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Thanks!milkshakelake said:Sorry, missed this comment in the maelstrom of things. The quote button is like 4 steps to the right of "image", 6 steps to the left of "preview" when you're typing a reply.
My response to this as well as comments I've heard (mostly from contractors) about a design being "over engineered" is this: Every structure standing today is over engineered. In reality, particularly with most of the structures I've worked on, the critical loading condition is roof live load which the structure will only experience a few times in its life, namely during construction, during a re-roof or during a fire.DaveAtkins said:have never heard of a column like this failing in axial plus bending due to ignoring the moment in the column
KootK said:Rescind! Or it's pistols at first light...
KootK said:Is that true? That's really what you are doing in your practice and is the message that you want to be putting out into the world with respect to your understanding of what the standard of care is here?
phamENG said:So if we fail to design the connection for the appropriate moment that is transferring through the joint, you can pop the bolts with the added tension from prying, we could yield the cap plate, or do any number of things that could hurt the connection's ability to remain stable even just as a "shear" connection.
KootK said:271828 said:FWIW every firm I've worked for (reputable firms) would design the members as if there's a hinge at the top of the column and create a non fully-restrained moment connection by using:
1. a non-thick cap plate;
2. non-large bolts; and
3. one set of stiffeners at the column centerline.
If the detail had a beefy cap plate, large bolts, and two sets of stiffeners like shown in the OP, then I might take the continuity more seriously.
Same for the firms that I've worked for. That said, I feel that approach serves mainly to obfuscate the important truth of the situation which I feel is this:
In many practical situations, appropriate joint modelling has more to do with what's going with the members coming into the joint than with the restraint offered by the joint itself.
human909 said:Your initial claim of simply assuming away moment transfer is what started the debate. And from my perspective it remains absurd after dozens of posts as it did originally.
I would like to take you up on that challenge, when I get a little bit of free time. I do fairly simple structures (residential remodeling), but I occasionally run into a situation where I need a steel beam because a wood beam would not accommodate the architecture. I support these on HSS 3"x3"s. I've always looked at this condition as pinned end, but now that I have a new "toy", I've modeled it. As pointed out, it's entirely possible that the resulting moment in the top of the column is compensated for a k = 1.0 to a k ~ 0.7, which I don't disagree. I've book marked this thread and will come back to it when I get a little time, using a "real world" example, rather than extrapolating from anecdotal and often outdated references. What I will do is model based on a fixed connection and adjust the loadings/members so that I get a CSR = 1.0. Then, I will change the model to pinned connection and see what the resulting CSR is. I'm truly interested in this result. Of course, there is a resulting shear at the base if it is a moment connection which does not exist if it's a pinned connection, but I don't anticipate neglecting this shear would be a problem. Just about any two anchors should resist the resulting shears, again, in the types of structures I deal with on a daily basis.Eng16080 said:I would be curious to see an example of a structure which does not meet my hypothesis that:
Hypothesis: A structure designed with pinned connections versus fixed or partially fixed will result in a conservative design.
This however, is not what my hypothesis is. It's that a code compliant structure designed assuming pinned connections would be conservative if the connections were actually fixed or partially fixed. So, you would first design it with pinned connection to get a CSR = 1.0 and from there you would change the connections to fixed without changing anything else.SE2607 said:What I will do is model based on a fixed connection and adjust the loadings/members so that I get a CSR = 1.0. Then, I will change the model to pinned connection and see what the resulting CSR is.