論文 - 小畑 誠
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支承用ゴムの多軸載荷下の応力ひずみ関係の改良 査読あり
小畑誠，海老澤健正，後藤芳顯
土木学会論文集A1 76 ( 2 ) 320 - 330 2020年08月
担当区分：筆頭著者 記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：土木学会
ゴム支承は橋の耐震設計において重要な役割を果たすため，その変形特性と破壊特性を正確に評価すること
が必要である．ゴム支承のゴム材料は，破壊するまで数百%もの巨大なせん断変形を受け，超弾性，可塑性，粘
性などのゴム材料に固有の材料特性を持っているため，必然的に大変形問題と複雑な応力ひずみの関係を考慮
する必要がある．そのため，ゴム支承の挙動の正確な数値シミュレーションについての多くの研究がなされて
いる．本研究では，充填ゴムに特有の Mullins 効果およびこれまで深く論じられることが少なかったゴム材料の
塑性挙動に注目する．そしてこれらの定式化に必要かつ合理的な改善を加え，実験結果をよりよく再現できる
ことを示した． -
腐食環境評価のための浮遊塩分量調査とその数値予測について 査読あり
小畑誠，村上太郎
構造工学論文集A 60 ( A ) 596 - 604 2014年04月
担当区分：筆頭著者 記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：公益社団法人 土木学会
It is important to estimate corrosion environment of steel bridges for an appropriate corrosion prevention and maintenance program. Estimation of environment has heavily depended on insitu observation and many data have been collected. However, versatile numerical approaches to this problem has not fully pursued yet. To this end, observation of airborne sea salt particles was performed with a standard low volume sampler (JIS Z 8814) beginning from April, 2013 to August, 2013 in the city of Nagoya and compared analytical estimation. A meso scale meteorological analysis employed here is WRF-Chem Ver. 3.4. Although WRF uses land use and terrain data based on USGS by default, the data is sometimes incorrect in Japan and yields inaccurate results especially for wind. Introduction of more accurate land use and geographic data supplied by the Geospatial Information Authority of Japan improves accuracy of basic meteorological data and therefore concentration of airborne sea salt particles. Other factors affecting accuracy of airborne sea salt concentration will also be discussed.
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局所および広域解析を組み合わせた付着塩分量推定法に関する研究 査読あり
小畑誠,李国泰,渡辺泰成,後藤芳顯
構造工学論文集A 58 668 - 678 2012年03月
担当区分：筆頭著者 記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：公益社団法人 土木学会
It is important to estimate corrosion environment of steel bridges for a proper
corrosion prevention and maintenance program. Adhered sea-salt particulate
matter (SSPM) is an influential factor especially in coastal areas. To this end, it is
better to know the adhesion behavior of SSPM to bridge girders. The objective of
this manuscript is to pursue numerical method to simulate the adhesion behavior of
salt particles oriented from sea surface. Specifically, two scale approach is
proposed. Mesoscale Meteorological Analysis and Lagrangian type two phase
flow analysis are used in global and local analyses respectively. The comparisons
between the numerical and observed results showed that the numerical analysis can
reproduce essential behaviors of airborne SSPM. -
円形鋼製橋脚の局部座屈部に生じた一つの延性破壊現象に関する解析的検討 査読あり
藤原英之,小畑誠,後藤芳顯
構造工学論文集A 58 310 - 318 2012年03月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
In the 1995 Hyogoken Nanbu earthquake, steel structures failed in brittle failure modes that have been rarely observed before. Among them is brittle failure of a circular steel column after a severe elephant foot type buckling. These observations are followed by researches in various points of view. A convincing scenario is that an initial ductile fracture triggers eventual brittle crack propagation and it is in fact supported by some observations. The objective of this work is to pursue the possibility of a numerical analysis predicting initiation of such ductile cracks. Gurson type void damage plasticity model is modified to be valid for cyclic loading. These numerical results are compared to experimental observations.
