ABSTRACT
Mathematical models for structural dynamic analysis may be generally classified into three approaches: lumped mass, dynamic stiffness, and consistent mass. The lumped mass and consistent mass approaches are similar in terms of motion equation: both of them have independent mass and stiffness matrices; their mass matrices, however, are not the same. Consistent mass may be considered an alliance of finite elements normally used in continuum mechanics. This method is often used for frameworks as well as plate structures. The fundamental concept of finite element is able to model a structure or continuum by dividing it into a number of regions. Each region behaves as a structural member with nodes compatible to the nodes of neighboring regions. The governing motion equation of a structural system can be treated separately as two structural models: rigid frames and elastic frames. The stiffness, load, and mass matrices involve an integral over the natural coordinates and Jacobian scale factor.
