Dynamic design analysis method

DDAM stands for the Dymanic Design Analysis Method and is the primary method used by the US Navy for UNDEX shock design of foundation structures. The document describing the method, NAVSEA 0908-LP-000-3010, Rev 1., is public release, but the values needed to actually perform an analysis are classified.

The DDAM is based on a standard spectral response analysis technology but uses a modified modal summation technique called the NRL Sum. The NRL Sum differs from the similar Root Sum Squared method used by most modal summation methods by holding the largest value aside during the RSS and then adding it into the sum.