Study On Seismic Fragility Analysis Of A Medium-speed Mill With Spring Vibration-isolated Foundation

The medium-speed mill is one of the important dynamic equipment in the powerplant，the vibration due to its high power at work impact their normal operation， andsecurity around the plant structure, and therefore the basis of the form of the mill becomesvibration isolation using springs instead of the form of using chunks of concrete. Atpresent，in the base isolation design，structural engineers tend to focus on mitigatingequipment vibration， but there is no in-depth studyon the structural seismic performanceof the isolated base during the seismic. Therefore，it is necessary to analysis seismicperformance ofthe mills with spring isolated base， whichhas important application valueto reduceearthquake damageofthe equipment and avoid secondarydisasters.In this paper， the medium-speed mill and its basis were simulated by ANSYSsoftware for the dynamic analysis. The dynamic characteristic of the mill-foundationcoupling systemwasobtained. Numericalanalysis chooseEl-Centro wave， Taft wave andLanzhou artificial waves as seismic input， studied seismic response of mills consideringthe isolation and non-isolation foundation，then accelerationand displacement time historycurve of each measuring point on the two structures were obtained and compared， andcurve analysis showed that the equipment-basic coupling system is capable ofwithstandingearthquakes when use the spring isolated basic and superior the seismic performance of themill with non-isolation. Finally， the medium-speed mill with spring isolated base wasstudied for incremental dynamic elastic-plastic analysis， and the seismic vulnerabilityanalysis was launched basedon incrementaldynamic elastic-plastic analysis，evaluatedtheseismic performance of the medium-speed mill with spring isolated base. The results showthat the equipment and the foundation basically meet the objective in Chinese code " no collapsing with strong earthquake"，but the equipment wasrequiredhigh precision，whentheearthquakeoccurred， theoverallstructuredoesnot collapse， equipment damage hasoccurred.Through computational analysis， which showed that the medium-speed mill withspring isolated base can not only effectively reduce the impact of the vibration of theequipment on the security of plant and the surrounding building， but also meet theregulatory requirements in the seismic performance; through the comparison onvulnerabilitycurve ofthe equipment and infrastructure，operationalprinciple ofequipmenthas been damaged before the foundation has been destroyed，so，the connection betweenfoundation and equipment should be strengthened to ensure that the device is workingproperly when the earthquake happened， and then some useful reference in the futuredisaster vibration damping design work of mill with the spring isolated foundation areprovided.