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Title :折れ板断面鋼桁の強度評価に関する研究
Title alternative :A Study on Ultimate Strength of Folded Steel Plate Girders.
Authors :有住, 康則
矢吹, 哲哉
山田, 義智
Authors alternative :Arizumi, Yasunori
Yabuki, Tetsuya
Yamada, Yoshitomo
Issue Date :Mar-2004
Abstract :平成14年度~平成15年度科学研究費補助金(基盤研究(C)(2))研究成果報告書
研究概要:本研究では,橋梁構造物の使用を目的とした新しい桁構造形式の一つとして,折れ板断面鋼桁を提案し,その折れ板が桁の強度特性に及ぼす影響について検討を行った.折れ板断面桁は,折れ線上に光と影のラインを与え,桁高を低く見せる効果が有り,景観上優れた構造部材になり得るものと考えられる.更に,構造上の特性として,折れ鋼板材に力学線が存在することによる側方への補剛効果が期待される. 本研究では,まず初めに,折れ板断面鋼桁について模型桁を製作し,耐荷力実験を行った.耐荷力実験により,折れ角θ=5°の折れ板断面桁の曲げ耐荷力は,I形断面鋼鈑桁のそれを上回り,ウェブ断面の「折れ」による補剛効果が期待できることが明らかとなった.次ぎに,面内曲げを受ける折れ板断面鋼桁について,その強度に影響を及ぼすと考えられる因子を種々変化させ,パラメトリック解析を行い,構造諸元等が折れ板断面鋼桁の耐荷力に及ぼす影響について検討を行った.更に,パラメトリック解析によって得られた座屈変形モード図及び耐荷力曲線等に基づいて,折れ板断面を有する鋼桁の崩壊様式の分類を行った.その結果得られた主な結論は以下のようである.(1)折れ板断面桁の曲げ耐荷力は,折れ角がθ<10°の区間では,折れ角が大きくなるに従って,増加する.(2)折れ角θ=5°の折れ板断面桁の曲げ耐荷力は,I形断面桁のそれを上回り,その差は,細長比パラメータが大きくなるに従って,増大する. (3)残留応力度を有する折れ板断面桁の曲げ耐荷力は,部材細長比パラメータが大きくなるに従って,残留応力度の無い桁と比較して僅かではあるが低下する傾向がある.(4)折れ板断面桁の崩壊形式は,桁全体の横倒れ座屈崩壊,圧縮フランジのねじれ座屈崩壊(局部座屈崩壊)及びそれらが連成した座屈崩壊(連成座屈崩壊)の三つの基本的崩壊様式であることが確認された.
要約(欧文):In this research, the stability strength of steel plate girders assembled by folded web plates and flange plates under equal end moments about their strong axis are investigated. This paper compares experimental buckling resistances of I-shaped steel girders having unfolded web plates with those of the folded plates. The tests show that the buckling resistances of the girders with folded webs can be higher than those of conventional I-shaped girders. To analyze the ultimate carrying capacity of folded steel plate girders with initial imperfections due to initial deflections and residual stresses caused by welding, an elasto-plastic finite element analysis was used based on geometric and material non-linear isoparametric shell elements. It was assumed that material constitutive relationship follows the Von Mises yield criterion and the Plandtl-Reuss plastic flow rule, combined with material and geometric invariance law, strain hardening law and linear unloading law. The non-linear behavior is solved numerically according to both the Newton-Raphson and the Updated Lagrangian formulations where the displacements increase step-by-step. Actual measurements were used for the initial imperfections of residual stress and initial deflection. The ratio of the test results to analysis results for the ultimate carrying capacity is between 0.98 and 1.028, with an average of 0.996. Thus, it may be concluded that this analysis is quite accurate in evaluating the ultimate load carrying capacity of folded steel plate girders. A parametric study using nonlinear finite element approach is also conducted to evaluate the effects of folded angle, width thickness ratio of plate, slenderness ratio of beam, residual stress and yield stress ratio on the ultimate strength of folded steel plate girders. This paper also presents the instability classification of folded steel plate girders based on the parametric study. Three buckling modes are confirmed, i.e., an inelastic lateral-torsional buckling mode, an inelastic local buckling mode and an interactive buckling of the two. From a parametric study, it appears that the effects of folded web element on the ultimate strength of folded steel plate girders.
Type Local :研究報告書
Publisher :有住康則
URI :http://hdl.handle.net/20.500.12000/13847
Appears in Collections:Research Report (Faculty of Engineering)

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