Experimental Study On The Size Effect Of Axial Compression Performance Of Concrete Columns Confined With CFRP

Strengthened concrete structures by CFRP is one of the commonly used means in structural strengthening works, and the research on mechanical properties of CFRP reinforced concrete structure have been much more mature. But Existing theories are basically built on a single size specimens, the concrete structures is the size effect, in-depth study on the size effect of FRP confined concrete is less.With C30and C60concrete, this paper produced24pieces of specimens in12groups with the same ratios of height to diameter, tested the axial compression in different strength, different size, different layers, studied the deformation process and stress-strain curve, analysis their size effect, and corrected the Lam and Teng’s model with a factor for size effect at last.Test study found that, CFRP can improve the ultimate compressive strength of concrete effectively and improve the ductility in a certain extent, but the damage still exists a certain fragility; CFRP confined concrete cylinder exists size effect, and the ultimate compressive strength and peak stress and strain decrease with increasing size; with the increase in the number of layers of CFRP, the ultimate stress and strain increase. However, these increases are not linear, its growth rate relate with CFRP layers and concrete strength, the more layers of CFRP and the higher grade of concrete, the smaller growth in each layer.The test result shows that CFRP confined C30concrete in φ200mm×400mm are in good agreement with Teng’s model in stress-strain curve. Comparing specimens in (φ100mm×200mm and600mmφ300mm with Teng’s model in stress-strain curve, Lam and Teng’s model can not reflect the effect of FRP confined concrete. After analysis, a correction factor K1for size effect was introduced to correct the formula of FRP lateral binding, and proposed a modified formula; On the basis, the paper also corrected Teng’s model in ultimate strain, proposed the correction formula, and provides a reference for further research and application of CFRP confined concrete reinforcement works.