As is the case for wood, soil response is dependent on the rate of loading.
Long-term displacements generally govern the static allowables for soil.
Geotechnical engineers often take this effect into account by allowing
larger soil pressures for short-term loading. The code is indicating that
although a 1/3 increase in allowable stresses is not permitted when the
1612.3.1 combinations are being used, the soil allowables can take into
account the short-term nature of the load.
> -----Original Message-----
> From: SEConsultant [mailto:seconsultant(--nospam--at)earthlink.net]
> Sent: Thursday, January 20, 2000 1:47 PM
> To: JayLCrawf(--nospam--at)aol.com
> Cc: seaint(--nospam--at)seaint.org
> Subject: RE: Diaphragm Design Per 1633.2.9 Using ASD
> Section 1809 states:
> " 1809.2 Soil Capacity. The foundation shall be capable of trans-
> mitting the design base shear and overturning forces prescribed in
> Section 1630 from the structure into the supporting soil. The
> short-term dynamic nature of the loads may be taken into account in
> establishing the soil properties."
> I guess the reference is to the "short-term dynamic nature of the loads"
> based on certain soil conditions.
> Can anyone explain the intent of this reference?