RAM Connection: DG16 sec 2.5 vs DG1 eq 3.3.13

[X4vier]

RAM CONNECTION:
The bending capacity of an endplate for a beam splice is by DG16 Sec 2.5
The bending capacity of a moment base plate for a column is by DG1 Eq 3.3.13
Why are those capacities so different if they look so similar?
Capacity for bending of endplate can be 4 times the base capacity!!

 

[Flotsam7018]

I don't have the two DG's in front of me to reference the exact section/equation, however DG16 accounts for all of the yield lines that are required for the connection to form a hinge and/or yield lines/bolt rupture, whereas DG1 equations account only for the 1st yield line to form. I believe some studies have been done on accounting for additional yield lines in baseplate and the induced prying forces in the anchorage/strain compatibility, but typically from what I have seen in practice is to conservatively use the DG1 approach for baseplates or other steel to concrete connections and DG16 or other YLA approaches for steel on steel connections.

 

[dold]

If you're designing a IMF or SMF end plate connection then the design forces are based on the max expected strength of the beam (E_cl: capacity limited ~= 1.1*Ry*Zx*Fy where 1.1 [I think it's 1.1] is another safety factor and Ry is a material overstrength factor depending on what material the beam is made of) instead of the actual applied load, as opposed to designing the baseplate you use the actual applied forces at the base of the column. I have also used expected strength of the column as E_cl for baseplate design in one funky situation.*

I suspect you'll find that if you increase/decrease the earthquake loads on the end plate connection you will end up with the same plate thickness regardless of applied load. Alternatively, change the beam section to a much smaller size and you'll see a reduction in plate thickness due to reduction in maximum expected plastic moment capacity of the beam.*

IMF/SMF as a system are designed with the expectation of a plastic hinge forming near the end of the beams. The columns are required to be twice (?) as strong as the maximum force the beam can develop.*

Check out some of the examples in AISC 341.

Also, RAM Connection will often throw a warning for something about "thin/thick plate behavior" which really drives up plate thickness. I think it has something to do with bolt prying.

*(I think... - it's been a while).