Variability in
seismic response of secondary systems due to uncertain soil properties
S. Ray Chaudhuri and V. K. Gupta
Department of Civil Engineering, Indian Institute of Technology, Kanpur-208016,
India
A mode acceleration formulation is presented to investigate the variability
in the response of a secondary system which is supported on a flexible-base
primary system at multiple attachment points. The response functions are
considered to be uncertain due to uncertainties in the values of shear wave
velocity and Poisson's ratio of the foundation soil. Both soil parameters are
assumed to be statistically independent variables with Gaussian distributions.
A numerical study with the help of an example primary-secondary (P–S) system
shows that dynamic response should be ignored only for very stiff secondary
modes, say > 7 times as stiff as the dominant mode of the primary system,
for the proposed formulation to work well. It is also seen that uncertainty in
shear wave velocity can be ignored in case of limited soil-structure
interaction, while uncertainty in Poisson's ratio should be considered only
when soil damping is sensitive to the Poisson's ratio and there is significant soil-structure
interaction.
Author Keywords: Multiply-supported secondary systems;
PSDF-based seismic response; Soil-structure interaction; Uncertain soil
properties; Mode acceleration approach; Mode truncation