Diaphragm Effects on Ultimate Strength of Horizontally Curved Thin-Walled Box Girders.

平成8年度～平成9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:1.本研究では、中間ダイヤフラムによって補剛された鋼薄肉曲線箱桁の終局強度及び非線形挙動を評価することのできる新しい合理的な解析手法を提案した. 本解析手法では,有限変位の影響,曲げとサンブナンのねじりによる組み合わせ応力を受ける材料の降伏の影響,ひずみ反転によって生じる除荷の影響,断面内及び桁軸線に沿った降伏域の進展,除荷域及び再載荷域の影響,及び溶接による残留応力等の影響が,非線形有限要素法に基づく三次元骨組構造解析において全て考慮されている.更に,構成鋼曲板要素の局部座屈の影響,応力勾配の影響及びずり変形の影響が非線形解析の中に取り込まれている. 2.初期たわみ及び残留応力を有する構成鋼曲板要素に面内圧縮力と曲げが作用する場合について,構成鋼曲板要素をアイソパラメトリックシェル要素でモデル化し,強度に影響を及ぼすと考えられる因子を種々変化させて弾塑性有限変位解析を行った.そのパラメトリック解析によって得られた結果に基づいて,構成鋼曲板要素の局部座屈の影響を考慮した構成式モデル(修正応力－ひずみ関係)を提案した. 3.中間ダイアフラムの配置数の異なる鋼曲線箱桁の大型模型桁2体について,耐荷力実験を行った.終局強度について本解析結果と実験結果は良い一致が見られた. 4.構成鋼曲板要素の局部座屈の影響を考慮した構成式(修正応力-ひずみ関係)を用いた終局強度解析結果は、実験結果との比較により,局部座屈発生荷重及び発生領域を比較的良く評価している. 5.曲線箱桁の終局強度に及ぼすずり変形の影響は,ずり変形によって生じたひずみを付加ひずみとして三次元非線形骨組構造解析過程の初期ひずみ場に組み込むことによって,評価することができる.要約(欧文):1.An analytical procedure is proposed to predict ultimate strength and nonlinear behavior of thin-walled, welded steel box-girder curved in plan and stiffened by intermediate interia diaphragms. In the approach, the effects of finite deformation, yielding of material under combined bending and St. Venant's torsioning, unloading caused by strain reversal, spreads of yielding, unloading and reloading zones in the cross-sections and along the gider, and residual stress due to welding are all taken into account in flexure analysis by nonlinear finite element method. How to consider local buckling of component plates and distortional warping in the nonlinear flexure analysis is also proposed. 2.The comparison of the analytical with the experimental results on the ultimate strength was judged satisfactory. 3.The local buckling of component plates can be evaluated by the proposed model of stress-strain curve allowing for plate buckling as shown in Fig. 3 and this model can be incorporated into the nonlinear flexure analysis. 4.The breadth of buckling plate can be taken to be width of the compressive flanges of the cross-section of the girder and equal to the depth of the compressive zone of the web plate. 5.The constitutive model predicted the local buckling compared well with the experimental results. 6.The effect of distortional warping can be simulated in an incremental way at the initial strain-state in the nonlinear flexure analysis, where the strain increments for distortional warping are applied in a step-by-step procedure until an external distortional moment is reached. 7.From lower level of loading, bowing deformation which is characterized by covnex form was experimentally confirmed at the compressive part web plate. This phenomenon might be considered to be that the cross-sectional part in compression in the curved girder acts as so-called nonlinear behavior of column with initial crookedness. The above results on the model tests in the conclusions are based on a limited amount of experimental work. Research is clearly needed on the experimental program of larger amount of the model-tests. Though some verification is necessary if the proposed constitutive models allowing for local plate-buckling is to be applied to the girder also stiffened by horizontal and/or vertical stiffeners, the assumed breadth of buckling plate is generally conservative.未公開：P.52以降(別刷論文のため