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Ultimate Foundation Design.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Ultimate Foundation Design.
- From: <Tjb5424744(--nospam--at)aol.com>
- Date: Wed, 29 Jul 1998 13:14:07 EDT
I have to appoligize for my spelling error the other day. It is Terzaghi not Terghazi. I was writing from memory, not looking at my text book until after sending the e-mail. I also want to mention Peck, who also worked on this important area of structural design. If the supporting soil is not understood (at least an attempt at understanding), we would have leaning towers of pisa everywhere. or at least sinking builldings like the John Hancock tower in Boston. Anyways back on the subject at hand. You are correct, allowable bearing pressure for foundation design is often given a large factor of safety, typically 4 or more. The strength reduction factor, phi, takes care of this. For simplicity sake lets use a load factor of 1.7 for soil. The resulting phi factor would then be 4/1.7=0.425. A reasonable value of phi would then be in the range of 0.4 to 0.45. On the issue of settlement, The settlement is a function of the applied load ("working level"). Almost all of the settlement occurs immediatly due to structural dead load. Additional settlement will occur later due to live load. Here again, the segregation of the loads is important and the "ultimate" resistance to settlement can be adjusted from the "allowable". I am more inclined to SE, but GE is important. Without it our structures will collapse. Of course, this is all my humble opinion. Ted Beckwith SFA, Inc.
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