How to determine the thickness of mat foundation with only walls on top
How to determine the thickness of mat foundation with only walls on top
(OP)
Hi, all
I'm designing a mat foundation for a building with only concrete walls (without columns).
I know we need to check beam shear (one-way shear), but how to check it? the width is the midline of the two walls?
Can you recommend any books that talk about the mat foundation design?
Thank you very much!
Graceli
I'm designing a mat foundation for a building with only concrete walls (without columns).
I know we need to check beam shear (one-way shear), but how to check it? the width is the midline of the two walls?
Can you recommend any books that talk about the mat foundation design?
Thank you very much!
Graceli





RE: How to determine the thickness of mat foundation with only walls on top
I looked at a bunch of books and mat foundations are kind of neglected. I found a chapter on them (very technical with all kind of soil stiffness interactions) in "Foundation Engineering Handbook" by Fang and Winterkorn. Good luck in finding that as it's been out of print for about 40 years.
I guessing what most people do is to overdesign the mat thinkness, so that the soil loads are evenly distributed and design it as a beam, with the load upwards and the walls acting as the supports.
RE: How to determine the thickness of mat foundation with only walls on top
RE: How to determine the thickness of mat foundation with only walls on top
The approach of most of the older foundation books is to use conservatism i.e. a thick mat, then assume that the Mat is rigid in comparison to the soils. Then in this case you will get uniform loads and it simplifies the structural analysis / design. However now we realize that the mat really isn't rigid and there would be higher pressures at columns (or walls). Basically the pressure depends on the deflection of the mat. Well there were / are several ways to model this but I'd say the most common is to use the modulus of subgrade reaction which is modeled as a spring (actually many springs below your mat). However the modulus of subgrade reaction really depends on the applied load and location of interest. So the modulus of subgrade is typically varied (i.e. lower value toward the center than at the edges).
References:
For new modeling descriptions:
Foundation Design Principles and Practice by Coduto
Older references:
Foundation analysis and design by Bowles
Substructure analysis and design by Anderson
Foundation Engineering Handbook by Fang and Winterkorn
EIT
www.HowToEngineer.com
RE: How to determine the thickness of mat foundation with only walls on top