The emergency bridge shown in picture above is constructed in the form of a framework with 11 bars. On one bank, the bridge is anchored by the bivalent fixed bearing A and on the opposite bank by the monovalent sliding bearing B. It is assumed that a truck with the weight FG is at a standstill on the bridge and this is statically loaded. The wheels of the truck touch the bridge exactly at junctions III and IV. The center of gravity of the truck is at distances k and l to these junctions.
Use the torque balance in node III. Is this node subject to compressive or tensile forces? Where does the center of gravity of the vehicle have to be in order to maximize F6? To do this, specify the values for k and l as a function of a?
How can I calculate that if I know that all forces are coming through III expect $F_g$ and $F_6$?
In my case Torque Equilibrium would like something like this:
Which isn't correct, where am I making the mistake?