can anyone tell me what is the equa 1

[DNaimat]

can anyone tell me what is the equation for calculating long-term deflection in post-tension and a reference please?

 

[Ingenuity]

To undertake such a calculation you need to know a lot more about: element type (presumably beam or slab, etc), concrete properties (creep, shrinkage data), level of prestress, , reinforcement, loading history, humidity and temperature, cracking, and other factors that many PhD's have been the subject of.

Tell us a bit more about what you have and we may be able to give you a direction/path.

Right or wrong, if you are in the USA and this is a slab that is load balanced for say 80% of SW, then you probably not going to check deflections, period.

 

[DNaimat]

it`s for a slab, and I am looking for a general or any kind of equation for long-term deflection in post-tension, thank you.

 

[Ingenuity]

What is the magnitude of your (short-term) deflection under self-weight and superimposed dead load?

And is the section 'cracked' at this load level?

 

[DNaimat]

it`s not a particular section that I`m working on I just need to find the equation for research purposes, if you can point me towards a source where I can find the equation I would really appreciate it.

 

[Ingenuity]

IMO, one of the better and practical resources on time-dependent analysis of both cracked and uncracked prestressed concrete is Gilbert and Mickleborough's book "Design of Prestressed Concrete" Link

Another is "Time-Dependent Behaviour of Concrete Structures". Link

 

[rapt]

There is no "equation" for it! Just as there is no realistic equation for long term deflection for any concrete member.

Combined effects of cracking, tension stiffening, creep and shrinkage cannot be defined in an equation.

 

[KootK]

The "equation" may well be a system of equations and look a bit like below. Seriously, that's from one of the Gilbert books. And if you're conducting research, I imagine that you would want to take it that far as anything less than state of the art is probably unacceptable.

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.

 

[Ingenuity]

...that's from one of the Gilbert books

Classic! I recall taking one of Ian's post-grad courses in prestressed concrete back in the early 90's - and prior to Prof's using digital PowerPoint presentations that they email to you after the lecture - and a class of about 20+ students scrambled to write down his blackboard notes with correct nomenclature. Literally speaking "greek" with all those sysbols!