Research Themes

• Evaluation methodology and modular systems to enable steel reuse
  Grants-in-Aid for Scientific Research
  Jun. 2024 - Mar. 2028
  岡崎 太一郎, CHEN ZHIPENG
  Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Hokkaido University, Principal investigator, 24K21220
• 鋼構造建築物の破壊過程の解明と倒壊余裕度の把握
  科学研究費助成事業
  Apr. 2024 - Mar. 2028
  岡崎太一郎、松井良太、長江拓也
  日本学術振興会, 基盤研究(A), 北海道大学, 24H00340
• High-Seismic-Performance Building with Sliding Foundation System and Reinforced Non-Structural Components
  Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
  07 Oct. 2022 - 31 Mar. 2027
  長江 拓也, 浅井 竜也, 柏 尚稔, 高橋 典之, 梶原 浩一, 藤原 淳, 岸田 明子, 松宮 智央, 岡崎 太一郎
  Japan Society for the Promotion of Science, Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)), Nagoya University, 22KK0063
• 環境負荷軽減を実現する座屈拘束ブレースの開発
  科学研究費助成事業
  30 Jun. 2023 - 31 Mar. 2026
  松井 良太, 岡崎 太一郎, 丸山 一平
  日本学術振興会, 挑戦的研究(萌芽), 北海道大学, 23K17781
• Developing rational design metholodogy for chevron braced frames　　　　　　　　　　　　　　　
  Grants for Research and Education in Steel Structures
  Apr. 2023 - Mar. 2026
  岡崎太一郎、松井良太、田川浩、陳星辰
  The Japan Iron and Steel Federation, Grants for Specified Research Areas, Principal investigator
• Numerical analysis of large deformation and stability response of steel structures under earthquake loading　　　　　　　　　　　　　　　
  Researcher Exchange Support for International Researchers
  Apr. 2024 - Jun. 2024
  Ali IMANPOUR, Taichiro OKAZAKI
  The Kajima Foundation
• Ultra-Low Cycle Fatigue Behavior of Steel Connections
  Grants-in-Aid for Scientific Research
  08 Mar. 2023 - 31 Mar. 2024
  岡崎 太一郎, WANG YUANZUO
  地震を受けた鋼構造建築物において、極小数回の繰返し載荷で破断に至る鋼材の挙動を解明する目的で、下記の3つの研究項目を推進した。（１）鋼材に亀裂を生じる力学的条件を把握するために、材料の引張試験と引張・圧縮繰返し試験を実施した。（２）実験データに基づいて、鋼材の引張特性と塑性力学の構成則の一般的な関係を導く。（３）実験データに基づいて、鋼材の機械的特性と亀裂発生条件を関連づけ、機械的特性に応じた亀裂発生条件の予測式を導く。（１）と（２）では、二種類の鋼材について、５種類のノッチ入り供試体を製作し、それぞれに引張試験と引張・圧縮繰返し試験を実施してきた。ひずみ硬化とひずみ時効の影響を把握するために、大部分の試験体は、2%までの予ひずみを与えたあと、30日の養生期間をおいて、再度試験を実施した。（３）では、精緻な有限要素法解析を実験データに対して較正することで、予ひずみの有無、応力三軸度やロード角が、鋼材の引張特性と構成則、亀裂発生条件に与える影響を分析した。外国人特別研究員がこれまでに実施してきな研究の完成度を高めるとともに、地震被害を罹災した鋼構造建築物の残存性能やリユース性の評価を視野に、ひずみ硬化とひずみ時効を経たあとの引張特性と構成則の変化を新たな切り口として、実験と数値解析、データの分析を進めた。いずれの項目も、細部まで、外国人特別研究員と受入研究者との協議で立案したもので、外国人特別研究員が、受入研究機関の大学院生の補助を受けて実施した。
  Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 22KF0014
• Analysis and assessment technology for seismic collapse safety of steel building structures
  Grants-in-Aid for Scientific Research
  Apr. 2020 - Mar. 2024
  Taichiro OKAZAKI, Ryota MATSUI, Tomohiro MATSUMIYA, Noriyuki TAKAHASHI, Takuya NAGAE
  鋼構造建築物の倒壊過程を実験的に解明する研究目的に沿って、国立研究開発法人防災科学技術研究所の大型耐震実験施設で、2020年11月から12月にかけて、縮尺1/2のパイロット試験体による振動台実験を実施した。同研究所の兵庫耐震工学研究センターで、2020年12月に実施された日米共同実験に参加し、次世代型鋼構造システムを開発する研究を推進した。大型耐震実験施設で、2021年12月に、縮尺1/3の4層ラーメン構造の倒壊実験を実施した。一方で、倒壊に至る鋼構造の非線形・動的挙動を追跡するコンピュータ解析技術を確立する研究目的に沿って、数値モデル化技術を種々検討してきた。一連の研究活動で得られた成果は、下記のとおりである。（１）倒壊実験によって、柱や梁が降伏し破断する過程と、損傷と破壊が架構全体に伝播する状況に関する実データを収録できた。（２）複数の実験から得た、鋼構造架構の非線形動的応答に関する実データを、既往の大規模振動台実験のデータと合わせて、数値解析技術の検証を進めてきた。特に、破断を模擬するための現状のモデル化手法では、既往の重層架構実験で観察された、部材破断後の部材力再分配を正しく再現できないことを突き止め、今後の課題を特定した。減衰モデルの選択によって、架構の応答変位や応答加速度が異なることに注目し、定量的な検討を進めた。（３）部材破断の再現方法を含めて、ブレース付鋼構造架構の解析手法に関する知見を蓄積し、現状のブレース付鋼構造架構が保有する耐震性能を検証した。
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 20H00269
