Analysis And Research On The Mechanical Behavior Of A New Type Of Five-spiral Stirrup Rectangular Concrete Column

With the development of high-rise buildings and prefabricated buildings,traditional reinforced concrete column are difficult to meet the requirements of bearing capacity and ductility.Existing studies have shown that the application of spiral stirrup to reinforced concrete column can significantly improve the bearing capacity and ductility,and is widely used in construction and bridge structures.As a new type column,the five-spiral stirrup rectangular column has little research at present.This paper will study the mechanical properties of the five-spiral stirrup rectangular concrete column.The main research contents are as follows:(1)Research on stress-strain curve of the five-spiral stirrup rectangular column under axial compression.Based on the Mander confined concrete model,a theoretical study on the axial compression stress-strain curve of the five-spiral stirrup rectangular column was carried out using the section division method and the overall analysis method,and the stress-strain curves obtained by the two analysis methods was compared with the test curve.Because the overall analysis method is simple and the result curve is closer to the test curve,it is used as the axial compression stress-strain curve,and the curve is used for ABAQUS.(2)Study on axial compression behavior of the five-spiral stirrup rectangular concrete column.Firstly,based on the various test results reported in the literature,the finite element analysis results are compared with the test results,and it is found that the ABAQUS results agree well with the test results,and hence the correctness of the finite element model is verified.Secondly,the finite element model is used in a parametric analysis to study the likely influence of concrete strength on axial bearing capacity and ductility of rectangular short columns with different stirrup configuration.In a term of equal material consumption principle,the four types of stirrup configuration are in forms of five-spiral stirrup,five-hoop stirrup,rectangular stirrup and rectangular-spiral stirrup respectively.The analysis results clearly indicate that five-spiral stirrup rectangular columns exhibited higher compressive strengths and ductility capacities.Through the analysis of influencing factors for the five-spiral stirrup rectangular short column,a calculation method of axial compression bearing capacity is proposed.Then,compared to the formulas recommended by codes of different countries,the calculation method proposed in this paper possesses high precision.Finally,the stability of the five-spiral stirrup rectangular long column is studied,the influence of the slenderness ratio on its stability is mainly studied,and the calculation method for the stable bearing capacity is proposed.(3)Research on seismic performances of the five-spiral stirrup rectangular column.Firstly,the two-fold line model and the hysteretic constitutive model of steel bars were used to finite element model separately and compared with the test results.It was found that although the load of the two-fold line model was consistent with the test,the hysteretic curve did not "shrink",and the hysteretic constitutive model considered the stiffness degradation is in good agreement with test results.Therefore,in order to ensure the correctness of the finite element model,the stiffness degradation should be considered.Secondly,analyze the seismic performances with parameters,mainly study the influences of axial compression ratio,shear span ratio,stirrup spacing and strength of longitudinal reinforcement on hysteretic curve,skeleton curve,hysteretic energy dissipation and stiffness degradation;Finally,combining the above four parameters,increasing the strength of longitudinal reinforcement can significantly increase the energy dissipation capacity,the fullness of the hysteresis loop,the bearing capacity and the ductility,which is regarded as the most advantageous way to improve the seismic performances of the five-spiral stirrup rectangular concrete column.