Single Plate Connection Using Long Slotted Holes

[cfc]

Are long slotted holes prohibited for single plate connections if the holes are oriented normal to the design load? The AISC Steel Manual verbiage only addresses standard and short slotted holes but I can't find any LSDT holes prohibition.

Furthermore, can a ST joint be used in this situation if a continuous PL type washer is placed over the slotted holes?

BACKGROUND - This connection type is for new steel beeams placed below (in order to reinforce) an existing elevated one way joist/slab type concrete floor. Existing M/E/P/S construction occurs between the joists so the steel erector is requesting the long slots to provide flexibility dutring erection.

Thanks

 

[nutte]

There have been several discussions on this forum on this topic. I don't know of any AISC literature discussing long slotted holes in shear tabs, even though they're commonly used, especially when going to an embed plate in a concrete wall. I design them using the extended configuration shear tab procedure, and make the bolts slip critical.

 

[cfc]

Nutte -
I'll track down these posts.

Thanks

 

[strucguy]

Have them weld the shear tab to beam web after the beam is in place and adjusted to right elevation.

 

[strucguy]

Other option is to use slip critical bolts. But as the load is not normal to the slot, you may be required to use plate washer with standard holes to achieve the required slip resistance.

 

[connectegr]

I would not recommend welding the plate to the beam web. A welded/welded connection is very "rigid", minimum beam end rotation. We design the connection for eccentricity. And in most cases we use slip critical connections. These are typically skewed connections to embed plates. For orthogonal connections to embeds, we typically use knife angles or single angles with long slots, which provides for better connection flexibility. These connections require some field adjustment, and necessitate long slots. Also, embed designs rarely consider moment caused by fixed connections. Bearing bolt shear values apply to short and long slots normal to the direction of load. Some research has been done regarding slots in single plate connections, with bearing bolts. Refer to AISC Engineering Journal. As noted above, plate washer is requireed if long slots occur in an outside ply.

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