How to determine foundation design parameters when using US code 2

[TTTKAO]

Hello,

i am a newer to use north America code and practice. I have a few questions regarding to foundation design, hope to get you some explanation and advice.

1. is it necessary to consider foundation self-weight inducing seismic load ? my understanding is not necessary as default, this should be specified clearly in geotechnical report if some of seismic load need to be considered due to the weight of foundation? is there any code address this topic?

2. for the friction factor used for sliding checking under seismic load combinations and non-seismic load combinations, this should be specified as well in geotechnical report or text book? I can't find any code to specify this value.

3. for the detail content provided in geotechnical report, is there any code or practice to regulate the minimum information geotechnical report need provide to client or this totally depends on the contractor between geotechnical consult and client ?

Thank you in advance for your time.

Cheers

 

[BulbTheBuilder]

1. is it necessary to consider foundation self-weight inducing seismic load ? my understanding is not necessary as default, this should be specified clearly in geotechnical report if some of seismic load need to be considered due to the weight of foundation? is there any code address this topic?

I don't speak for all regions in North America. In certain geotechnical reports I have seen, when the weight of the soil is almost the same as the weight of concrete, it stated in the reports you can ignore it.


Please refer with a geotechnical engineer or report for more specific details about your location. I wouldn't recommend you assuming values...worst case, use a geotechnical report about 1- or 2-mile radius from your current job location.

 

[JStephen]

"this should be specified clearly in geotechnical report if some of seismic load need to be considered due to the weight of foundation?"
I don't recall ever seeing that in a soils report.

Friction factors- quite often included.
Otherwise, extent of exploration and recommendations are negotiated between customer and the geotech. The more information you can give the geotech about what is planned, and what is needed, the better off you'll be. Total weight, type of construction, type of foundation(s), allowable differential movement, anticipated grading, etc. Work in high seismic area will quite commonly have site-specific seismic criteria given.
From a contracting standpoint, comments on groundwater, difficulty of excavation, mobility on the surface, trench protection, site location are helpful.
Usually the reports recommend that the same geotech also inspect/observe excavations, try to get that cost worked in.

I've seen this sheet attached in a number of soils reports:

http://www.dbaengineering.com/pdf/Important Information about your Geotechnical Report.pdf

 

[TTTKAO]

Thank you so much BulbTheBuilder_EI and JStephen for your sharing with experience, as per my experience, i never considered foundation itself seismic load as it's berried in the soil.

Currently, i am designing a foundation only half of height burried in the soil, that's reason why i asked the first question. i have raised my concern to lead, i sill hope can get some suggestion from the forum at the same time.

Thank you again.