結構自體調諧質量阻尼系統之振動台試驗研究

Abstract

近年來使用隔震技術之建築物數量快速成長，但一般基礎隔震在基礎施工以及和相鄰建築物相接處理上較為繁瑣，因此中間層隔震（Mid-Story Isolation System）應用日益廣泛，然而中間層隔震之結構動力特性不同於基礎隔震，高模態參與比例較高，造成隔震層下部結構反應放大。而調諧質量阻尼器（Tuned Mass Damper）是常見於高樓結構的減震裝置，利用一附加在主結構上的質量，配合特定頻率比與阻尼比之設計，在結構受外力擾動時消散能量，進而降低主結構反應，一般常用於控制風力造成的振動。 本研究欲結合中間層隔震及調諧質量阻尼器概念，提出一新型結構系統，稱之為結構自體調諧質量阻尼系統（Building Mass Damper System），結合兩種系統之優點，同時控制隔震層上下部結構之受震反應。在此系統中，將上部結構作為調諧質量，其勁度和阻尼則由隔震層的支承墊和阻尼器提供。以一三自由度模型模擬BMD系統，分別代表上部結構、隔震層和下部結構，進行不同上下部結構質量比對於系統參數之敏感度分析，其結果為試驗設計參考依據。 本文將規劃一振動台試驗，驗證此系統之有效性及變異各參數對系統反應之影響。根據上述參數分析結果選定一八層縮尺鋼構架設計為BMD系統，並設計一系列變異各系統參數之試驗構架，考慮不同地震特性，測試構架於單軸向地震力作用下之受震反應。配置一套完整量測機制，將蒐集後數據使用轉換函數、FFT、SRIM等系統識別方法分析試驗結果，分析得試驗構架的頻率、阻尼比、模態振形、模態參與係數等參數，並使用SAP2000軟體建立數值模型與試驗結果互相比較。最後，藉由理論推導及試驗結果，瞭解BMD系統耐震行為及各參數變異下對系統受震反應的影響，並計算實際結果和原始設計參數差異，探討試驗誤差原因，進而提出最佳化構架之設計。

The effectiveness of mid-isolation systems in reducing the seismic demand of the superstructure above the isolation layer had been proved in many previous researches. It was also indicated, however, the response of substructure under the isolation layer may be enlarged due to the flexibility of the substructure and the contribution of the higher modes. On the contrary, the adoption of tuned mass damper (TMD) design can effectively control the dynamic response of the main structure (or substructure) induced by wind or seismic loads. Therefore, the concept of tuned mass damper system is incorporated into mid-story isolated design to control the seismic response of both superstructure and substructure, which is building mass damper (BMD) design. In BMD design, the superstructure above the isolation layer can serve as a tuned absorber mass whose stiffness and damping are provided by the isolation system composed of elastomeric bearings and additional dampers. Therefore, the advantages of conventional tuned mass damper and mid-story isolation systems can be integrated in the BMD design. This paper presents a shaking table test scheme, in order to verify the effectiveness of the BMD system with the design parameters deduced in the previous studies on the seismic protection of a building structure, the response of a series of specimens with optimum and non-optimum design parameters under different excitations had been measured. After the test, some system identification methods were performed to acquire the modal information such as frequency, damping ratio and modal participation mass ratio of test specimens. Based on the above information, numerical models which stimulate the test results can be established and the numerical analysis results and experimental results can be compared. Finally, in combination of the parameter analysis and experimental results, the behavior of BMD system and the influence of each parameters of interest on the seismic responses were realized. Also, the factors which caused errors in the experiment can be discussed and a modified optimal numerical model was proposed.