Research On Passive Controlling Methods For Showcase Of Cultural Relics Under Seismic Load

ABSTRACT:Study on shock absorption and seismic isolation of showcase is a key link of sesimic research on cultural relics of museum collection. At present, there were few damping devices and seismic isolation devices invented for showcase in China, it is necessary to carry out related research works. With the specific engineering background, three passive control methods, TMD damper, energy dissipation and seismic isolation, were used to obtain the vibration reduction effect of showcase booth surface by mean of dynamic time history analysis. These may serve as the basic theory foundation for seismic research on cultural relics of museum collection, and also for shock absorption and seismic isolation design and application of showcase. The study includes three aspects:(1) According to the energy dissipation principle and the equivalent linear theory of viscous damper, energy dissipation showcase structure was designed and analyzed. Parameters were analyzed under1～30Hz simple harmonic waves, and then the optimal damping coefficient was obtained.Based on the selected parameters, vibration reduction effect was analyzed under the seismic waves and the waves of floor vibration. On the basis of shock absorption research with viscous damping, damping coefficient was obtained as50000by parameter analysis. Decreasing amplitude ratio was around40%under the different frequrency simple harmonic waves.The average decreasing amplitude ratio was41.15%under the seismic waves and21.82%under the waves of floor vibration. Viscous damping can dissipate the earthquake energy effectively to decrease acceleration and deflection of showcase booth surface and reduce seismic action on cultural relics.(2) According to the TMD damping principle and showcase structure style, a single TMD was arranged for vibration control of showcase surface.According to DenHartog optimization method for calculating related parameters, the reasonable mass ratio, stiffness and damping ratio were analyzed under the1～30Hz simple harmonic waves. According to the selected parameters, vibration reduction effect was analyzed under the seismic waves and the waves of floor vibration. Parameters were obtained by TMD shock absorption research under the different frequrency simple harmonic waves including0.03Mass ratio and0.12damping ratio. Decreasing amplitude ratio of TMD was around70%under the resonance frequency simple harmonic wave.The vibration reduction effect was poor under the simple harmonic waves away from resonance frequency. The average decreasing amplitude ratio was25.14%under the seismic waves and3.04%under the waves of floor vibration, whose vibration reduction effect was poor.(3) According to the isolation principle, horizontal stiffness and damping ratio were adjusted to isolation bearings of showcase. Under the1～30Hz simple harmonic waves, natural vibration period and damping ratio of shock isolation system were analyzed and selected for showcase. Based on the selected parameters, vibration reduction effect was analyzed under the seismic waves and the waves of floor vibration. On the basis of seismic isolation research of showcase shock isolation system, natural vibration period was2.5s and damping ratio was0.03. The excitation frequency is bigger than the natural frequency of isolation system, the better vibration reduction effect is. The average decreasing amplitude ratio was50.51%under the seismic waves and15.20%under the waves of floor vibration. The prolonged natural vibration period of isolation system can avoid the predominant frequency of external excitation.The seismic response of showcase surface could be reduced so that to keep the cultural relics from earthquake damage.