indicates that the traveling wave effect has the greatest impact on the response,and that there is a certain relationship between structural response and a traveling wave.更多还原