| The column limbs of special-shaped concrete-filled steel tubular(CFST)column are flush with the wall,avoiding the exposure of the indoor column corner,improving the indoor use environment of the house,and improving the utilization efficiency of the indoor space,which is increasingly welcomed by architects,developers and users.Under the same conditions,the special-shaped CFST column structure has higher bearing capacity,better ductility and better seismic performance than the reinforced concrete special-shaped column structures,and its maximum applicable height and seismic fortification intensity are improved,which promotes the application of the special-shaped column structure.Although the special-shaped CFST column structure has been applied in many projects,the design method of the bearing capacities of the special-shaped CFST column has no relevant provisions in the existing specifications.It is mainly numerical calculation in the literature,which is not convenient for engineering design.In this situation,it is necessary to research the bearing capacity of special-shaped CFST columns to provide a theoretical basis for the design of special-shaped CFST columns structure.Based on the existing axial compression,bending,bias and shear experiments of special-shaped CFST columns,the finite element software ABAQUS is used establish finite element model(FEM)under various loads,and the rationality of the calculation results is verified.On the basis,further parameter analyses(a total of 3046 finite element models)were carried out and the design methods of bearing capacity of special-shaped CFST columns were proposed.The main results of this paper are as follows:(1)Six L-shaped CFST stub columns with opening vertical stiffener subjected to axial compression were experimented in this paper.The test results show that the opening vertical stiffener can effectively limit the deformation of the steel tube at the corner and enhance the constraint effect on the concrete in the area.Based on the existing axial compression experiment of L-shaped and T-shaped CFST columns,the effects of parameters such as limb width-to-thickness ratio,steel ratio,material strength and slenderness ratio were analyzed by ABAQUS.Based on the unified theory and superposition theory,the calculation formulae of the sectional axial bearing capacity of the special-shaped CFST columns were proposed,which considering the constraint effect of steel tube for concrete.The calculated values of the formulae are good agreement with the experimental results.On the basis of the sectional axial bearing capacity,considering the influence of the slenderness ratio,the design formulae of axial compressive stability coefficient of special-shaped CFST column were also proposed in this paper.(2)Based on the existing pure bending experiment of special-shaped CFST column,the finite element model and fiber model are established.The finite element software ABAQUS and MATLAB were used to analyze the influence of parameters such as limb width-to-thickness ratio,steel ratio,steel yield strength,concrete strength and bending angle on bending behavior.The simplified calculation formulae for the flexural capacity of special-shaped CFST were proposed,which can accurately predict the bending capacity.(3)Based on the existing eccentric compression experiment of special-shaped CFST columns,the finite element models are established.The effects of parameters such as limb width-to-thickness ratio,steel ratio,steel yield strength,concrete strength,loading angle and eccentricity on mechanical behavior were analyzed.According to the stress distribution of the section,the simplified mechanical models were proposed and the calculation formulae of the unidirectional eccentric compression bearing capacity of special-shaped CFST columns were derived.The calculated values obtained by the formulae are consistent with the numerical calculation results,and have a certain safety reserve.Based on the research on unidirectional eccentric compression bearing capacity,the formulae for checking the bidirectional eccentric compression bearing capacity were proposed.(4)Based on the existing shear experiment of special-shaped CFST columns,the finite element models are established.The finite element software ABAQUS was used to analyze the effects of parameters such as cross-sectional shape(T-shaped and L-shaped),shear span ratio λ(0.1-2.0)and axial compression ratio n(0.0-0.6)on shear resistance performance.A method for simplifying the T-shaped and L-shaped sections into a rectangular section for calculating shear capacity was proposed.The shear capacity in this method includes steel tube contribution,concrete contribution and axial force contribution.The shear resistance capacities obtained by the method are consistent with the experimental results,which have a certain safety reserve. |
