全鋼型挫屈束制支撐局部挫屈研究

Abstract

摘 要 關鍵字:全鋼型、挫屈束制支撐、局部挫屈、全鋼型挫屈束制支撐、 局部挫屈研究 挫屈束制支撐（BRB）的應用已逐漸受到重視，但在因應BRB的使用快速成長同時，仍有必要研發能有效防治挫屈且更有經濟效益、更具空間配置優勢之全鋼型BRB構件的設計與製造方法。本研究目的主要在發展新全鋼型挫屈束制支撐，並提出局部挫屈強度計算公式供設計者參考使用，使BRB方便設計，並使其有更佳之經濟與空間配置之優勢。 本研究的項目主要包括：(1)研發新型全鋼型挫屈束制支撐構件並探討其力學行為。(2)藉由BRB構件試驗，推導BRB所需的束制鋼板強度需求估算公式與核心寬厚比b/t、束制鋼板高度h以及束制鋼板厚度a的關係。(3)薄化新型全鋼型挫屈束制支撐構件的研究。 試驗結果顯示新開發的全鋼型挫屈束制支撐在較大變形前尚具穩定的遲滯反應。所推導之BRB束制鋼板強度需求估算公式，以A572 Gr.50核心鋼板材料為例， ，束制鋼板強度需求與其高度成反比，相較於前人所提出之混凝土強度需求與厚度成正比之理論較適用於工程應用，而四組試體試驗結果可看出H200a14 、H200a18 、H200a22、H175a30皆因摩擦力過大引起拉壓差過大而發生局部挫屈，但從試體反應中可看出H200a18、 H175a30反應一致與設計之強度相同，而H200a22反應最好與預期大致相同，因此可見設計此種新全鋼型挫屈束制支撐時之設計邏輯可能正確。因此本研究提出之全鋼型BRB防止強軸挫屈之設計公式可供之後設計全鋼型構件時可以參考。

Key words: All Metal、Buckling Restrained Brace、Local Buckling、All Metal Buckling Restrained Brace、BRBs After lots of studies and tests in the laboratory, buckling restrained braces (BRBs) have played an important role in seismic building applications in recent years. However, in order to deal with the situation that the proportion of using steel in Taiwan is much less than foreign countries. Developing all-metal BRBs that can effectively prevent local buckling and save cost is necessary. The objectives of this study include: (1) developing the new type of all-metal BRB; (2) investigating the strength requirement for the confining steel rib intensity ; (3) sliming down the new type of all-metal BRB . Test results showed that the new type of all-metal BRB is feasible procedure to fabricate BRBs. Tests confirmed that the confinement requirements developed based on the compressive stiffness of the steel rib are not sufficient in the slim-lined BRBs. Based on the flexural mode, it is found that the required stiffness of the steel rib is a function of core steel plate width to thickness ratio (b/t) and width to confining rib height ratio (b/h). For example: if the brace core is made from ASTM A572 Grade 50 steel, the necessary steel rib a has to greater than 0.004424(b/h)3(b/t)b. In this formula, the requirement of steel rib is proportional to (1/h)3 . H200a18 and H175a30 are designed by same safety factor and they failed at the same time. H200a22 has the best performance in four specimens. This result shows that the design logic is not bad . On the other hand, preventing the strong axis buckling formula is provided. However, the construction space in Taiwan is limited. The space braces are used in buildings is very important. Sliming down the brace and increasing the proportion of using steel in Taiwan can improve designer and user using steel.