A continuous RC beam chipped off at midspan
A continuous RC beam chipped off at midspan
(OP)
I have a continuous RC beam 2.5ft wide(75cm) and 1.5ft deep (roughly 50cm). At midspan, for architectural reason, I am required to chip off from this rectangular section a segment 1ft x 1ft (30cm x 30cm). This leaves me an L-shaped section at midspan with the horizontal segment at the bottom.
*
* leg "a" (vertical)
*
* * * *
leg "b" (horizontal)
Which one is healthier?
1) use the leg "a" all over the length for stiffness and carry out design using only this leg, treating the rest as simply an added wt(dummy block), with constructively selected reinforcement in this dummy block
2) Use full section at support zones and reduced section at midspan and detail accordingly.
I am worried about cracks in leg "b" due to strain compatibility and I think this post is worth its creation.
respects
IJR
*
* leg "a" (vertical)
*
* * * *
leg "b" (horizontal)
Which one is healthier?
1) use the leg "a" all over the length for stiffness and carry out design using only this leg, treating the rest as simply an added wt(dummy block), with constructively selected reinforcement in this dummy block
2) Use full section at support zones and reduced section at midspan and detail accordingly.
I am worried about cracks in leg "b" due to strain compatibility and I think this post is worth its creation.
respects
IJR





RE: A continuous RC beam chipped off at midspan
RE: A continuous RC beam chipped off at midspan
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RE: A continuous RC beam chipped off at midspan
Agree with the diagonal. The beam cross section is very much like an edge beam with a brick ledge. We usually use typical stirrups (two vertical legs) in the "a" leg, and then add a similar "U" shaped stirrup, laid on its side, extending into the "b" leg.
Option 2 - agree that its best. With a continuous line of beam, the change in Ix will affect the resulting moments...but not by too much if the cut out is short.