Reduced Beam Section

[dherna45]

I have been reading about reduced beam section, and it says that it helps on the reduction of the need of continuity plates as well as doubler plates, but I dont understand the reason for this since having a reduced beam section increases the moment at the face of the column in comparison to just having the plastic moment develop at the face of the column.
Thanks

 

[Deker]

Per AISC 358-10 Eq. (5.8-6) the moment at the face of the column is M[sub]f[/sub] = M[sub]pr[/sub] + V[sub]RBS[/sub]S[sub]h[/sub]. But remember that M[sub]pr[/sub] is based on Z[sub]RBS[/sub], not the full Z. Therefore unless you have very high shear in the beam, the moment at the face of the column will be less.

 

[KootK]

Additionally, one of the reasons for placing the RBS away from the column is that, hopefully, it prevents the fracture sensitive bits of the beam to column connection from having to deal with inelastic straining.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.