Post tension design
Post tension design
(OP)
Hi everyone I'm a fresh employee.I'm learning to become a post tension(PT) designer.Usually my company do two-way PT slab with drop panel and Banded slab(PT beam +PT slab).In Designing these slabs and beams what should be kept in mind?And In continuous slab and beam,how should I balance the load to determine the prestressed force.I don't know too much about PT.And I really appreciate you answers thank you all.






RE: Post tension design
http://www.vsl.net/Portals/0/vsl_techreports/PT_Sl...
RE: Post tension design
The Post Tension Institute is a good place to start as well.
www.post-tensioning.org
RE: Post tension design
Just a precaution on starting with the PTI information...it really only applies to North America. Most of the world does post-tensioning differently.
RE: Post tension design
Find the minimum duct cover, generally about 1" cover for 2hr fire rating and 1.5" cover for 4hr. Best to put in tendons to reverse the bending moment diagram and try to have 1.4 to 2.0MPa prestress. Keep tendons about 800-1200 centres but can be closer spacing in bands or column strips.
I always place reinforcement over the columns to help with punching shear and peak moments, generally 16mm bars at 200mm centres.
Keep tendon lengths to about 30m otherwise losses are large and tendon loses it's effectiveness, also 30m x 30m is a good size for a concrete pour (200-250 cubic metres).
I generally like to size the slab thickness with 1.4-2.0MPa prestress for deflections and shears first. When designing for flexure the tendons will normally have capacity to do it by themselves except over columns or other supports.
To study up on it find a good PT publication, I think there is one by concrete society which is good and also read through some of rapt's post that he has put on this website because they know PT design better than most.
RE: Post tension design
RE: Post tension design
'Hokie66' speaks the truth!
RE: Post tension design
BA
RE: Post tension design
From a design perspective, ACI-318 has some peculiarities that appear somewhat unique to NA re banded and uniform tendons in flat plates and average moments across full slab panel.
RE: Post tension design
RE: Post tension design
RE: Post tension design
RE: Post tension design
I think one group in South Australia was doing them. Agree with both of you that the method does not work well. Both the lack of crack control mentioned by Hokie66 and also the very low levels of P/A used. The combined effect basically results in an unreinfored slab.