493 publications from this institution
せん断補強筋の定着不良を生じたせん断破壊するRCはりのせん断耐力の評価法の検討を行い,既往の実験結果および,数値解析を用いてその適用性について検討を行った.その結果,検討した評価法により,斜め引張破壊するはり,せん断圧縮破壊するはりのいずれにおいても,定着不良を生じたせん断補強筋の効果を概ね評価できることが確認された.また数値解析により,定着不良領域や付着強度,供試体寸法を解析パラメータとしてせん断破壊挙動の評価を行った.その結果,せん断補強筋の定着不良の影響は,斜め引張破壊するはりでは,引張側の支点近傍において,せん断圧縮破壊するはりでは,引張側の支点近傍,および圧縮側の載荷点近傍において生じたとき,その影響が構造物全体の挙動に対して支配的であることが確認された.
The mutual effect between electric corrosion of reinforcing bars and concrete cracks development caused by corrosion is investigated experimentally and analytically. In the experiment, a salt-water pool was set on the concrete cover of each specimen containing single round rebar for the implementation of electric corrosion. Then the radius losses around the corroded rebars were measured for the corrosion patterns. It was shown that the corrosion rates at various positions around the rebar were related to the crack width nearby. In the analysis, a numerical model based on the rigid body spring method combined with a truss network is proposed to simulate the coupled process by assuming the relation of current efficiency to the crack width. Satisfied agreement with the test results of non-uniform corrosion process and associated crack propagation is obtained using this model, offering a good tool to assist in the employment of the electric corrosion method.
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The structures of PDE-I and PDE-II, inhibitors of cyclic adenosine-3′,5′-monophosphate phosphodiesterase, were established as 3-carbamoyl-l,2-dihydro-4-hydroxy-5-methoxy-3-H-pyrrolo[3,2-e]indole-7-carboxylic acid and its 3-acetyl homologue, by X-ray diffraction study of monomethyl derivatives.
Abstract The influence of residual stress on fatigue crack growth was experimentally and analytically investigated for surface cracks. Fatigue tests were performed on straight pipes of low-carbon steel with a circumferential inner surface crack in laboratory air environment. Some of the test pipes had been subjected to special heat treatments so as to have compressive or tensile residual stresses along inner surface. The results show that the compressive residual stress remarkably suppresses the surface crack growth, while the tensile residual stress does not accelerate the crack growth very much. The crack growth analyses were conducted by the application of power relationship between ΔK and da/dN. The stress intensity factors due to the nonlinear stress field were calculated by the weight function method. The analyses resulted in a confirmation of the behavior of the crack growth observed in the experiments.
A time-dependent structural analysis method under multi actions in consideration of drying shrinkage due to moisture transfer and rebar corrosion due to chloride ions penetration as well as external load actions was developed. The Rigid-Body-Spring Networks (RBSN) model and the truss networks model were used for structural analysis and mass transfer analysis, respectively. In addition, mass transfer through bulk concrete and mass transfer through cracks by setting truss networks on the boundaries of Voronoi particles, was also considered. The developed method was confirmed to simulate well the deterioration process due to mass transfer for initial cracking behavior and ultimate behavior of concrete structures.
Collins らにより提案された修正圧縮場理論を, ひずみ・応力勾配を持つRC断面に拡張した解析手法の開発を行い, せん断補強筋を持たないRC断面の斜めせん断破壊耐荷力を解析的に評価する手法を示した. さらに, せん断耐荷力に及ぼす各種要因の影響を解析的に明らかにすると共に, 解析値が既往の実験回帰式とよく一致することを示した. 特に, RCはりのせん断耐荷力に対する寸法の影響に関しては, 本手法に有効高さを考慮したコンクリートの引張軟化曲線を用いることで, 解析的に評価し得る.
