拉索预应力损失机理及其对在役张弦结构性能的影响

Cable-supported structures have been widely used in various major engineering projects including stadiums and gymnasiums, convention and exhibition centers, and transportation hub stations. However, existing structures would have prestress loss problem that caused by cable relaxation and corrosion, and this will greatly threaten structural bearing capacity and safety. Current studies on prestress loss mainly focus on the effect of construction and temperature, but the influence of cable relaxation and corrosion on existing structures have been rarely involved in relevant studies. Based on the analysis of the factors that induce the prestress loss of the in-service cables, the cable relaxation and the corrosion mechanism will be explored, and the influence of cable twisting characteristics on cable relaxation model will be studied. Also a time-varying model of cable prestress considering the influence of cable relaxation and corrosion will be established in this project. In addition, considering the application scopes and the problems of current cable force measuring methods, a precise formula for calculating flexural rigidity of stubby cables in beam string structures will be established through elaborate numerical simulation and experimental study. Then based on the precisely modified flexural rigidity, the advanced cable force measurement will be explored. Influence of prestress loss on the bearing properties of existing cable-supported structures will be studied based on the time-varying model, with considering the prestress loss and the measured values of cable force. Mechanism of the cable force measurement, tensioning compensation and cable replacement will also be studied. The results of this project demonstrate a long-term significance in providing scientific support for the construction and operation safety of engineering structures.

张弦结构体系已广泛应用于体育场馆、会展设施、交通枢纽等重要工程，服役期内拉索松弛和锈蚀会导致明显的预应力损失，影响结构的承载特性和安全性。现有预应力损失的研究主要集中在施工阶段和温度效应上，对拉索松弛和锈蚀导致的预应力损失及其对结构影响的研究较为缺乏。本项目在分析服役期内拉索预应力损失诱致因素的基础上，探索拉索松弛和锈蚀机理，研究拉索绞捻特性对松弛模型的影响机制，建立考虑拉索松弛和锈蚀影响的拉索预应力时变模型；分析现有三点弯曲法等索力测试方法的适用范围以及存在问题，研制拉索弯曲性能试验装置并开展系列试验，建立拉索抗弯刚度计算公式，探索基于抗弯刚度修正的改进频率法；考虑服役期内拉索预应力损失的时变模型以及拉索内力实测结果，研究拉索预应力损失对在役张弦结构承载特性的影响，建立张弦结构索力检测体系判定、补张拉及换索机制。成果可为大跨结构建设和运营提供理论支撑，对张弦结构安全保障具有重要科学意义。

拉索及其预应力对张弦结构的安全性能至关重要。张弦结构在服役过程中会发生锈蚀与应力松弛现象，从而产生力学性能的退化，严重影响结构的服役安全。针对上述问题，本项目开展了拉索全寿命力学性能的精细化研究。.在考虑时变特性的拉索预应力损失机理研究方面，进行了张弦结构拉索应力松弛和锈蚀性能的试验与有限元数值模拟研究。得到了张弦结构中松弛造成的预应力损失的分析方法和理论计算公式；建立了单根拉索的精细化松弛模型。根据拉索锈蚀模型建立拉索弹性模量的时变折减模型；结合拉索松弛模型，得到了考虑拉索松弛和锈蚀影响的时变模型。.在基于拉索抗弯刚度修正的在役张弦结构索力测试研究方面，进行了拉索弯曲性能试验、三点弯曲法索力测量试验及基于拉索抗弯刚度修正的改进频率法研究。建立了拉索抗弯刚度计算公式；确定了采用三点弯曲法测量索力的拉索抗弯刚度适用范围；探索并验证了基于拉索抗弯刚度修正的改进频率法的适用性。.在拉索时变特性引起的预应力损失对在役张弦结构性能的影响方面，建立了张弦结构拉索预应力损失综合时变模型；研究了拉索服役期预应力损失对张弦结构性能的影响，在此基础上制定出在役张弦结构拉索安全保障机制。