索梁结构应急桥抖振响应分析

针对新型索梁结构应急桥结构刚度小、质量轻的特点,开展脉动风荷载作用下应急桥的抖振响应研究。利用ANSYS软件建立桥梁结构模型,分析其动力特性。采用谐波合成法模拟脉动风场,基于准定常抖振分析模型计算了主梁节点的静风力、抖振力。运用APDL编制程序分析轻型索梁结构应急桥的抖振响应,分析气动导纳函数和自激气动力对桥梁结构抖振响应的影响,并对提出的斜拉索抗风缆方案进行抖振响应计算。计算结果表明:索梁结构应急桥抖振横向位移远大于竖向位移,说明结构侧向刚度较弱;跨中主缆应力对风速变化更为敏感,而吊杆应力波动较小;索梁结构应急桥跨中横向位移主要受主梁正对称侧弯振型的影响;竖向位移主要受主梁一阶正对称竖弯振型的影响;扭转角主要受主梁一阶正对称扭转振型的影响;不考虑气动导纳函数会使索梁结构应急桥抖振响应计算结果偏大,气动自激力对结构抖振响应影响较小。与原方案相比,斜拉索抗风缆方案能够极大地降低横向抖振位移,对竖向位移和扭转角影响较小。

Buffeting Response Analysis for Emergency Bridge with New-type Cable-girder Structure

Aiming at the characteristics of small stiffness and light weight of emergency bridge with new-type cablegirder structure,buffeting response of emergency bridge under f luctuating wind load was studied.The emergency bridge model was established by using ANSYS software to analysis the dynamic characteristics.The weighted amplitude wave superposition(WAWS) method was used to simulate the f luctuating wind f ield,and the static wind force and buffeting force of the main girder joint were calculated based on the quasi-steady buffeting analysis model.The buffeting response of emergency bridge with light cable-girder structure was analyzed by APDL programming.The inf luences of aerodynamic admittance function and self-excited aerodynamic force on buffeting response of bridge structure were analyzed.The buffeting response of cable-stayed wind-resistant cable scheme was calculated.The calculation results show that the buffeting transverse displacement of emergency bridge with cable-girder structure is much larger than that of vertical displacement,which indicates that the transverse stiffness of the structure is weak.The stress of main cable in midspan is more sensitive to the change of wind speed,while the stress f luctuation of suspender is smaller.The transverse displacement in the midspan of emergency bridge with cable-girder structure is mainly affected by the positive symmetrical lateral bending mode of the main girder,the vertical displacement is mainly affected by the f irst-order positive symmetrical vertical bending mode of the main girder,and the torsion angle is mainly affected by the f irst-order positive symmetrical torsional mode of the main girder.Without considering the aerodynamic admittance function,the results of buffeting response of emergency bridge with cable-girder structure will be larger,and the inf luence of aerodynamic self-excitation force on buffeting response of structure will be smaller.Compared with the original scheme,the wind-resistant cable scheme can greatly reduce the transverse buffeting displacement,and has less inf luence on the vertical displacement and torsion angle.