Stress-strain Model For Cfrp Confined Concrete Under Uniaxial Compression In Consideration Of High Strain Rate

Structure reinforcement is becoming more and more because of structural damage caused by earthquake, explosion and impact, changes in the use of function, modification to the maintenance. CFRP is used widely as a result of its easy construction, speed and good results with more and more structure reinforcement works now. Concrete confined with CFRP research are many, but mainly for cylindrical and its static performance studies, and dynamic properties of the square columns less.By comparison analysis between 29 static CFRP confined concrete specimens and 55 dynamic specimens under three kinds constraints ratio(ξ=0.065,ξ=0.1025,ξ=0.205), the relationship between strain rate and stress-strain curve, strength, strain, Young's modulus and Poisson's ratio of CFRP confined concrete at different constraints ratio and different strain rate is studied. Two-line stress-strain model is established by fitting of stress, strain at ultimate and knee point.In the fast strain rate, stress-strain curve knee point overlap with knee point of the same constraints ratio specimens and non-binding specimens of plain concrete. Specimens that there is declining section are described by three-line model, descending straight line is described by connection between ultimate point and corresponding to point of 0.85 times ultimate point; knee point and ultimate point stress increases with strain rate; average axial compressive strength of square column when strength is 21.8MPa and constraint ratio is 0.065 can be increased by 18% in the rate of 10^-5s^-1, by 63% in the rate of 10^-2s^-1, average axial compressive strength of square column when strength is 26.4MPa and constraint ratio is 0.065 can be increased by 19% in the rate of 10^-5s^-1, by 47% in the rate of 10^-2s^-1; conception of dynamic and static Young's modulus ratio is introduced, dynamic and static Young's modulus ratio increased slightly with the increase of strain rate; Poisson's ratio increased slightly with the increase of strain rate, also increased slightly with the increase of constraints ratio; effective strain coefficient of CFRP confined concrete is 0.464 by CFRP strain when destroyed.