傾斜滑動支承應用於柔性結構之數值分析

Abstract

隔震系統是利用降低地表加速度上傳至結構的方法。常見傳統的線性隔震系統，如鉛心橡膠支承與摩擦單擺支承等研究已日趨成熟，且在過去十年以來被廣泛應用在各式結構物中。然而此類的傳統隔震支承回復力與位移呈現線性關係，使得該系統具有一特定的隔震頻率。為了改善傳統隔震系統的缺點，本文將介紹一種新式非線性隔震支承─傾斜滑動支承(Sloped Sliding-type Bearing, SSB)。傾斜滑動支承以上下 V 型斜面的支承板與中間的摩擦子所組成，其最主要的特色係上傳加速度為定值，且透過斜面之摩擦力作為主要能量消散機制。 本文延續前人在傾斜滑動支承於剛體受雙向地表擾動之研究，將此研究延伸至傾斜滑動支承應用於柔性結構的數值模型建立。藉由一振動台的實驗，將實驗數據與數值模擬結果進行比較，結果均顯示此數值模擬方法可掌握到傾斜滑動支承之非線性的力學行為，且本系統應用於柔性結構亦具有不錯的隔震效果。 此外，將傾斜滑動支承與先前的傾斜滾動支承研究進行參數分析。傾斜滾動支承中心處的曲率半徑對於上傳加速度的頻率內涵與相同設計條件下的傾斜滑動支承並無太多的差異。同時，以較小的摩擦力設計傾斜滑動支承時，會造成此系統在斜面上的位移反應過大，進而影響在長週期範圍的頻率內涵。 透過傾斜滑動支承應用在柔性結構的數值參數分析，得知不論建物的自然振動頻率為何，其上傳的加速度皆能維持在一定範圍內。經過建物上傳至頂樓的加速度反應也不致有過大的放大效應，亦能將其控制在可接受的範圍。

Isolation system is an effective way to reduce the earthquake load transmitting to superstructure. The research on the common traditional linear isolation systems such as Lead Rubber Isolation Bearing and Friction Pendulum Bearing has become increasingly mature and has been widely used in various structures in the past decades. However, these isolation system possess a specific isolation period due to the linear relationship between the restoring force and the isolation displacement. In order to avoid the shortcoming of tranditional isolation systems, an innovative nonlinear isolation system called Sloped Sliding-type isolation Bearing is introduced in this paper. The isolation bearing is comprised of an upper bearing plate, a lower bearing plate and a slider sandwiched between two plates. It features a constant transmitted horizontal acceleration and friction-based energy dissipation mechanism. Based on the previous study on sloped sliding-type isolation bearing supporting a rigid body subjected to a biaxial excitation, this study develops a numerical model of sloped sliding-type isolation bearing supporting a flexible structure. By comparing the simulation results with the shaking table experimental data, the feasibility of numerical model of SSB appied on flexible structure is verified and simulation method is proved to be valid in order to present the nonlinear behavior of SSB. Foucs on the parameter analysis of SSB and SRB which previously studied. The curvature radius on the center of two sloped sliding surface has no influence on frequency content of SRB. Regardless SSB or SRB, the freauency content of superstructure will be affected by friction force. No matter what the natural frequency of the structure is, the acceleration response on the isolator can be controlled within a certain reange and the roof acceleration is also smaller than the ground motion.