Investigation on Effect of Different Steel Section on the Performance of Encased Composite Column

Abstract

Composite columns are constructed by providing structural steel inside concrete or concrete inside the structural steel. These columns are being used worldwide for the construction of high rise buildings since it can reduce the size of the columns in the building and increase the usable space of the floor plan. In addition, composite column enhances the overall rigidity of the building and provides significant shear resistance to strong earthquakes and other lateral loads. This study presents the behavior and performance of fully encased composite column subjected to axial load and horizontal cyclic load. In order to achieve the goal of the study, a parametric investigation procedure is undertaken, on a series of eighteen (18) sample column with different study parameters. A parametric study was conducted using the numerical model to investigate the influences of geometric properties of fully encased composite (FEC) columns. The geometric variables were shape of structural steel, column slenderness ratio (L/D) / the ratio of length of column (L), to the depth of the column cross-section, (D) and ties spacing ratio (s/D)/the ratio of transverse tie spacing, (s), to the depth of the column cross-section, (D).The column specimens were modeled as fixed cantilever columns with concentric axial load level of 50% of their axial load capacity as well as cyclic loading similar to that suggested by Applied Technology Council guidelines (ATC 1992 ATC 24).The material quality used for all composite column are the same grade. The nonlinear combined hardening and the concrete damage plasticity (CDP) model were used to define properties of steel and concrete respectively. In the Finite Element Analysis (FEA) C3D8R was used for solid elements and T3D2 was used for reinforcement. Nonlinear 3-D finite element output was then examined to know the response of column. The finite element analysis results demonstrate that the profile of encased section affect the performance of fully encased composite columns. Encased Tube Section (ETS) columns had good performance than Encased Circular Section (ECS) and Encased H- Section (EHS) due to its high stiffness. Increasing slenderness ratio of column from 7.5 to 11.25 and 15 reduce the lateral resisting capacity by 6.74% and 15.83% respectively. Spacing of tie also have a significant effects on axial and lateral resistance capacity of composite column. The effect is more observed on the buckling effects: as the spacing of lateral tie increases longitudinal reinforcement fail in bucking failure followed by crushing of concrete material before they reach their yielding stress