The Strength and Ductility of Lapped Splices of Reinforcing Bars in Tension

Abstract

When designing a reinforced concrete member for strength, ductility and robustness, it is essential that the tensile reinforcement at the critical section can not only develop the yield strength of the steel f sy, but that it can sustain this level of stress as deformation increases. At a lapped splice, each bar must be fully anchored beyond the lap length. The minimum lap lengths of deformed reinforcing bars in tension specified in the Australian Standard for Concrete Structures AS3600-2009 were recently revised and a procedure similar to, but less conservative than, the provisions in Eurocode 2 was adopted. The new provisions require longer lap lengths for small diameter bars in slabs, but considerably shorter lap lengths for larger diameter bars in beams and columns. This paper reports on several series of tests that examine the efficacy of the AS 3600-2009 provisions from the perspectives of adequate strength and ductility. Over 50 specimens containing both contact and non-contact lapped splices have been tested. The aim was to assess the current Australian provisions and to examine the reliability and consistency of the factors of safety associated with lapped splices. It is concluded that the strength requirements of AS3600-2009 are adequate for small diameter bars in slabs but may not provide an adequate factor of safety for large diameter bars in beams. Also, the AS3600 provisions may not ensure sufficient ductility of a lapped splice in members that use high strength concrete. Further tests are required to investigate these aspects.