Product Technical Guides : US-EN Post-Installed Rebar Guide - Page 29

Post-Installed Reinforcing Bar Guide
Equivalent ( uniform ) bond stress values corresponding to development lengths determined in accordance with ACI 318-19 are shown in Figure 45 :
Bar size
Concrete Compressive Strength ( psi )
3000 4000 5000 6000 7000 8000 ≤ # 6 570 658 735 806 870 930 ≥ # 7 456 527 589 645 697 745
Figure 45 — Equivalent bond strengths ( psi ) for uncoated bars developed in accordance with ACI 318-19 Section in normal weight concrete with ( c b
+ K tr )/ d b
= 2.5 .
In the absence of confining reinforcement , the confinement term achieves the limiting value when the ratio of c b to db equals 2.5 . Theoretically , the development length of a reinforcing bar with cover equal to or greater than 2.5d b is no longer controlled by splitting . Since practical considerations often dictate edge distances for post-installed reinforcing bars greater than 2.5d b
, the presence of transverse reinforcement is often not a factor for determining the development length .
The development length provisions of the ACI code are predicated on the assumption that bars may be closely spaced and may be placed at cover depth from the concrete surface .
Limited reduction in development length is afforded for bars placed at or greater than 2.5d b away from edges , since it is assumed that pullout should control for these bars ( as opposed to splitting ). Increases in edge distance should permit further reductions in development length ; however , closely spaced bars carrying higher bond stresses could lead to concrete breakout failure , a failure mode not anticipated in the development length formulation .
However , when post-installed reinforcing bars are not lapped with existing reinforcing and are installed sufficiently far from edges , it may be appropriate to employ other design approaches as described in the following sections .
27 2021