Experimental work on a tied column showed that strain in confining reinforcement was only 20% of main reinforcing steel strain at first peak and stress level in confining steel was only 28.
In order to study the effect of lateral confinement on compressive strength of axially loaded rectangular tied column, the variables are concrete compressive strength, ties yield strength and configuration, the volumetric ratio of the transverse reinforcement, the tie spacing, and the volumetric ratio of the longitudinal reinforcement.
Deformability (toughness) of concrete tied column can be improved by replacing the circular tie bar with equivalent area steel plate.
Over 90% of columns in buildings in non-seismic areas are tied columns.
Monotonic Axial Compression Test on Ultra High Strength Concrete Tied Columns, Proceedings of the 10th World Conference on Earthquake Engineering, Madrid, Spain, July 19-24, 1992, V.
Analytical Model for Concrete Confinement in Tied Columns, Journal of the Structural Division, ASCE, V.