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RE: Soil report seismic acceleration minimums??

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Wait till you see the IBC or the new NEHRP.  The accelerations will blow you away, but when you calculate the base shear, it washes (kind of, sometimes).  

The soils report acceleration needs definition.  Was it a PGA?  What was the probability?  Was it site specific, regional, etc.?  Put the zip code into the USGS Golden magic acceleration finder, and see how it compares.

The 97 UBC is good advice, since it takes near fault into account.  The increase in construction cost should not be that significant for a 1 story wood frame.  And it takes you out of the legal cross hairs by using the most current provisions.

In response to your PS.  If it takes more time (which it does), you should bill for it.

Harold Sprague
Krawinkler, Luth & Assoc.

-----Original Message-----
From:	Harris3803 [SMTP:Harris3803(--nospam--at)aol.com]
Sent:	Tuesday, May 19, 1998 8:51 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	Soil report seismic acceleration minimums??

A fellow engineer called me today to ask what others are doing now that soil reports have expanded into discussing seismic accelerations for design.
This case is a one story wood frame office in Piru. The soil stated a maximum near fault earthquake of magnitude 7 with an acceleration of 1.3G . 
My experience plan checking other projects of this type is nearly all ( all . ? ) design for '94 UBC Z= .4G and ignore the soil report . The building department can only enforce the code with local amendments so this will get a permit.
The '97 code will require a 30% increase since it is a near source fault type b area. 
The engineer wanted my opinion but i was not sure of my advice : Design to the '97 code requirements since for this type of structure, a 30% increase is not a significant cost increase and one story wood frame to L.A. city standards ( Ventura Co requires this ) should do well anyway. 
Is there a way to equate an acceleration from a soil report to a design force for wood frame?
I would appreciate any opinions on how you would ( will ? ) handle similar situations.
Thanks in advance.
Tom Harris , SE
Thousand Oaks, CA

P.S. Should there be a surcharge for providing '97 code design now ( optional ) since it takes more time?

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