Steel Joist Bearing Depth 1

[cfc]

The typical bearing depth for a K-Series joist is 2 1/2". I have an alteration project where new joists will bear atop existing steel beams. I can add a new strucutral member atop the existing beams to achieve the standard 2 1/2" bearing depth. The other option is to specify a 3 5/8" bearing depth. Is this a viable option(i.e., do joist manufacturers allow this alternative)?

Thanks,
Charlie Canitz,PE
Bel Air, MD

 

[dik]

Short span joists, those 24" or less in depth have a seat of 2.5" and long span joists, ie. greater than 24" deep typically have a seat depth of 5". This allows the diagonal web member to clear the bearing.

 

[JAE]

You can specify whatever joist seat you need for most SJI joist manufacturers. It does add to the cost a bit. Either way, there is additional cost as adding the steel to the top of the existing beam will include small material costs but field labor/welding.

Also, be aware that if your deck takes lateral shear forces and has to drag them into the beam below, the higher joist seat could be a problem (with lateral loads perpendicular to the joists, the seats will be loaded to roll over sideways). You can take care of this by adding steel between the beam and deck to take the lateral forces.