Splice strength of large diameter, high strength steel reinforcing bars

The results of an experimental program conducted to study the splice strength of large diameter, high strength reinforcing bars, either No. 20 (63.5 mm diameter) or No. 9 (28 mm diameter), are presented. The parameters included in the experimental program are the bar size, splice length, concrete compressive strength, and the amount of transverse reinforcement provided within the splice zone. The ability of several models including the current ACI 318 Building Code, to predict the maximum steel stresses at the onset of splitting failure was examined for these high strength, large diameter bars. The influence of the moment of inertia of the bar on the induced splitting stresses was evaluated numerically using finite element analysis. Test results showed that the presence of transverse reinforcement has a more pronounced effect for large diameter spliced-bars compared to regular size bars. It is also shown that the current ACI 318 Building Code provided more conservative bond strength predictions for regular bars compared to large diameter bars.

► The study provides unique data on the bond behavior of large diameter steel rebars.
► Large diameter rebars will not develop its yield strength without the presence of transverse reinforcement within the splice region.
► The ACI 318 Code provisions for bond can be extended to large diameter rebars.
► It is recommended to increase the development length by 25 for large diameter rebars.