疊層式科技廠房之結構耐震補強研究

Abstract

科技廠房結構耐震設計考量不周，乃震害問題之主要來源，尤以疊層式廠房為甚。疊層式廠房內含兩層(甚至三層)無塵室，軟弱層導致側向位移過大，二次應力效應則使問題更為惡化，並放大上層無塵室的振動反應，不僅威脅廠房結構安全，亦增加設備受損風險。現行建築物耐震設計規範乃基於「大震不倒」的設計理念所發展，惟科技廠房在中、小地震衝擊下損失不貲，顯示現行耐震設計無法確保科技廠房在中、小地震﹙震度三~五級﹚下免於設備受損、生產中斷的性能要求，須加以補強。有鑑於科技廠房有其特殊性，非習用之結構耐震補強技術與工法所能克服，因此本研究提出科技廠房之性能設計目標及創新之補強工法，並以一座典型三重疊層式面板廠為對象進行分析與驗證。無論由極限層剪力、層間變位角…等指標去檢核，分析結果均顯示廠房結構現況之耐震能力不足。本研究提出以雙向各六跨之空間桁架外覆於結構的補強方案，則能有效提升結構之勁度與極限強度，在設計地震下均能滿足各項耐震評估指標，惟中、小地震下之動態歷時分析結果仍顯示廠房補強後未能滿足樓板振動加速度小於160 gal之性能設計目標。本研究考慮在加勁補強為前提之下，以速度相依型阻尼器作為輔助，證明可有效提升結構之耐震表現，確保科技廠房在中、小地震下免於設備受損之性能設計目標。

The seismic hazards of high-tech manufacturing fabs are primarily due to insufficient considerations in the earthquake-resistant design, in particular for those containing multiple fabs. Multi-fab structures pile up two or even three clean-room fabs in one site. Excessive lateral deformation of the soft-story causes P-Δ effect and deteriorates the problem further. This not only endangers the structural safety but also integrity of the facilities by amplifying the earthquake floor vibration of the upper fabs. The seismic design specifications of the building code are meant to prevent the structures from collapse under destructive earthquakes. However, the high-tech fabs frequently suffer from significant losses due to facility damage or production interruption in moderate earthquakes﹙Grade 3~5﹚, indicating that the current seismic design does not meet the desired performance, and suggests the need for seismic retrofit. In view of that the high-tech fabs are special in many aspects that the conventional seismic retrofit techniques are not feasible, this study proposes performance-based design criteria and innovative seismic retrofit strategies, and justifies the ideas by analyzing a typical triple-fab structure. Results show that the target structure is seismically vulnerable in its current form, by examining the indexes of ultimate story shear capacity or storey drifts, etc. With the proposed seismic retrofit design of using six space truss structures externally covering the fab in each principal direction, the stiffness and ultimate storey shear capacity of the structure have been effectively enhanced with all the seismic indexes satisfied. Nevertheless, dynamic analysis indicates that the maximum floor acceleration still exceeds the desired 160 gal threshold under moderate earthquakes. With auxiliary velocity-dependent dampers further considered in addition to the stiffness reinforcement, analytical results confirm that the desired seismic performances under moderate earthquakes can be achieved.