Research On Tension Strengthening Of RC Members With Externally Bonded CFRP Sheets

Theoretical analysis, experimental research and numerical simulation are conducted on the performances of reinforced concrete (RC) members strengthened with externally bonded carbon fiber reinforced plastic (CFRP) sheets in flexure, shear, compression, seism and torsion at home and abroad at the present time, Whereas, the documents of researches are few in these aspects of tension of RC members. The bearing capacity is insufficient of some existing RC members with tension for several reasons including load increasing, structure aging, design miss and so on. All these result in an urgent need to strengthen many of these structures with an effective and reliable method. Wherefore, experimental researches of 24 RC members are conducted to examine the influences of various factors on the cracking load and ultimate load of the RC members strengthened with externally bonded CFRP sheets. Some factors such as layers of CFRP sheets, ratio of reinforcement, preloading degree and continual loading degree are mainly analyzed, and the formulas for calculating the tension capacity of these RC members are put forward. At the same time numerical simulations are carried on tension of RC members. The major conclusions are mainly summarized as follows:1. The experiment researches show that it is obvious to increasing ultimate load about 13.6ï¼…-32.8ï¼…using CFRP sheets to strengthen RC members under axial tension, and cracking load is lesser increase too. The bearing capacity is rising along with the increasing layers of CFRP sheets on a nonlinear manner and strengthening effect is falling along with the increasing ratio of reinforcement. The effect of preloading and continual loading on the cracking load and ultimate load is lesser and biggish before and after concrete is cracking. Externally bonding CFRP sheets is an efficient technique to restrict crack width and spacing, especially on the edge, the study is instructive and useful in improving the durability of RC members under axial tension. The calculation formulas agree with the experimental data, and the experimental results can give the references to the practical projects.2. The numerical simulations show that it is obvious to increasing ultimate load about 17.9ï¼…-53.7ï¼…using CFRP sheets to strengthen RC members under axial tension, and cracking load is lesser increase too. Strengthening contributing is adding along with the increasing concrete grade and the bearing capacity is rising along with the increasing layers of CFRP sheets on a nonlinear manner. The calculative outcomes agree with the experimental data, and the methods of model building on RC members with externally bonded CFRP sheets under axial tension can give the references to the practical projects.3. The experiment researches show that it is obvious to increasing ultimate load about 17.4ï¼…-34.2ï¼…using CFRP sheets to strengthen RC members under small eccentric tension, and cracking load is lesser increase too. The bearing capacity is rising along with the increasing layers of CFRP sheets on a nonlinear manner and strengthening effect is falling along with the increasing ratio of reinforcement. The effect of preloading degree and continual loading degree on the cracking load and ultimate load is lesser and biggish before and after concrete is cracking. Extemally bonding CFRP sheets is an efficient technique to restrict crack width and spacing, especially on the edge, the study is instructive and useful in improving the durability of RC members under small eccentric tension. The calculation formulas agree with the experimental data, and the experimental results can give the references to the practical projects.4. The numerical simulations show that it is obvious to increasing ultimate load about 13.9ï¼…-39.5ï¼…and 19.0ï¼…-57.1ï¼…using CFRP sheets to strengthen RC members under small eccentric and large eccentric tension, and cracking load is lesser increase too. Strengthening contributing is adding along with the increasing concrete grade and the bearing capacity is rising along with the increasing layers of CFRP sheets on a nonlinear manner. The calculative outcomes agree with the experimental data, and the methods of model building on RC members with externally bonded CFRP sheets under eccentric tension can give the references to the practical projects.