高科技廠房中之精密機台，例如精密之光學儀器等，通常對震動非常敏感。量測報告發現，某些精密機台所含之構件，其自振頻率落在地震波頻率區間，因此在地震中易與樓板震波共振，進而破壞。1999 年9 月21 日，台灣地區發生集集地震，震後新竹科學園區預估約有4 億美元的損失，其中大部份來自於半導體產業的機台破壞及產品毀損。然而，在新竹地區所量測到的地表加速度僅達120 gal，並未造成任何廠房結構上的損壞。這事件使產、學界開始檢討：傳統上，僅針對結構桿件著墨之耐震設計哲學，是否適切？也讓大家意識到，就降低震災損失而言，建築物中之非結構物(NC)及功能性設備物(OFC)，其耐震保護的重要性與必要性並不亞於結構體本身。
有鑑於此，本研究乃針對高科技廠房中之精密機台，發展一滑軌隔震保護系統(GSI)，來降低機台之反應加速度，並於GSI 系統中提供非線性回復力，包括間距彈簧及磁力彈簧，以降低隔震系統位移以及避免因系統具有固定之自振頻率而與樓板震波共振。間距彈簧(Gap spring)是指：彈簧在靜止時並未與系統接觸，當震動發生時，系統可於間隙中自由水平滑移；一旦滑動位移大於間距而使間距閉合時，彈簧始提供回復力，故系統在間距開合之間呈非線性運動。磁力彈簧(Magnetic spring)則是利用磁鐵同極相對時，其超距磁斥力大小具有隨距離呈非線性變化之特性，來提供系統非線性限位機制。本研究在Matlab Simulink 電腦程式中，建立GSI 系統含間距彈簧及GSI系統含磁力彈簧之數值模型，來分析非線性GSI 系統之動力行為。為驗証GSI系統數值模型之正確性，本研究以一質量為22 噸之鋼構架試體模擬精密機台，規劃一足尺振動台試驗。試驗結果除可供數值模型比對外，亦可驗證非線性GSI系統之隔震效能，進而設計理想且具高效能之非線性隔震系統。
試驗及分析結果發現，兩組非線性GSI 系統均能有效降低試體受震反應加速度至100gal以下。在GSI 含磁力彈簧系統方面，當系統受160 ~ 940gal遠域樓板震波作用下，相對位移約控制在10~20mm左右。進一步的參數分析顯示，提供充足的磁力，並控制磁力彈簧之勁度不要進入劇烈硬化的階段，能有效降低系統反應位移而不增加系統過多之反應加速度。當GSI 系統含間距彈簧時，系統受160~940gal遠域樓板震波作用下，相對位移則約控制在10~25mm左右。若進一步採用衝程較大之彈簧，則系統在承受160 gal 之近域樓板震波時，反應位移約在45 mm 左右。試驗結果顯示出GSI 系統含非線性回復力控制位移能力較純摩擦滑移系統佳，且亦不使反應加速度過大。針對本研究假設條件之下進行之試驗顯示，間距彈簧之最佳間距為5 mm。
除了隔絕水平地震力作用於精密機台使其免於發生破壞之外，精密機台之基座亦需具有高動態剛度(Dynamic Stiffness)，來維持其正常運作。例如，某廠牌之掃描機即要求其基座在20~30Hz區間，動態剛度必須高於100000000 N/m以上。傳統上，為滿足此需求，精密機台之基座通常以環氧樹脂(Epoxy)黏固於樓板上，此工法雖可提升基座之剛度，卻使基座與樓板無法產生相對位移，喪失以GSI隔震器保護精密機台的可能性。為同時滿足基座動態剛度與隔震滑移之需求，本研究乃提出半主動開關式電磁吸力來解決此問題。其機制為當平常機台運作時，藉由電磁吸力來固定基座與樓板；而當機台偵測到地震發生時，則送出訊號解除電磁吸力，使隔震系統能正常運作。另外，磁吸力可由市面上可購得之超導體電磁鐵提供，其在充磁、消磁之間，僅需各供電一次，與傳統電磁鐵需持續供電之狀況不同，故沒有能源消耗之問題。藉由衝擊鎚進行衝擊試驗結果驗證，裝備開關式磁鐵之試體，其動態特性皆能被有效增進，特別是系統阻尼比以及動態剛度，皆有數倍之提升。
最後，本研究設計一組可水平兩向隔震之非線性GSI系統，應用於一長、寬、高各為: 1.8×1.8×0.25m之高架地板系統，並輸入滿足AC156之非結構物振動台耐震測試反應譜之震波，進行三軸向之振動台試驗。輸入方向包含水平兩向及垂直向。試驗結果發現，在960 gal震波之作用下，高架地板系統試體之水平反應加速度最低可控制在250 gal，位移可控制在75mm左右。所有試驗中，高架地板系統試體並未發生任何破壞，顯示本研究所開發之非線性GSI
系統，在適當的配置下，可有效保護建築物中之功能性設施免於震損之風險。

Precision machinery in hi-tech factories is generally very sensitive to vibration. Unfortunately, the natural frequencies of elements inside precision machines are often low and may be destructively resonant with the earthquake oscillation frequency of the factory floor. For instance, after the 921 Chi-Chi Earthquake in 1999, losses from damage to precision machines and product in Hsinchu’s Science Based Industrial Park were estimated at US$ 400 million, despite a horizontal PGA of only around 120 gal was measured in Hsinchu, which caused almost no structural damage to factory buildings. This event revealed the fragility of vibration-sensitive precision machinery and showed the need to provide suitable protection system to avoid loss caused by the damage to critical equipment, nonstructural components (NC), and operational and functional components (OFC) in buildings.
