コンクリート構造物が不安定になる領域に対する理論的検討を行うとともに, 有限要素解析によりRCはりのポストピーク挙動に対する解析的検討を行った. その結果, 構造物の不安定を定義する構造特異点のうち特に, bifurcation point がRCはりの破壊に密接な関係があり, bifurcation point 後の bifurcation path を選択することで構造物が破壊に至る可能性を解析的に示した. 本手法により, RCはりのポストピーク挙動あるいは破壊時の挙動を一貫した数値理論で再現することを可能にした.
The typical failure modes of a bolt-nut assembly subjected to static overload are breaking at the bolt shank (free thread portion) and stripping of the bolt or nut mating threads. Standard nuts specified in ISO 898-2 and ISO 898-6 are designed based on "Alexander Theory" to avoid stripping failure mode by controlling the nut height. However, the applicability of the Alexander Theory has not been confirmed for bolt and nut (or screw and tapped hole) assemblies whose specifications are not perfectly conforming to ISO standards. This study deals with the loadability for such types of bolt-nut assemblies. Experimental investigation for critical nut height using staircase method and elastic-plastic FEM analysis considering face-to-face contact at mating threads and bearing faces are performed to establish the design rules for predicting the failure mode and the failure load. The results show that the stripping strength can be predicted with good accuracy by using the load and the shear area of individual mating threads and the shear strength of the material, and the Alexander Theory can be applicable for bolt and non-standardized nut assemblies by modifying the factor for nut dilation.
本研究では，鉄筋補強した繊維補強セメント系複合材料の引張破壊を，繊維1本1本をモデル化した解析手法を用いて検証した．ひずみ軟化型とひずみ硬化型の繊維補強セメント系複合材料を対象に，繊維の混入率，鉄筋比，鉄筋－マトリクス間の付着特性，ならびに繊維の分布状態を変動させた解析を行い，引張破壊挙動を検証した結果，各パラメータの組合せによっては鉄筋降伏後にひび割れが局所化して進展する場合があることを確認した．そして，そのメカニズムとそれを抑制する方策を，架橋力に着目することによって明らかにした．ひずみ硬化型の材料においては，繊維分布のばらつきに伴う材料不均一性によって力学特性が低下した場合でも，鉄筋との併用により終局ひずみを向上できることを解析から提示した．
Cracking behavior due to rebar corrosion for concrete specimen with single rebar was evaluated analytically. The evaluation was performed by comparing with results of the electric corrosion test. Three-dimensional RigidBody-Spring-Method (RBSM) with three phase material corrosion expansion model was applied to simulate internal cracking patterns and surface crack width propagation. The effect of rebar local corrosion and penetration of corrosion products into cracks during the corrosion process were investigated and cracking behavior due to rebar corrosion was evaluated quantitatively.
Summary A free air CO 2 enrichment (FACE) system in which rice was grown under elevated CO 2 conditions by releasing high pressure, pure CO 2 from emission tubes surrounding the crop is described here. Unlike other (FACE) systems, blowers were not used to mix the emitted CO 2 with the surrounding air. Four 12‐m diameter emission structures (‘rings’) were constructed. Monitoring and control of CO 2 emission was carried out by a series of CO 2 and wind sensors, data loggers, controllers and valves. The target CO 2 concentration ([CO 2 ]) was 200 µmol mol −1 above ambient; enrichment was carried out continuously. Temporal [CO 2 ] control was adequate, with c . 60 and 90% of the air samples at ring center having a [CO 2 ] within 10 and 20% of the target, respectively. Spatial [CO 2 ] distribution was also adequate, with 60% of the ring area having a [CO 2 ] that was within 15% of that at the center. At comparable wind speeds, the pure CO 2 injection FACE system described here had a similar performance to that of FACE designs that use blowers to mix the injected CO 2 with the air.
When a reinforced concrete (RC) member is subjected to cyclic loading, the shear failure after flexural yielding of tension reinforcing bars (called as shear failure after flexural yielding in this study) is often observed at a small deformation, although it ordinarily suffers flexural failure and shows good deformation ability under monotonic loading.This study presented a numerical method to quantitatively evaluate shear strength degradation of RC member utilizing three dimensional Rigid-Body-Spring-Model (3-D RBSM).The behaviors of a RC column subjected to cyclic loading and repeated loading on one side were simulated by 3-D RBSM, and the behaviors of shear strength degradations were quantitatively evaluated.As a consequence, the different degradation rate of shear strength between cyclic loading and repeated loading on one side was clarified, and the reasonability of the numerical method was confirmed by comparing numerical shear strength degradation curve with previously statistically proposed degradation curves based on the test results.
Sulphostin, a novel dipeptidyl peptidase IV (DPP-IV) inhibitor, was isolated from the culture broth of Streptomyces sp. MK251-43F3. Determination of the absolute configurations of two asymmetric atoms using the natural product was not achieved due to the small amount of the compound obtained. We synthesized four possible stereoisomers of sulphostin from d- or l-ornithine and compared their physicochemical and biological data to naturally isolated sulphostin. As a result, the absolute configurations at C-3 and the phosphorus atom of sulphostin were determined to be S and R, respectively, by X-ray crystallography. Synthetic sulphostin and its C-3 epimer have strong inhibitory activities against DPP-IV, IC50 values of which are 6.0 and 8.9 ng/mL, respectively. Thus it appears that the configuration of the phosphorus atom is primarily responsible for the activity; in contrast, the configuration of C-3 does not appear to affect the activity.
