PT Tendons in Moment Frame Beams?

[bertiskorny]

Quick Question

Would you normally put PT Tendons in Moment Frame Beams? I say no but I would like to get a second (or third or fourth) opinion.

 

[JAE]

With stress reversals possible, would the tendon anchorage wedges work loose over time?

If not, the other thing that pops into my mind is that I'd probably go with a bonded system rather than unbonded.

No logic to that, just "feels" better.

 

[WillisV]

I've PT'd plenty of moment frame beams. No problems - you just have to make sure you look at all the possible cases including secondary moments and provide bonded reinforcing where necessary.

 

[bertiskorny]

Another note. I am currently in California, so this is Seismic country. Are you comfortable putting PT in Moment Frames in Seismic Country?

 

[haynewp]

PT moment frame beams are used all the time. You will have to supply the required amount of mild steel at the connection as the PT can help negative moments at the joints but not positive when there is moment reversal from lateral.

There are limits on the amount of prestressing you can count toward lateral resistance and additional requirements for prestressed/PT frames in high seismic regions. See ACI chapter 21 and also IBC 2006 CH 19 (or the equivalent chapter for whatever code California is on these days).