FRP拉索锚固体系优化及其静力性能评价

针对大吨位多筋FRP拉索锚固存在应力集中、锚固效率低等问题,提出了一种性能可设计的分段变刚度锚固方法,以同源变刚度为设计理念,开发了一种磨碎玻璃纤维改性树脂荷载传递介质。首先,以常用的石英砂改性树脂为对照组,对比分析了2种改性树脂在不同体积掺量下的压缩性能,并利用数值拟合方法揭示了磨碎玻璃纤维改性树脂的压缩强度和弹性模量与体积掺量之间的关系;其次,利用三维实体有限元模型对FRP拉索锚固体系进行了参数分析,并以加载端FRP拉索的应力降低为优化目标;最后,在前述优化基础之上,开展了Φ4-37BFRP拉索的足尺静力试验。结果表明:当改性物体积掺量相同时,磨碎玻璃纤维改性树脂的压缩性能始终优于石英砂改性树脂的压缩性能;磨碎玻璃纤维改性树脂的压缩强度和弹性模量均随着改性物体积分数的增加而增大,且其变化规律符合二次多项式拟合关系(R²>0.98);分段比例为1:1:1:1的磨碎玻璃纤维改性树脂荷载传递介质可有效降低锚固区FRP拉索的应力集中;BFRP拉索总体呈现理想的中部炸裂式破坏,且其荷载-位移关系近似呈线性关系;优化后的拉索锚固体系对BFRP拉索的静力锚固效率为101%,满足规范要求(≥95%);加载后的荷载传递介质未出现损伤,且未与BFRP拉索之间产生滑移;锚固区BFRP拉索的轴向应变自加载端至自由端逐渐减小。变刚度荷载传递介质可以显著减小锚固区加载端BFRP拉索的剪应力集中。

Optimization and Static Behavior Evaluation of Fiber-reinforced Polymer Cable Anchor System

Because of the stress concentration and low anchor efficiency of large-tonnage multiple-tendon fiber-reinforced polymer (FRP) cables, a segmented variable-stiffness anchoring method with different performances is proposed. A resin-based load transfer component (LTC) modified by a glass microfiber (RLTCGF) was developed based on the concept of homologous variable stiffness. First, the compressive performances of the two modified LTCs with different modified materials were compared and analyzed, with resin modified by quartz sand used as the control group. The relationships between the compressive strength and elastic modulus of the RLTCGF and the content were analyzed using a numerical fitting method. Subsequently, the FRP cable anchor system was optimized based on a 3D finite-element model to decrease the stress concentration of the loading-end FRP cable. The static performance of the optimized FRP cable was verified through full-scale experiments. The results showed that the compressive performance of the RLTCGF was superior to that of the resin modified by quartz sand when the content was the same. The failure modes of the two types of modified resin exhibited similar laws. The compressive strength and elastic modulus of the RLTCGF increased with an increase in the modified material content, and their relationship could be described by a quadratic polynomial fitting model with R² > 0.98. The stress concentration of the FRP cable in the anchor zone can be decreased by using an RLTCGF with a segmented ratio of 1:1:1:1. The failure modes of BFRP cables are ideal middle ruptures, and their load-displacement curves are nearly linear. The mean anchor efficiency of the optimized BFRP cables was 101%, meeting the requirements of the standard (≥ 95%). No damage was observed in the LTC after loading. Meanwhile, no relative slippage between the LTC and FRP cable was observed. The axial strains of the BFRP cable in the anchor zone gradually decreased from the loading end to the free end. The shear stress concentration of the loading-end FRP cable can be decreased using a variable-stiffness LTC.