Wide Flange Beam to HSS Column Connection

[learning2banengineer]

Hi, my question is related to wall doubler plate used for wide flange beam to HSS Column moment connection. Hollow Structural Section Connection and Trusses design guide (FROM CISC) talked about the design of this kind of connection by checking a few failure modes. Failure mode (d) discussed on P. 324 relates the length of the doubler plate. However, it is not clearly defined what Lp reprent in the formula (please refer to attached sketch). Was is the total length of the doubler plate or just the extension for the flanges plates? In addition, how much of the weld between the doubler and the HSS wall can we use to transfer load from flanges plates to the HSS wall?(please refer to attached sketch)? Can anyone shine me some light on this, thanks!