Lap splices of bars in bundles

European (EC2) and ACI 318-08 design code rules for lap splices
of reinforcing bars within a bundle differ markedly—the former
permits the same or shorter lap-splice lengths with respect to
splices of individual bars, while the latter requires longer laps. This
paper reports an investigation into the performance of lap splices
of individual bars within a bundle of two or three. The results show
that the bond strength of individual bars is not reduced on account
of their forming part of a bundle (contrary to the provisions of
ACI 318-08). Staggered laps were found to be weaker but fail in
a less brittle manner when splices are staggered longitudinally as
compared to equivalent laps, where all bars are spliced at the same
section whether or not bars were bundled. Therefore, the outcome
raises the question of the validity of reductions permitted by both
the ACI 318-08 and European (EC2) codes, where only a portion of
the bars is lap-spliced at a section. It is recommended that further
investigation of the influence of the proportion of bars lapped at a
section on splice performance be undertaken.