Bar continuity and strain compatibility for high-strength steel reinforcement in reinforced concrete structures

High-strength steel reinforcement in grade B600 with yield strength of 600 N/mm(2) is gaining popularity for its potential to reduce the total amount of reinforcement used and improve construction productivity. However, longer lapped length is required by the conventional lap splicing method for bar continuity. Besides, the conventional design methods are limiting the strength of reinforcement due to strain compatibility issue which suggest that the concrete would fail before B600 rebar yield. This study investigated the reliability of mechanical couplers as alternative splicing method. Statistical analysis showed that the performance of permanent elongation is well within the specified limit of <0.1 mm and the mean tensile strengths are 15.7%-22.1% higher than the requirement. This study also investigated the effectiveness of confinement on enhancing the strain compatibility between B600 rebars and normal concrete through finite element analysis. Results showed with adequately close stirrups, the B600 bars are able to yield and the overall load resistance could be improved by 24%-27% compared to the unconfined models.