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In biomechanics laboratories the ground reaction force time histories of the foot-fall of persons are usually measured using a force plate. The accelerations of the floor, in which the force plate is embedded, have to be limited, as they may influence the accuracy of the force measurements. For the numerical simulation of vibrations induced by humans in biomechanical laboratories, loading scenarios are defined. They include continuous motions of persons (walking, running) as well as jumps, typical for biomechanical investigations on athletes. The modeling of floors has to take into account the influence of floor screed in case of portable force plates. Criteria for the assessment of the measuring error provoked by floor vibrations are given. As an example a floor designed to accommodate a force platform in a biomechanical laboratory of the University Hospital in Tübingen, Germany, has been investi-gated for footfall induced vibrations. The numerical simulation by a finite element analysis has been validated by field measurements. As a result, the measuring error of the force plate installed in the laboratory is obtained for diverse scenarios.
Earthquake response spectra as defined by Eurocode 8 (German NAD) are restricted to soils with shear wave velocities greater than 150 m/s. For soft soil layers e.g. of clay underlain by bedrock special investigations are required because resonance effects of the layer significantly influence the shape of the spectrum. Numerical investigations are normally based on a one-dimensional theory of horizontally polarized shear waves propagating in vertical direction. The paper describes a parametric study to define acceleration response spectra for a soft soil over a half-space for a wide range of soil layer heights and material parameters. Based on this study a simplified method to describe response spectra for the model of a soft soil layer underlain by a viscoelastic halfspace is given.