Post-tensioning only portions of a structure

[bertiskorny]

Hello,

I just want to know what is your opinion on PTing only portions of a structure. I only need to really PT a cantilevered portion of my structure (the other slab and beams do not really need PT).

I hear from others that you should PT the entire structure due to shrinking and cracking. Only the small portion of the structure (cantilevered slab) needs the PT.

Thank you.

 

[csd72]

A couple of comments:

1. post tensioning only a small section of a structure can be expensive due to fixed site access costs e.t.c. If the whole slab was PT then this might have other offset savings that negate the aditional PT cost.

2. ensure that the slab is not restraining the section from being post tensioned - this would lead to restraint cracking at the interface of the PT. This should not be an issue with a cantilever - but it depends on the exact configuration.

 

[Taro]

How long is the portion that you want to PT? If the PT run is short, it is hard to maintain a consistent PT force due to the seating losses.