The K Truss design was a variant from the Parker truss design. The Parker, in turn, came from the Pratt truss. The idea of the K truss is to break up the vertical members into smaller sections. This is because the vertical members are in compression. The shorter a member is, the more in can resist buckling from compression. The K truss, probably because of its complexity, did not became very popular in the United States.
How the forces are spread out
Here are two diagrams showing how the forces are spread out when the K Truss is under a load. The first shows the load being applied across the entire top of the bridge. The second shows a localized load in the center of the bridge. In both cases the total load = 100. Therefore, you can take the numbers as a percentage of the total load.
The K truss shows the smallest amount of change from the two types of loads on the top and bottom chords. In fact, there is very little difference between the two for the top and bottom. For the internal members, however, there is a large change. As usual, the concentrated load increases the forces on most members. Interestingly, on the K Truss, some members change from tension to compression. Notice this on the top half of the vertical members.
K Truss and model bridges
I think the K truss, while being more complex and more difficult to build, could be a good option for model bridges. I have not build a K Truss bridge yet, but if I get the chance I would like to try it out. Many of my readers have reported success with this design.