Variations of Structural Response to Underwater Explosion with Charge Standoff and Unsymmetric Loading

摘要

This interim report summarizes results obtained in conjunction with continuing work toward extension of the Navy's Dynamic Design Analysis Method (DDAM) to multiple foundation motion. A dynamic model of a hull section containing simulated internal equipment with two supports was analyzed using the Variable Geometry Submarine Model (VGSM) for response to underwater explosions with varying charge standoffs. Charge weights were also varied such that the shock factor component normal to the hull was maintained constant for each standoff. Both symmetric and unsymmetric charge geometries with respect to the simulated equipment were examined. Results show that there is a trend toward reduced severity of shock predicted by this simulation for this equipment is the standoff is increased for constant shock factor. The unsymmetric loading resulting in different foundation motions of the two equipment supports shows a trend toward reduced severity of shock for many locations when the foundation motions are uncorrelated (small standoff). However, some locations, particularly those excited by unsymmetric modes of vibration, experience a significant increase in severity. As the unsymmetric charge geometry becomes more approximately symmetric for larger standoffs, the foundation motions become more correlated and the shock response approaches the symmetric case. (Author)