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Old 07-08-2012, 09:40 AM   #16
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Poorly placed Joists in Home being remodeled


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Originally Posted by Ghengisconrad View Post
also, fyi, the new joists have 5/16" lag bolts holding them in... as well as a &$*(#U#*($ load of construction adhesive so...

studs are in the wall vertically and joists are horizontal making the ceiling/floor.

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Old 07-08-2012, 11:53 AM   #17
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Poorly placed Joists in Home being remodeled


The project is not yet finished, thats why the original question was about the joists, not the studs. The stud you may see flying out there at an angle is actually going to be placed UNDER the orginal joist.

The idea here, is that by sistering and firing and glueing and screwing everything, it going to be just like having balloon framing with 4x6's instead of 2x4's.

What I am unclear of is the difference in deadload capacities in balloon framing vs. 'standard'-ish framing as well as, what is most important to me, whether or not that flex in one of the new sistered joists are going to cause structural integrity problems or not.

I'm not entirely certain, but Having one of the joists curved, I'd imagine the second may in fact be LESS likely to buckle under strain. Not sure if its true, but you ever try to fold paper that is bend slightly in a curve? Probably the same idea.

Or it could be worse of course, being that the wood fibers are under (albeit it sleight) strain from being in that curve.

The delema caused the post, to which I am still unable to understand an answer to the question.

Its a complex messy project; thus the simplified question based on principles of engineering.
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Old 07-08-2012, 03:11 PM   #18
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Poorly placed Joists in Home being remodeled


The installation is somewhat unorthodox, I don't know why the joists are curved. However, buckling of the joists is unlikely to be the primary mode of failure. Joist design is almost always controlled by bending, not buckling. The curve of the joists has a very complex effect on bending in the horizontal plane, but has little effect on bending in the vertical plane. Since your load is almost entirely vertical, you can analyze the vertical bending without getting too concerned about the horizontal curvature.

You may want to examine the horizontal bending to see if your boards are close to the breaking point, since there is very little strength in the horizontal direction. This is harder than it sounds, because the boards are old, and despite the bending they may not actually be carrying much stress in the horizontal plane, i.e. they may have achieved a near stress free condition due to the length of time they have been curved. This is unfortunately an unusual case, and would require a careful engineering analysis to fully understand.
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Old 07-08-2012, 04:22 PM   #19
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Poorly placed Joists in Home being remodeled


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Originally Posted by Daniel Holzman View Post
However, buckling of the joists is unlikely to be the primary mode of failure. Joist design is almost always controlled by bending, not buckling. The curve of the joists has a very complex effect on bending in the horizontal plane, but has little effect on bending in the vertical plane. Since your load is almost entirely vertical, you can analyze the vertical bending without getting too concerned about the horizontal curvature.
BEEEE-youtiful.

Thank you SO SO SO SO much for your explanation!

fyi, the joist horizontally being bent like that is a 'new' joist, installed by someone else who I had payed to do some work. Its installed on a stud that has another joist kind of 'hanging' off of it; this is common in so-called 'balloon framing' as I understand.

Although it hangs off the opposite side of the stud, the fellow decided to 'sister' that joist to the original (non bent) joist by means of glue and screw; and now a new subfloor is laid upon it (I am working from below on this remodel project, whereas before I was working from above) making it nearly impossible to remedy, thus my concern with what, if any, repercussion this will have on the system's performance.

However, like you said, the bend is horizontal, the pressure is vertical, therefor little to know effect.

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