Double Angle vs Shear Tab Connections 1

[HDStructural]

Hello,

At my new company (heavy industrial industry), I have been tasked with updating our general notes. Our steel general notes require that all shear connections be made with double angles and that shear plates and single angles must not be done. I understand the logic of not wanting a single angle but I don't see the issue with a shear tab. To clarify, I am not referring to any connections with crane runway beams or girders, just a standard shear connection for a typical beam, which may support equipment and live loads up to 500 psf.

I haven't found anything in AISC DG 7 or AISE Tech Report 13 forbidding shear tab connections.

Does anyone know why this would be required or if it is a code requirement somewhere?

Thanks

 

[JLNJ]

We have a fairly local fab shop who prefers bolted-bolted connections because it minimizes time for their welders. This is a little unusual.

Most shops like the single-plate "shear tabs". Fewer bolts. Easy welding. No need to worry about two-sided connections. You just need to worry about the lousy capacity - usually half of the bolted-bolted type. If the fabricator is really trying to be efficient, he might prefer the extended end plates where the intersecting beam can be cut short and not coped at all. (Though, I admit, those long extensions make me a little uneasy. Even if they "calc" out.)

 

[271828]

We have a fairly local fab shop who prefers bolted-bolted connections because it minimizes time for their welders. This is a little unusual.

I've seen this also. Interestingly, at one of my clients, one of their guys says to use bolted angles for everything for the reason you typed. Most of their guys say to use shear tabs instead. I guess this goes to show that it's good to ask the question early.

 

[human909]

From my perspective as somebody in steel engineering, fabrication and erection outside of North America.

The preference for bolted angles over welded cleats are a relic of the past and remain in North American design and fabrication more for historical reasons. From my observations in Australia/NZ/Europe bolted angles cleats aren't commonly used.

They definitely have their uses. I use them commonly to speed up site installation for retrofits which I do commonly. Also many sites I work on have strict controls regarding hot works so drilling holes is preferable to site welding.

 

[hokie66]

Agree with human909. If the rest of the world can do without double angle connections, why can’t the US?

 

[human909]

Thanks for the support on my observations hokie66.

On the same topic of cross continental differences... Flexible end plate connections seem to be quite common in Europe and far less common in NA/Aus.

Again they're lack of use seems .ore historical based on welding technologies rather than rigorous engineering assessment.

At present I don't use them often in my design. But I'm aware that this is likely due to my bias on what is 'normal' in the industry rather than a thorough engineering basis.

 

[HDStructural]

Human909, thank you for your input. I honestly haven't come across flexible end plate connections, but they look simple and easy to install. I see the benefit. This probably acts more like a true pinned connection than the other shear connections do. Does the code stipulate that the weld from the beam web to the plate be sized to fully develop the web based on its thickness?

 

[271828]

We use "shear end plates" in the US sometimes. Just not very often compared to angles or shear tabs because of some fabrication and erection issues. If the beam is cut a little too long, that's no big deal with angles or shear tabs. With end plates, the beam needs to be cut a little short and then finger shims might be needed. I try to get around this by using angles or a shear tab on the other end of the beam.

Is that what you guys do with these?

 

[dik]

All the clip angle connections for the Cornwall Centre in Regina were single angle connections... and that was nearly 50 years ago. I've always liked single angle connections.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[canwesteng]

Yeah, not sure if it's because labour is cheaper in Europe, but end plates are generally avoided due to higher costs to erect the beam, since they are harder to place. Shear tabs are basically the default in light duty applications, but the OP is talking about heavy industrial, and in my (very limited) experience, double clips are still used in Europe in these cases.

 

[Klitor]

15yrs of European industrial/o&g... Mostly end plates and some double angles for lighter stuff.
Never once saw or designed a shear tab.

 

[dik]

Flexible end plate connections[/b] seem to be quite common in Europe and far less common in NA/Aus.]

To clarify, that's just BAR stock welded across the web, and not attached to the flanges, just for shear connection.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[human909]

The preference for bolted angles over welded cleats are a relic of the past and remain in North American design and fabrication more for historical reasons. From my observations in Australia/NZ/Europe bolted angles cleats aren't commonly used.

It took only two days for me to pick up a job that would prove me wrong here. Now a week later I'm busy designing angle cleats and double angle cleats as my primary connections!

(In this case the humble pie I'm eating tastes delicious as I'm pickup up a new client that is likely going to stick around as they've been badly screwed around by other consulting engineers who didn't have a clue on what they were doing.)

The reason for the selection of single and double angle cleats is simply high shear loads with deep members. Welded cleats would require minimum 10-12mm multipass welds for them to work comfortably. I tend to avoid anything above the standard 6mm weld unless I have to (8mm is ok), both because it is expensive and because fabricators are often less used to performing such welds.

I could get a single angle cleat to work. But I decided on the double angle for symmetry and to standardise the connections somewhat. The largest members get the double angle while the smaller members get the same angle design, but just a single side. The the connection on the 'medium' tertiary beams will will end plates or cleat plates as they aren't perpendicular to the supporting beam.

15yrs of European industrial/o&g... Mostly end plates and some double angles for lighter stuff.
Never once saw or designed a shear tab.

Your comment is crystal clear to me now. Flexible end plates would also work nicely for my current job with small weld sizes. However the client had already expressed a minor preference for angle cleats which is more than enough to push my decision towards angle cleats.


(For context my work is mostly in medium industrial. I do occasionally get high shear loads in one type of structure supporting elevated bulk storage, but moment plates are needed in at least half of the high shear connections there so the problem hasn't come up previously. This particular job has shear loads about 70% higher than the highest ones I've dealt with previously.)

 

[lexpatrie]

This thread has a severe image deficiency. The terminology is so different between US and AUS and Eurocode, as well. A picture or two would really help me.