Inverted Tee Hanger Bar Offsets

[BK76]

I have an inverted tee that requires quite a bit of hanger reinforcement designed under AASHTO. I'm currently designing the section for four legs of stirrups fairly evenly spaced across the cross section.

LRFD 9th Ed., Art. 5.8.4.3.5 mentions that the arrangement for hanger reinforcement in single beam ledges shall be shown as in Fig. 5.8.4.3.5-1, and this makes sense to me since single ledges are much more imbalanced and the tension ties are near the face of the stem. However, I can't find any requirements for the location of the hanger bars in an Inverted Tee. It's unclear whether the interior stirrups should be resisting the hanger bar loads. Say, the stirrups on the right half of the stem should resist the hanger bar loads for the bearing on the right ledge.

I believe that the hanger bars resist the crack labeled (2) in Figure 5.8.4.3.1-1, so I can see how the bars closer to the face of the stem are engaged earlier. However, I would imagine bars 6" away would also engage before the exterior stirrups fail.

In short - are the stirrup legs that are near the interior of the stem contributing to the hanger reinforcement?

 

[KootK]

In short - are the stirrup legs that are near the interior of the stem contributing to the hanger reinforcement?

In general, I would say no. It kind of depends on your proportions however. If you look at the beam hanger provisions in ACI 318, you will see that there are some scenarios in which multiple stirrup legs can be meaningfully engaged. I've not seen many IT beam ledges proportioned where this would be appropriate however.