Simon wrote:
On 11 Aug, 22:32, sm_jamieson wrote:
I have just exposed the existing RSJs to which new load is to be
applied to support my roof.
The BCO said the bearings may need to be exposed but has said nothing
more. For peace of mind I
probably need a structural engineer to check things, but can anyone
give a rough feel for the loadings here ?

Old fashioned RSJ, width 125mm, height 150mm, flange thickness 10mm
at the edges, 15mm at the web,
web thickness 10mm. Span is 2800mm. Can anyone tell me what type of
loads this beam can take (assuming bearings are OK). Also, what type
of point load could it take near the middle of the span ?

Thanks,
Simon.

Right, I've thought of the best solution now, assuming the RSJ can
take the point load (struct eng ?)
Fix some timber into the web both sides of the RSJ by bolting throught
the flange M10 bolts every 600mm or so.
Then remove a single brick from the headers that are bearing directly
on the RSJ (could there be some slippage ??),
and wrap a long leg hanger up the timber, over the top and down the
back and nail in. Will hang below the RSJ like is
often done in loft conversions. Joist may need to be notched at the
top if it ends up just a little higher than the top of the RSJ.

Variation: no brick removal just fix hanger up and over the timber
infill and bolt this to the flange.

Only question - this is an RSJ with tapered flange, so I guess the
timber should be shaped at the bottom to follow the flange,
and bear in mind the bolts will be doing more than in a UB with flat
flanges. Up and over RSJ probably best, since force is more
direct onto RSJ and less the timber infill.

Which of these variations sound the best ?

Cheers,
Simon.


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 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.