Continuous Beam theory

[tammypoo]

Just a quick question... I'm trying to calculate the moments n reaction for a shaft with 7 bearings... I understand the 3 moments theorem but i m not too sure on how to implement it with 7 moments.

please can anyone provide me an answered example of a beam with any number of moments from 5 to 7 so i can try to figure out how i can solve my model?

thanks

 

[msquared48]

Calculate the simple beam shears, then use Moment Distribution to find the + and - moments, plus the additional shears at the supports due to fixity over the supports.

Easier said than done.

Mike McCann
MMC Engineering

 

[rb1957]

quick question, long answer ...

you have a highly redundant beam (5 redundancies). Moment distribution, as suggested by mike, is one way to solve this. 3 moment equation can be applied, i think it is an iterative process applied two two bays at a time; but this doesn't look near as elegant as MDM. FEA would be a simple approach too, the model would be small enough to fit within most demo versions.

 

[FeX32]

Yea, FEA would be the simplest. You will get a headache trying to find 5 more equations to utilize.
If you simplify to 1-D this can be done by writing your own code. I would write this preferably in Matlab.

I never heard of the "Moment Distribution" method. Maybe someone has a reference?



Fe

 

[rb1957]

Bruhn (Analysis of flight vehicle structures)

i think it is a reasonably typical "old school" structural analysis method (ie "back in the day" when FEA was difficult ...)

 

[FeX32]

Oh ic.
Thanks rb1957.


Fe