Why helical reinforcement gives better strength than ordinary columns?

Helical reinforcement has the potential advantage of protecting columns/piles against seismic loads so due to this reason most of the engineers tends to use helical reinforcement instead of ordinary columns. Using of helical reinforcement increases 5% of more strength on spirals.

Moreover, when the columns reach the failure state, the concrete outside hoops cracks and falls off firstly, followed by the eventual failure of the whole columns. The peeling off of concrete outside helical reinforcement provides a warning signal before the sudden failure of columns. In addition, it can take up a higher working load than normal link reinforcement. Hence helical reinforcement is adopted in the design of marine piles in government piers.