• Fracture of steel connections under very-low-cycle loading
  Grants-in-Aid for Scientific Research
  Sep. 2022 - Sep. 2023
  Taichiro OKAZAKI, WANG YUANZUO
  Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 22F22042
• Development of a post-earthquake quick inspection method utilizing the movement data and video image of non-structural components in existing buildings subjected to a strong earthquake
  Grants-in-Aid for Scientific Research
  01 Apr. 2020 - 31 Mar. 2023
  長江 拓也, 梶原 浩一, 岡崎 太一郎, 松宮 智央, 高橋 典之, 藤原 淳, 岸田 明子
  本提案では，即時応急危険度判定として，地震被災建物の非構造材の動作に関する計測値分析と，屋内外のビデオ映像に基づく外観損傷や部材変形の画像解析を統合し，構造体の安全性はもとより建物機能の健全性を判定する方法を開発することを目標としている。さらに，判定結果を速やかに周囲に伝達することで，人間避難行動を適切に誘導する判定情報伝達技術の開発までを射程とする。本年度も引き続き，鋼構造架構を準備し，間仕切壁，カーテンウォールの加振実験を実施した。部材角を評価するGyro，表示のLEDの適用性について検証した。判定基準整備の一環として，確率論的性能評価の適用性について検討を重ねた。
  Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Nagoya University, 20K20435
• Proposal of Structural Design Method for Steel Structures Based on Ultimate Performance using Collapse Analysis
  Grants-in-Aid for Scientific Research
  01 Apr. 2020 - 31 Mar. 2023
  松井 良太, 岡崎 太一郎, 竹内 徹
  本研究課題では，鋼構造物の限界性能を検証できる構造設計手法を提示することを目標としている。2021年度では，鋼構造物の中でも，鋼材ブレースと合成梁の力学的性能を検証することに焦点を当てて研究計画を立てた。
  第一に，2020年度に構築したデータベースを参照して製作した鋼材ブレースを対象とした模型載荷実験を実施した。試験体の断面には，H形鋼，円形鋼管，角形鋼管の3種を選定した。接合部には，境界条件の剛柔によるブレースの力学的性能の差異を確認すべく，端部のエンドプレートと溶接接合した形式と，ガセットプレートを介して接合した形式の2種を設定した。細長比を19から28とした太短いブレースを6体，比較のため51から65の比較的細長いブレースを4体用意した。H形鋼のフランジ幅厚比を6，円形鋼管の径厚比を31から39，角形鋼管の幅厚比を22から33となる断面を採用した。全試験体を繰返し載荷し，ブレースの耐力および塑性変形能力を検証した。本研究を計画した時点で予期していなかったブレースの破壊挙動を確認した。
  次いで，鋼材の破壊力学の考え方を導入し，代表者が提案してきた繰返し載荷を受ける鋼材ブレースの塑性変形能力を評価する手法を発展させた。有限要素解析により，既往の載荷実験における角形鋼管ブレースの最大圧縮耐力，局部座屈による耐力劣化などの挙動について再現を試みた。他研究者が提案した破壊力学における鋼材の空隙進展モデルに適合する，鋼材ブレースの局部に集中した塑性歪を抽出するため，部材の要素分割，鋼材の材料特性などの条件を調整した。有限要素解析より得られた結果から，要素の歪をブレース軸方向にわたって抽出し，材全体の変形で局所に集中する塑性歪を評価するために必要となる事項を整理した。合成梁については，2020年度に実施した実験を参照し，コンクリート床スラブの有効幅の設定が性能に及ぼす影響を検討した。
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 20H02292
• Demountable and reusable modular steel construction
  Grants-in-Aid for Scientific Research
  Nov. 2020 - Mar. 2023
  岡崎 太一郎, ZONG LIANG
  Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 20F20354
• Development of Modular Steel Construction to Promote Reclaiming and Reusing Structural Steel
  Grants-in-Aid for Scientific Research
  Nov. 2019 - Mar. 2022
  岡崎 太一郎, XU FEI
  建築用鋼材は、建築物の供用期間が終了した時点でも、当初の性質をほとんど維持していると考えられるが、実際の建築物では、解体後に回収された鋼材はスクラップに回される。そこで本研究は、解体される建築物から採取した鋼部材を、新設建築物に再利用するための基礎技術を開発することを目的に掲げる。工学的な課題は、地震等によって塑性変形を受けた鋼材が、時間を経てその力学的特性を変える、ひずみ時効の影響である。2020年度は、代表的な鋼材について、塑性履歴とひずみ時効を受けたあと、力学的特性が変わる過程と要因を分析するための手法を開発した。試行的に、塑性変形と養生時間を経た鋼材において、微細構造が初期状態とどのように異なるかを調査した。微細構造分析には、後方散乱電子回折と透過電子顕微鏡、X線回析の組み合わせが有益であることを確認した。一方で、これまでに蓄積した実験データに基づいて、塑性変形とひずみ時効の影響を関数化して、鋼材の繰返し履歴則に組込む方法を整理した。有限要素法解析において、第一段階目の解析で生じた累積塑性ひずみに応じて、各要素の繰返し履歴則を分布的に更新したあと、第二段階目の解析を実施する方法を考案した。この有限要素法解析の有効性を、過去に実施した実験結果に対して検証した。結論として、過去の地震で塑性変形を受けた構造部材が、次に地震を受けたときにどのように違った挙動を示すかを、提案する解析法で適切に再現できることを示した。
  Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 19F19360
• Rapid post-quake estimation of structural damage and performance based on modern ima ge processing technology
  Bilateral Joint Research Project with National Natural Science Foundation of China
