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Re: ACI Reinforcement in Moderate Seismic Seismic Zone - "Pedestal" Tie Spacing

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In my oponion, short stubby column will need more ties than long slender
column, since the failure mode for stubby column will be in shear. 
Stiff stubby column will also attract more seismic force than long
slender column.  The Kobe's earthquake had demonstrated that stiff
highway columns will not work without adequate ties.  So you should tell
the contractor what you want in your design.  Don't let them dictate
your design.

Good luck,

Tom Chiu, SE
Thomas Engineering

Eqbal M. Kassam wrote:
> In Pertrochemical Industry, there are a lot of conrete pipe supports
> supporting heavy pipes, valves and sometimes equipment.
> Pedastal are short stubby upright concrete members (unsupported height
> to least dimension is less than 3) and are frequently designed as axial
> compression members. Alternative way of design is as a cantilever beam.
> ACI has tie/stirrup spacing requirements for columns and beams in
> moderate seismic zone. Pedestals (h/d < 3) tie spacing is not stated in
> the body of the text. My question is are the rules for column (h/d > 3)
> tie spacing applicable to pedestal tie spacing ?
> In my view, pedestals being stiff members, should be reinforced
> according to ACI rules for columns. The local design contractor on our
> project disagrees.
> I appreciate your views on this. E-Mail kassamem(--nospam--at)
> Eqbal M Kassam, P.E Texas