This study presents a global sensitivity analysis approach based on entropy to investigate the influence of excitation and structural parameters on the engineering demand parameters. The sensitivity of the nonlinear dynamic structural response using synthetic earthquake ground motions to major uncertain sources, propagation paths and site variables of the simulated ground motion, and physical characteristics of the structures is investigated using an entropy-based sensitivity index as a measure of importance to determine which variables are most significant. The results show that the uncertainties of ground-motion variables are more significant than those in the structural properties. The greatest contributor to the variability in the seismic demand is the uncertainty in earthquake source parameters. Our analysis also revealed that viscous damping is the most important structural source of variability in seismic structural demands. Structural dynamic analysis due to simulated excitation opens the door for the wider use of seismological theory to understand the relationship between the structural response and seismological variables.
