appear in the higher frequencies and can be damped numerically
with appropriate time-stepping schemes, such as by employing
the damped Newmark [35]. Note that in the Newmark's algorithm,
the artificial damping introduced in the time-stepping procedure
is controlled by the parameter δ: a value of δ¼1/2 corresponds to
an undamped formulation, while by increasing δ41/2 the artifi-
cial damping can be influenced [36]. The parameters α and δ can
be chosen independently, however, in the case of symmetric positive-definite
matrices, the method is unconditionally stable for