Study On The Axial Compression Performance Of Concrete Filled Multi-barrel Steel Tubular Short Columns

With the development of building structure, new sections of CFST appears in the modern high-rise building, which is called concrete filled multi-barrel steel tubular short columns. It can supply higher capacity, great fire resistance and more convenient to connecting with outrigger truss or waist truss.On the domestic and foreign research, there is some deficiency as following: one aspect is the multi-barrel CFST is few, the other one is the axial load bearing capacity formulas are not unified, which is not convenient to the practical application of engineering. To solve the two problems above, this paper presents a study on that. The main contents are divided into the following four parts: Theoretical derivation, experimental research, finite element analysis, and unified formula of the axial compression bearing capacity of concrete filled multi-barrel steel tubular short columns.Firstly, the limit equilibrium method is used to derive the formula of axial bearing capacity of concrete filled multi-barrel steel tubular short columns, and introduce the concept of equivalent hoop coefficient. The results show that the equivalent hoop coefficient of it is linear superposition of the different layers’, which can effectively solve the axial load bearing capacity of short columns with more barrels or more layer steel tubular. The equivalent hoop coefficient of hollow concrete filled steel tubular column with inner steel is related to the occupancy rate of concrete. If the occupancy rate of concrete is more than 0.5, we consider hoop effect of the corresponding steel, otherwise ignore it.Then, a test of 26 members in the 5 groups of concrete filled multi-barrel steel tubular short columns is carried out, which is mainly observed the deformation and the failure style of all member.In the end, according the relation of the equivalent hoop coefficient and hoop coefficient of every layer, which is given in the second chapter, combining the idea of unified theory, give the unified formula. The results show that the calculated results are in good agreement with the experimental results and finite element results. And the cross section reduction coefficient of the steel tube columns with square steel tube filled with steel tube columns and rectangular steel tube columns is 0.7.