Experimental Study On Confined Concrete With CFRP Strip

Fiber reinforce polymer(FRP),possessing the advantages of lightness,high-strength,corrosion resistance and so on,has been widely used in Civil Engineering.An important application of FRP reinforced concrete specimens is to confine concrete.Domestic and foreign scholars have proved through a large number of experimental studies that external FRP confined concrete can greatly improve the mechanical properties of concrete structures.In practice,strip reinforcement is more common.However,the premise of the application of FRP strip confined concrete in practical engineer ing is that is should have a more accurate constitutive relationship model of stress-strain.The constitutive model is the basis for the calculation of the bearing capacity and the seismic performance analysis of FRP strip confined concrete.Based on the above research background,this thesis studies the axial compression test of CFRP strip confined concrete specimens,and the influence of three parameters on the axial compressive properties of CFRP strips confined concrete.The three parameters are width of strips(25mm,30 mm and 35mm),number of strip(3,4 and 5)and layer of CFRP(1,2 and 3).This thesis finds out the laws of failure mode,compressive strength,stress-strain curve,lateral restraint stiffness and ultimate strain varying with the changes of the three parameters.Taking into account the difference of strain variation laws between CFRP strip confined concrete specimens and strip concrete,The PIV technology was used to study the surface strain variation of CFRP strip confined concrete specimens.The test results show that compared with unconfined concrete,compressive strength of different CFRP strip confined concrete specimens with 1 layer wrap cloth of 25 mm,30mm and 35 mm can be increased respectively by 11.30%,10.06%,12.76%(three strips),16.92%,27.95%,43.13%(four strips)and 29.40%,55.83%,66.64%(five strips);compressive strength of different CFRP strip confined concrete specimens with 2 layer wrap cloth of 25 mm,30mm and 35 mm can be increased respectively by 16.71%,29.20%,25.87%(three strips),42.09%,50.00%,74.76%(four strips)and 82.45% ?93.27%?122.19%(five strips);compressive strength of different CFRP strip confined concrete specimens with 3 layer wrap cloth of 25 mm,30mm and 35 mm can be increased respectively by 24.83%,23.37%,40.64%(three strips),55.41%,74.76%,92.02%(four strips)and 109.71%,153.61%,175.87%(five strips).Under the condition of the same amount of cloth,the ultimate axial strain and ductility of strip confined concrete are better than those of fully wrapped confined concrete.By using the linear regression analysis method,the thesis achieves the strength model and strain model of CFRP strip confined concrete considering different width and number of wrap cloth and the effect of layers.