Raft foundation OR Strap Foundation????

[TekEngr]

Below is the general view of footing for light gauge steel double storey hospital , please guide me that the below foundation will be design as strap footing or raft footing , if concrete pouring will be done once in whole plot??
Anyone can provide the design calculation example for this type of footing???
Thanks in advance.

 

[KootK]

In my market, it would work like this:

1) Neither a strap foundation nor a raft but, rather, strip footings. Perhaps you are confusing "strip" with "strap" here. By strip footing, I mean a continuous narrow footing that follows the wall. In your case, the 100mm slab on grade is too thin to be considered any kind of raft.

2) Some contractors prefer to construct the strip footings -- and some short stem walls -- ahead of the slab on grade. This way, the slab on grade can be poured when it is somewhat sheltered from the elements by the surrounding structure. Additionally the amount of potentially damaging construction traffic on the slab on grade prior to facility turnover is reduced.

3) Some contractors prefer to pour the strip footings monolithically with the slab on grade similar to what you have shown in order to minimize the number of operations. In that case, the footings normally have sloping sides. Additionally, since the footings become locations of slab on grade shrinkage restraint, control joints are often placed beside the footings and running parallel to the.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TekEngr]

Thanks for your valuable comments KootK!!
Yes! Your understanding is correct I am talking about the strip footing which is monolithic ally poured with floor slab.
So do I need to check the floor slab as it is monolithic with strip footing or I can just simply design the strip footing (with tapered sides as you suggested above) under the UDL loads (100 KN/m) which is coming from the wall?

 

[KootK]

No need to check the slab on grade. The footing probably does "hang" from the slab on grade a bit but, to my knowledge, nobody checks that and things work out just fine.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.