摘要
對於單柱系統，多維地震力下容易產生彎矩及扭矩的組合載重，減低構件強度與韌性。在地震頻繁的台灣，鋼結構被廣泛地應用在橋梁及房屋的耐震設計上。箱形斷面除了具有較高的強度/質量比、雙軸皆具有較高之抗彎強度，並且具有較開放型斷面高之扭矩強度和側向扭轉挫屈強度等特性。所以此種斷面極適合應用在橋墩設計及柱設計上。
當結構物受強烈地震擾動時，構件在此複雜組合載重作用下，結實斷面仍有可能因此產生局部挫屈而破壞。本篇論文以三組不同斷面參數之結實斷面共二十一個，分別進行軸力、彎矩、扭矩之三維組合載重實驗，以此探討箱型斷面在局部挫屈發生後強度遞減的變化，以及不同斷面參數在反覆荷重下，軸向力對構件斷面挫屈強度及韌性之影響。

ABSTRACT
Steel structures possess high strength and significant ductility thus are effective structural forms for earthquake-resistant designs. In general, structures designed for seismic resistant purposes must develop effective performance when they are subjected to general combined loads, including axial load, bending moment and torsion. This study is focused on the experimental evaluation of seismic performance of hollow steel box sections under combined three-dimensional load. Although hollow steel box sections possess high torsional rigidity and significant flexural strength on both directions, the member’s flexural performance is affected when coupled torsion is applied because twisted sections will alter the flexural characteristics of the sections.
A series of three-dimensional loading tests of hollow steel box members with different aspect ratios were conducted to evaluate the members’ performance under earthquakes. Test results show that the member’s flexural performance is governed by the section’s aspect ratio as well as the magnitude of applied torsion. An interaction equation among axial load, bending moment and torsion is also proposed for design references.

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