Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Presumptive Bearing Capacity

Status
Not open for further replies.
cgseso

cgseso

Civil/Environmental
Joined
Oct 24, 2012
Messages
21
Location
PH
Does any one know how presumptive bearing capacity of foundations was derived?



excav-deep-foundations-fall-09-103-728_1_ntlcn1.jpg
 
Sort by date Sort by votes
How were they derived? Lots and lots of experience.

Those values are codified in the IBC, among other sources.

----
just call me Lo.
 
Upvote 0 Downvote
That table looks pretty crude. More like a guess if you ask me.
 
Upvote 0 Downvote
That table has been in most building codes in the Northeast for a long time. The values are averages based on soil type and allowing for a maximum of 1” settlement.
 
Upvote 0 Downvote
Anyone interested in this as to where it came from, get out the 1948 edition of "Soil Mechanics in Engineering Practice" by Terzaghi and Peck. Art. 54, page 413, 1948 edition John Wiley & Sons. They have a rather compete history and explanation of these tables, so many out there. In my review the 1" settlement is not mentioned. Hey you youngsters, that was the textbook for my first Soil Mechanics course, the most popular at the time.
 
Upvote 0 Downvote
Some geotechnical guys I work with have always said those values were based on a factor of safety of 3 and would ensure a maximum settlement of 1”. I don’t know if that is true.
 
Upvote 0 Downvote
The numbers appear to be conservative, but do not consider any property other than classification. If the granular soil is very loose, or the foundation is both narrow and shallow, those number could be unconservative, Same comment if the fine-grained soils are soft. Good judgement is still needed.
 
Upvote 0 Downvote
Thank you for all your response. I just thought that, maybe there is some statistical basis behind these values. Does the author perform monte carlo simulation or something.
 
Upvote 0 Downvote
Again, I’ve only seen these in the Residential Building Code. The Residential Code is limited to dwellings up to three stories, so you are talking very light loads for which these presumptive values are fine for use. For a much more expansive table see AASHTO LRFD Chapter 10. The list is much longer with better descriptions for the service limit state. The same tables are probably published in other codes too. The expansive tables will give you more soil classifications and values for dense to loose soils.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

DTS419
  • Question Question
NYC Building Code Presumptive Load Bearing Values
Replies
3
Views
2K
CarlB
CarlB
Struct123ure
  • Question Question
ASD (SLS) to LRFD (ULS) Bearing Capacity
Replies
0
Views
6K
Struct123ure
Struct123ure
Alexis7
  • Locked
  • Question Question
Questions about Hansen Bearing Capacity
Replies
0
Views
944
Alexis7
Alexis7
pelelo
  • Locked
  • Question Question
Meyerhof's correction factors for Bearing Capacity Calcs
Replies
2
Views
1K
Smoulder
Smoulder
pelelo
  • Locked
  • Question Question
Design allowable bearing capacity based on Overburden pressures
Replies
10
Views
3K
Celt83
Celt83

Part and Inventory Search

Sponsor

Back
Top