In frequency-domain dynamic soil-structure interaction analysis, the consistent transmitting boundaries by Waas (1972) can be used to take into account the wave-absorbing effects of the semi-infinite layered strata as shown in Fig. 1. These boundaries are exact in a finite-element sense in that no further approximations are made in the computations except for the ones already made for discretizing the structure and near-field soil. However, the consistent transmitting boundaries have a certain restriction in that the geometric shape of the boundary must be vertically straight. Although this is quite satisfactory in many applications, as Fig. 2 suggests, there are other numerous situations where we can achieve, using a boundary of more general shape, a significant improvement in computational efficiency in terms of the size of the near-field soil region where spatial discretization is necessary. In this work, we will consider boundaries containing inclined segments. These boundaries will take a form of zigzag shape, in general, and will be referred to as zigzag boundaries.
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