Research On Mechanical Behavior Of Multi-cell Special-shaped Concrete-filled Steel Tubular Stub Columns Under Axial Compression

The square column cannot provide prominent architectural functions with regular indoor space,which leads to have a poor applicability for the building.Based on the reinforced concrete special-shaped column,a multi-cell special-shaped concrete-filled steel tubular(CFST)column has been proposed to solve this problem,which the structure form is relatively novel.In this thesis,experimental research and numerical analysis of axial behavior have been carried out for I-shaped multi-cell CFST stub columns and L-shaped multi-cell CFST stub columns.The main contents include the following four parts:①Experimental research on the axial mechanical behavior of I-shaped multi-cell CFST stub columns were performed.The test parameters included the width-thickness ratio of steel tube on column limb and concrete strength.According to the failure phenomena,load-displacement curves and load-stress curves,the influence of test parameters on the failure mode,the load bearing capacity and the ductility was summarized and analyzed.The results showed that the confinement effect to concrete provided by I-shaped multi-cell steel tube was in good condition,and steel tube could basically yield before the load bearing capacity.With the increased of the width-thickness ratio of steel tube on column limb,the load bearing capacity increased but the ductility decreased.With the increased of concrete strength,the load bearing capacity increased but the ductility decreased.②Numerical analysis on the axial mechanical behavior of I-shaped multi-cell CFST stub columns were performed.ABAQUS finite element models were established,and the finite element results agreed well with the experimental results,which proved the validity of the finite element models.On this basis,the parametric analysis was carried out to study the influence of the ratio of steel,steel yield strength,concrete strength and the width-thickness ratio of steel tube on column limb on the initial stiffness,the bearing capacity and the ductility.According to the comparison results of experimental bearing capacity and design bearing capacity of several codes,technical code for concrete filled steel tubular structures(GB50936-2014)was recommended to calculate the axial bearing capacity of I-shaped multi-cell CFST stub columns.③Experimental research on the axial mechanical behavior of L-shaped multi-cell CFST stub columns were performed.The test parameters included the width-thickness ratio of steel tube on column limb and the strength of the concrete.Similar to I-shaped specimens,the influence of test parameters on the failure mode,the load bearing capacity and the ductility was summarized and analyzed according to the failure phenomena,load-displacement curves and load-stress curves of the specimens.The results showed that the confinement effect to concrete provided by L-shaped multi-cell steel tube was in good condition,and steel tube could basically yield before the load bearing capacity.With the increased of the width-thickness ratio of steel tube on column limb,the load bearing capacity increased but the ductility decreased.With the increased of concrete strength,the load bearing capacity increased but the ductility decreased.④Numerical analysis on the axial mechanical behavior of L-shaped multi-cell CFST stub columns were performed.ABAQUS finite element models were established,and the finite element results agreed well with the experimental results,which proved the validity of the finite element models.On this basis,the parametric analysis was carried out to study the influence of the ratio of steel,steel yield strength,concrete strength and the width-thickness ratio of steel tube on column limb on the initial stiffness,the bearing capacity and the ductility.According to the comparison results of experimental bearing capacity and design bearing capacity of several codes,technical code for concrete filled steel tubular structures(GB50936-2014)was recommended to calculate the axial bearing capacity of L-shaped multi-cell CFST stub columns.