韌性斜撐之結構消能減震應用

Abstract

挫屈原為一種不穩定的結構行為，若無適當支撐，將導致軸力構件側向不穩定之現象；若經適當設計將其變位控制在引導之方向與範圍內，則因其幾何大變形導致材料極易達到非線性，可在往復運動中產生遲滯消能行為。本研究旨在利用挫屈構件之幾何及材料非線性行為，研發一種稱之為「韌性斜撐」之抗震消能裝置。經由實尺寸挫屈連桿元件之往復荷載測試，掌握其遲滯消能特性。試驗結果顯示，挫屈連桿之力–位移遲滯消能行為屬位移相依型阻尼器，而非對稱配置之挫屈連桿其力學行為會有拉、壓不對稱的現象。以ANSYS非線性應力分析模擬挫屈連桿之元件測試結果顯示，測試結果介於固接與鉸接邊界條件之模擬分析結果之間，顯然目前以螺栓接合之方式無法達到理想化固接條件，實際之材料降伏程度未如預期。儘管如此，經由一系列的耐震性能測試，驗證「韌性斜撐」以其目前之設計型式仍具極佳之結構防震效能。未來在實際應用時，接合處除將螺栓鎖緊外，可考慮於定位完成後輔以焊接之方式加強，以提升挫屈連桿之效能。

Buckling is usually conceived as an unstable structural behavior leading to lateral instability of axially loaded members if not properly supported. However, if a buckled strut is deformed in a guided direction and range, geometrical large lateral deformation of the steel struts in buckling will lead to inelastic behavior of the material and dissipate energy as a consequence. The purpose of this study is to develop a new type of seismic damper, named ductile braces, based on the concept of the geometrical deformation and the inelastic behavior of the material of the buckled strut. The energy-dissipative characteristics of buckled struts are investigated via full-scale component tests under cyclic loads. Experimental results indicate that, the force-displacement relationship of buckled struts exhibits mechanical characteristics of displacement-dependent dampers and the nature non-symmetric behavior of buckled strut is in non-symmetric layout. Numerical prediction of the component test result is further conducted using ANSYS with a non-linear model of the buckled strut. It is observed that the actual boundary condition of the tested buckled strut is in between those of the fixed and hinged conditions. The connection of buckled strut by bolts is not perfectly clamped as ideally, and the yielding behavior of the material is not as significant as expected. However, excellent control performance of the ductile braces in present design has been confirmed via a series of seismic performance tests. In practical application, energy-dissipative capacity of the buckled strut may be improved if the end connection could be welded in addition to bolting to make it closer to a clamped condition.