Unbonded, Post-tensioned Shop Drawing
Unbonded, Post-tensioned Shop Drawing
(OP)
The query I received in a recent eMail was as follows:
Can you please provide me the easy way to draw shop drawing for Post Tesnion Drawing? Is there any software ? I am doing it from AutoCAD and getting some errors on elongation and CGS. Is there any precise way? Please help.
Can anyone provide me with a copy of a typical unbonded, post-tensioned flat slab shop drawing that shows the essential information. My work does not generally include this information. The query came from Nepal.
Thanks in advance, Dik
Can you please provide me the easy way to draw shop drawing for Post Tesnion Drawing? Is there any software ? I am doing it from AutoCAD and getting some errors on elongation and CGS. Is there any precise way? Please help.
Can anyone provide me with a copy of a typical unbonded, post-tensioned flat slab shop drawing that shows the essential information. My work does not generally include this information. The query came from Nepal.
Thanks in advance, Dik





RE: Unbonded, Post-tensioned Shop Drawing
Attached are your 'typical' USA-standard UNbonded PT shop drawings for a 2-way slab consisting of layout, banded tendons and uniform/distributed drawings. Project data has been removed.
We typically do the shop drawings with AutoCAD and not custom software, however, we do use a lot of 'blocks', and occasionally LISP routines.
I personally do NOT like stating the tendon elongations on shop drawings, but when we have to we usually use a XLS spreadsheet and insert it using dynamic OLE.
RE: Unbonded, Post-tensioned Shop Drawing
Dik
RE: Unbonded, Post-tensioned Shop Drawing
I've sent the drawings on as *.dwg files and have checked for 'remnants'... my pdf2dwg converter sometimes finds 'erased' information that was not intended to be included. Nothing found. Thanks so much for the information.
Dik
RE: Unbonded, Post-tensioned Shop Drawing
I've sent him information on calculating the elongation of strand. Is there an easy manner of calculating chair heights, other than drawing out the profile?
[Added] High point: thickness less concrete cover and strand dia,
PI at 2'-0 from support centre line for spans to 20' and 2'-6 for others,
Height of strand at PI, 1" less than height of strand at support centre line,
Low point: concrete cover.
End span low point at 0.6 of span.
anything more? Do you provide height of strand at other locations?
Dik
RE: Unbonded, Post-tensioned Shop Drawing
I use RAPT software to both design and detail the PT: Link
Typical output for elongations and tendon drapes to underside of tendon/s:
Alternatively, a spreadsheet using compound parabolas (to account for the reverse tendon curvatures and flat profiles over supports), and accounting for the transition lengths at tendon stressing ends, work okay. However, it is a bit of a pain to take into account non-typical cases.
RE: Unbonded, Post-tensioned Shop Drawing
Dik
RE: Unbonded, Post-tensioned Shop Drawing
PT drapes are referenced from the top of forms (bottom of concrete), except in circumstances where there is ambiguity, and that is usually tagged next to the profile dimension to avoid confusion, usually using a "*" or some other symbol.
Typically tendon profiles are given at 3 ft (1m) spacings, and rounded, based upon equal spacing of profiles, for the given drape/span. For short spans, minimum of 5 profiles (top each end, midspan, and one each between btm and top).
RE: Unbonded, Post-tensioned Shop Drawing
Dik
RE: Unbonded, Post-tensioned Shop Drawing
Dik
RE: Unbonded, Post-tensioned Shop Drawing
dik: It is a starting point for single span conditions.
However, you need to consider the straight 'tangent' length that is applicable at the stressing-end of tendons, and that is something that is somewhat system dependent (less so for UNbonded monostrand system), and PT shop drawings are the appropriate place to address it.
Also, for multi span conditions, and/or spans with cantilevers, you are going to have to address: reverse profiles (over supports) with realistic tendon curvatures; flat portions over supports with transition profiles to go from 'span profile' to 'support profile'...etc,
RE: Unbonded, Post-tensioned Shop Drawing
There will be a cusp at the points of inflection due to the parabolas not having the same slope...I think due to the stiffness of the strand, this would give an approximate solution.
First kick at the cat... from grade 11 or 12 math of 50 years ago... not too shabby.
Dik