Bundling of Strands in Post Tensioned Concrete Beam

[dcarr82775]

For slabs there are some clearly defines rules (in the US anyway) regarding how to bundle unbonded tendons in slabs. Are there any similar such rules for bundling tendons in beams? I would think you wouldn't need to have them in nice straight strips like in a slab, and could group them into more circular bundles that then splay out at the ends.

If not rules, I would appreciate knowing how other do it. Thanks

 

[AUCE98]

Try to bundle the tendons in a single row, if you don't have that many tendons. If you have several tendons that are not able to be spaced out across the width of the beam in a single row, use two rows. The idea is that you want to maintain the CGS of the tendons while bundled in the beam, which corresponds to the height you need to provide the support stirrup.

For example, a beam with 15 tendons may be broken into (3) groups of 5. The bundle of 5 would be 2on top 3 on bottom. This will keep the CGS of that bundle approximately in the middle of the group. Then the support height would be calculated to be 1/2" lower than the CGS at a particular location.