P/S box beam end reinfocement 1

The anchorage zone reinforcing required in Article 9.22 is to distribute the force after release. It is usually a lot of steel at a very small spacing. Like 1.5" clear or 2" c-c. This helps prevent cracking and possible crushing. I believe some states use end blocks to thicken the web. It's a very simple method so you don't have to do the strut-and-tie.

I usually spec #5 stirrups in the anchorage zone.

Anyway, the rebar grillage from PennDOT is probably for post-tensioned girders to meet the anchorage zone requirements. Normally, this is designed using a strut-and-tie model. Maybe they pulled the detail from PT Girders and are using for PS Girders?

MikeD

I agree with you. PennDOT may just use post-tensioned detail for pre-tensioned. Now the issue for me is how to fit 4 sq. in. steel into 6 in. end zone. With 2 in. c.c., only 3 #5 stirrups could fit in, and gives 1.86 sq. in., less than 50% required by AASHTO. But larger bars seems not a good choice for crack control? Any advice?

I think I have a relatively large prestress force in the section (48 0.6in. strands in 48x33 box beam). This makes the anchorage steel req't difficult to meet. Is there any way to get around AASHTO? I do have a 12 in. end block though (from bearing center to the end of the beam).

You need to use the 12" end block. Place a bunch of stirrups or even the grillage within the 6" region. If you use the 1.5" clear you can easily add 20 more rows of the stirrups by adding transverse rows in the end block. The girder is 48" wide so you can fit 20 rows of stirrups in the end block (4" clear and a 2" spacing for the strands). Switch to #4 and you may have to fiddle with the cg. It sounds like you are only using stirrups in the webs for the anchorage zone. In order to maintain clear you may have to move some strands. In the past I've also gone to 1" clear to meet this requirement.

PennDOT probably just adds this grillage and doesn't give it a second thought.

In a way it is easier to fit the added rebar in a PT girder since the strands are in ducts. In a PS Girder they are spread out and you'll have trouble fitting the stirrups in between.

Two options: 1)You can call this a disturbed region and check it as a strut-and-tie model. 2)Call a local fabricator and ask them how the detail is usually handled.

Last word: You might check with local fabricators anyway because if you have too many strands their beds might not be able to handle it. They also may have a slightly different pattern in their beds. In past experience the PCI max number of strands cannot be reached by the fabricators. The available locations and number of strand is pretty much theoretical in my opinion. Your software may say 48 strands works but sometimes they cannot hold down that much.

Good Luck
MikeD

Indeed, I didn't think of adding steel transversely in the block. Thank you for pointing it out! I do need to call a precaster as well. Greatly appreciate your input!

Koo