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Construction of a practical finite element model from point cloud data for an existing steel truss bridge 査読あり
Nao Hidaka, Naofumi Hashimoto, Kazuya Magoshi, Tetsuya Nonaka, Makoto Obata, Ei Watanabe
Proceedings of 23° International Conference on Construction Applications of Virtual Reality 1155 - 1166 2023年11月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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点群データを活用した鋼橋の解析モデルの構築および精度検証 査読あり
日高菜緒，橋本尚史，中村真貴，馬越一也，野中哲也，小畑誠
構造工学論文集 69A 637 - 647 2023年04月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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YIELDING STEEL DAMPERS TO REPLACE CONCRETE SHEAR KEYS FOR SEISMIC RETROFIT OF BRIDGES WITH UNEQUAL HEIGHT PIERS 査読あり 国際共著 国際誌
Nailiang Xiang, Y Goto, Makoto Obata, M. Shahria Alam, Jianzhong Li
Proc. 17th World Conference on Earthquake Engineering 2020年09月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
Irregular multi-span continuous bridges with unequal height piers are commonly adopted in mountainous areas when crossing steep-sided valleys. As common practice, economical unbonded laminated rubber bearings and concrete shear keys are usually installed in such bridges as superstructure-to-substructure connections. In strong earthquakes, the sliding of rubber bearings and the shear key failure are mostly expected, which may weaken the seismic resistance of the irregular bridges. The current study is mainly divided into three parts: the first one investigates the effect of concrete shear keys on the transverse seismic performance of the irregular bridges by incorporating the potential sliding of laminated rubber bearings; the second part proposes the concept of using yielding steel dampers to replace shear keys for mitigating the irregular seismic responses of the unequal height bridges with the practical design method being developed; the third part demonstrates the retrofit effectiveness by conducting nonlinear time-history analyses. The results indicate that the existence of concrete shear keys increases the bridge irregularity by inducing a significant in-plane superstructure rotation response around the vertical axis, posing nonuniform displacement demands at the substructures. The shear keys also contribute to the unbalanced ductility demands on the unequal height substructures, rendering the taller piers more vulnerable to the seismic damages. This differs from the case with fixed bearings, where the shorter piers are more subjected to damages. Using yielding steel dampers that are appropriately designed as per the proposed method, the seismic rotations of the bridge superstructure can be considerably mitigated with a relatively uniform superstructure movement maintained. The steel dampers are also effective in distributing the inertia forces among the unequal height piers. The effectiveness of yielding steel dampers replacing concrete shear keys in unequal height irregular bridges is successfully verified by the results from the numerical simulation.
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Shake-table tests of an innovative structural fusing system for small to medium-span highway bridges
Nailiang Xiang, Y Goto, Makoto Obata, M. Shahria Alam, Jianzhong Li
Proc. 17th World Conference on Earthquake Engineering 2020年09月
記述言語：英語
Irregular multi-span continuous bridges with unequal height piers are commonly adopted in mountainous areas when crossing steep-sided valleys. As common practice, economical unbonded laminated rubber bearings and concrete shear keys are usually installed in such bridges as superstructure-to-substructure connections. In strong earthquakes, the sliding of rubber bearings and the shear key failure are mostly expected, which may weaken the seismic resistance of the irregular bridges. The current study is mainly divided into three parts: the first one investigates the effect of concrete shear keys on the transverse seismic performance of the irregular bridges by incorporating the potential sliding of laminated rubber bearings; the second part proposes the concept of using yielding steel dampers to replace shear keys for mitigating the irregular seismic responses of the unequal height bridges with the practical design method being developed; the third part demonstrates the retrofit effectiveness by conducting nonlinear time-history analyses. The results indicate that the existence of concrete shear keys increases the bridge irregularity by inducing a significant in-plane superstructure rotation response around the vertical axis, posing nonuniform displacement demands at the substructures. The shear keys also contribute to the unbalanced ductility demands on the unequal height substructures, rendering the taller piers more vulnerable to the seismic damages. This differs from the case with fixed bearings, where the shorter piers are more subjected to damages. Using yielding steel dampers that are appropriately designed as per the proposed method, the seismic rotations of the bridge superstructure can be considerably mitigated with a relatively uniform superstructure movement maintained. The steel dampers are also effective in distributing the inertia forces among the unequal height piers. The effectiveness of yielding steel dampers replacing concrete shear keys in unequal height irregular bridges is successfully verified by the results from the numerical simulation.
