Cut Double Tee Stem
Cut Double Tee Stem
(OP)
Has anyone sucessfully seen a cut stem of a double tee? I have a double tee roof that needs to have the stems of the tees cut for an elevator. The stems will be supported where they are cut and the span is signifigantly reduced. I have a design that considers the structural integrity of the tee's to be non-existent after they are cut and I have steel framing designed to re-support this area.
However... if it turns out the existing tees have a straight strand pattern (Meaning the strands are in the same position throughout the length of the double tee, as opposed to a draped strand pattern) the structural property of the tee will remain un-changed and the shorter span will give that much more capacity.
Thoughts anyone?
However... if it turns out the existing tees have a straight strand pattern (Meaning the strands are in the same position throughout the length of the double tee, as opposed to a draped strand pattern) the structural property of the tee will remain un-changed and the shorter span will give that much more capacity.
Thoughts anyone?






RE: Cut Double Tee Stem
If you cut a double tee too short, there may not be enough development length to maintain the prestress in the strands, and you could lose some or all of the prestress. That is the only potential problem I am aware of.
RE: Cut Double Tee Stem
Per the PCI Tables, a straight strand pattern could have been used in my application, but it is close. I think I am going to go the x-ray route again to make sure. I can't ignore the cost savings to be able to salvalge the existing tees after they are cut. If it is a straight strand pattern, I will analyze the section as a simply reinforced tee beam (Not prestressed) to see if it works in its shorter span position.
A local precaster who works on Hollow core slabs says they make them 300 feet long and cut them to length for each project. I feel like this is a similar thing.
RE: Cut Double Tee Stem
RE: Cut Double Tee Stem
RE: Cut Double Tee Stem
RE: Cut Double Tee Stem
Also, cutting the beam will probably eliminate most of the prestress camber. At the actual opening you can simple set the steel framing tight to the existing soffit to avoid movement at that point. This may still have some effect on the existing beam profile in the remaining spans if they're long enough. May be negligible but worth considering as it may result in some cracking.
RE: Cut Double Tee Stem
Don't take the PCI charts as gospel, only as a guide - you are better to try and investigate which of your local producers may have made the DT's - you'd be surprised they may still have shop dwgs for the double tees.
Scanning the legs of the double tees is a good idea, even if you have the shop dwgs as sometimes production may change the strands and it gets handled by an internal memo.
You probably could still check the strands as stressed rather than reinforced - if your loads are all UDL loads and the span isn't too short (so the strands can't fully develop) I'd be ok with it.
RE: Cut Double Tee Stem
Mike McCann
MMC Engineering
RE: Cut Double Tee Stem
If you mean the entire length of the strands, I don't think double tees are ever made with unbonded tendons. The strands are often unbonded for short lengths for the reason given by coopDBM and to avoid high splitting stresses.
RE: Cut Double Tee Stem
RE: Cut Double Tee Stem