Inclination and Shape factors for shallow Foundation

[courtpara]

FHWA SA-02-054 (Geotechnical Engineering Circular No. 6) states on Page 62 that "The simultaneous application of shape and load inclination fators can result in an overly conservative design. Henceforth, the inclination factor will be ommitted in calculation of bearing capacity". Does anyone have any idea of how to quatify the overdesign if both factors are used or know any paper discussing this issue. Thanks in advance.

 

[BigH]

I'll admit I've not seen that before, but then, again, I probably haven't done any more than 5 or 10 computations of bearing capacity since it is almost always the settlement (serviceability) that governs the allowable net bearing pressures. The key is to know when the settlement doesn't control. So, sorry, I can't help in this regard.

 

[Mccoy]

Bowles, in his popular handbook "Foundation analysis and design" suggests the other way around, that is to ignore shape factors when there is a load inclination.

Other sources, like the Eurocode7, suggest a formula where shape and inclination factors stay together, but depth factors are omitted.

In others sources again, I've seen all factors used regardless.

Probably the only way you can quantify the difference is to use a spreadsheet and evaluate all the different scenarios.

 

[ntschwanz]

There is a textbook by Perloff and Barron that discusses bearing capacity factors where some partly compensate each other in some cases and then again can reinforce each other in other cases. Don't have it at my fingertips.

 

[ishvaaag]

Just a Mathcad 2000 worksheet accounting inclination, proportion between sides and depth. Sources are named but opinion on relative conservatism is not commented.