文献一覧: 山田義智 (著者)

2 0 0 0 セメントペーストのレオロジー定数測定とマーカー粒子粘塑性有限要素法によるセメントペーストフロー解析

著者: 山田義智東舟道裕亮上原義己崎原康平
出版者: 日本建築学会
雑誌: 日本建築学会構造系論文集 (ISSN:13404202)
巻号頁・発行日: vol.84, no.756, pp.139-148, 2019
被引用文献数: 4

In order to conduct flow analysis of cement paste, mortar and concrete, it is important to obtain rheological constants representing the flow characteristics of the material. In this study, we measured cement paste's rheological constants by using rotational viscometer. Here, it was measured in consideration of flow history on cement paste. Furthermore, in this study, we derived the flow constitutive equation of the cement paste and proposed a marker particle visco-plastic finite element method. Using this marker particle visco-plastic finite element method, simulation of flow test of cement paste was attempted.  The results obtained from the experimental study and analytical study of this research can be summarized as follows.  Using a rotational viscometer, the flow curve of cement paste was measured for various shear conditions. It was confirmed that the flow curves of all cement paste samples can be approximated by the Bingham model under all shear conditions. And the obtained flow curve was approximated by the Bingham model, and the rheological constants (yield value and plastic viscosity) of the paste sample was determined. Thixotropy was confirmed in the flow characteristics of the cement paste sample from the obtained flow curves and rheological constants.  The cement paste was regarded as a visco-plastic fluid and derived the flow constitutive equation of visco-plastic fluid using overstress theory. The obtained flow constitutive equation considers non-Bingham characteristic, flow history, and pressure dependency of yield value. It was confirmed that the flow curves of cement pastes differing depending on shear conditions can be expressed by the proposed flow constitutive equation.  Marker particle visco-plastic finite element method was used to analyze the flow test of cement pastes. The results obtained by the analysis agreed well with the experimental results. Therefore, the marker particle visco-plastic finite element method and the rheological constants are effective.

2019-03-20 12:03:43
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1 0 0 0 沖縄県の暑中期におけるレディーミクストコンクリート温度の実態調査と機械学習による温度推定に関する研究

著者: 清水寛太山田義智肖春彦小山智幸
出版者: 一般社団法人日本建築学会
雑誌: 日本建築学会技術報告集 (ISSN:13419463)
巻号頁・発行日: vol.28, no.68, pp.76-80, 2022

In this study, we survey on ready-mixed concrete shipped in Okinawa prefecture, including material temperature, concrete temperature at the time of kneading and unloading, and outside temperature. As a result, It was found that the concrete temperature at the time of unloading must be about 33℃ or less so that the concrete temperature at the time of kneading does not exceed 35℃. We also showed that random forest and LightGBM, which are a type of machine learning, can estimate concrete temperature at the time of kneading and unloading with high accuracy from the unit quantity of material, material and outside temperature.

2022-03-02 17:34:46
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1 0 0 0 フレッシュコンクリートのレオロジーモデルと流動解析の現状

著者: 山田義智
出版者: 一般社団法人日本トライボロジー学会
雑誌: トライボロジスト (ISSN:09151168)
巻号頁・発行日: vol.67, no.1, pp.14-21, 2022

This paper first outlines the rheological model used for flow analysis of fresh concrete that has not yet hardened. Next, the classification of the flow analysis method for fresh concrete is shown, and examples of analysis by the MPS method, which the authors have been working on in recent years, is described. Finally, I would like to describe the expectations and prospects for the rheology of fresh concrete.

