傾斜滑動支承之數值模擬與實驗驗證

Abstract

隔震系統乃一有效降低由地震力上傳至上部結構剪力之方法，滑動式隔震支承即為一常用之隔震系統類型。前人對於傳統線性滑動式隔震支承─摩擦單擺系統之研究已日趨成熟，然而諸多研究亦逐漸發現摩擦單擺系統由於其回復力與位移呈一線性關係，使得系統具有一特定之隔震頻率。故當地表外力頻率較接近隔震頻率時，則會因共振效應導致隔震效果不彰。因此，近年來隔震技術之研究逐漸轉向非線性隔震系統。在此，本文將探討一種新式非線性滑動式隔震支承墊─傾斜滑動支承(Sloped Sliding-Type Bearing, SSB)，其滑動面為一斜面，並以摩擦力作為其主要消能機制，相較於現行之鉛心橡膠支承或摩擦單擺系統實務設計，當本支承之設計參數─摩擦係數及斜面角度決定時，無需經由迭代便可定出一固定之最大上傳剪力值。有別於傳統之線性系統，本支承具有回復力固定之特性，使其無特定之隔震頻率，故不具共振情形之疑慮。本文首先藉由結構動力學之觀念推導出系統之運動方程式，並整理出模擬之方法。藉由參數分析，以掌握系統反應對參數之敏感度，同時證明本系統之絕對加速度對地表外力之振幅及頻率不敏感，亦表現系統不具特定隔震頻率之特性。由於本系統尚未具有一完整之設計流程，故會提出一套簡易之設計方法以決定設計參數，並藉由一真實隔震案例將本系統與摩擦單擺系統做一隔震行為之比較。模擬結果顯示，當本系統經適當設計下，不論於遠域或近斷層地震下均能有效發揮隔震效果，且不若摩擦單擺系統，本系統於近斷層地震作用下，仍保有不錯之隔震效果。最後，藉由一振動台實驗，對實驗數據與數值模擬結果進行擬合，結果均顯示本系統具有不錯之隔震效果，亦證明本系統於實務應用之可行性且模擬方法對系統之非線性力學行為亦有不錯之掌握度。

Isolation system is an effective way to reduce the earthquake load transmits to superstructure. In addition, sliding isolation bearing is one of the most commonly used isolation systems. The research on a conventional sliding isolation bearing, Friction Pendulum System (FPS), is known thoroughly nowadays. FPS possesses a specific isolation period due to the linear relationship between the restoring force and the isolation displacement. However, more studies have shown that FPS will be ineffective when the earthquake frequency approaches the isolation frequency, which may cause a resonant phenomonen. Therefore, the development of isolation technique has gradually focused on nonlinear isolation system these years. This article will introduce a new nonlinear isolation technique, Sloped Sliding-Type Bearing (SSB), which has a sloped sliding surface and the energy dissipation mechanism is mainly provided by the frictional force. Different from the design procedures of Lead Rubber Bearing (LRB) and FPS, the maximum base shear of SSB can be easily determined without iteration procedures when the two system parameters of SSB, friction coefficient and inclination angle, are decided. Besides, due to the nonlinearity between the restoring force and the isolation displacement of SSB, it does not possess a specific isolation period, which will be able to prevent the resonant phenomonen. This article will first derive the system’s equation of motion and arrange the simulation method. By a parametric study, the sensitivity of the system response toward the system parameters is able to comprehend. Furthermore, the system is proved that it does not possess a specific isolation period, and the absolute acceleration response is insensitive to the amplitude and frequency content of the earthquake. Due to not having a design procedure for SSB, a simple design method is proposed to determine the design parameters. By comparing SSB with FPS using a real isolated structure, SSB is shown to be effective under both far-field and near fault earthquake. Besides, it will show a better result than FPS under the near fault earthquake. Finally, by comparing the simulation results with the shaking table experiment results, the feasibility of SSB is verified and the simulation method is proved to be valid in order to present the dynamic behavior of SSB.