No abstract

The optimal values for the distribution of passive dampers interconnecting two adjacent structures of di erent heights are determined. The dampers are selected to minimize the seismic response in the ÿrst and second modes of the taller of the two structures. For simplicity, the structures are represented as uniform damped shear beams subjected to a common ground motion. Under certain conditions, apparent damping ratios as high as 12 and 15 per cent can be achieved in the ÿrst and second modes of lightly damped structures by the introduction of interconnection dampers. The largest reduction of the response in the ÿrst mode is achieved when the taller structure is about twice the height of the second structure.? 1998 John Wiley & Sons, Ltd.

SUMMARYAn indirect boundary-method formulation to obtain the three-dimensional response of an infinitely long canyon of uniform but arbitrary cross-section cut in a layered viscoelastic half-space is presented. Seismic excitation in the form of plane elastic waves acting at an arbitrary angle with respect to the axis of the canyon is considered. Numerical results for SH-, SV-and P-wave excitation of a circular canyon and of a canyon with a topography similar to that in the vicinity of Pacoima Dam are discussed in some detail.

SUMMARYThe two-dimensional response of a viscoelastic half-space containing a buried, unlined, infinitely long cylindrical cavity of circular cross-section subjected to harmonic plane SH, P, SV and Rayleigh waves is obtained by an indirect boundary integral method based on the two-dimensional Green's functions for a viscoelastic half-space. An extensive critical review of the existing numerical results obtained by other techniques is presented together with some new numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity for P, SV, SH and Rayleigh waves.