Effctive length of steel beam

[tony1851]

Hi all,

Steel beam spanning 9.6m in masonry opening, simply-supported on the masonry each end. Top flange is adequately restrained by two incoming steel beams; the top flange of the subject beam supports a de-stabilizing wall load along its full length. - see image.
How would I evaluate an effective length?

 

[LeonhardEuler]

I would say the effective length is the entire length, but you can increase the LTB strength by considering the cb value for the loading condition. I'm sure there is merit in reducing the effective length with those beams, but it depends on stiffness of the connection.

 

[dik]

I usually 'chuck' a 1' (for masonry 1.33') length on to the clear span. If really an issue, determine the length of bearing required for each end and add half the value of this at each end to the clear span length. Due to deflection the point of bearing is closer to the clear span edge.

Dik

 

[KootK]

As I see it, you've got three segments to evaluate. One with 2.9m effective length; one with 3.2m effective length; one with 3.5m effective length. It may be that you can eyeball the most critical segment. An interesting question is whether or not you have effective rotational restraint at the masonry bearings. We usually say that exists but it's not an easy thing to prove in most cases, particularly if you'll be resisting a torsional load rather than just providing torsional restraint in the stability sense.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[tony1851]

Thanks Leon,dik and koot, advice appreciated and noted.