87-0021 Horizontal Impedances for Radially Inhomogeneous Viscoelastic Soil Layers A.S. Veletsos and K.W. Dotson 1987 Rice University 56 PB88-150859 10 A study of the dynamic impedances of horizontally excited, radially inhomogeneous, infinite viscoelastic soil layers with a circular hole, and of piles embedded in a medium represented by such layers is made considering the shear modulus of the material to increase radially within a narrow annular boundary zone. Unlike a previous study in which the boundary zone was presumed to be massless, in the present study the inertia effects of this zone are taken into account. The impedances are evaluated over wide ranges of the parameters involved and the sensitivity of the results is assessed. The results are also compared with those obtained for similarly excited homogeneous layers and for vertically excited inhomogeneous layers. For purposes of analysis, the inhomogeneous boundary zone is represented by a series of concentric rings of constant properties, and the transfer matrix technique is used to evaluate the results. The analysis and the computer program used to implement it are applicable to layers or arbitrary radial variation of material properties. Viscoelastic Soil Layers, Seismic Performance, Ground Motion, and Impedance Coefficients.