| Concrete-filled steel tube(CFST)column is a vertical load-bearing column commonly used for super high-rise structures and large heavy-duty structures because of its high bearing capacity,good plasticity and toughness,superior seismic performance,good fire resistance and significant economic benefits form.Compared with round CFST columns,square CFST columns have relatively more cross-sections,and have the advantages of greater flexural rigidity,higher flexural bearing capacity,simpler node structure,more convenient construction,more convenient construction space and fireproof plate layout,etc.It has wider application in practical engineering.The buckling problem of CFST columns with square cross-sections is extremely prominent,and there are strict width-thickness ratio limits during design,which weakens its own advantages to a certain extent.In view of the above shortcomings,the paper proposes a diagonallystiffened steel plate stiffened CFST column,which can effectively improve the local buckling performance of the plate and improve the bearing capacity and ductility of the member.In general,for the CFST column,the concrete inside the steel tube can increase its flexural rigidity and improve the overall bearing capacity,so that the CFST column can be designed to reduce the size of the column section to a certain extent and increase its shear-span ratio.Therefore,the load-carrying capacity of CFST frame columns in general construction projects mainly depends on the ultimate load-bearing capacity under axial compression or bending.It is necessary to consider that there are few cases of lateral shear resistance.However,with the development of engineering practice,it has been found that in some cases,such as nodes with braces between CFST columns,beam-column node areas of large-span heavy-duty beams,etc.,small shears of CFST columns that may affect the design may appear Cross shear problem.At the same time,short columns are also common in the frame tube structure,and the characteristics of the frame tube structure are the use of deep beams and short columns.Even in the frame structure,due to the constraints of non-structural members,the shear-span ratio of the column may become very small.Therefore,the research on the shear resistance of CFST short columns of the other party is a very meaningful work.In view of the weak points in the current research on the shear resistance of CFST columns,the main work content and results of this paper are as follows:(1)A total of four diagonally stiffened rib stiffened CFST short column specimens under low-cycle reciprocating load were tested for shear performance.The main parameters were the axial compression ratio,the width-to-thickness ratio and the presence or absence of the diagonally stiffened ribs.Test data of hysteresis curve,shear force-shear angle curve,failure shape and strain development of each specimen.The results show that the CFST stiffened thin-walled square CFST short column with shear-span ratio 1has shear failure under low-cycle reciprocating load,and the specimens with diagonal ribs have better seismic and shear performance.(2)The finite element software ABAQUS was used to establish the finite element model of the CFST stiffened thin-walled square CFST short column specimen,and the necessary parameter analysis was carried out.The shear-span ratio,axial compression ratio,steel strength,concrete strength,and presence or absence of slope were studied.Influence of the parameters such as the diameter of the ribs and diagonal ribs on the shear performance and failure mode of the short column specimen.(3)Summarized the existing shear strength formulas and verify their accuracy with test data;based on the test results and finite element analysis,the shear mechanism of the square CFST column is analyzed according to the failure phenomenon and failure mode of the specimen.And improved the mechanical calculation model and the calculation formula of shear capacity. |
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