Application of Polymer Materials for Base Isolation of Seismic Structures

[[abstract]]隔震技術應用於土木結構已超過二十年，經過實際地震証實為有效之減震方法，不過國內外文獻中有關近斷層區之研究資料卻不多見，尤其是實測資料更是缺乏，因此，近斷層區隔震建物是否能達到如遠域建物般之減震效果，實有必要再進一步加以探討。 本文之研究目的有二：(一)利用國內現有加工與製造技術自行研發滑動式摩擦隔震元件，(二)利用自行研發之隔震支承進行近域隔震之相關研究。為達目的(一)本文採用高分子材料作為摩擦材，採用高分子材料之原因為摩擦係數穩定、抗摩損能力佳及具較低之摩擦係數，並對數種高分子材料進行一系列之力學性能測試，以作為選擇適當隔震材料之依據。另為達目的(二) ，本文採振動台試驗法來探討滑動式隔震系統在近、遠域震波作用下之行為差異，同時，亦提出近域隔震之改進策略。經由實驗及數模擬結果發現，因受近斷層震波具有長週期脈衝之特殊效應所致，滑動隔震結構之基礎最大位移量與上部結構最大加速度值於近斷層震波中有急劇放大之現象，但於隔震系統加入黏滯性增補阻尼則可有效改善近域隔震之安全性與效能。同時，振動台實驗亦驗證乙烯龍高分子材料於滑動式隔震系統應用之可行性及可預測性。[[abstract]]Presently, there are thousands of base isolated structures constructed worldwide. The number of the isolated structures has been increasing rapidly in the last few years primarily due to the maturity of the isolation technology itself and also the awareness of earthquake risk. Some of these constructed cases were even subjected to real-live earthquakes and proved the effectiveness of the technology. However, very few of them were ever subjected to near-fault ground waves that possess very different characteristics and response spectra from those of far-field waves. It is for these reasons that even though the seismic isolation has been proven of being effective for protecting structures from far-field earthquakes, further studies on the safety and effectiveness of near-fault base isolation are still required. The purposes of this thesis are: (1) Develop and fabricate sliding isolators for seismic structures using domestic mechanical workmanship. (2) Study experimentally the performance of sliding isolated systems subjected to near-fault earthquakes. In order to serve the first purpose, friction and mechanical properties of several polymer materials were tested for possible use in the sliding isolators. The reasons of choosing polymer materials are due to their low friction and high resistance to wearing. For verifying the feasibility of the self-developed isolators, a cyclic element test was also conducted. Furthermore, in order to achieve the second purpose of this study, a shaking-table test with the self-developed isolator system subjected to near-fault and far-field ground motions was performed and the results were compared. The experimental results demonstrate that, due to the pulse-like long-period waveform possessed in most near-fault earthquakes, the isolator displacement of the sliding isolated system can be considerably amplified. The test result further shows that a supplement viscous damping is effective in reducing the isolator displacement without much increase on the superstructure acceleration. Finally, the experimental and simulated results together demonstrate that the use of polymer material, such as UPE (Untra High Molecualr Weight Polyethylene), for seismic sliding isolation is feasible and predictable