封閉式面內撓曲阻尼器之設計與試驗

Abstract

本研究沿襲面內撓曲卵形阻尼器之優點，提出巢型面內撓曲卵形阻尼器，透過增加內環圈的方式提升阻尼器承載容量，讓材料效能發揮極致，兼顧抗震與環保目標。 元件試驗結果顯示，巢型阻尼器較諸同尺寸的前世代有更高的強度與消能能力，其力學行為主要呈現兩階段。初始階段為雙環並聯作用，勁度與出力相對較大，內環因應力較高會先行破壞，然後進入第二階段，由外環持續承載變形直至極限容量為止。第二階段的力學特徵，包括極限位移及降伏後勁度，與對應之單環阻尼器十分接近，因此其設計方法可以直接套用。在往復載重測試的數值模擬部分，由於ANSYS無法自動預測巢型阻尼器在內環圈破壞後之行為，本研究提出兩階段分析模式，以完整之巢型阻尼器模型與對應之唯內環(inner-loop only)模型在相同載重條件下平行分析，並根據試驗結果決定內圈破壞時所對應的臨界位移，凡測試振幅超過臨界位移的部分皆扣除內環的計算結果，模擬分析所得結果與試驗相當契合。此外，本研究發現面內撓曲卵形阻尼器元件測試所得力學性能指標與設計尺寸相關之無因次參數滿足二次曲線變化趨勢，透過曲線擬合所建立之經驗公式可供未來設計時參考，有助於實現面內撓曲型阻尼器之實用化目標。最後，本研究完成兩組圓拱型阻尼器之元件測試以期驗證先前提出之彎–剪耦合曲梁彈–塑性應力分析理論應用於面內撓曲型阻尼器是否可行。分析結果與試驗差異極大，並不可靠，推測可能曲梁模型並不適用於封閉式環形結構，抑或彈–塑性應力分析的數值計算程式仍存在盲點，相關問題仍待進一步探索。

In this study, the Nested in-Plane Oval Damper (Ni-POD) is proposed by adding to its ancestor, the i-POD, an inner loop to increase its loading capacity. While reserving the merits of i-POD in a closed-form, the descendant improves the efficiency of material utilization in a way to simultaneously meet the desired seismic performance and environmental concerns. Component tests of the dampers indicate that the Ni-POD exhibits higher strength and energy dissipation capacity than those of the previous design, and its mechanical behavior appears primarily in two phases. In the initial phase with both inner and outer loops working in parallel, the damper presents higher stiffness and strength. With higher stress developed, the inner loop of the Ni-POD will be damaged first and enter the second phase where the outer loop continues to sustain loading and deform until the ultimate state. Mechanical characteristics such as ultimate displacement and post-yielding stiffness of the damper at the second phase are closely similar to those of its i-POD counterpart, and therefore the design method for i-POD can be loaned directly. As far as numerical simulation of the cyclic loading tests is concerned, recognizing that ANSYS is unable to discriminate the behavior of the nested damper after damage of the inner loop, a two-stage approach is proposed in this study by analyzing the full model of the nested-type damper and the corresponding inner-loop-only counterpart in parallel under the same loading condition. With the critical displacement corresponding to damage of the inner loop predetermined from the test results, the resisting forces of the full model are deducted from those of the inner-loop-only model as long as the testing amplitude exceeds the critical displacement. Simulation results proved to be adequate. In addition, it is found that mechanical characteristics of the i-POD are related to the dimensionless parameter defined from its design dimensions in a trend of quadratic curves. The empirical formula derived from curve-fitting are eligible for future design references and help in making the practical use of the in-plane flexural dampers a reality. Lastly, component tests of two circular dampers have been conducted to verify the feasibility of the elasto-plastic stress analysis theory for curved beams under bending and shear coupling developed earlier for analyzing the in-plane flexural dampers. The numerical results so obtained, however, deviate from the tests in a great extent and thus considered unreliable. It might be that the curved-beam model is not adequate for structures in a closed-form, or the computer code for elasto-plastic stress analysis contains unfound errors. This requires further investigation.