Study On Compression Mechanical Behavior Of Concrete-Filled Corrugated Steel Tubular Column With Polygonal Steel Tubes(CFCST-PST)

For the purpose of improving the high-risk problems such as variable longitudinal strain and local buckling of steel tubes in steel tubular concrete columns,the group had proposed a concrete-filled steel tubular columns(STCFCST-),in which the corrugated plates are welded to the square steel tubes with four limbs to form a steel multi-cavity and concrete is cast in the interior of it.It is studied and discovered that the steel tube and corrugated plate of the column can provides a relatively uniform restraint effect on the concrete compared with the ordinary steel tube concrete column,and its bearing capacity is higher and its ductility performance is better,which has been widely used in the field of assembled buildings.To further enhance the composite effectiveness of steel tube and corrugated plate in the composite column,a new type of concrete-filled corrugated steel tubular column with polygonal steel tubes(PSTCFCST-)column was advanced in this article.The investigation work on its axial compressive mechanical properties is carried out in this paper through three aspects: experimental,finite element and theoretical,as follows:(1)The axial compression tests of PSTCFCST-specimens and STCFCST-combined column comparison specimens were completed.The shape of the steel tube and the wave height of the corrugated plate were used as the main parameters to observe and record the whole process of damage of each specimen,focusing on the analysis of the mechanical property indexes and the strain development law of the specimens.The test results show that the axial compression load capacity of PSTCFCST-combined column is higher than that of STCFCST-combined column;the corrugated plate wave height has a certain influence on the load bearing capacity of the combined column,the larger the corrugated plate wave height is,the larger the column stiffness is,the higher the load bearing capacity is,and the better the ductility is.(2)Based on the experiments,a composite column model was established by using ABAQUS,and the finite element simulation was compared with the load-displacement curve and load-strain curve extracted from the tests to verify the validity of the model.The load capacity and transverse-longitudinal stress distribution patterns of typical specimens were studied and analyzed in order to investigate the axial compression stress mechanism of polygonal steel tube-corrugated plate restrained concrete columns.Comparing with the STCFCST-composite column with square steel tube,the polygonal steel tube and corrugated plate form a multi-cavity body that can provide stronger transverse restraint to the core concrete under the premise of the same steel ratio;the corrugated plate almost does not bear the longitudinal load,and the longitudinal stress transfer is disconnected due to its special pleated structure,and the crest has a stronger effect on the hoop with the concrete compared with the trough.(3)On the basis of the effective finite element model,a lot of parametric analysis was carried out,among which the diameter-width ratio,restraint coefficient,wave height and length-thin ratio have a great influence on the ultimate bearing capacity of the concrete-filled corrugated steel tubular column with polygonal steel tubes,and provide examples for the calculation formula of axial compression bearing capacity of PSTCFCST-column.(4)Summarize the existing methods for calculating the compressive load capacity of steel pipe concrete composite column,and use the test and finite element results to compare and analyze whether the formulas in codes and literature are applicable to the new column proposed in this paper.Combined with the calculation method of the restrained concrete bearing capacity proposed by Mander et al,the calculation formula of the axial compression bearing capacity of PSTCFCST-column is established by considering the influence of parameters such as strength and length to slenderness ratio on the restrained effect of concrete.The results show that the proposed bearing capacity calculation formula values of PSTCFCST-columns are in good agreement with the experimental and finite element values,and are on the safe side,and have reference value for engineering design applications.