Simplified Dynamic Analysis Methods for Metallic Bellows Expansion Joints

An investigation into dynamic characteristics and seismic response of bellows expansion joints is described. For axial and lateral vibrations of the bellows, simplified methods are developed to evaluate their natural frequencies and seismic response, based on analogies with those of a uniform rod and a Timoshenko beam, respectively. For the lateral vibration modes, effect of fluid-structure interaction between the convolutions and flow-sleeve is taken into account. The validity and applicability of the simplified methods are shown, by comparing with the results of vibration experiments using a simple bellows model and a piping model with bellows, along with corresponding detailed FEM analyses’ results.