弦支穹顶结构拉索滑移摩擦机理及其对结构性能的影响研究

The suspen-dome has been widely used in large-span spatial structures because of its advantages of high efficiency and convenient construction, however the friction of cable sliding have adverse effects on the structure’s bearing capability. While, the friction phenomena are complicated because they are caused by many different physical mechanisms, resulting that it’s coefficient can not be determined accurately. Also, it seems difficult to consider the friction effect into static and dynamic analysis of the whole structure. In this project, the influence rules of both friction loss during construction and dynamic sliding in operation on the structure will be revealed, based on the sliding friction mechanisms. By coalescing theory analysis and experiment study, the influencing mechanism of the cable’s twisting way on the contact status between the cable and cable-strut joint will be studied firstly, and then illuminating the cable-joint contact pair’s working behavior of friction, leading to a set of friction coefficient calculations between the cable and cable-strut joint. Secondly, the mechanics of the friction element will be studied during both construction and operation, leading to building the geometric and internal force constraints under different contact conditions, and then the friction elements used in static and dynamic will be derived by avoiding calculating the stiffness coefficient and iterative calculating. Lastly, a test model of a suspen-dome with adjustable contact status between the cable and cable-strut joint will be built up, then the quantitative indicators of the influence of friction loss during construction on structure can be obtained, also the influence rule of friction sliding in operation on structural dynamic performance can be revealed, via carrying out the static comparison and cable-broken experiments respectively. Later, a destructive experiment will be conducted to reveal the influence rule of sliding friction on the structure’s failure mode. The achievements of this project can provide theoretical basis and technical support for the design and performance evaluation of suspen-dome.

弦支穹顶因结构效能高、施工方便在大跨空间结构中应用广泛，但拉索滑移摩擦影响了结构的承载特性，而摩擦受众多因素的复杂影响，其系数难准确取值，结构静动力分析难以高效考虑摩擦效应。项目拟从滑移摩擦产生机理出发，揭示施工阶段摩擦损失与运营阶段动态滑移对结构的影响规律。项目采用理论与试验相结合的方法，首先研究拉索绞捻特性对其与节点接触状态的影响机制，阐明拉索—节点副摩擦工作机理，建立摩擦系数计算方法。其次，分析摩擦单元在结构施工与运营阶段的力学特征，建立单元内力、位移约束条件，避开求解刚度系数与反复迭代推导静动力摩擦的有限单元。最后，制作拉索与节点摩擦状态可调弦支穹顶试验模型，先开展静力对比试验与断索试验，确定施工阶段滑移摩擦对结构静力影响的量化指标，揭示运营阶段摩擦滑移对结构动力的影响规律；再进行破坏性试验，揭示滑移摩擦对结构失效模式的影响规律。成果可为弦支穹顶的设计与性能评估提供理论和技术支撑。

弦支穹顶结构采用张拉环索方式施加预应力时，不可避免会出现预应力摩擦损失，会降低结构效能。本项目即主要针对弦支穹顶结构拉索-索撑节点间的摩擦滑移问题开展了精细化分析与试验研究。项目针对拉索预应力在弦支穹顶结构体系中的重要地位，基于影响矩阵理论提出了一种不需反复迭代、可实现多目标同步优化、且适用于非线性弦支穹顶的预应力优化简化算法，并结合环索张拉时两端索力不等且存在随机摩擦损失的普遍现象，提出了一种能考虑两端张拉控制力不等、且能在各索撑节点处引入不同摩擦系数的找力方法；然后针对拉索-索撑节点副摩擦滑移系数变异性大的问题，建立了考虑拉索绞捻特征与内部复杂边界条件的拉索-节点副精细化数值模型，并开展了变角度摩擦滑移张拉试验研究，分析了拉索局部弯曲对拉索内部钢丝应力分布与接触状态的影响规律，理清了张拉力、捻距及索段夹角对摩擦滑移系数的影响规律；接着通过调研，基于概率统计原理分析了不同种类拉索节点的摩擦系数数理特征，并结合试验数据建立了滚动式拉索节点与拉索间摩擦系数的随机数学模型；随后为实现结构整体考虑摩擦效应的高效计算，结合弦支穹顶动力作用下摩擦滑移的高度非线性，提出了一种基于向量式有限元的拉索摩擦滑移计算方法，基于静力平衡条件，提出了一种空间五节点等效摩擦单元，实现了摩擦滑移的高效静力模拟；最后围绕一弦支穹顶结构缩尺试验模型，基于数理统计原理，系统分析了预应力随机摩擦损失对结构内力、变形以及极限承载力的影响规律。此外，考虑到弦支穹顶上部网壳的缺陷敏感性及其对结构性能影响的不可忽视性，项目还开展了弦支穹顶结构上部网壳焊接空心球节点焊接力学缺陷分布模式及其对节点力学性能影响的理论分析与试验研究，厘清了焊接残余应力随节点构造尺寸的变化规律，提出了节点焊接残余应力的简化计算方法以及节点刚度的修正方法；同时基于概率统计原理，分析了节点安装偏差、杆件初偏心等缺陷对结构整体性能的影响规律。