Abstract:
Transverse reinforcements have been used in reinforced concrete columns due to their
advantages to fix in position of longitudinal reinforcement during construction, to shorten the
buckling length of the reinforcement, to prevent shear failure and to confine the concrete.
However transverse steels have confinement advantage, the design of reinforced concrete
column is based on the simplified stress- strain model of unconfined concrete, and does not
account for the strength gain due to confinement. The existing column design charts are also
prepared based on the unconfined concrete and do not consider the strength enhancement;
consequently they are in conservative side and gives uneconomical longitudinal
reinforcement.
This research is conducted, analytically to determine the effect of confinement on reinforced
concrete column capacity in terms of the column axial force- bending moment interaction
diagram. The confined stress-strain model given in Eurocode-2 for normal strength concrete
was used. The lateral pressure for circular and rectangular column section was determined
for selected transverse reinforcement configurations, which are usually used for uniaxial
bending. The interaction diagrams were drawn using non-dimensional axial force and
bending moment capacities, which are computed at different neutral axis depths using C++
programing language.
The study shows that confinement increases the strength and ductility of the concrete, which
results a considerable enlargement of axial force -bending moment capacity in the
compression controlled region of the interaction diagram. Using additional cross and
overlapping ties as lateral reinforcement in reinforced concrete column, further increases the
column axial force- bending moment capacity. It is found that, confinement is more effective
in circular sections than rectangular sections. Numerical calculation for comparison also
made and it shows that reinforced concrete column designed by considering confinement
requires lesser amount of longitudinal reinforcement than a column designed with the
existing column design chart. Finally Uniaxial design charts for circular and rectangular
reinforced concrete columns with different transverse reinforcement configurations are
prepared and can be applicable for design
