Hanger Reinforcement

[juandaniellarrinaga]

Hi everyone:

I would like to ask one doubt, then thing is that I´m designing a ledge beam and as you know the transverse reinforcement that you have to provide is the shear reinforcement, the torsional reinforcement, but the thing that is not clear for me is when you check the hanger reinforcement, what you have to do with this Steel area, you have to add the hanger reinforcement to the torsional and shear reinforcement? or only have to check if this requirement is more that the shear and torsional and I take the mayor reinforcement? in resume the transverse area is Av(shear)+At(Torsion)+Ah(hanger) or the mayor area between Av(shear)+At(Torsion) abd Ah(hanger) and whatever that the answer is, where can I find that requirement, In ACI or PCA Notes because In PCA Notes didn´t tell you clearly this point, they only say that "Hanger reinforcement should be proportioned to satisfy strength" and when design by torsion they only take in count the Av and At and put a note that say that the ledge reinforcement not show in that part,they tell you that you check in part 15 (ledge beam part) for that design, and when you go to part 15 they design only the corbel of the beam and they did not considered the global effects and only check the hanger reinforcement, and they tell you that for more details see a reference that is "Klein, G. J., “Design of Spandrel Beams,” PCI Journal, Vol. 31, No. 5, Sept.-Oct. 1986, pp. 76-124." and in that reference say that "Furthermore, there is no agreement as to whether or not hanger reinforcement should be added to shear an torsion reinforcement" so I dont know what to do because this paper is from 1986.

If anyone can help me to find this requirement if we have to add or only check??

Regards

Ing.J. Daniel Larrinaga Cano

 

[ishvaaag]

You need to ADD he hanger reinforcement. You can understand why easily if you see that shear reinforcement (be it from just shear or shear plus torsion) is traditionally derived of one "Mörsch" analogy, in which shear reinforcement takes the role of web members in a truss cage. Hanger reinforcement has nothing to do with such Mörsch scheme... even if placed at webs, its role is to hang the load from atop the truss, as a cable would do. So the two reinforcements cover separate structural functions and both need to be disposed in place. Then comes the question on if some designers have imagined that with the safety factors etc just the check may be enough etc, but, since the rationale is a per above, my definite view on the matter is that BOTH required reinforcements need be added in the webs.

 

[juandaniellarrinaga]

Thanks a lot, I added both reinforcements at the end, I prefer be conservative.

Thanks.