1.6.1 Panel Zones

The design intention is to limit yielding of the joint panel zone to a moderate amount. Where the shear demands are below the yield strength, it is considered sufficient to model the panel zone with effective end offsets to represent the finite joint size. Otherwise, where panel-zone yielding is expected, the panel zone should be modeled with an inelastic hinge. Guidelines for nonlinear modeling and acceptance criteria for panel zones are provided in ANSI/AISC 342, Section C4, and in Chapter 3 of NIST (2017b).

1.6.2 Partially Restrained Connections

Partially restrained connections may be part of the seismic force-resisting system, and they may be intentionally designed as moment connections or gravity shear connections, which are not designed to resist moments but naturally provide flexural restraint. Guidelines for nonlinear modeling and acceptance criteria for partially restrained moment connections are included in ANSI/AISC 342, Section C5. Additional guidelines for modeling gravity connections that resist moment through composite action with the slab are included in Chapter 4 of NIST (2017b).

1.6.3 Column Bases

Where the column base is not designed with sufficient strength and stiffness to be treated as rigid, it should be modeled inelastically. Guidance for modeling and behavior of column base connections are included in ANSI/AISC 342 and in Kanvinde et al. (2013), Kanvinde et al. (2015), and Grilli et al. (2017).

1.6.4 Brace Gusset Plates

Where the brace connection is capacity designed as a force-controlled component to force inelastic response into the connected brace, the gusset plate may be modeled with rigid offsets between workpoints and brace ends. Otherwise, in-plane and/or out-of-plane yielding of gusset plates should be modeled in the analysis. Guidelines for modeling gusset plates are included in ANSI/AISC 342, Section C5, and Chapter 5 of NIST (2017c).