P/S Strands in the top of a box beam?

[Hemifun]

Has anyone ever placed P/S strands in the top slab of a box beam? I have a project that requires 33-48"X17" adjacent P/S box beams. I have transverse post tension tendons at each end of the beams. Due to the large number of beams, I need staged construction to install the transverse tendons. My problem is my tendon pockets extend over half way down the sides of the beams and interfere with the P/S strands. I need 18 strands and a cgs located 4.67" above the bottom of the beams. I was wondering if it would be possible to place 16 strands in the bottom slab of the box and 2 strands in the top of the box. This would allow me to achieve the required cgs and eliminate strands from the sides of the box. Would this work??

 

[crossframe]

For precast, prestressed (pretensioned) members, there are usually at least two strands in the top corners. The ironworkers use these to hang and tie the top of the stirrups. The actual location may be able to be adjusted as required.

If the pockets are a problem, have you considered partial length (debonded) strands?

 

[yakpol]

Hemifan, a sketch would be helpful to your problem.

 

[broekie]

I put 2 strands in the top of a box beam all the time with no problem.

 

[hokie66]

Strands in the top are fine, but you can't just put the required bottom strands in the top. I suppose that is obvious, but you did say "I need 18 strands".

 

[MichSt]

Why not thicken up your bottom flange a little bit and use two rows of bottom strands?

 

[bags1235]

You definitely can place strands in the top slab. I've attached some standard ConnDOT box beam strand pattern details.

 

[Hemifun]

I would like to thank everyone for their suggestions. We solved the problem by eliminating the tendon access pockets and the staged construction. The contractor and the P/S plant both feel they can install the tendons and post-tension the beams without staging the construction.