HELP! Mesh & Interference trouble - Simulation

Let me start by saying this is my first time posting so glad to be here.

I'm working on a school project and have been trying to simulate a 2000 lb load an an assembly of my bridge however ho luck what so ever, even my instructor has failed to help me.

I keep getting an interference error when meshing even after applying mesh controls etc

Any suggestions are appreciated

SolidworksSimulation