Cut off point of extra bottom bar of continuous beam at support .
Cut off point of extra bottom bar of continuous beam at support .
(OP)
I want to verify if my judgement (as shown in figure below) is correct. .
We know that the extra top bars of a continuous beam would terminate at the middle third from the support . and the extra bottom bars at midspan would terminate usually at quarter length of the beam.. but what about the extra bottom bars at the support ? is the figure above correct? is there any section of the aci code that would verify this.. will the cut off point be the same for tie beams, grade beam , 2nd storey and above beam?

We know that the extra top bars of a continuous beam would terminate at the middle third from the support . and the extra bottom bars at midspan would terminate usually at quarter length of the beam.. but what about the extra bottom bars at the support ? is the figure above correct? is there any section of the aci code that would verify this.. will the cut off point be the same for tie beams, grade beam , 2nd storey and above beam?





RE: Cut off point of extra bottom bar of continuous beam at support .
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Cut off point of extra bottom bar of continuous beam at support .
the beam is indeed a part of a frame and it is a SMF. . .so where would you suggest to cut of the bottom bar? if the inflection point due to lateral load like earth quake would cause the inflection point to move near mid span (the moment diagram would be like a shear diagram ).
RE: Cut off point of extra bottom bar of continuous beam at support .
I don't think that there's a rule of thumb that would be universally applicable Penpendrum. I'd analyze the beam, locate the inflection points, and plan any cutoffs around those locations. As I'm sure you know, ACI318 has a lot of prescriptive requirements for rebar detailing in special moment frames (Link). When all is said and done, I find that you don't have all that many choices left to you as a designer other than rebar quantity. And you usually end up with top and bottom steel running the entire span.
Link
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Cut off point of extra bottom bar of continuous beam at support .
For a typical beam - you'd have all sorts of bottom bars for gravity loading and your through-column bottom bars used for the wind moment would probably simply splice with certain gravity bottom bars. Splices can be anywhere but usually preferred at locations of minimum stress where possible.
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