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IBC 2000/ ACI 318-99 - high seismic zone- concrete shearwalls w/ Vu>Acv*sqrt(f'c)- Requirement for horizontal reinforcement termination?

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1997 UBC 1921.6.2.2 required horizontal concrete shearwall steel to engage
end vertical end steel when Vu>Acv*sqrt(f'c).  This was similiar to the
non-seismic flexural member requirement  that minimum shear steel is
required when Vu>.5*Vc per UBC 1911.5.5.1 and that shear reinforcement needs
to engage flexural reinforcement per UBC 1911.5.3-UBC 1912.13.2.1-1907.11.2.

The 2000 IBC adopts ACI 318-99 which does not spell out this requirement
clearly.  The IBC does not amend ACI 318-99.  ACI 318-99 section 21.6.2.1
indicates only reinforcement that is required for shear strength needs to be
continuous.  ACI 318-99 section 21.6.2.3 indicates that continuous
reinforcement needs to be spliced and anchored per ACI 21.5.4.   

ACI 21.5.4 does not mention engaging end bars and shear reinforcement is not
required for strength until Vu>Acv*2*sqrt(f'c).  Even if the shear
reinforcement is required 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?
How are engineer's in California-Washington-other places handling this [ I
thought I heard CA was not going to adopt the IBC]? 

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