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RE: 4 Story Wood

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Title: RE: 4 Story Wood

To expand on Bill and Desi's thesis:

Wood stud walls in 1-hour construction can only be 78% stressed with le/d>=33 per 97 UBC Table 7-B footnote 18 . Studs supporting more than 2 floors exceed limits of 97 UBC Table 23-IV-B  and need to be specifically designed.  Bottom plate and top plate compression perpendicular to grain  can control spacing or size of wall studs.    Make sure manufactured rim-joist distributed load is not exceeded.  Make sure squash blocks are not required in floor to floor space between bearing walls.  Make sure lower level walls work for combined transverse wind and axial loads.  Foundation walls need to be 10" thick and footings need to be 18" wide when supporting 3 floors or an analysis is required per 97 UBC Table 18-I-C.

New codes don't allow toe nails for shear transfer greater than 150 plf - saw one hotel that used 16 toe-nails.  Stacked tiedown anchors and posts need to be designed for cumulative overturning effects, not just the effects on that level.

Shrinkage is not a small issue especially if you mix wood with steel or a CMU or PCC stair tower with wood or Desi's steel stud walls with wood stud walls.  If you are using wood with steel, then keep the steel at the lowest level only.  Say you have a steel post supporting a girder truss at the roof.  If you have .25 inch of moisture shrinkage per floor  for 4 stories then the girder truss is going to remain at the same elevation when the rest of the building wants to move 1 inch.  Also movement occurs from more than just shrinkage from moisture because every joint between studs, plates, joists, decking has small gaps and these close when the walls are loaded.  If the wood shrinks and the toilets pop through the floor and you told the architect about it that is some elses fault but if structural beams pop through the floor it is the structural engineer's fault for not accounting for it.  I would make sure and specify kiln dried lumber that is maintained bone dry in covered storage and that all bearing wall framing is flush without gaps

The IBC says fire walls = area separation walls need to be built so that if one side falls down the other side is not pulled over.

-----Original Message-----
From: desi j kiss [mailto:djkiss55(--nospam--at)juno.com]
Sent: Wednesday, October 09, 2002 4:29 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: 4 Story Wood


free advice:

USE METAL STUDS !

Desi J. Kiss, PE
http://djkeng.tripod.com/


On Wed, 9 Oct 2002 11:02:18 -0600 "Jake Watson" <jwatson(--nospam--at)utahisp.com>
writes:
> We are going after a 4 story wood project.  I have a not-so-simple
> question,
> what are the code issues relative to this aside from wood shrinkage?
>  It
> will be student housing (Dorms).  I am doing a code study now, but I
> am open
> to free advice.
>
> Respectfully,
>
> Jake Watson, P.E.
> Salt Lake City, UT



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