KISS Method for Gusset Plate

[SALTRAM4567777]

Hi!
Can anyone please provide an example for design of gusset plates using KISS Method.
If someone could pen it down on a paper with just a simple example as I am trying to understand the basics

 

[271828]

The AISC Design Guide 29, Section 4.1 describes the KISS Method. I am not aware of any example problems for this, but the distribution is so simple that the explanation in Section 4.1 is probably sufficient. When you get the forces between the gusset and beam and column, the limit state checks are the same as when you're using the Uniform Force Method. Design Guide 29 has many examples of the UFM.

The KISS Method, like all of the common methods for assigning these forces, is based on the lower bound theorem of plastic analysis, which is also described at the start of Chapter 4. In a nutshell, if you can identify a statically admissible set of forces, the brace force that causes these is the ultimate strength, which we'll call Rn for this subject, or an underestimate. In other words, you're either conservative or correct. If you can find an older textbook that includes plastic analysis or plastic design, look for the "statical method." It's the same thing. It's the opposite of the mechanism method that is used in yield line analysis.

 

[SALTRAM4567777]

Thanks for explaining.
Can you please solve one simple example.

 

[271828]

Sorry, I don't have one handy. I'd recommend checking out the sections in Design Guide 29.

 

[SALTRAM4567777]

Can you clarify ome doubt. I am attaching one figure for KISS Method.

As seen in the figure the ewuilibrium is maintained by introducing the moments at Gusset Interaface.
For what forces do we nees to design the gusset plate.
Should we design the gusset plate for moments also or just we need to design the beam and column for moment.
Please clarify.

 

[JoshPlumSE]

So, for KISS, the following happens:
a) The vertical portion of the brace force goes completely into the column to gusset connection. But, there is ZERO axial force in the column to gusset connection. This is checked with a pure shear check on the column to gusset weld (or bolts).
b) The horizontal portions of the brace force goes entirely into the beam to gusset connection. Similarly, there is ZERO axial force in this connection. And, this demand vs capacity is checked with a pure shear check on the beam to gusset weld (or bolts).
c) However, there is moment in each of these that needs to also be checked. Per your image, it is equal to the shear force in that connection time the eccentricity between the working point of the connection and the location of the connection. This is V*(dc/2) for the vertical force in the column to gusset weld, and H*(db/2) for the horizontal force in the beam to gusset connection.
d)Then you just need to determine the capacity of the weld to resist that moment. I just look at the nominal moment capacity as the moment that will cause yield (or rupture) in the extreme fiber of the weld is that were the only force applied to the weld.
e) Lastly, you might want to do some kind of code check that checks the connection for Shear + Moment interaction. I don't see a reference for exactly how this should be done. But, maybe one of the following:
Vu/(Phi*V) + Mu/(Phi*Mn) < 1.0
{Vu/(Phi*V)}^2 + {Mu/(Phi*Mn)}^2 < 1.0

The first one is going to be more conservative, but I tend to think that the 2nd one is closer to what I've seen before.