Mass values are calculated for structural elements according to volume and material density. Mass is then automatically concentrated at joint locations. During dynamic analysis, mass translation along each of the three joint displacement degrees-of-freedom (DOF) correlates with acceleration to create inertial forces. Additional concentrated mass may be assigned to joint locations. Further, mass moment of inertia may be applied to each of the three joint rotational DOF to account for rotational inertia. Mass is uncoupled between different joints, and between DOF at a joint location. Mass units are given as W/g, and mass moment-of-inertia units are given as WL²/g, where W is weight, L is length, and g is gravity.

Mass Tips

• Extract joint mass after analysis by selecting Display > Show Tables > Analysis Results > Joint Output.