Lumped mass - lmass

This is a single-node lumped mass element, characterised by three translational and three rotational inertia values. The latter are defined by means of the mass moment of inertia (not to be confused with the second moment of area, commonly named also as moment of inertia), and may be computed using formulae available in the literature [e.g. Pilkey, 1994; Gere and Timoshenko, 1997]. The inertia mass values are to be defined with respect to the global reference system (X, Y and Z), and lead to a diagonal 6x6 element mass matrix.