Post tensioned slab - cable distribution

[hsn199]

Hey there, attached is an image(preliminary one of course) of a post tensioned slab. Does it seem to have anything wrong concerning cable distribution (for example spacing between adjacent cables, etc...)?

p.s. cables in horizontal direction: 4 strands per cable / cables in vertical direction: 5 strands per cable.

 

[BAretired]

You have not shown spacing between adjacent cables, so how can anyone comment on it?

BA

 

[Ingenuity]

What do the numbers on the JPEG represent - distance/span between the tick points?

 

[rapt]

Some sort of dimensioning information might help us to know the tendon spacings, but generally, I would say that the tendon arrangement shown is awful!

 

[hokie66]

Agree with rapt that the tendon arrangement shown makes little sense, and there is not much PT. With such a small amount of PT, and with such an irregular shape and heavy restraint, I would tend to do it with all non-prestressed reinforcement. You will need a lot of reinforcing steel at any rate, so I would just eliminate one trade. Maybe just me...

 

[asixth]

Doesn't look like there would be enough tendons to achieve minimum prestress required for crack control. I am guessing that this is a residential floor plate and it doesn't look very big (<400sq.m) so PT might not be the best solution. Some of those tendons are very short (less than 10m) and it will generally slow down construction because of the stressing process and extra trade. Is there balconies? The balcony setdowns could create an issue with some of those cantilevers.

For very small floor plates like that I have only ever seen minimal PT and often it is only provide the lessen deflections along the slab edge where the facade runs.

 

[hsn199]

Yes it's a 280 sq m residential floor slab. Never mind of the numbers in the jpg they're irrelevant in this matter... & yes there are 2 balconies: one at the bottom and one in the left.

I only did this since I was asked to take post tensioning as an alternative. It will be compared later on with flat and hourdi systems, to see which one will be used.

 

[hokie66]

What you have shown is a flat plate, whether prestressed or not. For such a small and irregular plate, I agree with asixth...post-tensioning is not an option. I have never heard of "hourdi systems".