侵蚀环境下预应力GFRP锚杆结构应力松弛特征

Stress relaxation characteristics of prestressed GFRP anchor structure in corrosive environment

钢筋锚杆的腐蚀问题是锚固结构工程的安全隐患,GFRP锚杆因其耐腐蚀、高强度成为解决途径之一。为研究GFRP锚杆结构的耐久性,研发FRP筋锚杆结构应力松弛实验装置,利用该装置对侵蚀环境与荷载交叉下预应力GFRP锚杆结构应力松弛特征开展研究,进行3组不同侵蚀环境和荷载的实验,获得锚杆结构应力及杆体应变时程曲线,据此分析侵蚀环境与荷载对预应力GFRP锚杆结构应力松的影响。研究结果表明,FRP筋锚杆结构应力松弛实验装置可以设置环境影响条件,实现侵蚀环境与荷载条件叠加。GFRP锚杆结构应力松弛受环境和应力交叉影响,环境的影响较应力大,应力松弛绝大部分发生在加载后早期。GFRP锚杆结构应力松弛主要来源于锚固段黏结蜕化,部分来源于杆体弹性模量蜕化。相比于碱性环境,蒸馏水环境中锚杆体界面黏结状态蜕化速率更大。在溶液长期侵蚀作用下,通过黏贴耦合的光栅传感器与GFRP筋杆体变形同步性难以保证。

Corrosion of steel bolts is a potential safety hazard in anchorage structure engineering. GFRP bolt has become one of the solutions because of its corrosion resistance and high strength. In order to study the durability of GFRP anchor structure,a stress relaxation experimental device for FRP anchor structure was developed,and three groups of experiments were performed to study the stress relaxation characteristics of pre-stressed GFRP anchor structure under the combination of corrosive environment and load. The evolution curves of stress and strain of the anchor structure were obtained and the effects of corrosive environment and load on the stress relaxation of pre-stressed GFRP anchor structure were analyzed. The results show that the developed experimental device can efficiently set up environmental impact conditions and capture the combination effect of corrosive environment and load conditions. The stress relaxation of GFRP anchor structure is affected by the environment and the stress,and the environment has greater influence. Most of the stress relaxation occurs in the early stage after loading. Stress relaxation of GFRP anchor structure mainly comes from bond degradation of the anchorage section,and partly from elastic modulus decrease of the bolt body. Compared with alkaline environment,the degradation rate of interface bond state of anchorage section in distilled water environment is higher. It is difficult to ensure the synchronization of deformation of GFRP bar and grating sensor by bonding coupling under long-term solution corrosion.