Experiment and analysis of isolated structure with variable curvature sliding isolation

[[abstract]]傳統滑動隔震支承(如摩擦單擺支承)屬於週期固定之長週期結構，因此極易與近斷層震波中之長週期脈衝產生共振，使隔震效果不彰。爲改善此一問題，本文採用具有變曲率滑動面之隔震支承，以探討此類支承於近域震波中之減震效果。由於變曲率支承並無固定隔震週期，因此不易與震波產生共振反應。本文考慮以下二類變曲率隔震支承：一為錐形摩擦單擺支承 (Conical Friction Pendulum Isolator)；另一為變頻式摩擦單擺支承(Variable Frequency Pendulum System)。 本文針對上述變曲率支承進行一系列之理論與實驗研究。其中，理論研究部分有：(1)推導通用之變曲率支承遲滯迴圈公式，此一公式適用於任何曲面之滑動隔震元件。(2)探討變曲率隔震元件之最佳設計用參數，以方便未來工程之實務應用。(3)比較各類變曲率隔震支承之動力行為與減震效果。另則，在實驗研究部分如下：(1)自製變曲率隔震支承並進行元件測試：為實現上述變曲率隔震構想，本文自行研製變曲率滑動支承，且採用具極佳延展性之高分子聚合物作為支承摩擦子之摩擦材料。使摩擦子之摩擦面可隨曲面之曲率而變化，克服變曲率支承摩擦子可能產生之應力集中問題。元件實驗所得之遲滯圈與理論公式預估者相符，因此証實變曲面支承之可行性。(2)進行變曲率隔震結構之震動台實驗：利用前述自行研發之變曲率支承進行動態測試，實驗結果顯示變曲率隔震元件對近域震波具有良好之隔震效果。最後經由實驗及理論分析相互比對，証實本文分析方法確可預測變曲面滑動支承之隔震行為。[[abstract]]In order to eliminate low-frequency resonance that usually occurs in a FPS system under a long-period pulse-like near-fault earthquake, sliding isolators with variable curvature (SIVC) were investigated in this paper. Since the isolation frequency of a SIVC is not a constant, it will not resonate with near-fault earthquakes, which have rich low-frequency components. Two types of SIVC were considered in this study, namely, Variable-Frequency Pendulum Isolator (VFPI) and Conical Friction Pendulum Isolator (CFPI). Both theoretical and experimental studies were carried out in this work. The theoretical study includes: (1) derivation of a general formula that describes the hysteretic behavior of a sliding isolator with any given geometric surface function. (2) Parametric study on the optimal design parameters of VPFI and CFPI, for engineering application. (3) Comparison of seismic performance of various sliding isolators with variable curvature. On the other hand, in the experimental study, two tasks have been accomplished: (1) several VFPI and CFPI were fabricated and an isolator cyclic test was conducted. In-filled polymer materials were used as the friction material of the slider. Since polymer materials have excellent ductility, the contacting surface of the slider is transformable, according to the shape of the sliding surface. The result of the isolator test verifies the previously derived formula for isolator hysteretic behavior. (2) A shaking table test for a structure with CFPI was also conducted, in order to verify the theoretical response. It is shown that the experimental data of shaking table test matched well with the theoretical one. This concludes that sliding isolation with variable curvature is a feasible technology, and its behavior can be predicted by the proposed analysis method