表层嵌贴预应力CFRP-strip加固钢筋混凝土梁的受力性能研究

STUDY OF MECHANICAL BEHAVIOR OF REINFORCED CONCRETE BEAMS STRENGTHENED WITH NEAR-SURFACE-MOUNTED PRESTRESSED CFRP STRIPS

体外粘贴预应力FRP技术和表层嵌贴FRP加固技术均是FRP应用于混凝土结构加固的重要技术,但存在各自的局限和不足。表层嵌贴预应力FRP技术有望结合上述两种技术的优点,进一步提高FRP加固混凝土结构的优势和效能。该文在研制成功FRP板条夹具的基础上,加固并进行了5根钢筋混凝土受弯构件的试验研究,深入考察了各试件尤其是表层嵌贴加固试件的力学行为与破坏形态,对比了体外与表层嵌贴加固试件的承载与变形性能差异,分析了预应力的存在对表层嵌贴加固构件力学性能与破坏模式的影响。试验结果表明:表层嵌贴预应力FRP板条加固显著提高了受弯构件的承载性能,其改善效果与体外粘贴预应力FRP板加固非常接近;嵌贴方式可使粘结树脂代替机械锚具锚固预应力FRP板条,但该文试验中表层嵌贴加固试件的破坏形态为粘贴端部的树脂-混凝土界面剥离和保护层混凝土撕裂,因此有需要就提高界面粘结能力和抑制保护层混凝土撕裂的构造措施开展进一步研究。

The strengthening technique of external-bonded prestressed FRP plates and near-surface-mounted FRP strips are all important techniques of strengthening a concrete structure with FRP. However, there are considerable limitations of the two techniques. It is attractive to develop the technical of near-surface-mounted prestressed FRP strips, by combining the advantages of the above two strengthening methods, to further promote FRP applications in retrofit of concrete structures. In this paper, a total of 5 reinforced concrete beams strengthened with FRP was constructed and static load tests were conducted. The behavior and failure mode of specimens were investigated intensively, especially the specimens strengthened with NSM FRP. Furthermore, the difference of mechanical performance due to various strengthening techniques was shown through a comparison, and the effect of initial stress on the behavior and failure mode of specimens was analyzed. The testing results showed that the mechanical performance of flexural member can be improved significantly by strengthening with NSM prestressed FRP strips, and the improved effect was similar to that of the technical of EB prestressed FRP plates. The prestressed FRP strips can be anchored by epoxy through the method of near-surface-mounted. However, the failure modes of beams strengthened with NSM FRP strips were debonding of epoxy-concrete interface and tearing of concrete cover. Therefore, the further work of NSM prestressed FRP technique should be focused on the constructional method of improving bonding strength of epoxy-concrete interface and preventing tear of concrete cover.