Influence of harmonic and pulse excitations on response of foundations

ABSTRACT This investigation reports analysis of foundations to study its time-displacement response with due consideration to hardening and softening behaviour under combined harmonic and pulse loadings. Based on time of application of pulse loading to foundation and the occurrence of maximum deflection, two cases of analysis are considered and solutions are obtained for underdamped system using semi-analytical approach. The influence of combined action of two different loading is studied. Detailed parametric study is carried out to understand the influence of parameters such as mass of machine-foundation system, ratio of plastic to elastic stiffnesses, damping, frequency ratio and, resistance of soil on time-displacement history of system. Maximum displacement of the system increases to the extent of 48% with 22% increase in initial pulse load magnitude. Damping, mass and stiffness of SDOF system affected the response significantly. Results showed interaction due to combined action of harmonic and pulse loading should not be neglected.