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Re: Ungrouted Base Plates?

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> From: "Polhemus, Bill" <wlpolhemus(--nospam--at)sbinfra.com>

> I've noticed that the typical highway sign supports (i.e. "sign bridges"
> etc.) and even the very tall "high mast" lighting structures here in Texas
> have base plates that are NOT grouted. The loads into the foundations go
> through the anchor bolts for tension AND compression.
> 
> The plates rest on the levelling nuts.
> 
> Again, no grout.
> 
> What if any is the advantage in this? I can sort of see it for big, thick
> annular base plates attached to circular or polyhedral columns, which have
> only enough "meat" to allow an anchor bolt hole, since the bending is not
> likely to be great.
> 
> But I can't see the advantage for rectangular base plates, since the bending
> and punching forces are likely to be severe. It seems to me that you'd want
> a grouted pad beneath them so they'd "behave" more responsibly.

For structures that support significant gravity loads, the grout may be
a necessity. However, if the base plate is designed for moment
resistance and the gravity load is small in comparison, then it doesn't
matter to the plate if the bolts are in tension or compression.

Advantage? No grout. It has no purpose in this application and can be a
maintenance issue and corrosion concentrator.

The tall mast structures that I've seen tend to have a fairly
significant moment base rather than a simple plate.

-- 
Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada
<mailto:ad026(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>