Raft foundation design 1

[aqibusman]

i m designing a raft foundation after importing the reactions from the etab file.

my soil bearing capacity is 5.8 ksf
modolus of subgrade reacton is 200

what i m getting is the extreme soil pressue on outer column for D+L case.
i m attaching the model file for refrence.

i have made the whole plot as raft foundation.
the over all area of raft is much more than required as compared to total applid load as we can see from soil reaction diagrame.

can any body tell me how i can overcome this type of problem.

thanks

 

[zeemas]

I just checked your model and the model look fine to me. The only thing which concerned me was loading, you might need to go back and check your reaction from ETABS. Only for dead load the soil pressure is exceeding 5.8 ksf.

Second thing which I might do is to check the units for Subgrade modulus.

Also for your load combos, what is the difference between LIVE and LIVE1? do you mean floor live load and Roof live load? If this is the case then you can neglect roof live load while checking soil bearing pressure for D+L case See ASCE chapter 2, Allowable stress design load combination.

Please correct me if i am wrong. Good luck.

Zee