Single Plate Shear Connection Depth 1

[MILRAD]

I am designing single plate shear connections and wonder if there is a rule for the minimum length of the plate vs beam depth.

For example a 2 bolt connection may have adequate capacity to support a W16 beam but the plate is only 5 1/2" long or about 1/3 of the 16" beam depth. Is that sufficient depth to prevent rotation?

Is there a rule of thumb that says the plate needs to be, say, between 1/2 and 2/3 of the beam depth?

I tried to find an answer here on the forums, the specification, and AISC but couldn't.

Thanks

 

[r13]

You should design the connection per function of the beam. AISC does not address the plate length (that meeting minimum bolt spacing and edge distance), nor the maximum bolt spacing. However, I wouldn't space bolts too far apart from the common practice, 3". Add more bolts if necessary.

 

[MILRAD]

Thanks

I am using the geometries shown in the Table 10-10 form the steel manual. I guess what I am asking is should I use 3 bolts to get the plate length more than 1/2 the beam depth even though 2 bolts has sufficient strength?

You say to add more bolts but how many to get a plate length that prevents rotation of the beam end?

 

[JoelTXCive]

I'm not sure where it is at in the steel manual, but I know AISC recommends that your connection plate is at least 1/2 of the 'T' dimension shown in Table 1-1 for all the sections...

They also address the maximum size of a connecting plate and 'riding the fillet'.

 

[JoelTXCive]

I found it. This snip is from page 10-106 of the 14th edition.

They do recommend a length, but their recommendation is for stability during erection. I suppose you could deviate from that if you had a good reason.

 

[JoelTXCive]

Also, don't you want a small amount of rotation so that you have a pinned condition and not fixed?

 

[r13]

It is rare occasion that you have W16 but only requires 2 bolts. However, if this is the case, I would first to chose a bolt with smaller size, so instead of two, you'll need 3 bolts or more. If you are already using the smallest bolt, then just add another one, so the plate will be at least equal to/greater than 1/2 the beam depth, which is preferred, but not a mandate from the code.

 

[MILRAD]

Thanks JoelTXCive and retired13.

In the fifteenth edition the text JoelTXCive posted is split between page 10-7 (with Figure 10-3) and 10-91.

I am not thinking about rotation in the plane but preventing rotation about the longitudinal axis at the ends for LTB.

 

[GC_Hopi]

I have seen some firms go with a fitted stiffener opposite the shear tab unless there is an opposite beam framing into the same girder within 6" of the aforementioned shear tab. Expensive maybe but the you know the girder is braced against LTB at the location where the beam frames into it.

 

[SteelPE]

I shoot for 1/2 of the depth of the beam.... At least I thought that was the requirement until Joel posted his reference above. Lots of times fabricators will just "stuff" the beam full of bolts. I don't discourage this practice.

 

[cliff234]

GC Hopi said, "I have seen some firms go with a fitted stiffener opposite the shear tab unless there is an opposite beam framing into the same girder within 6" of the aforementioned shear tab. Expensive maybe but the you know the girder is braced against LTB at the location where the beam frames into it."

In my opinion that is expensive and unnecessary. I don't know of any problems that have ever occurred due to single plate shear connections on only one side of a beam. Add to that the fact that the fitted stiffeners will be more expensive that the single plate shear connections.

 

[human909]

I shoot for 1/2 of the depth of the beam.... At least I thought that was the requirement until Joel posted his reference above. Lots of times fabricators will just "stuff" the beam full of bolts. I don't discourage this practice.

Within reason this.

You are scraping the bottom of the economy barrel if you are choosing tiny plate lengths with minimal bolts. Bolts are cheap, and the time taken to do an extra one is cheap. A few more inches of weld for your shear plate shouldn't break the bank. I'm all for costs savings but doing tiny shear plates for deep beams doesn't seem to be the worth the effort.