Background: The trimethadione (TMO) tolerance test was performed to evaluate its usefulness in the assessment of hepatic functional reserve in patients with biliary atresia. Method: Nineteen patients with biliary atresia after hepatic portoenterostomy (age range: 2 months to 25 years; sex: 6 males and 13 females) were studied. The study was performed in the morning after a 12-h fast. TMO was given orally, at a dose of 4 mg/kg, with 5 mL of 5% glucose 2 h before breakfast. Blood samples (0·5 mL) were collected to determine serum TMO and dimethadione (DMO), a metabolite of TMO, levels 4 h after the administration of TMO. TMO and DMO were measured by a gas-liquid chromatographic method. Results: A higher total bilirubin level (over 1 mg/dL) in patients with jaundice was reflected in the smaller serum DMO/TMO ratio 4 h after the oral administration of TMO. In addition, these patients with total bilirubin levels of 1 mg/dL or less had a significantly lower DMO/TMO ratio than the control group (healthy subjects). The serum DMO/TMO ratio showed a close correlation with the Child–Pugh score, which is used for overall evaluation of severity of cirrhosis and Mayo risk scores for primary biliary cirrhosis in adults (0·856, P < 0·01 and 0·788, P < 0·01, respectively). The TMO tolerance test shows the benefit of performing a relatively early test of dynamic liver function to evaluate hepatic functional reserve in pre- and post-operative biliary atresia patients.
The numerical method to evaluate the cracking behavior induced by hydration reaction in mass concrete was developed. The method is combined with structural and heat transfer analysis, in which the Rigid-Body-Spring Model (RBSM) is used as a basis of a structural model and truss network model is utilized as heat transfer model. Moreover, a hardening behavior model of concrete (stress-strain relationship) at early age was proposed and the solidification concept depending on time is applied to the constitutive model of concrete before and after cracking. For the application model (wall structure), the structural behaviors reasonably correspond with real structure.
The authors have reported from experimental investigation that the use of closed stirrups, U-shaped stirrups and rod-shaped reinforcements as shear reinforcements in reinforced concrete (RC) beams results in clear differences in internal crack patterns and maximum strength. In this study, simulations of the experimental beams were performed using a three-dimensional rigid-body spring model, demonstrating that the behavior observed in the experiments is a mechanical phenomenon that can be reproduced numerically. Using the stress distribution over the beam cross section obtained from the analysis, the beam and arch action components of shear resistance are decoupled and considered from the perspective of the shear resistance mechanism. Further, through analysis of additional cases, the role of the upper and lower horizontal legs of the shear reinforcement, the effect of end anchorages on rod-shaped reinforcements were clarified.
ASRを生じた構造物の膨張挙動とそれに伴う損傷が構造性能に及ぼす影響を明らかにすることを目的として,実験と解析による検討を行った.ASR膨張試験の結果,ASR膨張は構造物の配筋状態等の影響により方向性を持つことを示した.また,はり供試体から採取したコア供試体の材料特性は,膨張の程度に従った異方性に影響を受けるため,構造全体挙動を評価する際は,コアの採取位置や方向に注意する必要があることを示した.一方,ASR膨張解析と荷重作用解析を行なった結果,はり供試体から実構造物に至るまでASR損傷状況を概ね評価できることを示した.本研究の結果,RC構造はASR膨張が比較的小さい場合においても構造性能が低下するのに対して,プレストレス構造はASR膨張に対する抑制の効果が大きく,構造性能への影響は少ないことを示した.
曲げ降伏後に繰返し荷重を受けるRC部材のせん断耐力低下挙動の評価を数値解析的に試みた.数値解析手法としては,3次元剛体バネモデルを用い,まず,繰返し載荷を受けるRC部材の曲げ降伏後のせん断破壊の破壊進展挙動を再現した.次に,著者らが提案する実験的に直接求めることできない曲げ降伏後の繰返し荷重下のせん断耐力低下挙動を数値解析的に算出する方法を用い,変形の増大に伴うせん断耐力の低下挙動を評価した.その結果,数値解析により得られたせん断耐力低下曲線が,統計的に求められた既往の提案式と概ね一致し,同一の傾向となることが示された.また,帯鉄筋比・軸力・主鉄筋比がせん断耐力低下挙動に与える影響を,提案した手法を用いて評価した.
Abstract This study numerically evaluated the flexural capacity and fracture mechanism of precast reinforced concrete beams connected with in situ horizontal loop connections employing the three‐dimensional rigid body spring model (3D‐RBSM) for modeling of concrete and beam elements (BEs) for modeling of steel, respectively. The research analyzed the performance of continuous horizontal loop connections with and without transverse reinforcement, considering varying vertical spacing between loops and transverse steel ratios. The numerical model effectively captured the test load displacement relationships by incorporating the model parameters like Young's modulus, tensile strength, fracture energy, compressive strength, cohesion, and angle of internal friction for concrete along with mechanical properties of steel and revealed that loop joints without transverse reinforcement exhibited loop type failure. In contrast, specimens with transverse reinforcement improved the peak load and caused compression failure. It was discovered that transverse rebars on the continuous side of the joint experience more strain; particularly, the maximum strain occurred in the corner rebars within the curved sections of U‐rebars. Moreover, the increased vertical spacing between the loop rebars increased the diagonal crack propagation and demonstrated the loop‐type failure. Further, a larger circumferential area of transverse rebar offered greater bond strength and confinement to the concrete core and reproduced the maximum deformation capacity, ductility, and compression failure.
