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RE: MBR Tie-Down System

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Ron,
I've seen a building in the Seattle area which is a five story condominium 
that suffered extensive exterior wall water intrusion because of some 
flashing and sealing issues around the windows.  When the General 
Contractor opened up some shear walls, he found the holdowns were loose. 
 The threaded rods were pretty much sloppy in the stud bays.

When I toured the site, I saw some MBR 2B brackets with as much as a 3/4 to 
one-inch gap on the upper floors between the nuts and bracket.  The GC 
ended up opening EVERY location within the shear walls to retighten.  The 
interior shear walls displayed the same behavior.

Since we have a continous threaded rod connection here, the upper floors 
will display "collected" shrinkage as we go up floors with most of the 
shrinkage coming from the floor joists.

A representative from the original structural firm who designed the 
building actually try to state that he believed that passing cars in front 
of the building caused enough vibration to loosen these holdown brackets, 
yet WD-40 had to be squirted on the nuts to loosen from rust.  This person 
just couldn't visualize collected shrinkage issues when you use this 
system.

I know of some former MBR system installers who complain profusely about 
going back to retighten the system many times before the sheetrock is 
installed.  What happens after that?  The building will continue to shrink 
over time causing the holdowns to come loose.

There was plenty of talk about who is to blame for this situation and 
litigation rumors were flying rampant about this building.  Overall, the 
MBR System does not compensate for wood shrinkage.  If you examine their 
system closely, it is not much more than a simple nut and a plate.  If the 
wood shrinks, the system naturally comes loose.  Potential liability issues 
could be aimed at specifying engineers in this sue-happy world.

I do know of one system out there that does truly compensate for shrinkage 
and who has their ICBO ER#.

Does anybody else out there have similar experiences???

Ed Chin, PE
Seattle WA

----------
From: 	Ron O'Kane[SMTP:rokane(--nospam--at)leok.com]
Reply To: 	seaoc(--nospam--at)seaoc.org
Sent: 	Monday, March 16, 1998 7:48 AM
To: 	seaoc(--nospam--at)seaoc.org
Subject: 	MBR Tie-Down System

<<File: ATT00016.htm>>
Has anyone had experience with the MBR tie-down system?  I am interested in 
long-term effects as the bulding shrinks.

Ron