Page - 1053 - in Book of Full Papers - Symposium Hydro Engineering

(1) While the bonding length- frpl is equal to 150mm, the testing outcome can agree well with the calculation outcome. (2) While the bonding length- frpl is equal to 90mm, 100mm and 160mm, the difference rate between the testing outcome and the calculation outcome is about 15%. (3) While the bonding length- frpl is equal to 80mm, 110mm, 120mm and 180mm, the difference between the testing outcome and the calculation outcome is relatively big and higher than 25%. 3.4. EFFECTIVE BONDING LENGTH OF FRP PLATE - CONCRETE SPECIMEN Sharma [4] and his fellows put forward the concept of “effective bonding length” based on the results that the bonding strength of FRP-concrete will not keep increasing as the bonding length of FRP plate increases. Chen and Teng[13] put forward the calculation formula for effective bonding length through plenty of tests. The effective bonding length of FRP plate-concrete specimen is roughly estimated through analysis of strain-plate length, and compared with the Chen- Teng effective bonding length. In the discussion about specimen SS-100 and SS-150 in Chapter 3.2, it has been demonstrated that the effective bonding length of this batch of FRP plates is roughly estimated to be about 100mm. The effective bonding length calculated by Chen-Teng formula is: ' 256000 0.2 103.5 0.76 30 frp frp e c E t l mm f      On this basis, it is indicated as follows: (1) The analysis of strain-plate length curve can be estimated the effective bonding length of FRP plate-concrete indeed. (2) The effective bonding length calculation formula proposed by Chen-Teng is re-verified by amount of analysis. 4. CONCLUSION The direct shear and de-bonding test of FRP-concrete specimen are conducted by autonomously developed testing equipment. With the assistance of advanced DIC (digital image correlation) technology, the strain distribution on the FRP plate surface of FRP-concrete specimen is accurately measured. Besides, the surface strain distribution law of FRP plate alongside the length direction of plate and the bonding strength of specimen are researched. Furthermore, it reveals the de-bonding failure process of concrete interface and draws following major conclusions: (1) The shear strain stress of FRP plate and concrete interface is not evenly distributed, the de-bonding starts from the load end and presents itself as brittle failure. 1053