Reducing lateral/shear forces on a two wall structure
Reducing lateral/shear forces on a two wall structure
(OP)
I am having a problem with a simple structure that was built to shelter a cluster of mailboxes. After seeing it built and in place, it's obvious that the culprit is lateral forces causing it to rack from side to side. Steel angles were installed at the base of the columns to prevent the "racking" but the client does not like this solution. We can't put a shear wall on the back of the building because the mailbox cluster has to be loaded from the rear.
Is there any other solution? Here are some images of the building and the initial "solution."
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Is there any other solution? Here are some images of the building and the initial "solution."
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RE: Reducing lateral/shear forces on a two wall structure
RE: Reducing lateral/shear forces on a two wall structure
Knee braces could work. I would presume there are 2 beams supporting the rafters - why not make them deeper and try to develop a full moment connection between them at the vertical posts in each end wall? You could create a portal frame this way which should reduce the sidesway.
Ralph
Structures Consulting
Northeast USA
RE: Reducing lateral/shear forces on a two wall structure
Or you could make a wall that's flush with the front of the mailbox and extends base to roof. That could be a clean look.
RE: Reducing lateral/shear forces on a two wall structure
Something like a 12" 4x4 with a lag bolt on either end might be enough. It's tricky though because you don't get a lot of capacity out of knee braces. The limiting factor (I think) tends to be splitting of the wood along the grain.
You might be able to do some sort of decorative/structural black steel knee braces too.
RE: Reducing lateral/shear forces on a two wall structure
RE: Reducing lateral/shear forces on a two wall structure
To make this work, I would add a central shear wall (with an opening for the mailbox) over and under the mailbox, forming an effective "I" shape of all the available shearwalls.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Reducing lateral/shear forces on a two wall structure
RE: Reducing lateral/shear forces on a two wall structure
By the way, what's your brilliant input towards this solution other than your sophomoric slang?
RE: Reducing lateral/shear forces on a two wall structure
i'm sure you are a hundred times better engineer than i am.
i just LOL because it didnt occur to me that a mailbox shelter like that would still need a structural engineer.
cheers !
RE: Reducing lateral/shear forces on a two wall structure
BA
RE: Reducing lateral/shear forces on a two wall structure
Knee braces really jsut make this a moment frame.
I do agree that it is a rather curious situation for an SE.