Beam/Column Moment Capacity Ratio
Beam/Column Moment Capacity Ratio
(OP)
While designing special moment frame in ETABS, I have the following situation:
I have 20"x20" reinforced concrete columns supporting 16" Wide x 36" Deep beams on the top floor. Since there is no column above the joint, and at least 3 beams frame into my column at every joint, the Beam/Column Moment Capacity Ratio is exceeded. I would need too big of a column section to get it to work. Please advice as to any other possible solutions.






RE: Beam/Column Moment Capacity Ratio
BA
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
Did you play around with the beam size at all?
Though I don't think its recommended, fixing it at the base and designing the foundation for moment is another option...
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
NIST has a good paper on special moment frames.
http://
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
In addition to cutting of some bottom steel prior to the joint and increasing the size of my columns, wouldn't increasing the steel area of reinforcement at each face of the beam help as well?
RE: Beam/Column Moment Capacity Ratio
RE: Beam/Column Moment Capacity Ratio
Increasing the column strength would help. I assumed you'd done this prior to trying to increase the column size. But the column vertical bars need to be developed according to the beam requirements.
Did you download that NIST paper that I referenced? It's very good, deals with detailing procedures also.
RE: Beam/Column Moment Capacity Ratio
You obviously have to calculate the redistrubtion a bit more accurately than I have outlined. Will reducing all you beam end moments at the column by 30% be enough to get the column to work for the size you have chosen?
Your columns seems quite big for roof loadings. Do you have very long beam spans or cantilevers?
RE: Beam/Column Moment Capacity Ratio
I am currently working with the moment redistribution.
Thanks all for all your helpful comments.