Wall Bracing

[slickdeals]

Folks,
See attached sketch. I am reviewing a set of calculations by a delegated engineer for bracing a wall for out-of-plane wind loads.

The connection consists of an angle with the outstanding leg cut and the other leg bent to anchor back to the structure. The connection is only designed for shear due to the horizontal component of the bracing force.

I think the connection should be designed for a combination of shear and moment (as shown in sketch).

Am I out of line?

 

[engineertipsman]

No attachment

 

[slickdeals]

Sorry about that.

 

[engineertipsman]

I Agree, wouldnt you have a vertical and horizontal component at the end of the angle? It would cause some bending on the leg

 

[Lion06]

Is it bracing a metal stud wall or a CMU wall or something else? How is the gusset getting attached to the wall. I agree the detail to the underside of the beam looks silly. Why not suggest coming off the plate at the underside of the beam with another gusset to make the connection the same as to the wall?

 

[msquared48]

slick:

I would be less worried about the extra moment in the angle due to bending, and more about the apparent use of expansion bolts at the concrete beam.

Two concerns with that - spalling of the concrete and hitting the bottom steel of the beam. You can alleviate the first with chemical anchors, and the second with testing, or a better design.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[slickdeals]

It is bracing a tall masonry wall (146 mph wind). The gusset is attached to the wall by welding it to a plate that is epoxy anchored into a grouted cell. The detail I drew is not an exact replica of what exists, but the concept is similar.

I am only concerned about the detail attaching to the beam because of the forces that have not been accounted for.

I can suggest a alternate detail, but prior to doing it I have to let the engineer know why his detail does not work. Otherwise it will end up being a pissing contest.

 

[slickdeals]

@Mike:
Good point, it is going into a tensile zone in the beam. Epoxied detail would be better (but I guess they are trying to avoid overhead epoxy work)

 

[dcarr82775]

The bolts should be designed for tension/comp and shear, but I wouldn't worry about the moment. I just can't see a moment developing.

 

[larsacious]

Why not specify embed plates in the beam instead of post installed anchors? What is the spacing of the kicker/plate assembly? Is the masonry wall designed/detailed to span horizontally to the kickers? Why attach the kicker to the edge of the beam plate? Wouldn't it be better to center the kicker on the beam plate instead of trying to weld on the side of the plate?

Be careful with long term creep effects which could transfer load to the wall. It seems like there is some room between the outside face of the beam and the inside face of the beam. Could the connection be moved to there instead so that you have a horizontal kicker instead which could be vertically slotted to allow deflection?

 

[engineertipsman]

dcarr827775, look at it when in tension, the vertical component of the angle is going to cause bending of the angle at the bolt.

 

[woodman88]

Have you considered connecting to the side of the beam to completely avoid the bottom reinforcing?

Garth Dreger PE
AZ Phoenix area

 

[dcarr82775]

Engineertipsman,

I understand why a model would show a moment in both tension and compression. I am saying that in reality I do not see that moment happening. The clipped angle is effectively a plate and will just bend unless it is a thick angle and the bolts are shallow. If anything I would call it prying.

Is there any reason the brace can not be installed horizontal to eliminate this concern?

 

[BAretired]

Installing the brace horizontally does not remove the eccentricity.

There is a small eccentricity at the other end too. A double angle with gusset plate projecting down from the beam would be a better connection.

BA