Is the top beam helping? 2

[4thorns]

In the attached, the load is resting on a smaller beam. Does the smaller beam actually assist the bigger beam by resisting the 500# to keep the deflection within the allowable 1/2"

If so then can it be said that at the 1/2" deflection only 1000# plus the wall weight is being transferred to the bottom beam?

 

[4thorns]

Basically in this situation I need to determine what the bottom beam needs to be. I know what the top one is. The deflection is controlled by the bottom beam. If I know my deflection limit, I can find out how much load the top beam can handle to not surpass that limit.

Can I then subtract that amount from the overall load and design my lower beam based on the result?

I've been told to ignore the (in some cases small amount) that the upper beam can resit and design the lower beam to carry the whole load. That just didn't make sense to me.

Thank you all for your time.

 

[msquared48]

I do need to correct my last post here on thinking about my comment more.

It will not make a difference in the plywood wall shearing stress whether the larger beam is placed at the top or bottom as all three mechanisms deflect at the same rate and together. When I thought about it further, a difference in stress made no sense.

And, Hokie, you are correct. The answer ti the OP is yes. We were beating around the bush.

Mike McCann
MMC Engineering

 

[asixth]

Yep,

If the smaller beam deflects 1/2" when subjected to the 500# and the larger beam deflects 1/2" when subjected to 1000#. Then a 1500# load applied at the top beam will be shared in a ratio of 33.3% and 66.6% as long as the transferring elements (being the wall frame) has the ability to help share the loads.