Investigation of vibration attenuation by expansion joint in the SPring-8 Storage Ring

The expansion joint is made for the separation between building and tunnel in the SPring-8 storage ring. This expansion is useful for not only slow movement but also vibration. A 40cm deep expansion is cut between cooling machine room and maintenance path. This expansion reduced vibration amplitude by 5∼10 dB and is found to be valid. The phase difference by expansion makes complex changes with frequency. The phase velocity is measured to be about 1 km/s. The vibration of machine room seems to travel through the 40 cm slab because the soil under the slab is soft. (author)