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- To: <seaint(--nospam--at)seaint.org>
- Subject: RE:
- From: "Structuralist" <dennis.wish(--nospam--at)gte.net>
- Date: Wed, 21 Mar 2001 12:27:31 -0800
I'm not sure where on the website for SEAINT that you found conflicting information, but what is published in the code is law regardless of whether or not it is considered valid or not by the professional community. You are required to comply with the minimum provisions stated in the code and this includes the use of a 3x sill plate for shear loads exceeding 350-plf in seismic zones 3 and 4 as indicated in table 23-II-I-1.
As I recall, the provision started as an emergency measure after the Northridge Earthquake and was immediately adopted by the City of Los Angeles. The footnote does, however, allow you to reduce the sill plate to a 2x member as long as you design the anchor bolts to half strength and use plate washers 2-in square x 3/16" thick. Personally, I would also be careful about the drilling of anchor bolts in the plates. It's been my experience that the drilling of plates is generally done in a sloppy fashion and that holes are often drilled too large. Simpson has a plate washer that can also screw into the top of the plate to reduce the play between the shank of the bolt and the oversized hole in the plate. While this is more expensive, I believe it provides an inexpensive insurance against splitting the sill plate.
Another issue I have seen a great deal of are broken plates that split parallel to grain after they are installed. Often the plate splits through the centerline of some but not all of the anchor bolts. Simpson's product can help since it is generally not convient to replace the plate and the shank of the anchor is not long enough to allow for flat blocking to be installed above the original 2x plate.
In short, follow the provisions of the code to reduce your liability. Remember that while the opinion of professionals is important in the code revision processes, it is not a legal alternative to the provisions adopted by building officials in the form of the building code. The codification process is a process that converts submittals into laws. You are bound by law to design to no less than the minimum provisions indicated in the code publication. To deviate from this places you at risk.
Hope this helps to clarify the discrepancy.
Dennis S. Wish, PE
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- From: Evan Mizue
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