On 31 Dec 2004 03:02:22 -0800, (N. Thornton) wrote:

In message , Mike )
wrote:
"N. Thornton" wrote in message
. com...

Hate to be a harbinger of doom but if your BCO asks for strength
calculations it becomes a serious headache. Ours said he would so we
decided to buy one from a company that will do calcs if needed. Of
course
then he said he didn't need them from them.


Why is this a headache? Sagulator makes calculating this easy, does it
not?
http://www.woodbin.com/calcs/sagulator.htm

For a single piece of 2x5 pine, 110" long, 450kg will produce 0.5"
deflection. The stair uses 2 pieces of 2x5, so real world deflcetion
for 450kg closer to 0.25".

Apply a 4 ton load to the stair, evenly distributed, and total
deflection now 2.25". At 100kg a piece, 4 tons would represents 40
people on the stair. And thats 40x 220lb people! I reckon that should
do. (They would have to be evenly distributed to even think of getting
that many on there.)

For the individual treads, lets say 8" x 36" x 1.25", with 2 people
standing on a tread: deflection 0.13". All these deflections are well
within breaking point of softwood. Am I missing something?


NT

Cool, thanks.