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RE: intermediate ties for pedestals in pre-engineered metal building

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Title: Re: intermediate ties for pedestals in pre-engineered metal building

Jim:

The designer in this case is working for the contractor and I am working for you.  For a firm fixed price contract – I want them to do it right. 

 

You cannot reduce the section .5 per 10.8.4 in a high seismic design category.  For a 30x30 pedestal the compression from a pre-engineered metal building is negligible.  Thrust in this case is not a factor required to design the pedestal, the lateral force is not designed to be transmitted through the pedestal. The question ends up being if extra bars are added to meet a minimum reinforcement ratio do they need intermediate ties by the code even if the vertical reinforcement is not required for strength.

 

Respectfully,

Scott Haan.

 


From: Jim Getaz [mailto:jgetaz(--nospam--at)shockeyprecast.com]
Sent: Thursday, May 12, 2005 2:30 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: intermediate ties for pedestals in pre-engineered metal building

 

        Scott,

                Have your engineer read the commentary for ACI 318 10.8.4 and 10.9.1 (limits of section and limits of reinforcement). If he can use those concepts to stretch the Code, the use of ties per the Code may not be necessary. However, I am under the impression that a PEMB column usually induces thrust on its support. This probably induces a moment into the pedestal, which is a concern for the minimum axial reinforcing of the pedestal. It also puts greater compressive force on some of the axial bars, thereby increasing their chances of buckling, which ties inhibit.

                I hate paying taxes, but ties sound like cheap insurance to me. Could bigger bars make it easier? (4) #14s provide minimum steel for 30" x 30". Using 10.8.4, (4) #10s provide minimum steel for 50% of 30" x 30". Then only one #3 tie is required at 18" c/c.

        Jim Getaz

        Winchester, Virginia