Experimental Study on Lateral Buckling Behavior of Weld-Free Built-Up Member Made of H-Sa700a High-Strength Steel

Abstract

Researchers, including the authors of this paper, are striving to develop main members of built-up structures using 780N/mm 2 high-strength steel for a new built-up structural system that prevents buildings from collapsing or being damaged by a severe earthquake (JMA seismic intensity 6.5) and enables rapid functional recovery. The authors propose a weld-free built-up structural member that has a cross section of two channel steel members made of high-strength steel stitched together with bolts. This member has high strength, so that its cross section can be small and it becomes slender, thus creating the possibility of buckling problems.In this study, lateral-torsional buckling tests were conducted on beams with various stitching bolt pitch under uniform bending moment and bending moment gradient along the member axis. Then, a calculation formula for the flexural strength was presented. The values of the flexural strength obtained from calculation were compared with those obtained from the lateral-torsional buckling tests. As the long distance between the supporting points was required for the elastic lateral-torsional buckling tests, a new loading apparatus was fabricated. Precision, supporting conditions, and loading conditions of the apparatus were verified before the experiments.These results show that: 1) Although a twist angle appeared from an early stage, the initial stiffness remained substantially unchanged in the relationship between the bending moment M and the support point twist angle .2) When the bolt pitch was increased, the lateral buckling strength was reduced. The effect produced by the stitching bolt pitch on the lateral buckling strength was relatively large. 3) If the bolt pitch remained within the range from 200mm to 800mm, the calculated values of lateral buckling were almost same as the experimental values for both cases of uniform bending moment and linearly changing bending moment. Keywords：Built-up member, High strength steel, Lateral buckling, Bolt pitch 組立材，高強度鋼，横座屈，綴り材間隔 １．はじめに 激震 ( 計測震度 6.5) に対しても建築物は倒壊，損壊せず，さらに， 速やかな機能復旧を可能とする新しい建築構造システムとして，建 築物の主要部材に 780N/mm 2 級以上の高強度鋼材を使用した主要部 材の開発が，著者等を含めた研究者により行われている 1)-9) ． 材料の高強度化を比較的簡単にするには，接合時に溶接による熱 影響を極力生じさせないことが重要となると考えられる．こうした 背景から本研究では，溶接を用いない部材として，高強度鋼ででき た 2 本の溝形鋼の背を合わせてボルト接合した断面をもつ乾式組立 材を研究対象とする． この乾式組立材は，材が高強度のため作用応力度が高くなること， かつ，断面がスレンダーになることから普通鋼の部材と比べて，座 屈現象が問題になると考えられる． そこで，本研究では，高強度鋼乾式組立材について等曲げ･片曲げ 下の弾性，非弾性横座屈載荷試験を行い，横座屈性状を検証し，綴 り材間隔や加力形式の曲げ耐力に及ぼす影響等の基本性状を実験的 に明らかにする．弾性横座屈試験では，支点間距離が長くなるため， 新規に載荷装置を設け制作したので，その試験装置の支持条件，載 荷条件を含む精度の検定も本実験前に実施したので併せて報告する． また，設計の便を考えて，鋼構造設計規準 10) ，鋼構造限界状態設 計指針・同解説 11) に準じた横座屈耐力算定式を示し，実験値の傾向 を比較，考察する． †本論文の一部は既に文献 1 に報告している． ＊ 広島工業大学工学部建築工学科 准教授・博士 ( 工学 ) ＊＊ 広島工業大学高性能構造システム開発研究センター 研究員・博士 ( 工学 ) ＊＊＊ 広島工業大学工学部建築工学科 教授・Ph.D. ＊＊＊＊ 広島大学大学院建築学専攻 教授・工博

Shaping of Axially Compressed Bipolarly Prestressed Closely Spaced Built-Up Members

“…Zhang and Young [35] presented the results of the experiment and the numerical FEM solution with non-linear analysis for compressed members with a cross-section of pair of spacerless sections Σ. Tamai et al [36] theoretically analyzed and conducted experiments for members made of high-strength steel channel sections with spacers. There are known methods of strengthening com-pressed members of metal structures by increasing the surface area and/or radius of inertia of the crosssection by joining (welding, gluing, mechanical joining) of additional components, such as sheets or sections to obtain a multiple-chord cross-section.…”

“…Zhang and Young [35] presented the results of the experiment and the numerical FEM solution with non-linear analysis for compressed members with a cross-section of pair of spacerless sections Σ. Tamai et al [36] theoretically analyzed and conducted experiments for members made of high-strength steel channel sections with spacers.…”

Proposal of a New Structural Member Using a Recently Developed High Strength Material

“…Thus, the steel is more environmentally friendly and more suitable for mass production compared to other ultra-high strength steel. Several studies have been published on steel structural members using H-SA700 [2]- [4]. In this study, our aim is to propose a new building structural member using H-SA700 steel: a concrete-filled steel tube (CFT) structural column, which is frequently used in high-rise buildings, and to verify its seismic performance.…”