To calculate U for a W connected by 2 plates bolted or welded to the top and bottom flanges:

Xbar for the wide flange = Ybar for a tee cut from that W shape,. For example, for a W12x120, you cut it along an axis of symmetry down the loaded length of the W into two WT 6×60 sections. Then you get Xbar for the W (the distance from the flange face to the centroid of the unconnected element – the web) by using the distance from the WT 6×60 flange face to its centroid, denoted by Ybar in the manual.

Thus, if you have a W12x50 bolted or welded on the top and bottom plates with 5 bolts in a line where the bolts are spaced 3″ apart (down the load axis), Xbar will equal:

U = 1 – Xbar/L = 1 – 1.17″/12″ = 0.9025

where the 1.17″ is the Ybar from the flange face to the centroid of a WT6x25 on page [1-64] and the 12″ = 4 bolt spaces at 3″ each.