Cut an existing prestressed beam
Cut an existing prestressed beam
(OP)
I have an existing multi-span prestressed (bonded) concrete beam. I need cut a big opening in the interior span, which means I will lose one entire span. Does anybody have some experience in cutting existing prestressed beam? I think it is doable since the PT tendons are bonded to the concrete along its length. But I want to check with your opinion whether I miss something here.
Thanks a lot.
Thanks a lot.






RE: Cut an existing prestressed beam
RE: Cut an existing prestressed beam
RE: Cut an existing prestressed beam
1. The deflection in the adjacent spans will increase.
2. The shape of the moment diagram will change, will the tendon profile still be compatible?
3. The development of the tendon at the cut end.
Minimise the effects of 1 and 2 by specifying a cantilever that gives a similar moment over the columns. Then check existing moment versus proposed moment and existing deflection versus proposed deflection.
RE: Cut an existing prestressed beam
RE: Cut an existing prestressed beam
Are you going to cut the actual tendon? Even if the tendon is bonded to the concrete, if you cut through, isn't there the risk of 'explosive' failure? Sudden change on the tendon tension might be enough to break the bond with the concrete.
RE: Cut an existing prestressed beam
RE: Cut an existing prestressed beam
PTI has examples of cutting of tendons in bonded systems for new openings. The actual cutting process is not particularly complicated.
The analysis of what is left is complicated.
I would contact PTI for any examples, literature etc that they may have.
RE: Cut an existing prestressed beam
RE: Cut an existing prestressed beam
I did a quick google search (I am sure you did too) and I fount the following:
Contrary to popular opinion, PT slabs are no more difficult to alter or demolish than other structural forms. As for any construction method, the Health and Safety file must contain all structural design and construction information to enable future alteration and demolition. With PT, small holes can generally be accommodated between tendons, and larger holes can be accommodated away from the column strips as with RC slabs. With bonded systems, tendons can be cut without the risk of uncontrolled release of the pre-stess. More care is required for unbonded systems because cutting the tendon will distress the element over its full length.
http://www.concretecentre.com/main.asp?page=1089
I am afraid I stand by the 'popular opinion'. I would suggest you talk to some expert on the matter. VSL or somebody with experience in demolition. Certainly the decision should be taken by somebody with ample experience on the subject