2022-01-27 17:34:30
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1 0 0 0 フロー試験によるセメントペーストのレオロジー定数推定法に関する研究

著者: 東舟道裕亮山田義智
出版者: 日本建築学会
雑誌: 日本建築学会構造系論文集 (ISSN:13404202)
巻号頁・発行日: vol.86, no.784, pp.860-870, 2021
被引用文献数: 3

With the improvement of earthquake resistance and large scale of buildings, the number of cases where it is difficult to fill the form work with conventional slump-managed concrete is increasing. In addition, slump flows 45 cm, 50 cm, 55 cm, and 60 cm have been added due to the JIS (Japanese industrial standard) revision made in March 2019. In the future, it is estimated that the use of slump flow managed concrete will increase. Furthermore, in recent years, new admixtures have been actively developed, and it is necessary to correctly grasp the flow characteristics of concrete using these admixtures from a rheological point of view. It is the cement paste in concrete that is most affected by the flow properties of the admixture. Therefore, it is useful to be able to grasp the flow characteristics of cement paste. We have already examined the relationship between the rheology constants obtained from the rheology test and the flow characteristics obtained from the paste flow test, and we proposed a rheology constant estimation method. In this study, we reexamined the rheological constant estimation method based on the correlation analysis findings using the visco-plastic finite element method (FEM). First, flow analysis was performed by FEM using any combination of rheological constant and paste density (yield stress: 10 patterns, plastic viscosity: 7 patterns, paste density: 3 patterns, total 210 patterns) as input values. Next, based on the analysis results, the relationship between the paste flow characteristics (flow value, each flow arrival time, flow stop time) and the rheology constant and paste density was examined by correlation analysis. As a result, it was found that the yield stress can be estimated by the flow value, and the plastic viscosity can be estimated by the multiple regression equation of the paste density and the 150 mm flow arrival time. Furthermore, we proposed a new rheological constant estimation equation using the actual test results of the cement paste for the relationship obtained from the correlation analysis. After that, the rheology constant was estimated from the actual paste flow test results using the rheology constant estimation equation. Finally, a paste flow simulation was performed using the MPS method, which can consider the influence of the flow cone, and it was compared and examined: the actual paste flow test results and MPS analysis results. As a result, the actual paste flow test results could be reproduced by MPS analysis, and the validity of the rheological constant equation was confirmed.

2021-07-14 00:37:07
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1 0 0 0 ランダムフォレストによる高流動コンクリートのフレッシュ性状推定の試み

著者: 清水寛太山田義智古賀志門平野修也
出版者: 一般社団法人セメント協会
雑誌: セメント・コンクリート論文集 (ISSN:09163182)
巻号頁・発行日: vol.74, no.1, pp.265-272, 2021

本研究は高流動コンクリートのスランプフロー試験を対象として、機械学習の一種であるランダムフォレストによりフレッシュ性状(スランプフロー値、500mmフロー到達時間、空気量等)の推定を試みた。ここでの学習は、使用材料、混和剤の成分、調合、練混ぜ条件、経過時間などの特徴量(説明変数)を60項目からスタートして、その重要度を評価した。その結果、重要度の高い10項目の特徴量(説明変数)でフレッシュ性状の各値が推定できることを示した。また、推定したスランプフロー値、500mmフロー到達時間より既往の研究成果を基にレオロジー定数を推定し、目視材料分離判定や数値解析による高流動コンクリートの充填シミュレーションに用いることが期待できる。

2021-04-13 23:37:30
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1 0 0 0 ロジスティック回帰分析を用いた高流動・中流動コンクリートの目視材料分離予測手法の検討

著者: 野中潔目黒貴史石田征男山田義智
出版者: 一般社団法人セメント協会
雑誌: セメント・コンクリート論文集 (ISSN:09163182)
巻号頁・発行日: vol.74, no.1, pp.258-264, 2021

本研究では高流動・中流動コンクリートについて、従来目視で行われる材料分離の判定をコンクリートのスランプフローの挙動と関連付け、レオロジー定数である塑性粘度、降伏値および観察状況を説明変数とし、ロジスティック回帰分析により予測する取組みを行った。p値や調整済みオッズ比の指標から全ての説明変数が材料分離判定に影響していると統計的に判定され、得られた回帰モデルで実験データの最大90.7%において材料分離の有無を正しく予測できた。また、目的に応じてより安全側の判定を行うことも可能であった。本研究の結果においては、一般的に中流動コンクリートに分類されるスランプフロー径550mm以下のコンクリートでは材料分離はほぼ起こらないと予測された。