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Passive seismic unseating prevention strategies implemented in highway bridges: A state-of-the-art review 査読あり 国際共著 国際誌
Nailiang Xiang , Yoshiaki Goto, Makoto Obata, M. Shahria Alam
Engineering Strucures 194 77 - 93 2019年09月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Elsevier
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Analysis of rubber bearing behavior with material deterioration 査読あり 国際誌
Makoto Obata, Yoshiaki Goto
Proceedings of ICASS2018 2018年12月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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材料劣化を考慮した繰返し載荷下のゴム支承挙動の解析 査読あり
小畑誠，小岩千紗，後藤芳顯
第20回性能に基づく橋梁等の耐震設計に関するシンポジウム講演論文集 １ ( １ ) 335 - 338 2017年07月
担当区分：筆頭著者 記述言語：日本語 掲載種別：研究論文（研究会，シンポジウム資料等） 出版者・発行元：土木学会
橋梁の耐震設計においてゴム支承は重要な役割を果たしており，その変形特性，破壊特性の的確な評価の必要性が高い．ゴム支承は破壊にいたるまでに数100％のせん断変形に耐えること，またいくつかのゴム材料特有の材料特性を持つことから，これまでにもゴム材料の挙動の精度良い数値解析を目指す研究が多くなされてきている．本研究ではこの中でもMullins効果に注目する．これは繰り返し載荷下にゴムの剛性が低下する現象であるが，これまでに導入されている定式化，例えばOgden-Roxburgh)などの方法では必ずしも実際の挙動をうまく再現できない場合がある．Nasdalaらはこの点について別の状態変数を導入することによる解決案を提案しているが，本研究ではこの点において変形にもとづくアプローチを提案する．
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Ultimate Behavior of Steel and CFT Piers in Two-Span Continuous Elevated-Girder Bridge Models Tested by Shake-Table Excitations 査読あり 国際誌
Yoshiaki Goto, Takemasa Ebisawa, Makoto Obata, Jianzhong Li, Yan Xu
Journal of Bridge Engineering 22 ( 5 ) 2017年01月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：American Society of Civil Engineering
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鋼製橋脚で支持された連続高架橋における積層ゴム支承の水平2方向地震動下の挙動特性 査読あり
奥村徹，海老澤健正，後藤芳顯，小畑誠，Jianzhong Li, Yan Xu
第１８回性能に基づく橋梁等の耐震設計に関するシンポジウム論文集 1 49 - 56 2015年07月
記述言語：日本語 掲載種別：研究論文（その他学術会議資料等）
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円形断面鋼製橋脚を持つ連続高架橋模型の２方向加振実験のFE解析と終局挙動特性 査読あり
海老澤健正，後藤芳顯，小畑誠，Jianzhong Li，Yang Xu
第１８回性能に基づく橋梁等の耐震設計に関するシンポジウム論文集 1 ( 1 ) 57 - 64 2015年07月
記述言語：日本語 掲載種別：研究論文（その他学術会議資料等）
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Effects of land use data on numerical simulation of corrosive environment caused by airborne sea salt particles 査読あり
Makoto Obata, Masato Fukushima, Seiya Suzuki
Proc. the 7th ISSS 1 ( 1 ) 228 - 229 2013年11月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
Corrosion of steel bridges in a coastal area is mainly caused by sea salt particles coming from ocean. Appropriate estimation of such airborne sea salt particles is critically important for a proper anticorrosion management program. At present, the most reasonable simulation of sea salt concentration can be performed as a part of meso scale meteorological analysis. However, accuracy of such simulation is not verified well so far. The objective of this work is to verify and to improve the accuracy of numerical simulation of airborne sea salt particles by introducing enhanced land use data. Other factors affecting accuracy of airborne sea salt concentration will also be discussed.
