Studies On The Seismic Performance Of Four-tube Concrete Filled Steel Tubular Laced Columns

Concrete filled steel tubular(CFST) laced columns is a new type of composite column which takes material advantage of CFST columns and section advantage of lattice columns. Thus it is widely used in engineering circles. However, the research on seismic performance of CFST lattice columns at home and abroad is few. Present literatures usually focused on the study of the axial bearing properties while there are less research on the mechanical behavior in horizontal direction which limited the application and popularization of this superior structure form. In order to study on the seismic performance of limbs CFST lattice columns, this paper aims to study on its hysteretic behavior and restoring force model under cyclic loading.(1) Low-cycle loading experiment of six CFST laced columns was introduced in this paper, three parameters are considered in the experiment,they are:axial compression ratio, slenderness ratio and the decorated tube size. Test results indicate that the stiffness and ultimate load carrying capability of the CFST laced columns reduces with the increase of slenderness ratio. Improving the axial compression ratio properly can make level bearing capacity increases,but the ductility of members descends.(2) In addition, the finite element model of specimens are created with ABAQUS software and the analysis results proves to be reliable by test results. On this basis,67finite element models of CFST lattice columns are created and analyzed by ABAQUS software. The factors considered in expanding analysis are:slenderness ratio, axial compression ratio, concrete strength, strength of limp tube steel, lace bar size and the strength of lace bar steel. Analysis results show that the reasonable value of axial compression ratio is0.2-0.6and the suitable slenderness ratio is less than10. The slenderness ratio can be reduced by increasing the distance of limbs when the column height is certain.(3) With reference to relevant papers about the restoring force curve of circular or square concrete filled steel tubular column with single limb, basing on the results of the parameter analysis results, using EXCEL software,the restoring force curve computational formula of CFST lattice columns have been deduced and a reasonable hysteretic model has been put forward in this paper. The proposed restoring force model is verified by experimental results of the test and other related literatures. It can provide theoretical basis to elasto-plastic dynamic responses analysis.