Anchorage Systems Of High Strength Fiber Reinforced Polymer And The Applications In Strengthened Structure

FRP composite have many good properties, such as high strength, light weight, resistance to fatigue, corrosion protection, as so on. So FRP composite is the idea material that can be made cable and tension member and can be used to repair and retrofit of existing structure. However, FRP composite is different from steel, it's weakness in transverse direction and its sensitivity to notching make anchoring a very difficult task. Up to now the various FRP bar anchoring device in the world have some drawback, such as sophisticated manufacturing, large dimension, poor reliability, expensive cost, and so on. So these anchorage haven't popular in civil applications. Hence, the techniques of gripping and anchoring FRP composite have became the key technique and must be resolved.Because of structure aging and function changing, repair and retrofit have been the most widespread used of FRP in civil engineering application. The primary reason for prominence of FRP in repair is the economic viability of FRP, which stems from its ease of application without much need to heavy equipment or skilled labor. However, FRP sheets is prone to delaminated from the structure. To precaution the premature failure of FRP delaminated, the U-ferrule and steel plate ferrule are used. But the problems of FRP delaminated haven't been resolved. So it is necessary and important to develop new methods to anchor the FRP sheets, and the methods should be ease to apply. In addition the technique of prestressed FRP lamination have developed slowly many year. The main reason is that no suitable gripping and anchoring device are used in prestressing FRP laminations. So it is the key point that the anchorage of FRP sheets should be developed. To resolve the above problems, an innovative anchorage –WSGG (Wave-shaped-gear-grip) anchor (ZL02244587.0) was developed by long-term try and many experiments. The WSGG anchor is based on the FRP sheets or laminations. Because the FRP sheets is the type material of most quantity in engineering application, the WSGG anchor have the compact base in application. In this paper, WSGG anchor is the core, it's mechanism of gripping and anchoring FRP sheets was researched and 14 RC beams were strengthened by CFRP and tested. Though analysis the mechanism of WSGG anchor, the principle of gripping and anchoring was made clear. It anchors FRP sheets by three methods: bond effect, friction effect and bend effect. The formulas of anchorage length and development length were derived. The anchorage criterion of FRP sheets was given too. In addition the factors of FRP anchorage length in WSGG anchor were discussed, and we considered that the WSGG anchor should be designed by optimization. FRP sheets are different from FRP bars in tension. FRP sheets are prone to inhomogeneous. The factors of tension strength of FRP sheets were discussed and the strength formula was given. The author try to discussed the probability that big tonnage cable would be made of FRP sheets. To verify the formula of anchorage length, several tension members were constituted by various WSGG anchor and test them. The test results confirmed the correctitude of the formula and demonstrated the reliability of WSGG anchor gripping and anchoring FRP sheets. The strength of FRP sheets can be used fully by WSGG anchor. The experiment too confirmed that the WSGG anchor should be optimized. To resolve the premature failure of FRP sheets when strengthening RC structure, an anchorage method was given, that is FRP sheets anchored by WSGG anchor. 14 RC beams was designed and tested by loading. The test results demonstrated didn't delaminated when the both end of FRP sheet were anchored by WSGG anchor and the strengthening effectiveness is raised significantly. Although 10 layers CFRP sheets were bonded on the surface of RC beams, the strength of CFRP sheets is used fully. Through analysis the strain of CFRP sheets, we considered that the tension force in CFRP sheets had undertaken by the end WSGG anchor when the loading was arrived medium-term and anaphase. In the experiment when one end of CFRP sheet was anchored by U-ferrule and another was anchored by WSGG anchor, the U-ferrule was failure by sheering. This demonstrated that WSGG anchor is superior than U-ferrule. Two simplified and composite anchorage model of U-ferrule and WSGG anchor were given. The bond and slip mechanism of FRP sheets and concrete was explained. WSGG anchor is the uniform anchor which is based on FRP sheets. The techniques of FRP strengthening and prestressing about WSGG anchor is the uniform techniques which have independent patent rights in China. So the research in this paper is important and innovative. Because WSGG anchor is a new object, there are many problems need to be resolved in future.