Increasing Anchor Capacity with Reinforcement by ProQuest


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									   increasing anchor
      Capacity with
Q.    Is there any way to use additional reinforcing bars to
      increase the capacity of anchors designed according
to Appendix D of ACI 318-081?
                                                                         used. The increase in φ-factor for post-installed anchors
                                                                         is larger, but the use of supplementary reinforcement
                                                                         is often limited to cast-in anchors because the exact
                                                                         location and orientation of the reinforcement in an existing

A.    The answer to your question depends on the
      particular failure mode that is controlling the
strength of the anchor group you are designing. When
                                                                         member is often not known to a sufficient level of detail.
                                                                         The anchor capacity is calculated using the same equations
                                                                         whether supplementary reinforcement is used or not, but
the controlling failure mode is the steel strength of the                the φ-factor in some of the equations is higher. The area
anchor in either tension or shear, additional reinforcement              of supplementary reinforcement provided is not directly
will not affect the calculated strength of the anchor group.             used to calculate the anchor capacity.
Also, for the concrete failure modes of pullout and pryout,                  Supplementary reinforcement is defined in Appendix D
additional reinforcement does not affect the calculated                  as “Reinforcement that acts to restrain the potential
capacity. For the remaining failure modes of concrete                    concrete breakout but is not designed to transfer the
breakout in tension, concrete breakout in shear, and side-               full design load from the anchors into the structural
face blowout in tension, there are two ways that additional              member.”1 The commentary for this definition explains
reinforcement may increase the anchor group capacity.                    that “Supplementary reinforcement has a configuration
                                                                         and placement similar to anchor reinforcement but is not
Supplementary reinforCement                                              specifically designed to transfer loads from the anchors
   The first way that reinforcing bars can be used to                    into the structural member.”1 We’ll discuss anchor
increase calculated anchor group capacity is by allo
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