Which Foundation System Should I go for Strip Foundation or Strap Footing ?

[Dren Gashi]

I designed the structure of a two-storey residential building with 4.5 meter spanning columns under 250mm thick flat slab.During the design of the foundations these were the conditions:

- Soil Conditions NOT KNOWN but assuming medium soft clay with a loadbearing capacity of 150 kN/m2
- Earthquake zone of montenegro
- DL: 632 kN ; IL: 70 kN

I am suggesting the use of individual footings (1.5 x 1.5 meters) connected by straps, but my boss says that continuous strip inverted tee footings are more suitable. In my calculations it seems that my option is way more economical. My question is apart from the economy which one should I pick for better performance considering that we are not sure about the ground conditions?

 

[Tommy385]

Hello,

If your column load is 632+70 kN aren't your 1,5/1,5m foundation to small for 150kN/m2?
Are the earthquake forces taken with walls or are your columns fixed in footings?

I believe your boss doesn't wanna hire geotechnical engineer to save money, but wants to connect columns with stiff foundation beams to compensate possible differential settlement.
If it's up to you, hire a geotechnical engineer for advice, if not do what your boss tells you.

p.s. Die Montenegro implement Eurocode 2 or are you still on some version of PBAB?

 

[Dren Gashi]

I am using Eurocode 2 as I am more use to it and is acceptable in Montenegro. For the size of the Footing I used the strap beams as a way to spread the loads evenly and transfer moments. Only the critical column has that load the others have lower Axial Forces.