Abstract
Automated stocker system is widely used in semiconductor and liquid crystal display (LCD) industries for handling and storage of valuable wafers or glass panels. Massive front opening unified pods (foups) containing wafers, or cassettes storing glass panels, are placed in shelf stockers during manufacturing. Although several preventative measures have been taken, during the past earthquakes, substantial financial loss from the industries were reported, and one of the main causes was attributed to collision of the foups or cassettes and shake off from the shelfs. This paper proposes a methodology of incorporating viscous fluid dampers into the stokers to mitigate their seismic response. Unlike conventionally been done in buildings where dampers are placed between adjacent stories, it is proposed to install dampers in between the ceiling and top of the stocker. Such configuration utilizes the large velocity at the stocker top under vibration, resulting in smaller damper size, and enables a leverage mechanism that requires smaller damper force to resist the stocker’s vibration. Both shake table tests and simulation of a full-scale stocker under realistic earthquakes have been conducted. Results indicate that both displacement and acceleration responses of the stocker can be significantly reduced, and dynamic response of the stocker under seismic excitations can be well predicted.
Highlights
Locating at the boundary between the Eurasian and the Philippine Sea tectonic plates, Taiwan, an island in East Asia, has seen many earthquakes resulting from movement of the tectonic plates in its history
The grey dotted line is for the original stocker, whereas the solid line is with the added viscous dampers
A methodology is proposed in this paper for semiconductor and liquid crystal display industries to retrofit the stockers in the automated stocker system for protecting the valuable wafers and glass panels under earthquake events
Summary
Locating at the boundary between the Eurasian and the Philippine Sea tectonic plates, Taiwan, an island in East Asia, has seen many earthquakes resulting from movement of the tectonic plates in its history. For the case with four viscous dampers installed in the first shelf, results showed a reduced drift response of the stocker but in a less extent as compared to the braced counterpart; the measured shelf acceleration still increased slightly as compared to the original un-reinforced stocker, which failed to meet 75 the design objective. To tackle the 115 issues with simple yet feasible solution, unlike conventionally been done by Wang et al.[3] where dampers are placed between adjacent shelfs, it is proposed to install dampers in between the ceiling and top of the stocker Such configuration utilizes the large velocity at the stocker top under vibration, which results in smaller required damper size, and enables a leverage mechanism that demands smaller damper force on top against the ceiling to resist overall stocker vibration, as the moment arm measured from the floor level is fairly long. Simulation of the stocker system using commercially available software ETABS is performed, with a goal of simulating seismic response of the stocker
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