nodal bracing for columns
folks,
i am having a discussion with one of my senior engineers regarding the attachment of a nodal brace for a column.
the nodal brace is designed for 1% of the compression load on the column and meets the axial stiffness requirements.
my question is thus:
does the connection from the column web to the bracing beam need to be a slip critical connection or can it be a bearing type connection with fully tightened bolts?
even though the standard holes only have a hole diameter of 1/16 more than the bolt diameter, i am questioning whether things will be fine in the period between when the column goes into compression and then eventually into bearing at the brace?
thanks
find a job or post a job opening
use the same bolt design as the rest of the structure. if you start mixing connection theory on the job something is bound to get screwed up.
old ca se
are you then suggesting that it does not make any difference on whether there is movement in the connection prior to it engaging in compression?
i am using bearing type bolts a325 n.
in principle, i totally agree with your kiss concept. [
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if you are concerned, just take the (1/16") slip into account when determining the provided stiffness to check against the required stiffness.
i'm thinking that the additional 1/16" wouldn't change the physical reality enough to worry about considering the coarseness of the overall method.
it just changes *when* the brace starts picking up load--when the column is bent to its initial out-of-plumbness (oop) or its oop+1/16". the bigger its initial oop, the bigger the brace force and stiffness required.
i don't have my seminar notes here, but i think those equations are based on an initial oop = l/500. i guess it depends on how 1/16" compares to l/500 for your case. if the column is 30' long, the 1/16" wouldn't be adding much.
the way i look at calcs like this, right or wrong, is in the context of how closely we can actually predict what's going to happen. in a lot of cases, you could predict behavior one way versus another, go run a series of tests and who knows which method would correlate better with reality. splitting gnat hairs?