Experimental Study On Size Effect On Behavior Of Concrete Confined By Stirrups

Size effect is one of the basic properties of brittle material and quasi-brittle material. In terms of concrete, the size effect is related to the increase of fracture energy of specimens with the increase of specimen size, while strength decreasing as the increase of specimen sizes. Due to the importance of the size effect of concrete, a number of studies have been carried out from the beginning of the last century and lots of important conclusions are drawn. Compared with the situation in concrete material and plain concrete specimen, little research has been done on the area of reinforced concrete members. On the basis of the above condition, the contribution of the thesis is listed as following:(1). The main achievements in concrete size effect and confined concrete mechanical properties are briefly reviewed and summarized(2). Fourth-eight concrete prism specimens, which vary in size, stirrup form and volume stirrup ratio, are designed and tested. The failure mode, cracking of concrete, load-strain curve and ductility factors of confined concrete are studied, the effect of size on strength of confined concrete, strain peak and ductility of confined concrete is analyzed. The conclusion includes the following:The size effect of the axial compressive strength of confined concrete is minor; on the contrary side, that of the strain peaks and the ductility of confined concrete is significant.(3). Based on the analysis of the data of the test, the following result can be achieved:the effect of the size to the strain peak and ductility differs when the stirrup ratio and form changes.(4). The ductility and strain peak of the specimens can be improved by higher stirrup ratio; what's more, the more complex the stirrup form is, the better ductility can be achieved.