EARTHQUAKE STRESSES IN ARCH DAMS .2. EXCITATION BY SV-WAVES, P-WAVES, AND RAYLEIGH-WAVES

The cross-stream and vertical nonuniform motions of canyon walls caused by body SV-, P-, and surface Rayleigh waves are studied. Using a two-dimensional wave equation, the motion of an irregularly shaped canyon is computed. To illustrate only the basic physical phenomena in the dam response associated with "closing," "opening," and "out of phase" motions of canyon walls, examples of the responses of an idealized arch dam (see companion paper) type 5 to transient SV-, P-, and Rayleigh waves are presented. Accelerations and displacements along the canyon walls depend on the frequency and the incidence angle (for SV- and P-waves) of the arriving motions. Many components of the quasi-static stresses induced by nonuniform canyon displacements are larger than the dynamic stresses induced by nonuniform canyon accelerations. The dynamic stresses can be larger and distributed differently than those caused by the corresponding uniform canyon accelerations.