Wall bracing buckling

[DsTs]

Hi,

I have this cross-wall bracing. For some reason, I've connected the wall bracing to the underside of the floor beam, as shown below. Due to this configuration, the wall bracing may buckle under the gravity load applied to the floor beam. While I understand that wall bracings are allowed to buckle under wind and designed as tension-only elements, I am unsure whether I can disregard the buckling under gravity since I have a column designed to take the axial load. How can I determine the out-of-plane displacement of the wall bracing after buckling?

 

[human909]

Unless there is some very unusual circumstances your bracing member won't buckled from gravitational loads. The column and beam (at that location) are orders of magnitude stiffer than the bracing member.

Not to mention than you'll get insufficient deflection to engage a typical bolted connection in bearing.

Of course it would be a different story if you had chevron bracing. In those circumstances you could get member buckling.

 

[DsTs]

Thank you human909.
I was thinking the same thing when I had this connection.

However, unless I release the translation of one column base to avoid 'arching', the distribution of load between the column and wall bracing relies on the sectional area of the column and the vertical component of the wall bracing's sectional area. In this scenario, with a 310UB column and 100x10EA wall bracing, the wall bracing is expected to bear approximately 15% of the axial load. And the axial load on the wall bracing increases when considering say a 200mm offset for the wall bracing (i.e., shifting the wall bracing node to the beam by 200mm in my model).

 

[JAE]

the distribution of load between the column and wall bracing relies on the sectional area of the column and the vertical component of the wall bracing's sectional area.

Not really. In your pristine computer model where everything is first order and all connections have no slip (per human909) then yes, this statement is correct.
But in reality:
1. There is "give" or slip in the connection at the end of the brace.
2. There is a softening of the brace due to very small out-of-plane bowing under gravity loads or simply lack of perfect straightness in your brace.
3. The column has no slip or very minimal "give" and thus will take almost all of the gravity/axial loading.

If it's a tension-only brace, you can make it a tension-only member in your model and design from that, all while understanding that the brace will bow a little (I'm thinking tension rod or double angle type braces or similar).