Research On Mechanical Properties Of Reinforced Concrete Square Columns With Circular Compound Spiral Stirrup

A great deal of earthquake damages illustrate that the destruction of the column mainly cause the structural damage of building. The method of how to improve the ductility of column, especially in the bottom of the column, has become essential in the research of structural seismic performance. The performance of columns with spiral stirrups is much better than that of ordinary stirrups in terms of energy dissipation and resisting deformation, meanwhile spiral stirrups also strengthen bearing capacity and improve seismic performance of column substantially. As the circular spiral stirrup constraint ability is much better than the rectangular spiral stirrup, there is much more theoretical meaning and engineering value on the mechanical properties of reinforced concrete square columns with circular compound spiral stirrup.In this paper, axial and bias compressive experiment of eight concrete columns are tested, which is reinforced by circular compound spiral stirrups involving circular spiral stirrups and ordinary stirrups. The research mainly focus on ultimate bearing capacity and ductility of reinforced columns with the circular compound spiral stirrups in terms of axial and bias compression, comparing with mechanical performance of reinforced columns with rectangular spiral stirrup and ordinary stirrup. The paper analyzed the changing process of concrete, longitudinal reinforcement, stirrup along with load, and finally discussed factors of axial compressive bearing capacity and ductility according to the data of axial compressive experiment and finite element simulation. The results show that the circular compound spiral stirrup can effectively improve the ultimate bearing capacity, peak strain and ultimate strain of axial and bias compression for reinforced concrete square columns, on the other hand the ultimate bearing capacity and ductility of concrete column with circular compound spiral stirrups are much better than the figure for column with rectangular spiral stirrups. In the bias compressive experiments, the circular compound spiral stirrups lessen the restrain to concrete column, comparing to the axial compression. The factors, including space between stirrups, diameter of stirrup and the strength of concrete, would have an great effect on ultimate bearing capacity and ductility of concrete columns. At the end of the paper, it analyzes the mechanical characteristics of concrete with circular compound spiral stirrups, referring to the formula of existing criterions for axial and bias compression, and finally calculation methods of axial and bias compression for reinforced concrete square columns with circular compound spiral stirrups are proposed.