考虑钢索蠕变的索杆结构时变性能评估及预应力补偿研究

The stiffness of the cable-strut structure is provided by the prestress. The stress relaxation due to material creep affects the long-term performance and safety of the structure greatly. However, the existing study on stress relaxation does not truly reflect degradation of the structural performance caused by material creep, so it has important scientific significance and engineering significance to study the time-varying performance evaluation and prestress compensation of the cable-strut structure considering creep of cables. By means of experimental study, theoretical analysis, program development and numerical simulation, the creep constitutive model of steel wire is studied, and the numerical model of creep analysis of steel cables is established, which provides the accurate prediction of creep deformation of steel cables. Followed that, the nonlinear finite element method of the structural life-cycle performance considering material creep is proposed and the variation of the structural stiffness and strength is simulated. By exploring the relationship of the performance degradation, creep deformation and stress relaxation, the performance evaluation index is then put forward. Finally the prestress design method considering material creep is proposed to the structure in-design. The effective prestress compensation theory and method considering the mechanism and prestress flow circuit is explored to the structure in-service. The above work will provide theoretical basis and technical support for ensuring the whole-life safety and applicability of the cable-strut structures.

索杆结构由预应力提供刚度，钢索蠕变导致的应力松弛对索杆结构长期使用性能和安全性能影响巨大，而现有的应力松弛研究不能真实反应由于钢索蠕变导致的结构性能削弱，因此研究考虑蠕变的索杆结构时变性能评估及预应力补偿具有重要的科学意义和工程意义。项目拟通过试验研究、理论分析、程序开发、数值模拟等手段研究钢丝蠕变本构模型和钢索蠕变分析数值模拟方法，提出钢索蠕变应变计算公式；研究考虑钢索蠕变的结构时变性能非线性有限元分析方法，跟踪结构刚度和强度变化历程；探索蠕变变形、应力松弛与结构性能退化相关关系，提出结构性能评估指标；进一步针对拟建索杆结构，研究考虑钢索蠕变的预应力设计方法；针对在役索杆结构，研究结构受力机理和预应力流回路，探索合理有效的预应力补偿方案，为确保索杆结构全寿命安全和适用提供理论基础和技术支持。

钢索蠕变导致的应力松弛会影响索杆结构长期使用性能和安全性能。项目采用试验研究、理论分析、程序开发、数值模拟等手段对考虑钢索蠕变的索杆结构时变性能评估及预应力补偿进行了研究。主要工作包括：.开展了常温条件下钢索的长期蠕变试验，得到了不同预应力水平下钢索蠕变应变随时间变化曲线。建立了考虑间隙和点接触的钢丝绳细观数值模型，分析了钢丝间摩擦、间隙、捻角等参数对蠕变效应的影响。基于粘弹性理论和长期蠕变试验数据，提出了可考虑钢索非线性蠕变特性的Kelvin链改进模型，进一步得到了解析形式的钢索蠕变本构方程和蠕变应变迭代计算公式。.研究了考虑钢索蠕变的索杆结构时变性能非线性有限元分析方法，推导有时间变量特征的结构刚度矩阵以及应力-应变迭代公式，同时兼顾计算精度和计算效率，对服役期时间段进行合理划分。基于LM-QN法对索杆结构长期时变性能进行模拟分析，探索应力松弛与结构性能退化相关关系，提出时变性能退化程度快速评估准则。基于AMS理念，从结构的可用性、维修性以及安全性等角度出发，建立索杆结构长期时变性能动态评价方法。基于可靠度理论和非线性规划提出了考虑钢索蠕变的索杆结构可靠年限预测方法。.进一步针对性能退化的在役索杆结构进行预应力补偿和二次张拉。以一在役索穹顶为例，探讨了斜索二次张拉、环索二次张拉和同时对斜索和环索二次张拉三种补偿方案的可行性。针对拟建索杆结构，提出了包括预应力损失预测-叠加-验算三步骤的考虑蠕变的预应力设计方法，以一拟建索穹顶为例验证了该设计方法的有效性. .本项目研究为保障索杆结构使用年限内的安全和适用提供了理论基础和技术支持。