The use of links for column design is very popular. However, engineers tend to use helical reinforcement instead of normal links because helical reinforcement has the potential advantage of protecting columns/piles against seismic loads.
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.
For instance, helical reinforcement is adopted in the design of marine piles in Government piers.
Note: Helical reinforcement refers to shear reinforcement which is spiral in shape.
