Dynamic Response of a Four-Cylinder Compressor Foundation Considering the Effect of Soil-Foundation Interaction—A Case Study

The dynamic response of machine foundation system depends on several factors such as (1) the soil dynamic properties, (2) the geometric properties of the foundation, (3) the amplitude of the applied dynamic loads, and (4) the frequency of the exciting dynamic force. The main goal of machine foundation design is to keep the foundation response within a specific limit of response in order to enable a satisfactory operation of the machine. If the foundation response exceeds this limit, the foundation will adversely affect the performance of the machine and may damage the machine internals, or cause it not to function properly. Furthermore, the excessive vibrations will impose additional stresses on the machine resulting in an increased unbalance loading and thus leading to increased dynamic loads on the soil-foundation system. This paper presents the results of the dynamic analysis of a four-cylinder compressor foundation. The original design of the foundation was performed in the early 1960s and ignored the effect of the soil in the response of the foundation system, thus, the foundation has been suffering from excessive vibration. The foundation block supports a four-cylinder dress-rand compressor, suction and discharge bottles, a crank and driving motor with a total weight of approximately 219 kips. The results of a three- dimensional finite element model of the soil–foundation system were used to determine the dynamic response of the soil-foundation system and to assess the foundation response under the applied dynamic loading imposed by the compressor crank. The dynamic analysis is performed by: (1) performing eigenvalue analysis of the foundation block, considering the effect of the soil-foundation interaction to determine the soil-foundation natural frequencies and modal participation factors, and (2) performing forced response of the foundation under applied crankshaft unbalance load to determine the forced response amplitude of the soil-foundation system.

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