ANALYSIS OF IMPACT TYPE MACHINE FOUNDATIONS CONSIDERING DAMPING

Abstract

In engineering works and factories, usually engines, compressors, impact machines and other vibration generating machines are installed. The dynamic forces generating by shock and impact in case of impact machines are quite severe. Hence, effective vibration isolation is required for proper functioning of machines and their foundations. Impact machines produce transient dynamic loads of short duration. Hammers are most typical of impact machines. Conventionally the damping of soil and isolator/elastic pad are neglected in the analysis and design of impact machine foundations. Hence conventional design method will overestimate the vibrations and stresses produced. For a realistic study, Damped Single degree and Damped Two Degree Freedom System have been analyzed in present thesis by considering damping in soil and damping in isolator/elastic pad in case of impact machines. Computer program is developed for studying the effect of various parameters such as weight of Tup WT, Coefficient of uniform compression of soil Cu, damping ratio of soil1 and damping ratio of elastic pad z, on the behaviour of machine foundation soil system. By analysis and parametric study it has been found that damping of soil reduces vibrations produced and stresses in soil significantly only in the case of Single Degree of Freedom system when no elastic pad is used. In the case of Two Degree Freedom system, with increase in damping ratio of soil 41, amplitudes of vibration reduce significantly. Amplitudes just after one blow decrease after the introduction of damping. Hence consideration of damping will always be useful and in that case amplitudes will be in safer side.