BRAB AND WRI METHOD

[nrguades]

Greetings...

Im designing a ground supported foundation which is conventionally reinforced. The soil report recommended Wire Reinforcement Institute Method (WRI) and/or Building Research and Advisory Board Method (BRAB)method.I designed the waffle type foundation using finite element method but I would like to check the result based on the method I mentioned above.
I would like ask any information about these methods . thank you very much

 

[Focht3]

Okay, what's your question?



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[nrguades]

Focht3..
I would like to ask the following:
1. Where can I get the design procedure or a sample
computations of these methods or a sample
computations)
2. How does their results varies with the finite
element method?

thanks...

 

[Focht3]

Check your local university library for the BRAB report, cited as follows (I couldn't find an on line copy) -

Building Research Advisory Board "National Research Council Criteria for Selection and Design of Residential Slabs-on-Ground," U.S. National Academy Of Sciences Publication 1571, 1968.

You can buy the Wire Reinforcement Institute's guidelines from their web site:

http://www.wirereinforcementinstitute.org

Good luck!



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[nrguades]

thanks Focht3....
...but still can't find a copy of BRAB report.

In relation with this, I have some questions about the value of modulus of subgrade reactions that I used in the design of the foundation.
The soil report mentioned that the Average Weighted Plasticity Index of 30 was used.And considering slope of less than 5% and using an unconfined compressive strength of 2 ksf, a slope correction factor of 1.0 and over consolidation correction factor of 0.75 should be used with the WRI method.Effective PI is 38 and climatic rating of 20.
Support Index = 0.67 for BRAB, and 0.23(1-c) for WRI.
I used modulus of subgrade reaction of 26 kcf. Is this appropriate for the given condition? thanks..

 

[Focht3]

Hmmm,

How did you arrive at that value for modulus of subgrade reaction? What are your loads? Calculated maximum deflections?



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[nrguades]

Focht3...

This foundation is for One(1) storey residential building. I just loaded it with 40 psf live load and include the deadweight of the five(5) inches slab plus additional partition loads. Maximum calculated displacement
is 0.07 in.
I just based the value of modulus of subrage reaction on the allowing bearing capacity for grade beams mentioned in the soil report of 2 ksi.Grade beams are to penetrate 12 inches(min) below the finished grade.

 

[Focht3]

I don't know what your soil conditions are like - but the deflections look small. It's probably because your loads are fairly small; in reality the imposed loads are almost always fairly low, though. The real question has to do with how your site soils will behave -

Where are you located? If you are in the U.S., the BRAB report should be available at a nearby university library. Where have you checked?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[nrguades]

Thanks Focht3..

Actually, im working here in the Philippines but this particular project is for Texas, USA. Were doing the structural detailing here as well as Preliminary design of the structure.Cad works are very much cheaper here in the Philippines. I also coudn't find an online copy of the Brab but I was able to get a copy of the Guidelines for Foundation of Residential Buildings published by ASCE, Texas Section where it is stated there, that foundation can be designed either WRI,BRAB,Finite Element,Post Tensioned and others. Based on the Soil Report, total soil movement (PVM) are anticipated to be two(2) inches and recommends a ground supported stiffened slab, if small movement can be tolerated.
thanks...