Steel Angle Connection at Shear Wall

[iponom]

I am designing connections for steel "W" shape pieces to concrete shear wall. Most of the connections are shear only and have no moments or axial forces.

1. The EOR requested that we also take the moment at the steel/concrete interface due to that shear loading. If the geometry is such as specified in AISC 13th Ed. we would take out the moment in the bolts/welds on the beam or outstanding leg, but not at the concrete embed.
2. My shear connectors are double angles (L8X6X1/2)
3. Because the embeds were misplaced in the field, I am thinking about securing the double angles to the wall using HILTI anchors.
4. The angles are either field-welded or bolted at the beam webs.


The questions are:

1. Is this still considered a simple shear connection, or these angles are now subject to a moment force?
2. What kind of design checks do I need to make here? Other than the standard, shear yield, rupture, prying, weld/bolt strength as described in AISC's 13th Ed.
3. Should I be checking the outstanding angle legs for the moment due to EOR's request to apply the moment at the embed due to the shear loading?


Any ideas or literature suggestions?


Thank you all.

 

[structSU10]

It's important to note the assumptions for a simple shear connectors design. In general, the reason a moment is not distributed to one support is because something else in the connection is resolving the load.

It comes down to rotational ductility of the connection as outlined in AISC 13th part 9 page 9-13.

 

[Michel60]

Good morning iponom,

StructSU reference to ductility is spot on for this application...you potentially may find yourself will failed embeds/anchors if you do not allow for beam end rotations. I would advise strongly against welding any beams to the connecting angles even though there will likely be much push-back from the guys in the field doing the work. Clamping the beam in place and welding may be easier than aligning bolt holes but it's a bad idea. You should consider slotted holes for your bolted connections and pay attention to the loading sequence on the beam vs. tightening of HS bolts. If gravity loads are significant you may want to delay final tensioning until most of the dead load is applied.

regards,
Michel

 

[ToadJones]

Are you sure the EOR isn't asking you to design the anchorage for the moment due to the eccentric shear loading?

IMO, this should be done regardless. With such large clip angles, your beam reaction (shear) can be assumed to be at the centerline of the bolts in the web of the beam. This eccentric shear will cause pull-out forces on your Hilti anchors. The anchor assembly needs to be designed for shear and tension.

 

[MrHershey]

Agree with Toad. Sounds like they're going for anchor design, not the steel shear connection.

 

[connectegr]

With knife connection angles welded to embed plate, the flexible connection end rotation is provided by the flexibility of the outstanding legs of the angles. The angles should be welded with returns only at the top. This connection flexibility results in shear only in the embed plate and anchor/studs.

For standard connection angles with maximum GOL (gage of angle) in the back to back legs is 3" to ignore eccentriity and consider the bolts (or welds, if welded) in straight shear. With 8" angle legs, welded or bolted connection to the beam should consider eccentricity.

Hilti Profis can easily provide your anchor options considering the load applied eccentric to the face of the concrete. I would probably consider this eccentricity. But, it could be argued that the outstanding legs of the angles are a flexible support and only shear is taken in the Hilti anchors.

http://www.FerrellEngineering.com

Providing construction, fabrication, and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[connectegr]

Moment at the embed would result from a non-flexible connection; knife plates or single plate.

http://www.FerrellEngineering.com

Providing construction, fabrication, and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[ToadJones]

With such heavy and large angles, and being that the connection is to concrete, I would absolutely consider the eccentricity.

 

[a2mfk]

Connectegr makes good points, specifically about the ductility of double angles, but like ToadJones I have always just designed for the eccentricity in these types of connections. Especially given how critical concrete anchor connections are in tension, I like to be on the safe side in case someone in the field makes that connection transfer just a little moment...