大吨位FRP复合材料拉索整体式锚固理论分析

Theoretical analysis on integral anchor for large-tonnage FRP composites cable

针对大吨位纤维增强聚合物(FRP)复合材料拉索锚固问题,基于前期提出的一种适用于多根、大直径的FRP复合材料拉索整体式变刚度锚固方法(简称大吨位锚固),利用应力-应变关系分析了FRP复合材料拉索加载端应力集中产生的本质原因,推导了FRP复合材料拉索与荷载传递介质协同工作的界面摩擦系数关系式。基于功能原理,推导了大吨位锚固体系的锚固力计算公式,并基于锚固力计算公式进行了参数分析。理论推导结果表明:等刚度荷载传递介质会引起FRP复合材料拉索加载端应力集中,变刚度荷载传递介质的大吨位锚固方法可以有效避免FRP复合材料拉索"切口效应"。推导的界面摩擦系数关系式能够作为FRP复合材料拉索与荷载传递介质是否同步跟进的判断依据。参数分析表明:增加锚固长度和锥角(保持加载端厚度不变)有利于设计较小尺寸大吨位锚固体系,而增加锥角(保持自由端厚度不变)和同时改变加载端与自由端厚度不利于设计较小尺寸大吨位锚固体系。

In view of the anchor problem of large-tonnage fiber reinforced polymer (FRP) composites cable, basing on previous proposed integral variable stiffness anchor method suitable for multi root and large-diameter FRP composite cables( large-tonnage anchor for short), the essential reason of stress concentration at the loading end of FRP composite cable was analyzed based on the relationship between stress and strain, and the interfacial friction coefficient relationship of cooperative work between the FRP composites and load transfer component was deduced. Based on the principle of work and power, the calculation formula of anchor force for large-tonnage anchor was derived, and the parameter analysis was carried out based on the calculation formula of anchor force. The theoretical derivation results show that the stress concentration at the loading end of FRP composite cable can be caused by load transfer component with equal stiffness,and the large-tonnage anchor basing on load transfer component with variable stiffness can effectively avoids the cut effect of FRP composite cable. The derived interfacial friction coefficient relationship can be used as the basis for judge whether FRP composite cable and load transfer component follow up synchronously. The parameter analysis shows that increasing the anchor length and the cone angle (keeping the thickness of loading end unchanged) is advantageous to design small size and large-tonnage anchor system,while increasing the cone angle (keeping the thickness of free end unchanged) and the thickness of the loading end and the free end simultaneously is disadvantageous to design small size and large-tonnage anchor system.