Resistance factor of shallow foundation in Candaian code 1

[netjoy]

I prepare PE exam and had a question.
a question of footing give 2 resistance factors fc=0.6 and ff=0.8 (see attached). I guess 0.6 is for short-term and 08 is for long term, but I can't find any support in " Canadian Foundation Engineering Manual" 4th.

Could anyone give me a help.

Thanks a lot

 

[BigH]

See Table 8.1 on page 139, 1.(b) where (i) would be the ff factor (resistance factor (friction)) and ii would be the fc (resistance factor (cohesion)). the question is using c to mean cohesion and f to mean friction - with the first "f" being resistance factor. It is really a factor on sliding for shallow foundations - as the vertical bearing resistance factor is 0.5 which implies a safety factor of 2 if there is no factors put on the loadings. At least, this is my take on it.

 

[netjoy]

Thank you BigH.
It ask for bearing resistance. give vertical load and moments, not enough information to cal horizontal load.
I make a mistake for ff, it's f(fai). I don't know how to input special symbol in here. If you can open the attached, it'll clear. I'm not sure because table 8.1 give 0.5 for bearing resistance. Now we had 2 much higher value.

 

[VAD]

netjoy:

The factors fc and fphi relate to the cohesion and friction angle of the soil. These are modification factors (resistance factors) which reduce the values of cohesion and friction and are known as partial factors. This approach is used by the Eurocodes and not by the North American LRFD design approach which uses a single factor to reduce the resistance of the soil eg 0.5. Your example is likely pre or around 1985 see Table 7.2 Canadian Foundation Engineering Manual Second Edition. The CFEM 4th edition does not contain these partial factors as Canada has adopted the LRFD approach to design which is the same used by the Americans.

 

[netjoy]

VAD,

Thank you so much.
The question is from 2010 & 2012 paper, I think the guy create the exam is really crazy.

By the way, how do you calculated the settlement if the soil layer thickness was not given? My friend told me what he learn is used h=2B (footing width), but it's no recommendation in the CFEM 4th edition.

Thank you again for your help.