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OWSJ Backspan?

OWSJ Backspan?

OWSJ Backspan?

(OP)
I have a 2 metre 'w' beam cantilever from a 'w' column flange. I am wondering if I can utilize the OWSJ framing into the other flange of the 'w' column as a backspan. Has anyone ever done this? If so, would you specify a joist design end moment equal to the greater of the backspan moment and gravity moment? This seems very odd to me, not quite jiving.

Another question - do you typically show a joist schedule with all joist types sorted by the different joist loads? Or do you let the joist supplier determine the loads on each joists per the loads indicated on plan?

All help is appreciated. Thanks.

RE: OWSJ Backspan?

It seems possible, but the OWSJ is not a very stiff elements, and so the column is likely stiffer which make it attract more moment. You also run into the need for more bracing of the OWSJ due to the negative moment, and possibly a fairly stocky joist. In this situation I would run a steel beam as the backspan.

RE: OWSJ Backspan?

I agree with using a beam as backspan, but another option is to splice the column above and below the beam, providing stiffeners in the beam to carry the column above.

BA

RE: OWSJ Backspan?

I wouldn't say I agree with the opinion that a steel joist is "not very stiff". I would say just the opposite.

In this particular instance I would figure out the moment of inertia needed for the backspan and then increase the moment of inertia by about 20% (figuring for shear deformation of the web) and then tell the joist manufacturer what moment of inertia I needed. You will also need to give them the end moments on the joist so they can figure the joist design properly. If you are concerned about bracing the elements of the joist then just provide some extra X bridging on each side of the joist.

If you have enough of these, this may be an economical solution, otherwise, it my be more feasible to do as BA suggested and just "stack" the columns.

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