拉索应力不均匀分布理论及其改进型疲劳寿命设计方法研究

Tension structure system is widely used in domestic and foreign engineering projects. Cable (ring cable) structure is the main bearing member of tension structure system, which is often composed of a plurality of cables. Both the internal force distribution of cables and the stress distribution of each cable are not uniform, which would reduce the ultimate bearing capacity of cable (ring cable) structure and reduce the fatigue life of cable. Meanwhile, the rigid cable clamp at connection would easily cause damage to the cable body. The problems above would lead to security risks. The project will start from the interaction effects between the cables, and the ones between the cable wires: ① Carry out non-uniform distribution tests of the cable force of ring cable structure, the performance tests of cable-cable clamp and the fatigue performance and ultimate bearing capacity tests of standard cables and the cables with defects. ② Establish a stress distribution theory model of cable used in actual engineering design and analysis, according to the research on the non-uniform stress distribution rules of cable body and cable wires at cable clamp position. ③ Based on the above model, propose new design indexes of stress ratio of ring cable structure and advanced fatigue life design method for ring cable structure, to predict damage accurately. ④ Design a cable clamp connection which can prevent the relative sliding between ring cable and radial cable and also can avoid the damage of cable wires at clamp position. The research results would provide theoretical supports for the cables and cable clamp design of tension structure system, which have important scientific significance for security of tension structure system.

张力结构体系在国内外大型工程中得到广泛应用。拉索(环索)作为张力结构体系的主要受力构件，往往由多根索组成，各根索的内力及索内索丝的应力分布都不均匀，此现象会降低拉索(环索)的极限承载力并减少索的疲劳寿命。同时，索夹节点处刚性索夹易对索体造成损伤，存在安全隐患。本项目将从索与索、索丝与索丝之间的相互作用入手，开展如下工作：①环索索力不均匀分布试验研究、拉索-索夹受力性能试验研究及标准和带缺陷拉索疲劳性能及极限承载力试验研究；②通过研究环索索体及索夹位置处索丝应力的不均匀分布规律，建立适用于实际工程设计分析的索丝应力分布理论模型；③基于上述模型，提出新的环索应力比设计指标及改进型环索疲劳寿命设计方法，对结构的破坏进行准确预测；④设计一种既能防止环索与径向索相对滑动又能避免环索损伤的索夹节点。研究成果可为张力结构体系的索体和索夹设计提供理论支撑，对张力结构体系的安全保障具有重要的科学意义。

张力结构体系在国内外大型工程中得到广泛应用。拉索(环索)作为张力结构体系的主要受力构件，往往由多根索组成，各根索的内力及索内索丝的应力分布都不均匀，此现象会降低拉索(环索)的极限承载力并减少索的疲劳寿命。同时，索夹节点处刚性索夹易对索体造成损伤，存在安全隐患。本项目从索与索、索丝与索丝之间的相互作用入手，从拉索的构造出发，基于合理假设，提出索丝应力不均匀分布理论模型，开展拉索静力试验，得到拉索外层索丝应变随层数的变化规律，建立起三维数值模型并进行验证，对拉索及索夹节点展开数值分析，得到索丝应力不均匀分布系数，提出索夹节点的优化措施。结果表明：直索的不均匀系数在0.83~1.44之间，环索的不均匀系数在1.12~1.94之间。倒角尺寸在拉索直径1/4-2/5范围内时，可使拉索表面最大等效应力降低8%-11%，圆角尺寸在拉索直径1/5-7/20范围内时，可使拉索表面最大等效应力降低8%-10.6%。研究成果可为张力结构体系的索体和索夹设计提供理论支撑。