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Requirements for a Geo Report Seismic C+

Requirements for a Geo Report Seismic C+

Requirements for a Geo Report Seismic C+

(OP)
Also, posted question in Geotech area, but not sure which area it better applies, geo or structural.

According to 1802.2.6 & 7 of the IBC, it is required to have a Geotech Report for seismic categories C and above.  Is there something that is acceptable for a Geotech report not be performed if a more stringent analysis is used?  I was informed there was such an entry, but I am unable to find it.

FYI, this is more of an office discussion instead of me trying to design without a Geotech Report.

RE: Requirements for a Geo Report Seismic C+

If the soils are unknown, use D unless the building official states it is less.  It is in there somwhere.

RE: Requirements for a Geo Report Seismic C+

Section 1615.1.1 in the second paragraph it says use Site Class D unless the building official determines that E or F soil is likely present, provided soil properties are unknown.

-Mike

RE: Requirements for a Geo Report Seismic C+

(OP)
Sorry, maybe I did not state the question clear.  The above posts are refer to the Site Class (which it is acceptable to use D), but I am referring to the Seismic Design Catagory C and above as stated in 1802.2.6 & 7.

RE: Requirements for a Geo Report Seismic C+

DJYork,

What do you mean by "a more stringent analysis is used"?  Do you mean a more stringent geotechnical analysis, or a more stringent structural analysis?

RE: Requirements for a Geo Report Seismic C+

(OP)
Well, it seems a little difficult to put into words, but I'll try.

If you have a seismic design category less than C (for seismic purposes) the IBC does not require a Geotech report per 1802 (my understanding).  So if you have a seismic design category in C or above are there values, assumptions, or provisions that the code allows if you still do not have a Geotech report.

It is somewhat ambiguous question, since the design values do not have a great deal to do with the seismic design category.

It a short version is there any way to design a foundation/building without a Geotech report (by code) if the design category is above C.

Again, this is a long story how this question came about in our office, but I want to reiterate that we are not trying to design without a soils report.

RE: Requirements for a Geo Report Seismic C+

I guess I'd question your statement that with Category C you have to do a "Geotech report".  

What the text of IBC 2000 says is, "Where a structure....Category C in accordance with Section 1616, an investigation shall be conducted, and shall include an evaluation of the following potential hazards resulting from earthquake motions:  slope instability, liquefaction, and surface rupture due to faulting or lateral spreading.".

Those are three distinct items that simply need to be "evaluated" by the geotech, and, I presume, reported back to the design team to consider.  Its not saying here that a full geotech report is required.  That's taken care of in 1802.1.

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