Analysis and Experiment of Base Isolation Using Rocking Bearings

[[abstract]]隔震技術雖已被証實為實用之耐震技術，不過，傳統隔震支承仍有其應用之限制性，值得改進。本文針對搖擺式隔震支承進行理論與實驗研究，期能改進現有隔震支承之效能。本文研究目的有二：(1)提出定曲率形式之搖擺隔震支承，又稱為偏心式搖擺支承 (Eccentric Rocking Bearing)，簡稱ERB。此種支承之隔震行為近似於傳統之滑動摩擦支承，不過，其等效水平摩擦係數可透過支承本身之幾何參數輕易的加以調整。因此，即可增加支承摩擦材之選擇性，使得支承之水平摩擦係數設計變得更易精確施行。(2)提出變曲率形式之搖擺隔震支承，又稱多項式搖擺隔震支承 (Polynomial Rocking Bearing)，簡稱PRB。主要為改善傳統隔震支承在近斷層震波中易產生低頻之似共振現象，以提高隔震之安全性與效能。PRB支承之搖擺曲面係由六次方多項式所構成，因此其遲滯迴圈具有兩種不同功能之軟化與硬化區段。其中軟化段係用以降低結構之加速度反應，而硬化段則用以抑制隔震支承在近域震波中所可能產生之鉅大位移量。 本文除建立ERB與PRB支承之理論公式並進行理論分析外，更進行ERB與PRB隔震系統之振動台實驗，以驗證此二種支承之實用性。實驗結果顯示，本文所建立之理論公式確實可正確模擬ERB與PRB隔震系統之動力行為，同時亦証實ERB與PRB作為隔震支承的可行性。[[abstract]]In order to improve the effectiveness and safety of seismic isolation this thesis the possible usage of a new type of isolators called rocking bearings for seismic isolation There are two objectives in this study (1) To investigate an eccentric rocking bearing (ERB) which has a spherical rocking surface with constant curvature When the isolator displacement is small the ERB is similar to a conventional sliding bearing with a linear resilient force However the equivalent horizontal friction coefficient of the ERB can be easily adjusted by a geometric parameter As a result the design and manufacture about the bearing friction coefficient can be more precise (2) To investigate a polynomial rocking bearing (PRB) whose rocking surface has a variable curvature and is defined by a six-order polynomial function The PRB aims to improve the near-fault seismic isolation and to prevent the low-frequency resonant effect that usually occurs in an isolation system subjected to a near-fault earthquake with a long-period velocity pulse Both theoretical and experimental studies were conducted for ERB and PRB bearings in this thesis Shaking table test was performed on a steel frame isolated by the ERB and PRB respectively in order to verify the theoretical responses which were simulated by the proposed numerical methods The study shows that the theoretical and experimental results are consistent This shows the feasibility of the proposed rocking bearings and derived theoretical basis for the bearing