I have modelled the sectional structure of a building, but in the model analysis, it said there are 319 rigid body modes. I am not sure if the problem is the layers of truss doesn’t match…
“1. There are 319 rigid body modes in the system. This means some parts can move freely without causing deformation.
Try to use the ‘Eigen Modes’-component and activate the display of local coordinate axes: The first eigen-mode will be the rigid body motion.
If this does not help, check whether you have a pinned support directly attached to a hinge. A hinge introduces an extra node which may cause the problem.
When analyzing a flat shell structure one has to lock the rotation perpendicular to the plate in at least one node.”