Effect of negative phase of pulse loading on response of machine foundations vibrating under harmonic loads

Abstract

Analysis of a machine foundation system subjected to harmonic and pulse loading is investigated by modeling it as a linear elastic-perfectly plastic single degree of freedom (SDOF) system. Pulse loading, an idealization of explosion/blast, is represented by modified Friedlander's equation having both positive and negative phases. Analytical expressions are derived for equations of motion to obtain the response of SDOF system under combined action of harmonic and pulse loading in the form of displacement-time plots. Results show noteworthy influence of negative phase of pulse loading on the displacement of SDOF system and suggest that this should not be neglected by idealizing the explosion with the help of a triangular pulse loading. The developed solution and the displacement-time histories can help in the analysis and design of a soil-foundation system undergoing combined harmonic and pulse loading (such as a machine foundation).

Keywords:

• Elastic-perfectly plastic response
• harmonic loading
• pulse loading
• Machine foundation
• negative phase
• SDOF system