Tjr. Hughes et al., DYNAMIC ANALYSIS AND DRILLING DEGREES OF FREEDOM, International journal for numerical methods in engineering, 38(19), 1995, pp. 3193-3210
Finite element methods for dynamic analysis employing elements with dr
illing degrees of freedom are presented. The formulation is based an a
variational principle in which displacements and rotations are interp
olated independently. The issue of zero masses corresponding to rotati
onal degrees of freedom is addressed and techniques for defining consi
stent and lumped rotational mass matrices are presented.