Closed form solutions for response of machine foundations under accidental blast loads

An attempt has been made in this study to analyze and predict the response of machine foundations under operating conditions subjected to accidental blast loads. Three cases of machine foundations subjected to combined sinusoidal and blast loads have been analyzed, namely- i) response of soil remains elastic during the blast, and maximum displacement also occurs in the elastic state, ii) blast takes place in elastic state but maximum response is obtained in plastic state, and iii) during the blast, the state of soil-foundation system changes from elastic to plastic and the maximum response is obtained in plastic state. Closed form solutions have been obtained for predicting the displacement-time history of machine foundations for all these three cases. Parametric study has also been carried out to understand the influence of parameters like mass of machine and the foundation, stiffness of soil, damping ratio, frequency ratio, and the ultimate bearing resistance of soil on displacement-time history of machine foundations. Results of parametric study would be helpful in designing the machine foundations in the presence of combined harmonic and blast loads. •Machine foundations under sinusoidal and blast loads: closed form solutions.•Case 1: during blast, response of soil and maximum displacement remain elastic.•Case 2: blast in elastic state but maximum response is in plastic state.•Case 3: during blast, state changes from elastic to plastic.•Effect of characteristics of SDOF system on displacement-time history.