If you tilt a platform to tip over a bus and you want to know the angle of the platform at which the bus will tip off, then you don't need Ansys to answer that question. It is a simple geometry problem. Draw a line from the center of gravity of the bus to the the line connecting the edge of the tires. The angle of that line to vertical is the angle you have to tilt the platform to reach the critical angle. Beyond that, the bus will tip off the platform.