悬索桥主缆与索鞍间滑移行为及力学特征试验

为明确主缆与索鞍间的滑移机理，给相关理论研究提供必要基础，开展了试验研究以揭示主缆在不平衡力作用下的滑移行为及力学特征。制定了以两端张拉丝股模拟主缆平衡状态、以单侧顶推索鞍模拟主缆偏载状态的加载方案，并设计了相应的试验模型及测试方法；考虑索股侧面摩擦及试验索股数目的影响，开展了共8种工况的试验测试，利用实测数据对索力发展特征、索股滑移行为、滑移时变效应及名义摩擦因数变化规律等关键问题进行了系统研究。结果表明：顶推索鞍初期所产生的不平衡力在索股间平均分配，随着不平衡力增大，索股相继滑移且滑移后基本维持其索力差不变；索股均已滑移后的缆力差的发展具有单向性，但残余缆力差相对较小；索股位移发展包括弹性变形、局部蠕动和滑移3个典型阶段；主缆滑移时变效应有限，即主缆滑移后仍具备较可靠的稳载能力；名义摩擦因数随索股相继滑移而增加的同时会引起较突出的索力不均匀性问题，故在主缆抗滑措施研究中尚需对该问题予以重视；侧面摩擦是索股分批滑移及索股数目对试验结果产生影响的根本原因，鉴于侧面摩擦显著的抗滑贡献，对其继续深入研究并充分应用具有重要意义；建议多塔悬索桥主缆与索鞍间的摩擦因数取值可放宽至0.2。

Test for Slip Behavior and Mechanical Characteristics Between Main Cable and Saddle in Suspension Bridges

This study investigates the slip behavior and mechanical characteristics of the main cable under unbalanced forces to provide essential foundation for related theoretical studies. The loading schemes were established since the equilibrium state of the main cable was simulated by tensioning the strands at both ends, and the unbalanced loading states were simulated by pushing the saddle at one side. The corresponding test models and the measurement methods were designed. Eight experimental cases were carried out considering both the effects of lateral friction and the number of strands. The development of strand forces, slip behavior, time-varying effect of the slip, and change in the nominal friction coefficient were systematically investigated as key parameters using measured data. Results show that when the saddle is pushed, the initial unbalanced forces are distributed equally among the strands. With the increase in the unbalanced forces, the strands slip successively and the differences between the strand forces are almost invariant. The development of the differences between the strand forces is unilateral after all the strands slipped, but the residual differences are relatively smaller. The development of strand displacements involves three typical stages:elastic deformations, local creeps, and slipping. The time-varying effect of the slip is bounded such that the main cable still has reliable capacity even after slipping. The nominal friction coefficient increases with increasing number of slipped strands, and the strand forces become significantly uneven. This should be considered during the investigation of the anti-slip approach for cables. The lateral friction is the basic source that causes successive slipping and produces the effects of the number of strands on the test results. Further studies and applications are necessary since lateral friction obviously contributes to the anti-slip capacity of the cable. This study proposes that the value of the friction coefficient between the main cable and saddle in multi-pylon suspension bridges should be relaxed to 0.2.