Vibration tests and analyses of bellows

not registered; not registered ; not registered ; Iwata, Koji; Imazu, Akira

A series of experimental and analytical investigations was made into the vibration characteristics of bellows, as a part of works aiming at the establishment of seismic design and analysis methods for the piping systems with bellows expansion joints. Vibration tests were made using scaled models of bellows, and eigenvalue analyses were performed using both finite element method (FINAS program) and some simplified methods. Some axial, bending, and shell type modes were identified in the vibration tests in terms of mode shapes and eigenfrequencies. The analysis results by FINAS program were in good accordance with the test results for all the vibration modes, while the simplified formula provided in the EJMA Std. did not give good estimation for bending modes. A new simplified calculation method for bending mode eigenfrequency was developed, in which the fluid-structure interaction effect induced by flowsleeve was also taken into consideration. Through this study, analysis methods to evaluate the vibration characteristics of bellows with simplicity and precision, were established, which will be reflected on the provision of seismic design and anlysis methods for piping systems with bellows expansion joints.