Static Behavior Research On Circular Steel Tube Confined Steel Reinforced Ultra-high Strength Concrete Short Columns Under Axial Compressive Load

The application of high strength concrete and ultra-high strength concrete is limited in seismic fortified area because of there high brittleness and poor ductility. Steel-concrete composite structure is been widely used in long-span and super high-rise building structure which combines the advantages of steel and concrete. Steel tube confined concrete has better mechanical performance than traditional concrete filled steel tube(CFST) as a new type of composite structure, which is able to improve problems in the application process of ultra-high strength concrete. Previous studies on steel tube confined concrete limited to strength grade C80 below, ultra-high strength concrete must be studied deeply, thus breaking the bottleneck of its practical engineering application.This paper presented an experimental study of axial bearing capacity on 10 circular steel tubes confined steel reinforced ultra-high strength concrete short columns(CTSRC) and 1 concrete filled steel tube short column(CFST) which height-diameter ratio H/D are 3 and concrete strength grade are C100, it mainly studied how the strength grade of steel tube, the diameter-thickness ratio and the shape of section steel affect the mechanical performance of CTSRC and CFST specimens, specific tasks of this paper are as fellows:(1)A series of experimental studies were carried out to investigate the failure process and the failure mode of CTSRC. In this paper, the destruction of the whole process in detail were described, the failure process and the failure mode were analyzed theoretically, at last the failure mechanism were elaborated.(2)The effect of the section steel shape on CTSRC was considered firstly, three shapes of section steel(H, X and O) that can generate different "additional constrains" were studied, the effect on the specimens’bearing capacity and ductility were studied by load-displacement curves.(3)By comparing specimens of different steel tube strength and diameter-thickness ratio, this paper explore the bearing capacity and ductility performance of CTSRC and then analyze the differences by comparing the experiment results at home and abroad.(4) The steel tube strain data under different experimental factors were analyzed, the elastic-plastic theory model was used to analyze the stress of specimens. The law of steel tube and section steel’s development from elastic stage, elastic-plastic stage to plastic stage were explored.(5)By the axial bearing capacity data obtained in the experiment, the different triaxial compression strength model at home and abroad were used to compare. At last, a bearing capacity calculation formula of CTSRC was put forward.