Experimental and numerical investigations on attenuation response of machine foundations under vertical excitation

ABSTRACT The attenuation response from a series of block vibration tests performed on a model square machine foundation at a site near IIT Kanpur, India, is reported in this paper. The dynamic response at different locations from the vibration source is measured for a wide range of frequencies. The observed attenuation response is compared with the analytical and the finite element (FE) solutions to bolster the experimental findings. A parametric study is conducted utilising the FE analysis to predict the surface wave mitigation characteristics in various soils. It can be observed that the surface waves dominate the attenuation characteristics at the far-field locations and attenuate at a faster rate in soft soils compared to stiff soils. The material and the geometric damping characteristics of the surface waves influence the attenuation characteristics of horizontal and vertical vibrations at the far-field pick-up points. The attenuation characteristics of horizontal and vertical amplitude responses are found to differ significantly. Curve fitting and regression analyses are also performed to develop simplified design expressions to predict the attenuation response of horizontal and vertical vibrations. The proposed design expressions compare well with the values reported in the literature and can be utilised by practicing engineers.