GEO Afternoon Sampel Question from NCEES

[tall]

Any one tell me why the Factor of pressure I for p under the mat foundation the factor of " I" has been mutiplied by 4. Any idea is greatly appreciated.

Thanks

total I = I*4 = 4 * .18 = .72 & P = .72 * 500 psf = 360 psf :reading:

 

[DIZZEE]

Any one tell me why the Factor of pressure I for p under the mat foundation the factor of " I" has been mutiplied by 4. Any idea is greatly appreciated.
Thanks

total I = I*4 = 4 * .18 = .72 & P = .72 * 500 psf = 360 psf :reading:

What number is the problem? Is it from the pract. exam?

 

[wavelette]

?

 

[EL Nica PE]

Any one tell me why the Factor of pressure I for p under the mat foundation the factor of " I" has been mutiplied by 4. Any idea is greatly appreciated.
Thanks

total I = I*4 = 4 * .18 = .72 & P = .72 * 500 psf = 360 psf :reading:

i don't have this book, but I think the reason is that the point they asked for the induced stress is at the middle of the mat. Most of the equations/or graph are for the coner stresses. Therefore you will have to split the mat into four pieces and calcualte I according to one corner, but the total induced stress will be given by all the pieces.

NAFVAC 7.02 has nice samples you can follow. Ihope this help.

:unitedstates:

 

[codd0006]

I have a question about that last answer. I see that Influence value is for the coner of the rectangle. My question is do you multiple by 4 because a rectangle has four coners? Or how did you know to divide the rectangle into 4 areas?

Thanks,

Ryan

 

[EL Nica PE]

I have a question about that last answer. I see that Influence value is for the coner of the rectangle. My question is do you multiple by 4 because a rectangle has four coners? Or how did you know to divide the rectangle into 4 areas?Thanks,

Ryan

b/c the rectangle is divide into 4 areas.

 

[codd0006]

b/c the rectangle is divide into 4 areas.

OK. How do you know to divide it into 4 areas? Maybe I just do not get it. It just seems arbritary. Any further help would be appreciated.

Thanks

 

[EL Nica PE]

OK. How do you know to divide it into 4 areas? Maybe I just do not get it. It just seems arbitrary. Any further help would be appreciated.Thanks

It all depends where the point of induce stress id asked. In this particular example (more usual) they ask for the middle therefore you divide the rectangle by 4.

but in other cases the might ask you at a different location therefore you will divide accordingly.

Lookup any foundation book at it will have nice examples.

 

[codd0006]

Ok. That helps. I aprreciate the help.

Thansk again,

Ryan

 

[EL Nica PE]

here is a sample that asked for the induce stress outside the middle of the rectangle. 8.19