可更換核心板之挫屈束制消能支撐耐震實驗與有限元素分析

Abstract

本研究主要探討可更換核心之挫屈束制消能支撐耐震行為與有限元素分析，其中共進行四組實尺寸之挫屈束制消能支撐試驗，而試體均由一組核心單元與兩組圍束單元利用螺栓栓接組合而成，因此試體組裝及拆解過程簡易。四組試體中，其中ㄧ組為了求取挫屈束制消能支撐整體實驗挫屈強度，因此韌性容量未能滿足AISC(2005)耐震規範規定，而另外三組設計得宜之試體於試驗後其行為良好，且韌性容量均滿足AISC(2005)耐震規範規定。本研究並利用非線性有線元素分析程式ABAQUS(2003)，可預測試體之極限壓力強度及挫屈行為，並建立18組變化各項參數之模型以探討其可能破壞模式，而經由實驗與有限元素分析之結果，提出可更換核心板之挫屈束制消能支撐之設計方法。

This research presents the results from component tests and finite element analyses on a proposed type of a steel buckling-restrained brace (BRB) with a replaceable core plate. The proposed BRB is composed of two components: (1) a steel core element that carries the entire axial forces during both tension and compression and (2) two restraining elements that are bolted to prevent the core from buckling in compression. Since the two restraining elements are easily assembled and separated, the steel core can be replaced if it is damaged after cyclic loads. Four full-scale BRB subassemblages were tested based on AISC (2005) seismic provisions to investigate inelastic cyclic deformation capabilities and verify theoretical predictions on the structural stability of the braces. Test results indicated that three proposed BRBs with sufficient out-of-plane restraining stably sustain severe inelastic axial strain reversals up to 2.1%, and develop a cumulative plastic ductility capacity much higher than that specified by AISC (2005). However, one BRB, designed with inadequate out-of-plane restraining, experienced global flexural buckling after a large number of inelastic reversals. Non-linear finite element analysis conducted for each BRB showed that the ultimate compressive strength and post-buckling behavior could be predicted if the initial geometric imperfections were considered in the model. A parametric study was also conducted for 18 BRBs using the non-linear finite element computer program ABAQUS to further verify the effectiveness of the restraining element and number of bolts to prevent the core from global and local buckling. A design procedure for the proposed BRB was provided based on the test and analytical results.