Me. Panji, M. Kamalian, J. Asgari Marnani, M. K. Jafari,
Volume 12, Issue 2 (4-2014)
Abstract
In this paper, normalized displacement amplitude of the ground surface was presented in the presence of the semi-sine
shaped valley above the truncated circular cavity embedded in a homogenous isotopic linear elastic half-plane, subjected to
obliquely propagating incident SH waves as Ricker wavelet type. The proposed direct time-domain half-plane boundary
element formulation was used and extended to analyze the combined multi-boundary topographic problems. While using it,
only boundary of the valley and the surrounding cavity should be discretized. The effect of four geometric parameters
including shape ratio of the valley, depth ratio, horizontal location ratio and truncation thickness of the cavity and incident
wave angle was investigated on the responses at a single dimensionless frequency. The studies showed that surface behavior
was completely different due to complex topographic features, compared with the presence of either valley or cavity alone. In
addition, the cavity existence below the surface could play a seismic isolation role in the case of vertical incident waves and
vice versa for oblique waves.
Jafar Najafizadeh, Mohsen Kamalian, Mohammad Kazem Jafari, Naser Khaji,
Volume 12, Issue 3 (7-2014)
Abstract
In this paper, an advanced formulation of the spectral finite element method (SFEM) is presented and applied in order to carry out site response analysis of 2D topographic structures subjected to vertically propagating incident in-plane waves in time-domain. The accuracy, efficiency and applicability of the formulation are demonstrated by solving some wave scattering examples. A numerical parametric study has been carried out to study the seismic response of rectangular alluvial valleys subjected to vertically propagating incident SV waves. It is shown that the amplification pattern of the valley and its frequency characteristics depend strongly on its shape ratio. The natural frequency of the rectangular alluvial valley decreases as the shape ratio of the valley decreases. The maximum amplification ratio along the ground surface occurs at the center of the valley. A simple formula has been proposed for making initial estimation of the natural period of the valley in site effect microzonation studies.