2021-04-13 23:37:29
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1 0 0 0 スランプで流動性が評価されるモルタルのレオロジー定数測定とMPS法によるモルタルのスランプおよびスランプフロー解析

著者: 平野修也山田義智西祐宜崎原康平
出版者: 日本建築学会
雑誌: 日本建築学会構造系論文集 (ISSN:13404202)
巻号頁・発行日: vol.85, no.774, pp.993-1003, 2020
被引用文献数: 4

In order to conduct flow analysis of cement-based material such as cement paste, mortar and concrete, it is important to more accurately obtain the rheological constants representing the flow characteristics of the material. In this study, the rheological constants of mortar were measured by two rheology tests. The first was sphere pull-up test, the second was the measurement by using rotational vane viscometer. According to previous studies, the former was able to measure the rheological constants of high fluidity mortar, and the latter was able to evaluate the shear stress characteristics of cement-based material containing fine aggregate and coarse aggregate. Furthermore, in this study, the flow constitutive equation of mortar was derived and Moving Particle Semi-implicit (MPS) method was proposed. Using this MPS method, flow simulation of mini slump flow test was attempted. The results obtained from the experimental study and analytical study in this paper can be summarized as follows. Throughout the sphere pull-up test, the rheological constants (yield value and plastic viscosity) of mortar which was the same mix proportion as mini slump tested mortar were measured. In the test results, the larger mini slump flow value was, the lower yield value was, and the relationship between the two values was able to be approximated by an exponential curve. On the other hand, plastic viscosity and arrival time at mini slump flow of 115mm had positive correlation, and the relationship between the two values was able to be approximated by a linear function. Using a rotational vane viscometer, the flow curve of mortar was measured for various shear conditions. It was confirmed that the flow curves of all mortar samples were able to be approximated by the Bingham model under all shear conditions. And the obtained flow curve was approximated by the Bingham model, and the rheological constants of all mortar sample was determined. Thixotropy was confirmed in the flow characteristics of the mortar sample from the obtained flow curves. Also, contrary to the general tendency, the larger mini slump flow value was, the higher plastic viscosity was for water cement ratio of 30%. It was suggested that the rheological constants measured by rotating vane blade were affected by amplified apparent viscosity of mortar. As a result, the sphere pull-up test was more appropriate for the evaluation of rheological properties of mini slump flows. Applying the polygon model to the wall boundary as boundary condition of MPS method, a phenomenon that mini slump flow was shielded by mini slump cone was expressed on the flow analysis. Adopting the rheological constants obtained by the sphere pull-up test, it was attempted that mini slump flow spread of mortar sample was reproduced by MPS analysis. The results obtained by the analysis agreed well with the experimental results of mini slump flow. Moreover, in terms of mini slump shape, the analysis by MPS method largely reproduced the actual measured shape. Furthermore, following the analysis condition used in mini slump flow analysis, mortar flow spread with slump cone was predicted by MPS analysis. The results obtained by the analysis reproduced the actual measured value of slump flow. Therefore, the analysis by MPS method and the rheological constants obtained by the sphere pull-up test are effective in mortar flow spread.

2020-11-05 13:38:49
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1 0 0 0 MPS法による高流動コンクリートのスランプフローシミュレーション

著者: 山田義智上原義己崎原康平浦野真次
出版者: 日本建築学会
雑誌: 日本建築学会構造系論文集 (ISSN:13404202)
巻号頁・発行日: vol.85, no.771, pp.663-672, 2020
被引用文献数: 5

