Spandrel W/ Brick Relieving Angle

[jbjones2001]

We have an ongoing debate in our office about the best way to approach steel spandrels with brick relieving angles.

In most cases we use a bent plate pour stop with either angle struts or plate struts to the bottom flange of the spandrel. The struts reduce the torsion "drastically". In all cases we require the relieving angle to be field welded in place (to the pour stop) after the dead load (concrete) is on the structure. The real debate is whether the bent plate pour stop is field or shop welded in place. If the plate is shop welded, then erection and fabrication tolerances become a huge issue with regard to the horizontal leg of the relieving angle. You run the risk of the angle sticking out of the brick or maybe worse inadequate bearing width for the brick.

We have been addressing this by using strut plates (triangular full depth stiffeners) shop welded, and field welding the bent plate pour stops.

Does anybody have any better way to address the erection and fabrication tolerances with this issue?
Is there a better detail or design approach to use for this condition?
Do most people use some type of strut to resist the torsion? Or do you design for the total torsion and provide torsional connections at the spandrel ends?

 

[JAE]

A couple of comments:

1. I would try to avoid using the pour stop as the basis for your brick relief angle for just the reason you mentioned: there is no tolerance for lateral adjustment. Using shop welded stiffener plates is a good alternative, though, with field welded pour stops.

2. Alternatively, you could use the stiffener plates with horizontal slots in them and bolt the relief angle to each stiffener with a clip angle shop welded to the back of the relief angle. (must shop weld these to ensure that the spacing of the clips and stiffeners line up).

3. Another idea is to drop the brick joint below the beam and hang vertical L3x3's every so often, again, bolted or welded to the beam stiffener plates.

4. You mention the struts as "drastically" reducing torsion. In the spandrel beam, short diagonal struts from the relief angle to the bottom flange will do nothing to reduce the torsion in the beam. You must provide diagonal struts from the bottom of the beam up to the deck or some other extenal entity to provide a load path for these torsional forces. Stiffeners and other intermittant elements do not add to the torsional rigidity of a wide flange beam.

 

[redhead]

I heartily agree with JAE's comment #4. In this office we always try to use the system he notes in comment #3. In particular, you can create some field adjustment for the relieving anle by the judicious use of shims and horizontal slotted holes in the clip angles. The older AISC Manuals show some typical details of this type.