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Numerical simulation of adhesion of sea-salt particles 査読あり
Makoto Obata, Li Guotai, Yasunari Watanabe, Yoshiaki Goto
Structure and Infrastructure Engineering 52 398 - 408 2013年01月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
It is important to estimate corrosion environment of steel bridges for a proper corrosion prevention and maintenance
program. The governing factors of corrosion are temperature, humidity and various dusts on the surfaces. Among them, the
adhered sea-salt particulate matter (SSPM) is most important and therefore airborne SSPM near a bridge site must be
considered in its design. To prevent degradation of protective paint, removal of adhered SSPM by wash out has been tried in
some bridges. To this end, it is better to know the adhesion behaviour of SSPM to bridge girders. The objective of this
manuscript is to pursue numerical method to simulate the adhesion behaviour of salt particles oriented from sea surface.
Specifically, two scale approach is proposed. Mesoscale meteorological analysis and Lagrangian type two phase flow
analysis are used in global and local analyses respectively. The comparisons between the numerical and observed results
showed that the numerical analysis can reproduce essential behaviours of airborne SSPM.DOI： 10.1080/15732479.2012.757328
その他リンク： http://www.tandfonline.com/action/showAxaArticles?journalCode=nsie20
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Numerical Estimation of Corrosion Environment by Airborne Sea Salt Particles 査読あり
Liu Chen Chen, Makoto Obata
Advanced Materials Research 599 220 - 223 2012年11月
記述言語：英語 掲載種別：研究論文（学術雑誌）
Anticorrosion of steel bridges has been an increasingly important problem in Japan. For a proper anticorrosion
and maintenance program, it is important to estimate corrosion environment of steel bridges. In Japan, airborne
sea salt generated from ocean is a predominant factor. Authors have been working on establishing a consistent
framework to estimate corrosion environment numerically. It consists of a local and a global approach. While
adhesion of airborne sea salt particles to bridge structures are simulated locally by a CFD analysis, the large
scale analysis yields a boundary conditions of the local analysis and is given by a part of a mesoscale
meteorological analysis. The objective of this work is to numerically investigate reliability of such large scale
analysis in estimation of corrosion environment caused by airborne sea salt particles. -
Numerical Prediction of Ductile Crack Initiation in a Steel Column under Cyclic Loading 査読あり
Makoto Obata, Hideyuki Fujiwara, Yoshiaki Goto
Proc. of the 10th international conference on advances in steel concrete composite and 1 ( 1 ) 207 - 214 2012年07月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
DOI： 10.3850
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Numerical simulation of adhesion of sea salt particles for anticorrosion of steel bridges 査読あり
Makoto Obata, Shunya Yokoi, Li Guotai, Yoshiaki Goto
Proceeings of ASEM 1 ( 1 ) 5262 - 5269 2011年09月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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効果的な桁洗浄に向けた鋼橋の腐食環境調査と考察 査読あり
永田和寿，伊藤弘太，山田仁，小畑誠，宮本重信
構造工学論文集A編 57 2011年03月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
Generally steel bridges are protected from corrosion by the painting. It is
necessary to repaint them every ten-odd years. Hence, the maintenance of these
structures costs much expense. By washing the bridge, salt and dirt that adhere to
the bridge can be flushed. It seems that this means is effective for the
maintenance of the steel bridge. Therefore, in this study the corrosion
environment of the bridge named Mikumi-Ohashi located on the Sea of Japan
side was investigated. Moreover, computational fluid dynamics was carried out to
examine the characteristic of the dew condensation. In conclusion, the corrosion
environment of this bridge and the effective timing of washing were clarified.
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