Concrete flow analysis is important, because it is possible to visualize how high fluidity concrete flows in the concrete placing form and in the gap between reinforcing bars. In this study, MPS (Moving Particle Semi-implicit) method was used as a concrete flow analysis method. First, the flow of Bingham fluid between parallel plates was analyzed, and the validity of the analysis method was verified. Furthermore, the effectiveness of the proposed method was confirmed by comparing the results of slump flow analysis and test results. The research results of Kokado et al.3) were used for the rheological constants (yield value, plastic viscosity) of concrete used for slump flow analysis. The results obtained in this study can be summarized as follows. The flow of Bingham fluid between parallel plates was reproduced using the proposed MPS analysis. As the result, when the particle size was 20 mm, it was different from the theoretical value, and when the particle size was 10 mm, 5 mm, 2.5 mm, it agreed with the theoretical value. The flow of Bingham fluid between parallel plates was reproduced by changing the value of the stress growth index m of the regularized Bingham model with m = 1 and 10,100. As a result, the theoretical value agreed well with the MPS analysis result in the fast range of flow velocity. In the range of slow flow, the MPS analysis results at the stress growth index m = 1 were faster than the theoretical solutions at the center of the parallel plate. Therefore, in order to represent the Bingham fluid, it is necessary to increase the value of the stress growth index m. In this study, the stress growth index m was set to 100 and used for MPS analysis. The slump flow test was reproduced by MPS analysis using a regularized Bingham model with a particle size of 5 mm and a stress growth index of m = 100, assuming that the high fluidity concrete was a Bingham fluid. As the result, it was well reproduced in the range of slump flow value of about 500 mm, however, it tended to flow in the experimental result as the slump flow value increased from 600 mm to 700 mm. When the slump flow value is less than 600 mm, the spread curve of the flow can be reproduced within the range of the rheological constant within the 95% upper and lower limit prediction interval. However, at the slump flow value of 700 mm, the experimental value flows more than the analytical result using the yield value of 95% lower limit. According to the results of the finite difference analysis in the literature (4), at a slump flow value of over 600 mm, the measured value tends to flow more than the analytical result. Therefore, if the slump flow value exceeds 600 mm, the yield value by the lifting sphere viscometer test may have been evaluated higher. Furthermore, high fluidity concrete with a slump flow value exceeding 600 mm may exhibit non-Bingham properties in the low shear rate region.

2020-06-12 14:37:18
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1 0 0 0 UAV撮影画像の解析技術を活用した離島架橋のひび割れ点検に関する考察

著者: 富山潤須田裕哉崎原康平山田義智堀口賢一岡部成行
出版者: 公益社団法人土木学会
雑誌: 土木学会論文集F4(建設マネジメント)
巻号頁・発行日: vol.75, no.1, pp.11-23, 2019
被引用文献数: 2

琉球大学では,点検に多くの制約を受ける離島架橋に対して戦略的イノベーション創造プグラム(Cross-ministerial Strategic Innovation Promotion Program:SIP)インフラ維持管理・更新・マネジメント技術の開発技術のひとつであるひび割れ画像解析技術の実証実験を行い,目視点検の結果と良い相関を得た.この結果は橋梁管理者に評価され,本技術が実橋梁の点検業務の一部に利用された.本技術の実証実験に対する沖縄での取り組みは,新技術を地域実装に導いたひとつの実装モデルといえる. 本論文では,本技術が実証実験から地域実装に至った取り組み,経緯および課題について考察する.さらに,新技術のコストメリット,効率性および高度化についても考察する.また,新技術の地域実装を通して新しい技術開発が行われた事例についても紹介する.

2019-07-31 01:34:12
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1 0 0 0 OA フレッシュコンクリートのレオロジー定数推定に関する基礎的研究

著者: 山田義智赤嶺糸織伊波咲子浦野真次
出版者: 一般社団法人セメント協会
雑誌: セメント・コンクリート論文集 (ISSN:09163182)
巻号頁・発行日: vol.66, no.1, pp.661-668, 2013-02-25 (Released:2013-12-02)
参考文献数: 6
被引用文献数: 1 2

本研究では、ペーストからモルタルさらにコンクリートへと展開する新たな粘度式を提案した。そして、この粘度式を用いて、ペースト、モルタル、コンクリートのレオロジー定数を調合(配合)から推定する手法を示した。ここで、提案手法で求めたペーストとモルタルのレオロジー定数の有効性については、既往の実験結果との関係を比較・検討することで確認した。一方、コンクリートのレオロジー定数の有効性については、提案手法で求めたレオロジー定数を入力値として有限要素法でスランプシミュレーションを行い、実測結果と比較することで確認を行った。