On Thu, 13 Aug 2009 23:10:02 GMT BigWallop wrote :
If these timber joists are hanging on only one side of the RSJ, then you
have a twisting action as the loads increase and begin pulling on that side.
Is this something you are allowing for?

Timber is at least fifteen time weaker than steel, so any infill of the web
of the RSJ will mean nothing to actual load bearing properties of the steel.
Drilling into or through the steel can change its loading character
dramatically. Holes under stress can allow cracking to take place through
the rolled grain of the RSJ in certain circumstances. 600mm spacing sounds
like one of these circumstances.

I agree about considering the effects of torsion, but can't see that drilling
holes in the beam will have an effect on the steel that's left. I am though a
little puzzled at the OP saying he wants to drill holes in the flange rather
than the web. Running the same calc through our ProSteel program shows that
even a 50mm hole through the web is quite OK - smaller ones for through bolts
will have a negligible effect.

I still think spending a little time talking to, not hiring, a proper
engineer will help out on your project and let you do the works without any
faffing about. Even if you give the engineer a retainer for their
consultation, it's better than trying and failing with this type of job.

No argument there. We do have SuperBeam users who offer a calcs by mail
service and others who will not do them without a site inspection. If I were
offering engineering services I would definitely be in the latter camp.

--
Tony Bryer, 'Software to build on' from Greentram
www.superbeam.co.uk www.superbeam.com www.greentram.com