matt foundation

[pmtrevisan]

hello knowledgeable group. All the literature that I have found so far regarding matt foundation is for columns supporting slabs. I have a situation where there are no columns. We are designing a 1 way floor system 20+ stories, with walls. Openings for walls at the corridor, and interior units.
My question is how can I use what I've learned thus far (school, experience, and books) to design a matt foundation for this case.
For the situation of columns its relatively simple (supporting loads). do I break the wall up into infinitessimal elements and design it for 1' sections....

Any help would be appreciated.

 

[ARH]

I assume your walls are shear walls? If they are the highest compression loads will be coming with wind or quake loads.

Usually I do a simple hand calc to estimate the thickness of the slab required. Assuming you foundation slab is ridgid and determine the soil pressure using the ridgid slab and ecentricity of the load. Usualy gives a triangular soil pressure profile. From here just think of the soil pressure as a floor load on the slab and the walls as supports. This will get you close to the right size, but depending on the complexity of the wall layout, location of doors & openings ect.

You should also run this in a modelling program. Model the soils as springs, and you will see that in reality you slab is flexible to some degree.

Hope this helps.

 

[npthao121]

I assume you just talk about the concrete structure design for mat foundation. Normally, in case of building with column, in the mat foundation we have grounding beam (bracing beam) connected between each column and separated the slab. So the mat foundation can be calculated as the normal slab with load is soil pressure, colum is support…

Your case can also be solved in a similar way. Your shear wall play the role of support (as column case). You can add some grounding beams or not, it’s up to you. It is very easy if we model this foundation system by replacing soil by spring…please consider to input all of your load combination and also spring factor. After all we can have the envelope internal force diagram for the founadtion structure