Comments are made on the availability of a finite element solution, the material damping in the half-space analysis, the solution to the 30dimensional multilayered media, and results from arbitrary models. Attention is focussed on 4 underlying issues: input motion to half-space solution; hysteretic damping in soil; strain-dependency of soil properties; and streucture-structure interactions. Equations of motion of the sub-structure system show that the inertial forces in the structure are due to both the free field motion and to the modification of this motion due to soil-structure interaction. In the simpler models, the input motion is generally assumed to develop inertia forces in the structure associated with the free field and interaction effects and no distinction is made regarding the possible change of motion as a function of depth. The point is made that the more important source of energy absorption comes from energy radiated into the half-space. Damping functions in a dual role: as absorber of radiation and energy, and hysteretic soil damping. Modeling of radiation damping is discussed. Strain dependency is discussed and it is shown that increasing strains (due to only interaction effects) by 20 percent would decrease the shear modulus by about 6 percent and increase hysteretic damping, which is only a small part of the total energy abosrption, by about 10 percent. Strains in the free field due to the earthquake motion can be approximated by an auxilliary analysis using elementary shear beam theories. Comments are also made regarding the energy radiated from 2 infinitely long structures, energy attenuation is a is a 2-dimensional and a 3-dimensional environment, and the decay of both shear and compressional waves.

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  • Accession Number: 00133984
  • Record Type: Publication
  • Report/Paper Numbers: Proc. Paper #11318
  • Files: TRIS
  • Created Date: Jun 5 1976 12:00AM