Parametric Study On Behavior Of Rectangular And Circular CFST Columns Subjected To Different Loads

(CFST)Columns have high performance,strong load carrying capacity,good ductility,can be used for super structures and save building space.In this thesis inelastic analysis,concentric,eccentric and cyclic loads are used to predict the behavior and performance of rectangular and circular CFST columns.The study proposes analytical and FEM analysis to predict the failure mechanism after the ultimate different compressive loads and compare the load bearing capacity of each column by varying different essential parameters that affect the basic mechanical properties of the rectangular and circular CFST columns.This thesis proposes a new system development of a nonlinear FEM numerical models by using Abaqus 6.13 and OPEENSEES 3.0.3 simulation software.In this parametric study the ultimate axial load bearing capacity and lateral load bearing capacity of rectangular and circular CFST column is studied parametrically by changing(D/t)ratio,concrete grades and steel grades,slenderness ratio(leff/r),steel tube thickness and axial load ratio(N/No).The axial capacity of a rectangular CFST columns is increased as the slenderness ratio of the column decreased and increased as the increase in thickness of the steel tube but without increasing the overall diameter of column.When thickness of steel tube varied by 2 mm ultimate bearing capacity of CFST column is increased with 15 to 22 %.As the axial load ratio on rectangular CFST column increased the ultimate load of column decreased.As the column axial load ratio increased to 0.4–0.6,shear strength of CFST column began to decrease speedily resulting in axial failure of column.In case of concentric load on circular CFST column when the Depth/thickness D/t ratio increased from 15 to 37.5,the load carrying capability of the column decreased by66.9%.In case of cyclic load on circular column as the D/t ratio is increased from 15 to 25,the ultimate cyclic lateral load of the column is found to decrease by 31.458%.Increase in the axial force ratio from 0.30 to 0.50,the lateral load carrying capacity of CFST columns is reduced by 43.95%.When increasing the column slenderness ratio from 11.4 to 45.7,the ultimate cyclic lateral load of the slender column decreases by 86.6%.By changing the steel grade,the ultimate load carrying capacity increased as the yield strength of the steel raised.In case of circular columns under concentric load the load bearing capacity was found to increase by 24.4% with the increase of steel yield strength from 235 MPa to 425 MPa.By increasing the yield strength of steel from 235 MPa to 420 MPa,it is found that the maximum cyclic lateral load of the column is increased by 44.87%.Deformation decreases 18.20 %.If the column is subjected to a concentric load,if the compressive strength of the concrete increases from 30 MPa to 70 MPa,and the ultimate bearing capacity increases by 53.4%.In case of columns under cyclic load it is found that by increasing the compressive strength of concrete from 30 MPa to 70 MPa,the ultimate cyclic lateral strength is increase by 29.88%,and deformation decreased 10-15 %.It is concluded that in this parametric study that the ultimate axial load bearing capacity of RCFST under concentric and eccentric load increases as D/t increases and as the slenderness ratio of column decreased.As the axial load ratio on CFST column increase the ultimate load capacity of CFST column reduces.In case of circular CFST columns under concentric and cyclic load lateral strength is found to be increase as increase in steel grade,concrete grade and D/t ratio,as the slenderness ratio increased lateral load bearing capacity decreases and as the axial load ratio on CFST column increase the lateral load capacity of circular CFST column decreases.The length to thickness ratio(L/t)also plays a critical position in the performance of CFST columns.Higher the(L/t)lesser will be the axial bearing ability of column.