Spatial Seismic Coefficients, Some Sensitivity Results

Abstract

Dynamic coefficients in the format of response spectra are analyzed as simplified measures of spatial seismic effects on structures. The coefficients are formulated as dynamic response ratios in terms of point spectral density and unlagged coherency of excitations as well as frequency response function of an oscillator. The displacement ratio stays between 0 and 1, displaying the reduction of dynamic displacements for incoherent excitations, while the force ratio may also exceed 1, indicating additional spatial forces. The influence of two principal parameters: propagation velocity and loss of coherence on spatial seismic vibrations is studied. The analyzed ratios may find application as partial coefficients.