Steve wrote:


I have downloaded the software from Tony's website and had a quick play. But it is
clear that I need to follow the advice on there and print out the instructions!

I setup a beam with two loading entries: one "U" (i.e. uniform)
specified as 0.8, and one "P" (point) at .7m from distance, and a load
of 1.6kN.

So thanks also to Tony for generously making the software available to non
professionals like myself.

Yup, I will second that.

Coming back to the joists, I had a gut feeling that deflection would be
more than desired and your results back this up although you have quite
rightly taken the worst case with the load in the centre of the span. In
our case most of the load will be near to a sleeper wall for each leg.
But I would rather be conservative and use worst case!

That also assumed the leg directly over one joist - if it were to the
side a little the the load would be more spread between two (I did leave
the load sharing set to 2 however)

One idea was to double the joists up i.e. putting extra joists in
between but in the areas of high load to have double joists joined, but
I had thought of glueing them together and bolting through the neutral
access. Any problems with glueing and bolting?

I would be a little wary of bolting a joist that is only 100mm high.
Your standard 12mm bolts would hence be taking out over 10% of the joist
depth at the point.

You could glue, or use the spiked timber connectors on the bolts if
going that route. I would have though that just nailing the joists side
by side would be enough in this circumstance.

I also had an extension to this idea...I thought of cutting 8" strips of
18mm WBP, glueing two together and then sandwiching that between two
joists, all glued and bolted. In effect a 'T' beam. Obviously the ply
can't extend the total length because of the sleeper walls but that
would probably not matter as shear is unlikely to be a problem, I think.
Any comments on this idea?

Doable, but possibly overkill. If you wanted a beam stronger than a pair
of timbers side by side, then the next option would usually be a flitch
beam[1] (i.e. a pair of beams with a steel plate sandwiched between
them, and bolted together). Not sure how realistic that is on only 4" of
depth though.



[1] Example 8mm steel plate flitch (with red passivated coating):

http://www.internode.co.uk/loft/images/flitch.jpg



--
Cheers,

John.

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