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*; *; Imazu, Akira
PNC TN9410 88-080, 132 Pages, 1988/06
A series of analytical investigations were made into the seismic response characteristics of bellows, as a part of work aiming at establishing reliable seismic design and analysis methodologies for bellows piping systems. Simplified calculation methods were developed for the axial and lateral seismic response of bellows, in which bellows is modeled as an equivalent rod or beam, respectively. Using these methods, spectral response analyses were performed on the bellows with the number of convolutions as a parameter, and the results were compared with detailed FEM analysis by FINAS. Analyses were also made to compare with available vibration test data. The simplified methods were found to give fairly good results when compared with those by FINAS, and relatively conservative results when compared with experimental data. Through this study, simplified methods were established to evaluate the seismic response and stress of bellows with sufficient accuracy for practical design use.
*; *; ; Iwata, Koji; Imazu, Akira
PNC TN9410 87-112, 206 Pages, 1987/09
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.
*; *
PNC TN9410 86-093, 165 Pages, 1986/07
The core components of an LMFBR may show a complex nonliear vibration behavior as a cluster during a seismic event, which is induced by interaction between neighboring components due to collisions taking place at the load pads of hex-can ducts. Therefore, an analytical evaluation on this cluster vibration is essential when assessments are made on seismic safety of an LMFBR core in lights of structural integrity of core components, maintenance of coolant flow-path, and maintenance of control rods insertabity. Described in this report are the results of cluster vibration analysls and seismic safety assessment on the Large LMFBR core which was established during the course of the design study performed in FY 1986. The cluster vibration analyses were performed using a special purpose code "VIOLLON" that had been developed for the seismc design of Monju core. The results of this study can be su㎜arized as follows. (1)The dominant frequency of cluster vibration of the Large LMFBR core is around 5.0 Hz, which is about 2 Hz higher than the 1st natural frequency of a single element. (2)Stresses arising in a core comporent due to an earthquake load are sufficiently lower than the allowable limits, leading to a successful expectation of seismic design of the Large CMFBR core. (3)The design and configurations of the Large CMFBR core may be further rationalized and optimized as far sa the seismic design viewpoint is concerned.
