EXPERIMENT STUDY ON THE MECHANICAL PROPERTIES OF THE MULTI-CONSTRAINT CONCRETE IN THE STEEL TUBE

The joints of concrete filled steel tube with core steel tube were studied by loading the axial load in the core concrete.The joints were intercepted from the remanent joints specimens.The mechanical properties and the ultimate bearing capacity of the core concrete in multiply confined condition were studied and the constraint action of the joint components to core concrete was analyzed.The test results show that the strength and the deformation capacity of the core concrete are improved greatly.If the ultimate bearing capacity is divided by the area of loading,the compression strength of core concrete can be up to 250 MPa.According to the analyses of the loading-displacement curves and the bearing mechanisms to confined concrete,it proved that the force of friction between the concrete and the steel tube,the vertical force of the steel tube besides the confined concrete,have contribution to the ultimate bearing capacity.