Lever Rule - pedestrian load distribution
I am new to structural bridge design. I have been tasked to design the replacement for an existing adjacent box beam bridge. I am using PennDot's PSLRFD design software. Within the "PLD - Pedestrian Live Load Command" tab, the program asks for the portion of the ped live load that is acting on the girder you are investigating. The program's user's manual and AASHTO/DM-4 state that the user must calculate this using the lever rule. I cannot find a good example of how the lever rule is applied. I know it has to do with assuming each of your girders is a support and then applying plastic hinges to the interior supports, but that's about as far as my knowledge goes on the subject. If anyone has a good explanation or a good reference for the use of the lever rule, I would greatly appreciate it.
My other concern is that my sidewalk isn't the typical sidewalk that sits on the actual bridge deck. My sidewalk is aluminum grating that hangs off the side of my bridge deck. The edge of the grating sits on the very outside edge of my barrier (I've attached a diagram). So I basically have a line load acting on the extreme edge of my deck. In reality, it seems like the fascia beam would take on this load in its entirety, but I obviously don't want to violate the code.