While link reinforcement is favored for column design in Britain, U.S. engineers often opt for helical reinforcement due to its advantages, particularly in seismic regions. Helical reinforcement, a spiral-shaped shear reinforcement, offers enhanced protection against seismic loads compared to traditional links.
This preference stems from the distinct failure behavior of columns with helical reinforcement. As these columns approach failure, the concrete outside the hoops cracks and spalls off first, providing a visible warning sign before the complete collapse of the column. This phenomenon, as noted by G.P. Manning in 1924, offers a crucial safety advantage in earthquake-prone areas.
Moreover, helical reinforcement demonstrates a higher load-bearing capacity than link reinforcement, contributing to the overall strength and resilience of the structure. This increased capacity is attributed to the continuous nature of the helical reinforcement, which provides more uniform confinement to the concrete core.
The effectiveness of helical reinforcement is evident in its application in critical structures like marine piles for government piers. These piles, subjected to significant lateral loads and environmental stresses, benefit from the enhanced seismic resistance and higher load-carrying capacity offered by helical reinforcement.
In summary, while both link and helical reinforcement have their merits, the choice between them is often dictated by regional practices and specific design requirements. In the U.S., the prevalence of seismic activity and the desire for early failure warnings make helical reinforcement a preferred option for many engineers.