Shear behavior of large-diameter concrete filled tube (CFT)

Circular concrete filled tube (CFT) is composite structure to fill concrete in steel tube as formwork. By combining advantage of steel tube and concrete, CFT has more superior deformation capacity and strength than reinforced concrete and steel structure, since bond stress between steel tube and concrete has influence on prevention of local buckling and increase in strength of concrete. For such a reason, CFT has been applied to as columns in buildings, and pile and drilled shaft foundations. CFT drilled shaft is designed to large diameter due to large local shear strength by seismic load, liquefaction and lateral spreading of soil layer. However, it brings uneconomical design by the conservative shear equation of current design provision. Until today, shear studies of circular CFT to improve shear equation have been rarely conducted and they are limited to small scale test. In this research, the numerical and experimental results are compared to current shear design equations, with the ultimate goal to serve as an initial analytical study that aids in planning further experimental and analytical research on shear resistance and behavior of circular CFT, which leads to improved shear design equations.