Performance of Externally Steel Angle-Collared Concrete Columns Under Axial Compressive Load

Deficient Reinforced Concrete (RC) columns and higher demands of new codes are the
main reasons for retrofit works for RC columns. One of the deficiencies involves the lack of confining
elements which leads to poor ductility. Confining stress conventionally provided by transverse
reinforcement has been recognized to enhance the strength and ductility of RC columns. Nowadays,
the confinement method has been further developed to be applied externally which is more suitable
for retrofit works. In square or rectangular columns, providing effective confining stress is not as
simple as that of circular columns. In this research, displacement controlled compressive test on a
set of square RC columns retrofitted by steel angle collars is presented. The volumetric ratio of the
confining elements is the main parameter to investigate the effectiveness of the retrofitting technique.
Enhancement of axial strength and ductility are observed as the confining element volumetric ratio
increases.