A Study on Pull-Out Strength of H-end Rebar in Normal Strength Concrete

The objective of this chapter is to study the effectiveness of Helical end rebar (H-end rebar) in normal strength concrete. To avoid the bond failure between plain reinforcing bar and concrete, sufficient development length is to be provided. When the sufficient space is not available to provide the development length bends, hooks and mechanical anchorages are used. Similarly, to study the anchorage provided by H-end rebars, pull-out tests are conducted on concrete specimen of 150 mm × 300 mm size. The principal variables in this study are diameter of the rebar (6, 8 and 10 mm) and number of turns of helix (one, one and half and two turns). It is noticed that the load carrying capacity of pull-out specimen increases with increase in diameter of rebar and number of turns. Parameter influencing the behaviour of Helical end rebar is found to be diameter of helix, pitch and number of turns. All these parameters are combined into a new parameter named as Helix Coefficient (K). There is good correlation between helix coefficient (K) and bond stress (σu) with R2 value 0.99 and bond stress between H-end rebar and concrete decreased with increase in helix coefficient.