Study On Fatigue Property Of Bonding Anchoring Systems Focused On CFRP Tendons

As a new composite of civil engineering structures, CFRP(Carbon Fiber Reinforced Polymer) has many outstanding characteristics, including its light weight, good corrosion resistance and high tensile strength, which can be well applied in large span spatial structures and rope bridge in order to solve the problems of conventional prestressed reinforcement’s corrosion and low load efficiency and which also can bring broad prospects in application of civil engineering. However, with the low radial shear strength of CFRP tendens compared to its high tensile strength along with the direction of fiber, design and development of effective anchorage system for CFRP tendon has become one of the critical problems in practical projects. The article, relying on the Natural Science Foundation(Project ID: BK20140553) and the National Natural Science Foundation(Project ID: 51478209), carried out a series of static load test research、fatigue test research and corresponding theory analysis on the bond-type anchor for CFRP tendon. The main research contents and corresponding results are extracted as follow:1. Static load test researchBased on the difficent bonding medium instead of the common building glue, the Lica-adhesives and quartz sand involved in Lica-adhesives, the different combination of the bond-type anchor for CFRP tendon in the anchorage length and the angle of outer sleeve presented their anchorage performance.a. With the increase of the anchorage length, average bond stress of the CFRP has a rising trend;b. Keeping the anchorage length unchanged, the anchor with the angle of 3° and 4°is more effective than 0° in anchoring single CFRP;c. Compared with ordinary building glue and Lica-adhesives, the bonding strength of the anchoring system which is joined quartz sand in Lica-adhesives is improved and the anchorage performance of it is more outstanding.2. Fatigue experimentsThis research, with the quartz sand in Lica-adhesives as bonding medium, presents 500000 second-class load fatigue test on several groups of different types of anchorage system. The conclusions are as follow:a. The slippage of the anchorage system will increase first as the increasing of the cycling times; when reaching a certain number of looping times, the position of the anchoring system between the assemblies is relatively stable. and the slippage of the system doesn’t increase anymore, also it appear retraction.the force system is in stable condition and it is also in good working condition.b. In the loading process, the surface of the CFRP reinforcement material presents dynamic sine wave and the surface of the strain change is tiny; the strain of the toroidal and lateral anchor is small, showing the whole system in a stable state.3. The theoretical analysisThis paper does research on the average bond stress and the BBA model,also it analyses the fatigue damage and failure mode of composite material.Based on the research,it advances the unidirectional shear-lag model to analyze the interface damage.Then, the shortcomings and the key problems were pointed out during this study, followed by the current development trend of civil engineering, Finally, some critical problems and advices were provided.