stress calculations for round timber?

Hi.
I want to support my living room roof with round timber.
its a small roof by all acounts and the timber i have is treated spruce (class 1)minimum diameter 130cm. (this being the case i can use square timber calulations 130 x 130)
is there information that would help me calculate maximum spans for beams and purlins?
i would like to have an A frame and 2 x T frames if posible.
any input would be most helpfull
thanks
steve

Steve:
There are beam analysis programs out there, some of them you can download a sample version and you can use them (if you know how to) to check out beam loads.
Most of the demo versions are limited by only allowing you to do short lengths and you can't print your results.
If you do a search here on this forum for info about beam analysis you'll find quite a bit of info about it.
One message by Ed Levin lists web sites where you can go and find these demo versions. It's title is "Engineering software".

I recently found a program called BeamChek and it has a demo version and it has a button for round timbers. You can find it at www.BeamChek.com
I'm not sure if it has a setting for cm's or not you'll have to see.
Good luck with your research.
Jim

thanks, ill have a look. the size of the timber should have read 130mm (not cm)
i have paid for some calculations, but i cant use them, wrong truss type etc. but i have got the stress calcs with it. (just dont understand what is what)
ta
steve