stress in two planks

huangyhg

stress in two planks
if i have two 8x10 can i combine them and calculate the stress over the combined thickensss
thanks
check out our whitepaper library.
combine them how ... to get ...
16*10, 8*20, 10*16.
and then how are the loads oriented to the joint ?
and what is the primary load ... bending or compression ?

good questions, rb1957.  my question is "since when is an 8x10 a plank?"
it'd be a very thick one, or a very narrow one ;)
generally not.  if they're the same thickness and size, you could figure each carried half the load.  but that's not the same as figuring one plank twice as thick.
consider why a cable if flexible, but a bar of the same size is not.
bond, or fasten, the 2 8x10, then calculate as composite.
otherwise, the above is accurate enough for practical purpose.  
for two beams combined, the bending stiffness will be determined by the addition of the 2nd moment of inertias, ie. bd^3/6. this assumes the worst case that there is no friction between them and they slide. if you bolt the two together, however, then the moi will be based upon the combined thickness, ie. (2/3)bd^3
corus
i ususally assume each one carries half the load - assuming that the load rests rather evenly on each one.  fasten together to act as one beam.
we're assuming this is a beam ... what if this is a column ?
if it is a beam, and they're just stacked on top of each other, and there's a point load on the upper one, then doesn't the lower beam provide a distributed reaction to the upper ? ... imho not the same as saying each reacts 1/2
looks like technicalgirlca needs to provide a bit more information.
ba
it seems that technicalgirlcafff"> is not actively following this thread.  a clarification of the specific application is in order - beam or column?  orientation of the (2) 8x10s as rb1957fff"> stated?
ralph