Study Under Eccentric Load Of Circular Steel Tube Composite Column Filled With Steel Reinforced Concrete

The circular steel tube composite column filled with steel reinforced concrete (CSTCC-SRC) is a kind of composite structures, evolved and developed on the basis of hollow section shaped steel reinforced concrete column and built-up column of concrete filled steel tube(or circular steel tube compile column filled with reinforced concrete). In this type of steel-concrete composite column, steel tubular column is inserted into steel reinforced concrete column. The CSTCC-SRC can provide great advantages over either pure steel tube or steel reinforced concrete members. The structure remedies their defects respectively. The columns are required to not only have the high ability to carry load, but also excellently improves its ductility and plasticity to avoid collapse in the earthquake. Based on experiment and theoretical analysis,the mechanical properties under eccentric load of` CSTCC-SRC are researched. The major contents are summarized as follows:The experiment was done upon small eccentricity pressing CSTCC-SRC which has three types of steel ratio. Work mechanisms of this composite column are studied. The higher the steel ratio, the higher the capacity and ductility is. The results of theoretical analysis were proved to fit the test. It indicates that the circular steel tube concrete column and the steel reinforced concrete can work together well and its capacity is higher than the capacity of circular steel tube compile column filled with reinforced concrete.On the basis of the experiments of CSTCC-SRC, there are two methods for calculating flexural strength of the column being discussed. One method is based upon the method in building code for calculating the flexural strength of reinforced concrete member, while the other is based upon the method of superimposition of SRC member. And calculating flexural strength of the column is given in three cases according to hooping effect of SRC. The results are in good agreement with the experimental results.A theoretical formula for the limit value of axial compression ration of CSTCC-SRC is obtained. It is based on the equilibrium condition of internal forces in the case of critical failure. It is the case that a practical formula is forward. The limit values of axial compression ratio and limited values of axial pressure for such column are proposed.