Prestressed and Post Tensioned Concrete Design 2

[josecastjr]

My background is in structural steel design and construction management. Would appreciate suggestions for a good PT software and/or design book(s)with examples of prestressed and post tensioned structures, that include slabs on grade. I am aware of what PTI and ACI have. Any other recommendations? Thanks.

 

[Lion06]

Presto is a good Pre-stressed beam design software, although I don't believe it has any post-tensioned capabilities.
Beam from J&A is another Pre-stressed software. I don't know of any specifically for post-tensioning.

 

[pappyirl]

RAM Concept has the ability to model post tensioned slab on grade. Adapt probably has the same facility. One assumption inherent is that there is a slip membrane under the slab so there is no restraint between the slab and soil. This membrane can probably double up for waterproofing and radon protection. At cores and heavy point loads it is possible that the slip membrane might not be sufficient to allow relative slip so this must be considered as a stiff point in the analysis. The model essentially consists of a 2-d finite element plate supported on springs, essentially a Winkler spring model. The question always arises as to the stiffness of the spring but this can generally be approximated from the geotech reports and I have found it doesn't have large effect on the results. A sensitivity analysis should be carried out to prove this for yourself.

Slabs on grade generally follow the rules of normal post tensioned design. Imagine the bearing stress is a UDL with the columns coming down on the slab acting as supports. Depending on the loads being transferred and the soil conditions it might be possible to run the tendons straight with no profile. Otherwise the profile is the mirror image of what one would expect with a suspended slab.

I have never heard of a pre-stressed slab on grade, there would be a lot of issues with joints and installation.

 

[jhoulette]

You can use Ram Concept (I use it for Raft foundations) or Adapt (don't like it), but for a simple software for post tension slab on grades I recommend GTK (

http://www.gtksoft.com/).

They have software for the PTI 2nd and 3rd editions. Easy to use software. Basically a fancy spreedsheet, not a finite element program.