2.4connection design parameters

2.4.1 Resistance Factors

Where available strengths are calculated in accordance with the AISc Specification, the resistance factors specified therein shall apply. When available strengths are calculated in accordance with this standard, the resistance factors $\phi_{d}$ and $\phi_{n}$ shall be used as specified in the applicable section of this standard. The values of $\phi_{d}$ and $\phi_{n}$ shall be taken as follows:

• (a) For ductile limit states

$\phi_{d}=1.00$

• (b) For nonductile limit states

$\phi_{n}=0.90$

2.4.2 Plastic Hinge Location

The distance of the plastic hinge from the face of the column, $S_{h}$, shall be taken in accordance with the requirements for the individual connection as specified herein.

2.4.3 Probable Maximum Moment at Plastic Hinge

The probable maximum moment at the plastic hinge shall be

(2.4-1)

where

$C_{p r}=$ factor to account for peak connection strength, including strain hardening, local restraint, additional reinforcement, and other connection conditions. Unless otherwise specifically indicated in this standard, the value of $C_{p r}$ shall be

(2.4-2)

• $F_{u}=$ specified minimum tensile strength of yielding element, ksi (MPa)
• $F_{y}=$ specified minimum yield stress of yielding element, ksi (MPa)
• $\begin{aligned} R_{y} & =\text { ratio of the expected yield stress to the specified minimum yield stress, } \\ & F_{y}, \text { as specified in the AISC Seismic Provisions }\end{aligned}$
• $\begin{aligned} Z_{e} & =\text { effective plastic section modulus of section (or connection) at location } \\ & \text { of the plastic hinge, in. }^{3}\left(\mathrm{~mm}^{3}\right)\end{aligned}$

2.4.4 Shear Force at Plastic Hinge

Unless otherwise specifically indicated in this standard, the shear force at the plastic hinge, $V_{h}$, shall be

(2.4-3)

where

$L_{h} \quad$ = distance between plastic hinge locations, in. (mm)

$V_{\text {gravity }}=$ shear force resulting from $1.2 D+f_{1} L+0.15 S$ acting on the beam between plastic hinge locations, where $D$ is the dead load, $S$ is the snow load, and

$f_{1}$ is the load factor determined by the applicable building code for live loads, but not less than 0.5, kips (N)

In applying Equation 2.4-3, the values of $2 M_{p r} / L_{h}$ and $V_{\text {gravity }}$ shall be taken as having the same sign.

User Note: The load combination of 1.2D + f1L + 0.15S is in conformance with ASCE/SEI 7-22. When using the International Building Code, a factor of 0.7 must be used in lieu of the factor of 0.15 for S when the roof configuration is such that it does not shed snow off of the structure.

User Note: Equation 2.4-3 can be derived from a free-body diagram of the portion of the beam between plastic hinge locations, assuming the moment at each plastic hinge is $M_{p r}$ and with gravity load acting on the free-body diagram. The shear at the plastic hinge will be different at the two ends of the beam because the shear force due to $2 M_{p r} / L_{h}$ and the shear force due to gravity load will be additive at one end and will be of opposite sign at the other end. $V_{h}$ is defined as the larger of these two values—that is, the value where $2 M_{p r} / L_{h}$ and $V_{\text {gravity }}$ are additive.

Equation 2.4-3 assumes moment connections are provided at both ends of the beam. If only one end of the beam has a moment connection, the shear at the plastic hinge can be determined based on a free-body diagram between the plastic hinge at the moment connected end of the beam and the opposite end of the beam.

2.4.5 Probable Maximum Moment at Face of Column

Unless otherwise specifically indicated in this standard, the probable maximum moment at the face of the column, $M_{f}$, shall be

(2.4-4)

where

$M_{p r}=$ probable maximum moment at plastic hinge, kip-in. (N-mm)

$S_{h}$ = distance from face of column to plastic hinge, in. (mm)

$V_{h}$ = shear force at plastic hinge location, kips (N)

User Note: Equation 2.4-4 can be derived from a free-body diagram of the portion of the beam between the plastic hinge location and the face of the column. This equation neglects the gravity load on the portion of the beam between the plastic hinge location and the face of the column because this gravity load typically has a negligible contribution to $M_{f}$. If desired, the gravity load on the portion of the beam between the plastic hinge location and the face of the column can be included in the calculation of $M_{f}$.