How to model Connectivity between Raft Footing and Wall in Staad?

RE: How to model Connectivity between Raft Footing and Wall in Staad?

Muhammad Hasan — Wed, 12 Sep 2018 03:48:29 GMT

Thank you

RE: How to model Connectivity between Raft Footing and Wall in Staad?

Sye — Tue, 11 Sep 2018 17:58:24 GMT

I would suggest that you go with the wall and slab model rather than a wall with fixed support at the base as the former would be a more realistic simulation of the actual structure. You may consider the weight due to the water as well. You do not however need to design the wall for the moments that is within the slab and you may consider only the moment at the face of the slab for the wall design.

RE: How to model Connectivity between Raft Footing and Wall in Staad?

Muhammad Hasan — Tue, 11 Sep 2018 17:45:49 GMT

Thank you sir,

But the moments at last slab are very high for the same model i have removed the raft plates and replaced it fixed supports at the base of the give which give much lesser wall moments this is due to the dead weight of the liquid on raft the raft it self bends in response to the loading which in turn transfered to the walls.

But I reality the raft doesn't bend and the dead load of liquid is directly transfered to the soil. So I removed the weight of liquid in the raft and done the analysis for wall design.

Kindly clarify me is the first model or the modified model which I stated was more actual behaviour. Which model should i follow.

Thank you for your precious timei n advance.

RE: How to model Connectivity between Raft Footing and Wall in Staad?

Sye — Mon, 10 Sep 2018 19:57:43 GMT

It is a well accepted approximation to model the wall plates to the center of the slab. In doing so, there is a common portion that is accounted for twice as you mentioned, but I would suggest going with that modeling approach rather than trying to create the walls elements from the top of the slab and trying to connect the corresponding nodes using rigid links etc which itself introduces additional stiffness in the model. So I would rather prefer to keep it simple. As long as the wall and the slab plates share common nodes, there will be proper force transfer between the entities.