C-8.68.6 design procedure

For the WUF-W moment connection, many of the details of the connection of the beam to the column flange are fully prescribed in Sections 8.4 and 8.5. Consequently, the design procedure for the WUF-W moment connection largely involves typical checks for continuity plates, panel zone shear strength, column-beam moment ratio, and beam shear strength.

With the WUF-W moment connection, yielding of the beam (i.e., plastic hinge formation) occurs over the portion of the beam extending from the face of the column to a distance of approximately one beam depth beyond the face of the column. For purposes of the design procedure, the location of the plastic hinge is taken to be at the face of the column. That is, $S_{h}=0$ for the WUF-W moment connection. It should be noted that the location of the plastic hinge for design calculation purposes is somewhat arbitrary because the plastic hinge does not occur at a single point but, instead, occurs over some length of the beam. The use of $S_{h}=0$ is selected to simplify the design calculations. The value of $C_{p r}$ was calibrated so that when used with $S_{h}=0$, the calculated moment at the column face reflects values measured in experiments. Note that the moment in the beam at the column face is the key parameter in checking panel zone strength, column-beam moment ratio, and beam shear strength.

The value of $C_{p r}$ for the WUF-W moment connection is specified as 1.4, based on an evaluation of experimental data. Tests on WUF-W moment connections with strong panel zones (Ricles et al., 2000) showed maximum beam moments, measured at the face of the column, as high as $1.49 M_{p}$, where $M_{p}$ was based on measured values of $F_{y}$. The average maximum beam moment at the face of the column was $1.33 M_{p}$. Consequently, strain hardening in the beam with a WUF-W moment connection is quite large. The value of $C_{p r}$ of 1.4 was chosen to reflect this high degree of strain hardening. Combining the value of $C_{p r}=1.4$ with $S_{h}=0$ results in a moment at the face of the column, $M_{f}=M_{p r}=1.4 R_{y} F_{y} Z$, that reasonably reflects maximum column face moments measured in experiments.