Size Effect And Performance Of Concrete Confined By Stirrups Under Axial Compression

Extensive experimental and theoretical studies on behavior of confined concrete have been conducted in the past. However, research on size effect on behavior of concrete confined by stirrups under axial compression which proceed from the materials and their interaction is still rare. On the base of experimental study conducted by the research group, the further investigation was carried out in this thesis.Concrete specimens with different sizes confined by stirrups were tested under axial compression. Prisms with aspect ratio of3:1were used in the test. The specimens were divided into6groups named A-F. The sectional dimensions of specimens in the A,B,C and F groups were108,200,250and370mm. The sectional dimensions of specimens in the D and E groups were250and370mm. The F group was plain concrete columns. To ensure identical confinement coefficient for specimens with different sizes, the same type of confining stirrups were adopted in all specimens and both diameters and spacing of confining stirrups were properly scaled. The study compared the stress-strain curve of the specimens under different gauge.The influence of specimen size on axial compressive strength and its corresponding peak strain and ductility of confined concrete were investigated. The effects of the confinement on the behavior of the strain of stirrups are discussed. This paper describes the performance of the various stirrup ratios and type of stirrups and gives the contrast analysis of the constitutive model of previous researchs.The results show that, stirrups of the large size of the specimens cannot reach full potential of the constraint. The small size of the specimens had a better binding effect than the larger ones. Specimens with large size and less effective constraint showed obvious length effect. Taking into account the size-effect of the concrete material itself, the expression in Eurocode2was more in line with the results of the test than the model used in the US. The effect of the amount of stirrups on ductility was much more pronounced than on strength. The compressive strength of specimens with stirrups of high strength have not significantly improve. To the Attard model, Binici model was more suitable to fit the test results.