| Compared with ordinary steel,high-strength steel has higher yield strength,tensile strength and structural reliability.However,as the yield strength of steel increases,the yield ratio of steel increases and the elongation after breaking decreases.The length of the yield platform shortens or even disappears,and the strain strengthening effect of high-strength steel is not obvious.In the high-strength steel structure,the high-strength steel plate is relatively thin,and under the condition of unconstrained compression,local buckling failure is likely to occur in advance.In addition,for concrete-filled high-strength steel tube columns,the high-strength steel tube is continuous in the longitudinal direction,which is prone to local buckling failure.In order to make full use of the strength advantages of high-strength steel,this paper proposes a circular high strength steel tube confined high strength steel reinforced concrete columns,that is,a discontinuous high-strength thin-walled steel tube is wrapped outside high strength steel reinforced concrete.The high-strength steel tube is disconnected at both ends and mainly bears the hoop tensile stress,which can delay or even avoid the local buckling of the thin-walled steel tube;The built-in high-strength section steel is wrapped in the core concrete to avoid local buckling under compression.The strength and ductility of the core concrete are improved under the constraints of high strength steel tube and high strength section steel.In order to provide technical support for the design analysis and engineering application of this type of composite column,this paper carried out the following work:1.Carried out the axial compression test of 9 circular high strength steel tube confined high strength steel reinforced concrete stub columns,1 circular high strength steel tube confined concrete stub column,and 1 circular high strength steel tube high strength steel reinforced concrete stub column,mainly to study the influences of the yield strength of steel tube,the yield strength of section steel,the diameter-thickness ratio of high-strength steel tube,the thickness of high-strength section steel,concrete strength,the inner wall treatment method of high-strength steel tube,whether built-in high-strength section steel,and restraint mode to the axial compression behavior of the composite column.The test results show that:(1)For tubed steel reinforced-concrete stub columns,compared with ordinary strength steel tube,the member using high strength steel tube have greatly improved axial load bearing capacity and ductility;compared with the use of ordinary strength section steel,the member using high strength section steel have greatly improved axial load bearing capacity,and the ductility index remains basically unchanged;(2)Compared with circular high strength steel tube high strength steel reinforced concrete stub column,the axial compression bearing capacity of circular high strength steel tube confined high strength steel reinforced concrete stub column is slightly improved,and the ductility index is greatly improved;(3)For tubed steel reinforced-concrete stub columns,compared with using ordinary strength steel tube and ordinary strength section steel,using high strength steel tube and high strength section,the ratio of axial compression bearing capacity to simple superimposed bearing capacity has been increased from 1.37 to 1.49,indicating the use of materials is more fully utilized and the restraint effect on the core concrete is stronger;(4)The ratio of axial compression bearing capacity to simple superimposed bearing capacity of circular high strength steel tube confined high strength steel reinforced concrete stub column is 1.49,which is significantly higher than 1.43 of circular high strength steel tube high strength steel reinforced concrete stub column,indicating the use of materials is more fully utilized and the restraint effect on the core concrete is stronger;(5)When the peak load is reached,both the high-strength steel tube and the high-strength section steel have yielded,the strength of the high-strength steel is fully utilized.2.The eccentric compression test of 5 circular high strength steel tube confined high strength steel reinforced concrete stub columns and 1 axial compression test of circular high strength steel tube confined high strength steel reinforced concrete stub column were carried out,mainly to study the influences of the yield strength of steel tube,the yield strength of section steel,the diameter-thickness ratio of high-strength steel tube,the thickness of high-strength section steel and eccentricity to the eccentric compression behavior of the composite column.The test results show that:(1)For tubed steel reinforced-concrete stub columns,compared with ordinary strength steel tube,the member using high-strength steel tube have greatly improved eccentric load bearing capacity and the ductility index remains basically unchanged;compared with the use of ordinary strength section steel,the eccentric compression bearing capacity of the member using high strength section steel is slightly improved,and the ductility index is greatly improved;(2)When the peak load is reached,both the high-strength steel tube and high-strength section steel on the compression side have yielded,the strength of the high-strength steel is fully utilized.3.Finite element software ABAQUS was used to establish calculation models for the axial and eccentric compression members of circular high strength steel tube confined high strength steel reinforced concrete.The finite element analysis results are in good agreement with the test results,and the parameter analysis is performed.Based on the results of the test and parameter analysis,and on the basis of the relevant design specifications,a correction formula for the axial compression bearing capacity and the eccentric compression bearing capacity for circular high strength steel tube confined high strength steel reinforced concrete stub columns is proposed.The calculated results are in good agreement with the test results and the finite element results. |
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