The DYNA program returns the response of rigid foundations to all types of dynamic loads.  The rotation of centrifugal or reciprocating machines, shock-producing machines, earthquakes, traffic and other sources of dynamic forces can produce these loads. The foundation can be supporting a single or multiple machines.  The response to harmonic loading for a flexible, rectangular mat on elastic half-space or on a group of piles can also be calculated. The stiffness and damping constants of the foundation (needed for the analysis) are evaluated within the program for surface foundations, embedded foundations and piles, pile interaction in a group and other features. For rigid footings, all six degrees of freedom are considered as coupled. The foundation stiffness and damping constants (matrices) are also returned for possible use in soil-structure interaction analysis. These constants are available for rigid footings, flexible mats (caps) on piles, or piles without any connecting cap, and also for flexible mats on elastic half-space.