Connection of Steel Brick Lintel (For Support of Brick Weight) to Cold Formed Metal Studs

[labrown]

I am currently working on a CFMS submittal for a steel framed structure and have encountered a detail provided by the EOR which indicates that the light gauge studs spanning between high and low roof framing shall provide vertical support for the brick veneer along this wall. I have already sent an RFI to the EOR regarding this non standard detail and their response was that this detail has been used before. The centerline of brick is offset from the face of the 6" studs approximately 4 inches and the weight of the brick varies between 175 lbs to 408 lbs at the peak of the gable. I am looking for advice on the best way to model this section in order to determine the reactions at the screws (caused by this eccentric loading).

Any suggestions for solving this problem would be appreciated. Thanks.

 

[KootK]

I'd assume that the angle rotates about its heel. I might also assume that only the top two screws take tension. It's a tough thing to analyze with any great amount of confidence so some conservatism is probably in order. In the past, I've but blocking in the studs right behind the angle. It might be overkill by I worry about localized stud buckling. In the unlikely event that this is a shear wall, you might also give some thought to the interruption that the angle will cause in the plywood sheathing.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[DaveAtkins]

I have done a lot of these--but never with screws.

The brick shelf angle should be welded to each stud.

DaveAtkins

 

[XR250]

I hate that detail but have had to deal with it on many occasions. I have only done it by welding. Usually 14g a min. studs. and weld to the radius of the stud to keep the flange from bending.
A lot easier than field drilling a million small holes in the angle. Might wanna show flashing and weep holes (by others) as well just to cover yourself in case they are not shown elsewhere.

 

[Ingenuity]

Re screwing...TEKS Series 500 screws can be fastened directly through 3/8" thick steel without pre-drilling, using a 1/2" drive cordless impact wrench.

 

[hokie66]

Ingenuity,
That might be theoretically possible if the pieces are oriented correctly, but in this case when the screw hits the flimsy bit of the stud, I think it would tend to push rather than bite. Another issue is clearance for the tool.

 

[KootK]

Yeah, I've heard of the same issues fastening through new drag struts up into existing metal deck. Would it be possible to screw from the interior side or would that damage the envelope?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[labrown]

KootK, Hokie66 - we were also concerned about the problem of connecting from the 3/8" angle to the thinner stud flange. The EOR suggested that we could predrill the holes in the angle to avoid this issue - I don't believe that they want us to screw from the interior side.

I have attempted to model this angle/connection configuration in RISA in an effort to get an idea of the reactions at the screws, but I am not sure that the results I have seen are accurate. I was hoping to figure out a way determine these reactions, since it would help with convincing the EOR, etc. that this approach is not advisable.

Similar to what KootK mentioned, our initial thought regarding this connection was that the top screw would pick up most of the tension load and the other two screws would not pick up much of the load until the top one failed. At this point, I do not believe that the screwed connection will not work for this application - I will push for the welded connection.

Thank you all for your advice.

 

[XR250]

@Ingenuity:

Tek screws work best when fastening from thin to thick. I would not count on them in this situation without pre-drilling the thicker member. Either way, it is a pain in the ass. I have installed many Teks thru 3/8" steel and it takes awhile. Welding would be significantly faster.

 

[wannabeSE]

M = P e = 408#(4") = 1630 # in

Assume screws are 1", 2.5" and 4" above axis of rotation

I = 1[sup]2[/sup] + 2.5[sup]2[/sup] + 4[sup]2[/sup] = 23.3

T = Mc/I = 1630(4)/23.3 = 280#/screw

V = 480/3 = 136#/screw

 

[BAretired]

Place the angle directly on the steel joists; provide masonry infill and flashing to Elev. 14'-0".

BA

 

[msquared48]

480/3 = 160#/screw

Mike McCann, PE, SE (WA)

 

[BAretired]

408/3 = 160#/screw

BA

 

[BAretired]

oops
480/3 = 136#/screw

BA

 

[wannabeSE]

oops, I meant
408/3 = 136#/screw
not 480/3

 

[Ingenuity]

Tek screws work best when fastening from thin to thick. I would not count on them in this situation without pre-drilling the thicker member. Either way, it is a pain in the ass. I have installed many Teks thru 3/8" steel and it takes awhile. Welding would be significantly faster.

For TEKS Series 500 that I have used (Buildex/ITW from Australia), provided the length of the integral drill flute is greater or equal to the total thickness of the materials to the drilled (both materials plus any air gap), no predrilling is necessary, in my experience. I just completed a commercial project with my builder brother and I installed a few thousand 38mm long TEKS through 8mm steel to 1.2mm purlin section and we were installing 3 or 4 screws per minute. Hex-head TEKS with a impact driver at correct RPM assisted greatly.

I assume the 6" stud would have a BMT of greater than 1.0mm for this application, so not really flimsy. It is possible to install from the inside of the stud (may need a extension to the driver bit) at the web/flange interface and result in greater pull-through capacity as you mobilize the TEKS head through the cold-formed stud.

 

[DaveAtkins]

Perhaps the screw itself can be justified, but then the stud flange must be checked for bending. That is why I always show a weld, along the web side of the flange as mentioned by ExcelEngineering.

DaveAtkins

 

[Ron]

Assuming your project is in the US, the welder must be qualified to weld sheet metal (CFS is essentially sheet steel) as well as structural steel. AWS D1.1 and D1.3 are both in play on this one.

 

[SteelPE]

What a horrible detail. I have run into this before on my projects and I end up with the brick being supported directly on the joist and not relying on welds and screws to support the brick.

I find it frustrating when dealing with some engineers who say "it's been done before and it's not my problem". I could go on and on about this but at some point we need to stand back and see the big picture.

 

[DaveAtkins]

SteelPE,

Welding a steel shelf angle to cold formed steel studs is done successfully all the time. It is the typical way to support face brick above a continuous ribbon window.

DaveAtkins