ABSTRACT
In this chapter, the author considers dynamic problems, in which the forces are time dependent and cause vibration of the structure; hence, it is necessary to take into account the forces produced by the inertia of the accelerating masses. In practice, dynamic loading is produced by seismic forces, nonsteady wind, blast, reciprocating machinery, or impact of moving loads. An elastic structure disturbed from its equilibrium condition by the application and removal of forces will oscillate about its position of static equilibrium. Thus, the displacement at any point on the structure will vary periodically between specific limits in either direction. If external forces are applied, the author has forced motion. This may be damped or undamped, depending on the presence or absence of these energy losses. In structural analysis, damping effects are modeled as damping forces, which are often assumed to be viscous i.e. they are assumed to be proportional to the velocity.
