Pull out tests to study anchorage / bond on concrete specimen with embedded helical end rebar (HER)

Abstract

In order to develop full stress, rebar needs to be extended beyond a section for a length equal to development length in a reinforced concrete member. U-Hook or bent up bar is a solution to overcome the problem of development length, but congestion of reinforcement is an issue. Many a time, there will be shortfall, and mechanical anchorages or headed bars in place of hooks were used to overcome the congestion issue. An alternative method of anchorage with Helical End Rebar (HER) was investigated by conducting a pull-out test. HER may not fully address the issue of congestion. Parameters considered in the investigation are the diameter of the coil, pitch of coil and number of coils embedded in concrete. All these are combined as helix coefficient. It is found that the helix coefficient influences the anchorage of Helical End Rebar.