Abstract:
This thesis aims at developing a suitable constitutive model addressing the behavior of short
Concrete Filled Steel Tubular column on the compressive response under axial loads. Ultimate
load carrying capacities obtained by, Schnider (1998) and Huang et al (2002), using experiments
have been compared with the analytical model values. The nonlinear finite element program
ABAQUS 6.14-2 is used to study the force transfer between steel tube and concrete core. The
interaction between steel tube and concrete core is modeled using surface-to-surface contact, a
clamped end boundary condition is used (fixed at the bottom and allowing movement in the
loading direction at the top) and a displacement controlled loading is applied. The analytical
results validated with experimental data extracted from experiments by the Authors in terms of
axial load vs. axial deformation graphs.
Then a parametric study is conducted using twenty seven circular CFST columns to investigate
the load carrying capacities and confinement of CFST columns. Here, the main parameters are
the yield stress of steel, diameter of the column and thickness of the steel tube. 120-137% of load
carrying increment is shown for concrete filled steel tubes by addition of concrein the hollow
steel tube. And also 95% of load increment by changing the diameter of the column and keeping
other parameters constant. 8-16% of load increment is recorded by changing the steel yield
strength and keeping other parameters constant. And also a maximum 5.27% increase of load
carrying capacity is observed by changing L/D from 3 to 5 and a decrease in the load carrying
capacity is observed with an increase of L/D ratios from 5 to 7.
A comparison of ultimate failure loads from nonlinear finite element program ABAQUS 6.14-2
with the predicted failure load from Euro code Part-4 (EC-4), ACI-318 (2005) (American
Concrete Institute), for axially loaded columns will be carried out in this research study. A
difference in increase of 7% is calculated using EC-4 and a difference in decrease of 33% is
calculated using ACI-318 with comparison to the modeled data.
