Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Responsiblity for local conditions

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Title: Message
The problem with ANYONE providing SDC is that it is based upon the soil type that is located at the particular site AND the importance of the building in addition to the seismicity of the site location.  SDC is NOT just a function of seismicity, like Seismic Zones are in the UBC.  And since the soil can vary quite a bit just going from site to site, how do you expect a local jurisdiction to have that information.  It is reasonable to expect the soil type to be established by a soil consultant (aka geotech engineer) and then the engineer of record to determine the SDC based upon that soil type, the seismic parameters (which are available from the USGS sources) and the importance of the building.  I would agree that the local jurisdiction should provide the basic wind speed to use and the ground snow load to use (if applicable), especially if in a "special" wind or snow region.  The local jurisdiction might also reasonably provide the seismic parameters (S1 and Ss).
 
Regards,
 
Scott
Adrian, MI
-----Original Message-----
From: WISH DENNIS [mailto:dennis.wish(--nospam--at)verizon.net]
Sent: Tuesday, November 20, 2007 11:07 PM
To: SEAINT Listservice
Subject: Responsiblity for local conditions

In a private e-mail with another list member it occured to me that there should be more responsibility placed on the local building department to provide the engineer with the basic seismic and wind design criteria and thus simplifying the methodology. The reason is simply that the city becomes responsibile for a much smaller geographic area than what an engineer may run across while dealing not only within the same county but thoughout a state or in multiple states.
It would much easier for La Quinta California, for example to provide the SDC, Soil and wind design data as a worst case scenerio verses what is obtained through geotechnical reports (similar to the base design data that becomes more conservative until the cost of identfying any local changes from lot to lot. The same issue should hold true of the Counties that are not incorporated or under the jurisdition of a local city or municipality.
I've yet to find many building departments that are not represented online and it would be easy enough for them to post local design basics than for the engineer in charge to be chasing his tail only to try and determine what is the code basic that would be allowed for design in that region. For example, slab on grade foundations are required to be 12-inches below grade here in the desert but 18-24 inches in regions outside where expansive soils exists. Norco California was required to design with a basic 90 mph wind gust while La Quinta fell into a 70 mph gust and depending on whether or not you are in North Palm Springs or South Palm springs you design for either 90 mph or 70mph respectively.
What is going to harm us is the mistakes made when design professionals from outside the area assume a soil condition or relative location to an active fault based on a map or book when the majority of designs submitted in one jurisdiction will be pretty much the same time after time.
How would we go about instituting this kind of requirement of local jurisdictions to provide basic design data for their area using worst case conditions unless determined otherwise through geotechnical reports etc.?
 
I'd be interested in some comments.
 
Dennis
 
Dennis S. Wish, PE
California Professional Engineer
Structural Engineering Consultant