Seismic Data (Site Class / Soil Class)

[structural2010]

I am working on a new truck weigh station(Marshall, IL) about 50 miles west of Terre Haute, IN. The building is very small only 30' x 30'........I was told to assume 2000 psf for the allowable bearing pressure and just verify this later at time of excavation. However, this is a state job and they are requesting seismic data be put on our note sheet. I know I can get the Seismic Design Cat out of the 2006 IBC, but does anyone know where I can get information on the soil site class?? I highly doubt a website would give information on soil site class, but just looking for others opinions. Thank you!!

 

[Jalthi]

Usually the geotech consultant determine the site class. They generally recommend site class D(Kind of default). If the soils are 'weaker' then the class will be E or F. Higher classes such as A and B should be determined through seismic testing.

Since you are using a bearing capacity of 2000 psf, it could be a Class D. But don't take my word for it.

 

[JLNJ]

I believe the code lets you assume Site Class D unless you have reason to believe the soil is expectionally poor.

 

[HSIII]

There is a note within the '09 IBC about being able to assume site class D when the soil parameters are unknown. I would assume the same note is in the '06 IBC.

 

[jtx]

You are allowed to assume Site Class D if the geotechnical conditions are unknown

 

[azcats]

Note that if you have much seismic loading at all, assuming Site Class D can increase your loads enough to put you in Seismic Design Category C or worse which can require you to get a geotechnical investigation.