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Floor Beam Fixity data for Boeing Aircraft?

Floor Beam Fixity data for Boeing Aircraft?

Floor Beam Fixity data for Boeing Aircraft?

(OP)
I'm in the middle of evaluating a structural modification to install some extended first and business class seating to a Boeing 747 (upper and lower deck).  We are, of course, working conservatively but I'd prefer not to make unnecessary mods to primary structure.

I ran across some floor beam fixity data for a B757 (generally around 40%), but I was wondering if anybody had similar data for the B747 that was "blessed by Boeing" as it were?

Thanks

Joe

--
Joseph K. Mooney
FAA DER Structures

RE: Floor Beam Fixity data for Boeing Aircraft?

There is little data available for floor fixity on older A/C. You could use the values for 777 (similar size)ie rotational stiffness = 6,000,000.
By the way I am working on a 737 - same cross section as your 757. I have seen 50% used for frame fixity. I guess by 40% fixity you mean to use a value of 40% of the bending moment at the frame for the fixed condition as the bending moment in the frame due to floor loading???

RE: Floor Beam Fixity data for Boeing Aircraft?

More generally it is hard to get more than 60% without using a carefully designed joint. With care it is possible to get >90%, but they may not be economic, or of any functional value.

Cheers

Greg Locock

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RE: Floor Beam Fixity data for Boeing Aircraft?

if you could live with it (wihtout unnecessarily complicated or extensive mods) why not assume fully fixed when analyzing the ends, and simply supported when considering the mid-spans ? (ie the worst of all worlds)

RE: Floor Beam Fixity data for Boeing Aircraft?

(OP)
Thanks to all, that's kinda what I would guess as well.

rb1957 - That's what we wound up doing, I was just hoping to minimize impact to the overall structure.  Got a 767 coming up and we are just going to model the whole sha-bang.

--
Joseph K. Mooney
FAA DER Structures

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