Floor beam end fixity
Floor beam end fixity
(OP)
Hello,
I have a question concerning end fixity of floor beams. Am I correct in interpreting end fixity as the ratio of the end rotation of the beam when subject to a unit moment (theta1 = L / 3EI) to the sum of theta1 and the rotation of the end support when subject to a unit moment (theta2 = 1 / Ksupport)?
So,
fixity = theta1 / (theta1 + theta2)
Please clarify if I am incorrect. Also, how are end fixities typically modeled in FEM, using torsional springs? If so, how are the values of the torsional springs related to the fixity values. I have searched the popular aircraft analysis references (Niu, Bruhn) and have not been able to fully understand this subject. Any insight is much appreciated, thanks.
I have a question concerning end fixity of floor beams. Am I correct in interpreting end fixity as the ratio of the end rotation of the beam when subject to a unit moment (theta1 = L / 3EI) to the sum of theta1 and the rotation of the end support when subject to a unit moment (theta2 = 1 / Ksupport)?
So,
fixity = theta1 / (theta1 + theta2)
Please clarify if I am incorrect. Also, how are end fixities typically modeled in FEM, using torsional springs? If so, how are the values of the torsional springs related to the fixity values. I have searched the popular aircraft analysis references (Niu, Bruhn) and have not been able to fully understand this subject. Any insight is much appreciated, thanks.





RE: Floor beam end fixity
what type of aircraft?
some floor beam to frame connections are designed as pinned joints, some have moment continuity; what is your specific configuration?
how are you modelling the floor beams and frames in the FEM? beam elements, plates for webs + beams for chords, fine grid plates, solids, ??
do you need to use a torsional spring because its a beam FEM?
I don't think your fixity formula is correct or useful.
RE: Floor beam end fixity
RE: Floor beam end fixity
Make a pinned-pinned bendimg moment diagram and a fixed-fixed BMD. For 33% fixity your BMD is 33% of the way from PP to FF.
RE: Floor beam end fixity
RE: Floor beam end fixity