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Shear wall horizontal steel engaging end verticals when Vu>Acv*sq rt(f'c). 1997 UBC 1921.6.2.2 vs. IBC - ACI318/R99 Sect. 21.6.2.1

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Hello:

1997 UBC 1921.6.2.2 required horizontal concrete shearwall steel to engage
end vertical steel when Vu>Acv*sqrt(f'c). The 2000 IBC adopts ACI 318-99.
ACI 318-99 does not clearly spell out that horizontal steel needs to engage
end verticals when Vu>Acv*sqrt(f'c).  The IBC does not amend ACI 318-99 on
the subject.  

ACI 318-99 section 21.6.2.1 indicates only reinforcement that is required
for shear strength needs to be continuous. Shear reinforcement is not
required for strength until Vu>phi*Acv*2*sqrt(f'c).  ACI 318-99 section
21.6.2.3 indicates that continuous reinforcement needs to be spliced and
anchored per ACI 21.5.4. This means horizontal reinforcement is not required
to be continuous when Acv*sqrt(f'c)<Vu<phi*2*Acv*sqrt(f'c). ?  I see
Acv*sqrt(f'c)<Vu<phi*2*Acv*sqrt(f'c) all the time in low buildings.

ACI 21.5.4 does not mention engaging end bars. Even if the shear
reinforcement is needed for strength [Vu>phi*Acv*sqrt(f'c)] and is required
to be continuous it could be turned down or up and not have to engage end
verticals the way ACI 318-99 appears to be written.

What is the reason that the UBC requirement appears to be lessened in ACI
318-99? Is it to eliminate horizontals engaging end bars for tilt-up? 

This question is pertinent to our local  IBC code adoption.  Thanks for the
one private response the last time I asked this.


Thank you,

Scott M Haan  P.E.
Plan Review Engineer
Building Safety Division http://muni.org/building, 
Development Services Department,
Municipality of Anchorage
phone: 907-343-8183   fax: 907-249-7399
mailto:haansm(--nospam--at)ci.anchorage.ak.us