In this study, firstly, a guideway sliding isolator (GSI) system with very low frictional coefficient (below 0.01) were developed to protect precision machinery against horizontally floor seismic motions. Nonlinear restoring forces, including gap springs and magnetic springs, were applied to improve the performance of the GSI system. The gap spring is initially separated from the system by a gap, causing the GSI to slide freely when the displacement is smaller than the gap distance, and to perform nonlinearly once the gap is closed, therefore reducing the likelihood of resonance. The magnetic spring uses a noncontact magnetic repulsion force, also causing the GSI to achieve a nonlinear property. A numerical simulation model of the GSI system with magnetic/gap springs using step-by-step integration in Matlab Simulink program was developed. Full scaled shake table tests on the GSI systems with a 22-ton specimen were performed to verify the performance of the nonlinear GSI system and the accuracy of the numerical model.
The testing results showed that the nonlinear GSI systems were effective in reducing the response accelerations to below 100 gal in most experimental cases. The GSI with magnetic springs could control the response displacements to about 10 mm and 20 mm when the system subjected to 160 gal and 940 gal far-field seismic motions of the floors, respectively. A parametric analysis of the magnetic springs in the GSI system under far-field seismic motions showed that sufficient magnetic forces in the small stiffness region can reduce the system’s response displacements. For GSI with gap springs, the response displacements could be controlled less than 10 mm, 25 mm, and 45 mm when the GSI system was excited by the floor’s seismic responses of small (160 gal) far-field motion, large far-field motion (940 gal), and small near-fault motion (160 gal), respectively. It was found that the GSI system with appropriate gap springs was more effective in controlling response displacements than was a free sliding system. Furthermore, the optimal gap for a system subjected to far-field earthquakes was found to be 5 mm in this study.
Besides reducing horizontal response accelerations during earthquakes by the nonlinear GSI systems, we should also consider that the vibration-sensitive machinery requires a very rigid foundation for maintaining daily operation. For example, a scanner requires a foundation with a high dynamic stiffness of 100000000 N/m in the frequency band between 20 and 30 Hz. To satisfy this requirement, the practical foundation is usually glued to the floor by epoxy; nevertheless, it eliminates the possibility of sliding. For the GSI system developed in this study, the required dynamic stiffness can be provided by semi-active restraint, which is designed to use attractively magnetic forces that are active during the machine’s daily operation, but inactive when earthquakes are detected by the accelerometers installed on the machine. Therefore, a rigid machine foundation fixed to the floor by semi-active magnetic forces rather than epoxy adhesion can satisfy both the needs for the high dynamic stiffness of the precision foundation and the possibility of sliding. Moreover, the attraction force could be provided by electrical magnets made of superconductor. Rather than a continuous power supply, it needs the power only at the instants when magnetic forces are activated or deactivated. Hence, there is no additional energy consumption.
At last, a bidirectional nonlinear GSI system was also applied to the base of a 1.8 ×1.8 ×0.25 m raised access flooring (RAF) system. A tri-axial shake table testing series using excitations achieved to 960 gal were performed. The seismic inputs were compatible to the AC156 response spectrum, the acceptance criterion for seismic qualification by shake table tests on NC/OFC. The results showed that the GSI system was effective in reducing the response acceleration to below 250 gal, and controlling the response displacements to be around 75 mm. It revealed that the nonlinear GSI system developed in this study has been qualified to protect most of the NC/OFC on building floors against horizontally seismic motions that are threatening to them.

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