中央扣对悬索桥动力特性及短吊索车载激励响应的影响

为实现运营阶段中央扣对悬索桥动力特性及车载激励下短吊索响应影响的量化分析，进而为悬索桥设计及维养策略提供参考，基于已编制的车-桥耦合分析系统，引入制动惯性力及俯仰力矩模拟车辆制动力，建立了考虑车辆制动过程的车-桥耦合分析系统；以一座单跨地锚式悬索桥为工程背景，建立无、有中央扣2种缆梁连接体系的全桥空间有限元模型，研究中央扣对悬索桥动力特性及行车激励下短吊索缆梁相对位移响应的影响；采用建立的分析系统，考虑不同制动位置、初速度及减速度研究中央扣对短吊索制动激励响应的控制作用；考虑短吊索因缆梁相对错动产生的弯曲应力，建立车流激励下短吊索疲劳损伤的分析流程，研究中央扣对短吊索的等效疲劳应力幅值及疲劳损伤度的影响。分析结果表明：中央扣提高了悬索桥的纵飘及扭转刚度，改变了缆梁间的相对运动特性，减小了缆梁错动循环次数及位移幅值，可有效控制行车激励下60.3%以上的短吊索缆梁相对位移响应；考虑不同制动位置、初速度及减速度的取值，中央扣对短吊索缆梁相对位移幅值的减弱率可分别达92.9%、85.1%及85%以上，有效降低了短吊索制动激励响应对3个制动参数的敏感性；中央扣对随机车载下短吊索轴向应力幅值的影响较小，而对因缆梁相对错动产生的弯曲应力幅值影响较大，减弱了短吊索的等效疲劳应力幅值及疲劳损伤度，尤其是距中央扣位置最近的短吊索，疲劳损伤度降低了近71.4%；因此，中央扣可有效控制运营阶段悬索桥短吊索的车载激励响应。

Influence of Rigid Central Clamps on Dynamic Characteristics of Suspension Bridge and Vehicle Excitation Responses of Short Suspenders

This study carried out a quantitative analysis of the influence of rigid central clamps (RCCs) on the dynamic characteristics of suspension bridge and responses of short suspenders under vehicle excitations during the operational stage, and further provides some references for the design and maintenance strategy of suspension bridge. Based on the developed vehicle-bridge coupling vibration analysis system, the braking inertia force and pitching moment were introduced to simulate the vehicle braking force. A vehicle-bridge coupling vibration analysis system that considers the vehicle braking process was established. A single-span earth-anchor suspension bridge was used as the engineering model to investigate the dynamic characteristics of the bridge and vehicle excitation responses of short suspenders, by simulating the corresponding finite element models with or without RCCs. The control effects of RCCs on the vehicle braking excitation responses of short suspenders were obtained through the established analysis system, considering different braking locations, initial braking speeds, and braking decelerations. Considering the bending stresses of short suspenders caused by cable-girder relative movement, an analysis process for the fatigue damage on the short suspenders under traffic excitation was established, and the effects of the RCCs on the equivalent fatigue stress amplitude and fatigue damage were studied. The analysis results show that the RCCs improves longitudinal and torsional stiffness of the suspension bridge, changes the cable-girder relative movement characteristics, and reduces the cycle numbers and amplitudes of the cable-girder relative movement, which has effectively controlled cable-girder relative displacement responses of shot suspenders under running vehicle excitations by over 60.3%. Considering the different values of braking locations, initial braking speeds, and braking decelerations, the effects of RCCs on reducing the percentages of cable-girder relative displacement amplitudes of short suspenders could be over 92.9%, 85.1%, and 85%, respectively, noting that the sensitivities of the braking excitation responses of short suspenders to these braking parameters are effectively reduced. Under random traffic flow, the axial stresses of short suspenders are less affected by rigid central clamps; nevertheless, the amplitude of bending stresses caused by cable-girder relative movement is greatly affected. The equivalent fatigue stress amplitude and fatigue damage of short suspenders are reduced significantly. In particular, the fatigue damage of the shortest suspender, which is closest to the mid-span, decreased by nearly 71.4%. Therefore, the RCCs could effectively control different vehicle excitation responses of short suspenders in a suspension bridge during the operational stage.