## bending stress in compression

## bending stress in compression

(OP)

I am reinforcing a 4x roof beam, under a nailed diaphragm, by sistering a couple of microlams, designing it as a composite section such that the neutral axis is lowered, etcetera...

The result will be such that my extreme fiber bending stress in compression is greater than my extreme fiber bending stress in tension.

Given typical values such as for DF-Larch#1, Fb=1000, Ft=875 and Fc||=1500, I understand limiting the extreme fiber bending stress in tension to Fb (with all the factors), but do you think there is margin to allow the extreme fiber bending stress in compression to exceed Fb?

The result will be such that my extreme fiber bending stress in compression is greater than my extreme fiber bending stress in tension.

Given typical values such as for DF-Larch#1, Fb=1000, Ft=875 and Fc||=1500, I understand limiting the extreme fiber bending stress in tension to Fb (with all the factors), but do you think there is margin to allow the extreme fiber bending stress in compression to exceed Fb?

## RE: bending stress in compression

I certainly do. The trick, however, will be determining just what that margin is. I don't know the answer to that. And, of course, you'll need to satisfy yourself that you've jacked or considered locked in stresses etc.

I wonder if there might be some way to adapt the beam-column provisions to your problem. One could treat the reinforced member on its own as a beam-column loaded:

1) Transversely by whatever share of the transverse load belongs with the original member and;

2) Axially by the horizontal shears that the reinforcing members will impose along the length of the original member.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

## RE: bending stress in compression

## RE: bending stress in compression

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

## RE: bending stress in compression

## RE: bending stress in compression

I'm curious about the same thing. Not curious enough to prosecute if myself though. My suspicion is that the central member will be immune to axial load buckling concerns. Kinda like how axial prestressing of a precast column doesn't contribute to buckling.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

## RE: bending stress in compression

## RE: bending stress in compression

1. Find the stress in the top and bottom of the 4x.

2. See attached for example on calculating the equivalent bending stress and axial stress.

## RE: bending stress in compression

## RE: bending stress in compression

## RE: bending stress in compression

## RE: bending stress in compression

## RE: bending stress in compression