For imperial, set g=386.0886 in/s². For metric, set g=9.80665 m/s². (You can override.)
Nodes
Columns: node x y z delX delY delZ thetaXX thetaYY thetaZZ W
BC rule: blank => free DOF, nonblank (including 0) => prescribed.
W is nodal weight (force). It is converted to mass m=W/g and added to ux,uy,uz.
Segments
Columns: elem ni nj E G Izz Iyy Jyz Ayz rho x3 y3 z3 (header optional)
rho is mass density. Ayz is treated as area A.