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Effects of Radiation Damping on Vibration of a Shallow-Buried Rectangular Structure.
Final rept. Aug 77-Mar 78,
WEIDLINGER ASSOCIATES MENLO PARK CALIF
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Radiation damping from shallow-buried structures of rectangular cross-section was analyzed by means of an elastic, finite element model. The results show that radiation damping increases with the stiffness of backfill, which is consistent with results previously obtained for a buried arch. Implications are examined of including a viscous damping mechanism to simulate radiation damping in nonlinear single-degree-of-freedom models of the roof slab. In the examples considered, including radiation damping up to 20 of critical based on the stiffness of the slab in the elastic-cracked regime, reduces calculated peak displacements to as little as one-half of the magnitude as calculated by SDOF models without damping. To explain the dependence of radiation damping on deformational mode number, an exact analysis of a cylindrical elastic, plane strain section in an infinite elastic domain was performed. As expected, the findings indicate that higher radiation damping is associated with the lower modes. Author
APPROVED FOR PUBLIC RELEASE