Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
(OP)
I am designing 2-storey RC frame house,according to EC2 and EC8....common practise in my country is to use a monolithic raft foundation (45-50cm thick) with foundation beams connecting the columns.
This is the strongest design possible for a foundation.
Foundation Beams are designed using the capacity design principle so as to be stronger than the columns above
I am a young engineer and all of the projects i have seen up to now (not many) do not use torsional bars for the foundation beams, except in the case of very short beams.
I think this is reasonable due to the huge mass of the raft foundation which makes it hard to get any torsional moments in the members except in cases with very short beams.
The reason I am asking this is because my software gives out some torsional reinforcement therefore it got me thinking.
What do you guys think?
This is the strongest design possible for a foundation.
Foundation Beams are designed using the capacity design principle so as to be stronger than the columns above
I am a young engineer and all of the projects i have seen up to now (not many) do not use torsional bars for the foundation beams, except in the case of very short beams.
I think this is reasonable due to the huge mass of the raft foundation which makes it hard to get any torsional moments in the members except in cases with very short beams.
The reason I am asking this is because my software gives out some torsional reinforcement therefore it got me thinking.
What do you guys think?






RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
Dik
RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
DaveAtkins
RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
This is all i wanted, a second opinion from fellow engineers.
RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
BA
RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
Dik
RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
The foundation beams are embedded within the raft foundation,
Think of it this way, the other option you have for the foundations for such a structure in a seismic region is spread footings with tie beams or just use a continuous footing below each column in the form of foundation beams. Then you would have to fill up the space enclosed by the foundations with additional soil, compact it and then build a slab on top of it. Also think of the labour and time required to build the formwork for each footing and beam.
However if you use a raft foundation with foundation beams which is simply the same as the solution mentioned above but with concrete used to fill the gaps, you already have a slab for the house, therefore there is no need to add soil, compact it and then build a slab on top of it, also the formwork is mush simpler. In the end its cheaper, simpler and a lot faster.
RE: Raft foundation (45cm thick) with foundation beams...do i need torsional reinforcement?
Looking at how close the columns are to the exterior edge, I'd say you need to be concerned with detailing the steel for an "opening corner joint." Actually even worse since the corner joint will have stress reversals if you have lateral load reversals.