huangyhg

beam to column moment transfer
i am new to raised floor design and am working on a small water tank lid. the tank is long and narrow. i was told to design it as a one way slab with a beam and columns running down the middle. in designing the beams, would you want to fix them to the columns? and if they were fixed would the moments from each beam (one on each side) cancel each other out or transfer to the column ?
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suggest that you assume everything has simple supports for several reasons, here are a few:
1. simple supports are more forgiving if the actual loading is different than specified.
2. with all due respect, you are "new to raised floor design".
3. unless you have a high level of control over the construction process, it is difficult to insure that the finish product will be constructed so that the beam / column connection is truly fixed.
these are things you need to figure out. don't make the mistake of thinking that you can design concrete however you want and make it work. concrete is how it is, and you have to analyze it in a way that approximates reality.
an example would be saying there are two simple span beams on either side of a column. the reality is that there is a continuous beam, and the maximum moment will occur over that column. it will only act as a simple span beam when significant cracking occurs on either side of the column (right where the shear is at a maximum).
how much moment transfers into a column from a continous beam is a function of the stiffness of the column versus the beams. if it is a negligible amount, you could treat the column as a pinned support.
if i was you, i'd figure the moments in beams and columns out on paper as well as i could, and only then put the members into a software program such as risa 3d or sap and analyze it. make sure you figure out exactly why you made your mistakes. your boss probably wants an answer "quick", but if you just rely on software, without fully understanding, you'll be giving him a solution you aren't sure is right, and next time you have a similar problem, you still won't understand it.

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