Long Fin Plate

[ahmedhegazi]

Hello,

i am designing a simple beam to beam connection where secondary beam is connected to main beam using Welded Fin plate and bolts , for ease of fabrication and installation , contractor is requesting no cut off in beam top flange with long fin plate.

checking the design standards they say the following:

1-fin plate should not be thinner than (0.15*Distance from main beam web to first row of bolts)
2-In case the above condition is not satisfied plate has to be checked for local buckling and beam top flange should be restrained.
3- design force is quite low around 30 kN , but the BS standards and Euro code require weld to be both sides with size equals to (0.8*thickness of fin plate)

my question is , is the weld limit above a must?, what do the AISC say in this?
keeping in mind i may go with thickness of find plate to 20 mm to satisfy point 1 which would give me weld of size 16mm while main beam web thickness is 10 mm(not practical to weld 16mm)

 

[msquared48]

Can you post as diagram? I am unfamiliar with the term "fin plate".

I am wondering if it is the same as either a "kerf plate" or "side plate"...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[BAretired]

I agree. Post a sketch. Verbal descriptions can easily be misinterpreted.

BA

 

[structSU10]

this sounds like an extended shear tab connection per AISC. I've attached a paper that goes through the concept and its design. I hope this was what you are looking for.

 

[BAretired]

Looks like an interesting article. I have never used this type of connection and would hesitate in commenting further.

BA

 

[msquared48]

Figure 2 is what I have used for 30 years and have never had a problem. Why whould I change?

The eccentricity of this connection (which is compensated for in figure 2 with the welds to the top and bottom flanges) at the connected beam concerns me regardless of any research. It just does not feel right.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[ahmedhegazi]

Thanks StructSU,
this connection is called extended shear plate also
The detail I am looking for is figure 1,I will go through the paper but I agree figure2 details looks more reliable

 

[ToadJones]

We used these connections all the time in the power industry.

The detail I used most commonly was similar to Figure 2, but the tab only extended to the top flange of the supporting member in most cases. Usually the supporting beam had torsional braces preventing twist from the large connection eccentricity.

On extended shear tabs into column webs, we almost always used a horizontal stiffener above and below the extended tab.

The main reason driving this type of connection, from my experience, is all from the ease of erection.

Connectegr will likely chime in here.

 

[msquared48]

Why do they call it a Fin plate rather than a Swe plate or a Nor plate?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[ToadJones]

I guess they are trying to get together and agree to call it a Scan Plate or Euro Plate

 

[Enhineyero]

ahmedhegazi - The beam to beam connection using fin plate is designed by assuming that the reaction from the intermediate beam (beam being supported) is acting at the face of the web of the Main beam (being that is supporting the int. beam). Since the bolt connection is eccentric from the reaction, there will be a rotational force (moment) + shear force that will be resisted by the bolts, while the welds will only resist direct shear.

It is safe to say that if you have thick weld like 0.8(tp). plate or bolt failure will occur first rather than weld failure, because the bolt and plate will resist higher forces due to the additional rotational force.

tw = 0.8(tp) is a standard that the code adopted to reduce time in computing.

In my own opinion you can reduce the weld thickness to a thickness that is sufficient to resist the shear force.

I hope this answered your question.

I think they called it fin plate because it looks like a fin of a fish.