Steel Loose Lintel- Bracing at Ends

[LoneStarEngineer]

Hey Guys,

I have got a quick question on loose lintels. When designing a loose lintel we assume the loose lintel to be braced at the end points. I am curious as to how this is assumed. I came up with the following arrangements,

1. If the vertical leg is against the sheathing, is it nailed/screwed back to the metal studs? (If this is the case, I have never seen any arch/struct detail call out this connection). This configuration produces the most torsion as the brick is supported at the free end of a 7” leg.
2. If the vertical leg is closer to the inside face of brick, does the vertical leg pushing on the inside face provide the restraint? And somehow the force transfers to the metal stud backup through the brick ties? (I am not sure how viable the load path is in this case, but perhaps it is satisfactory based on past performance since this is the most typical case and torsion is minimal)
3. If the vertical leg is somewhere in between (the case I have currently, see below), how is the lateral restraint achieved? Nail/screw through the rigid insulation to the metal stud backup?

In my case, I have stacked bond brick (So no arching action) with openings between 3'-0" to 6'-4" (At openings>6'-4", we provide structural steel backup framing) and the loose lintel has to support about 12' of brick on top.

 

[JAE]

Loose lintels like what you've shown above would significantly rotate - angles have very little torsional stiffness and loose lintels typically are only pinched at their ends by the brick.

We usually push the vertical leg tighter to the back of the brick to avoid such large eccentricity.

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[XR250]

I would try to use an L6x4x5/16 or L7x4x3/8 LLV on the larger opening and figure out a different flashing detail. Brick lintels basically defy analysis however, historically, seem to work well (at least with running bond). Might want to spec some ladder wire in the bottom courses.
Also, who is dimensioning this drawing to the 1/32"!

 

[KootK]

You'll have defacto rotational restraint at the ends of the angle without doing any thing at all. If you think long and hard on the statics of it, there will be no free twist at the lintel bearings so long as the centroid of the applied load passes through the horizontal angle leg. While this is good news for the stability of the lintel, it does imply that that the horizontal angle leg is working pretty hard in flexure at the bearings as it imparts the requisite end torque to the lintel to resist the opposing, distributed torque collected along the span.



HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[LoneStarEngineer]

We usually push the vertical leg tighter to the back of the brick to avoid such large eccentricity.

I have seen a lot of architects wanting to push the vertical leg to the face of sheathing and the horizontal leg needs to be 7" to support the brick. They blame it on the energy codes. I am thinking if this is what they want than it has to be a shelf angle with proper structural steel backup support and not use a loose lintel?

The sizes you mention will work for vertical leg against inside face of the brick but have you ever had design with the longer horizontal leg requirement? Curious to see if other people have actually got a working design (7" horiz. leg) with numbers to back it up.

Also, who is dimensioning this drawing to the 1/32"!

That would be our esteemed client!

I am of the opinion that one should just neglect the vertical leg and the horizontal leg beyond the inside face of the brick when the vertical leg is not against the face of the brick. So essentially it would just be the plate below the brick that is effective. However, this could be very inefficient cost-wise and the design may just not work for deflection at double door conditions.

Since in my case the brick is also stacked bond, I might just go for additional back up misc steel support if the arch wants to push the leg to 7". But if anyone in their experience has in fact designed a loose lintel with 7" horizontal leg, please share your thoughts. Thanks.