Abstract:
Slender reinforced concrete column may fail in material failure or instability failure.
Instability failure is common problem which cannot be analyzed with first order analysis. So
second order analysis is required to analyze instability failure of slender RC column. In
second order analysis, the condition of equilibrium is satisfied in the deformed state of
structure. As the deformation increases the material and load-displacement behaves in
nonlinear manner. So nonlinear analysis is better for analysis of slender RC column.
In this study the capacity of uniaxial slender RC column which was illustrated by interaction
diagram was done using nonlinear FE analysis software which is called ABAQUS 6.13. The
key parameters which were studied in this thesis were eccentricity, slenderness ratio, amount
of steel reinforcement and shape of the column. Concrete damage plasticity was used for
modeling of material property of concrete and plastic for steel reinforcement bar and steel
plate. Material nonlinearity, geometric nonlinearity, effect of cracking and tension stiffening
effect were included in the modeling. Before modelling of specimen, validation was done by
taking bench experiment. Validation results shows that the experimental load was 85.581% of
FE result. Method used for validation was also used in modelling of all specimen. In
modeling tie, embedded and coupling constraints were used. Dynamic explicit with bulk
viscosity of 0.0015 was selected. Displacement control type with -0.004m/sec for loading and
0.02m mesh size for meshing was used. Using the job module, the analysis was run and the
results were collected. Consequently, the axial load-moment interaction diagram was plotted.
The diagrams reveal that as slenderness ratio increases, the balanced moment also increases
but the corresponding axial load was decreased. But increasing amount of steel to the column
increases the stability of the column and reduces the effect of slenderness ratio. For the same
slenderness ratio increasing the amount of steel also increase the capacity of column. And
also the capacity of square slender RC column is larger than rectangular slender RC column
with equivalent cross-section. But the difference is reduced as slenderness ratio increased.
Finally, axial load-moment interaction diagram was prepared for all specimens using
nominal stiffness method and comparison was done with the FEA results. It shows that the
capacity of the column that results from FEA was greater than nominal stiffness method.
