Max. number of spans for a PT beam

[ttoma]

Is there a maximun number of spans for a beam to be post tensioned?
Thanks

 

[271828]

The length of tendons is the deciding factor, not the number of spans. Over a certain length, losses start to become a problem.

 

[shin25]

What kind of structure is it? In segmental bridge industry, having eight to nine span continuous is common.

271828 is right, but this can be overcome by adding adequate number of tendons.

 

[ttoma]

It is a 4 storey parking building with 3-60' long beams.

 

[Zambo]

60' is not long. Should be possible to stress from one end if that is an advantage.

 

[ttoma]

I am sorry, the beams are continuous beams with 3-60' spans. The total length for each beam is 180'.

 

[Zambo]

180' is about 55m. This is not excessive. Depending on the profile still could be stressed from one end, but I expect will be designed for stressing both ends.

 

[hokie66]

That is OK. It is common to stress structures 180' long. But remember to consider any restraints you have to slab shortening, mostly from concrete shrinkage, with an added component from your stressing.

 

[shin25]

This has to be modeled as hinge-pin-pin support. Over 180' length, deformation due to creep, shrinkage and temp. tend to be significant.

Why do you want a post tensioned system? Three indivisual pretensioned sections doesn't work?

 

[ttoma]

Thanks all for your inputs.
Shin25:
This is a design build project. The contractor is looking at different options and off course, minimizing the cost. Cost of transportation is a considerable factor.