Minimum deflection of beam - posn of supports calc 1

[nigelt]

I know this is a trivial question, but I vaguely remember noting a ratio for the quick positioning of a pair of supports under a uniformly loaded uniform beam such that deflection of the centre and equal overhanging ends is minimum.
Am I dreaming this, or can anybody recall it, please?
Oh, I guess I could figure it, but it's more fun to ask!
Cheers to all.

nigelt

"The ideal client is one possessed of great good sense and perfect judgement;
that is to say, one who agrees entirely with the designer at all times and in every respect."
Fenwick Williams, Naval Architect.

 

[Neilmo]

Hello Nigelt,

I don't know about minimum deflection, because it depends on the second moment of area you are using, but I have a formula in my book of notes, which says -

For a uniformly distributed load, deflection at centre of beam to equal deflection at ends of beam, place supports at 0.553 x Length of beam.

I have never tried this, so don't know how accurate this is. Maybe you could do your calculation and report back.

Regards,
Neilmo

 

[dik]

I've typically used 1/5 and 4/5 as support locations... I'll try a quick model to see what the real answer is... I'm not sure if the above is for strength or deflection...

 

[Neilmo]

dik,

For equal stresses, I have support spacing = 0.586 x Length of beam. This is close to your 0.6.

REgards,
Neilmo

 

[Neilmo]

Nigelt & dik,

Have just checked my support spacings above on a beam program that I have and they work out just fine -

Equal deflection support spacing = 0.553 x Length
Equal stresses support spacing = 0.586 x Length

Neilmo

 

[dik]

Neilmo
Thanks... more stuff to add to the back cover of my steel handbook.

 

[Neilmo]

Thank you for all the `stars`.

Neilmo

 

[nigelt]

Thank you "Neilmo" and "dik", I very much appreciate the time and trouble you took.
Best regards,

Nigel T