I am modelling a solar racking structure (tilted 30 degree to the ground) under wind loading time history. The idea is to carry out performance based design using non-linear time history analysis. I have the static model up and running and is now ready to proceed to dynamic analysis. I was wondering whether you could provide some pointers as to how to go about assigning nodal masses for all the six degrees of freedom for self weight (dead load) at each of the nodes for eigen value analysis. Since the dead weight comes from the elements, do I have to calculate statically equivalent nodal loads (for the dead load of each beam-column element) for each of the connecting nodes of the elements and assign them to the nodal masses?? Right now the nodal masses are all considered zero (fr all the six degrees of freedom).