Optimization of truss structure by maintaining the force in one member

Hi all,

For my master thesis I am designing a bridge supported by multiple Warren trusses in Karamba. Everything works for making the geometry of one truss, applying uniform loads, defining boundary conditions etc. so that I can find the forces in all members of the truss.

My question is if it would be possible to work the other way around? For example: maintain a constant force in one member (must be constant and cannot be exceeded), and then let Karamba optimize the height of the truss to maintain this force? The length and width of the bridge must stay the same.

Thanks in advance!