  Apr. 2018 - Mar. 2022
  Japan Society for the Promotion of Science, Hokkaido University, Principal investigator
• Experimental study for MEMS sensor monitoring system to assess seismic response of Non-structural element of building
  Grants-in-Aid for Scientific Research
  01 Apr. 2017 - 31 Mar. 2020
  Kajiwara Koichi
  In order to maintain and continue normal living and economic activities in our society, preparing for the future large-scale earthquake event, it is necessary to judge the performance of the infrastructures after the earthquake as a matter of course to improve the earthquake resistance before the earthquake. For this reason, many investigations have been conducted on structural health monitoring.
  Here, we have researched a system that estimates the structural characteristics of a building after the earthquake by capturing the response of non-structural element installed in the building with MEMS(micro-electro-mechanical systems) sensor. In this research, we have finished the basic investigation for practical use.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), National Research Institute for Earth Science and Disaster Prevention, 17K06666
• Towards seismic design of steel buildings addressing collapse risk
  Grants-in-Aid for Scientific Research
  Apr. 2017 - Mar. 2020
  Taichiro OKAZAKI, Tomohiro MATSUMIYA, Noriyuki TAKAHASHI, Tetsuhiro ASARI, Takuya NAGAE
  The primary objective of the research was to obtain experimental data on failure of steel components and to advance the technology to numerically simulate the seismic response of steel building structures. The research was planned towards the larger goal of establishing a methodology to assess whether a steel building can safely survive, or maintain usable, after an extremely large earthquake beyond the consideration of building codes. Dynamic loading test of beam-to-column connections was conducted to examine how seismic performance may be affected by connection type and presence of composite floor slab. Numerical modeling techniques were examined to capture the gradual degradation of steel components due to start and propagation of ductile fracture. The model was used to demonstrate that good agreement can be obtained between simulated and experimental behavior of multi-story steel building systems. An additional study was conducted on damping models suited for nonlinear analysis.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 17H03336
• Comprehensive study on the 2018 Hokkaido Eastern Iburi Earthquake and its disaster
  Grants-in-Aid for Scientific Research
  04 Oct. 2018 - 31 Mar. 2019
  Takahashi Hiroaki
  Comprehensive investigation on the 2018 Hokkaido Eastern Iburi earthquake and its disaster was conducted. Mainshock rupture initiated at deepest part and major slip was occurred in 20-30km deep. Multiple simultaneous landslides in Atsuma town was induced by combination of strong ground shaking and weak sliding layer between pyroclastic fall deposit layers. Halloysite cray minerals was discovered in all sliding layers. Simulation suggested landslides might attack residential houses within 6 seconds. Observed peak ground motions in nearby area were larger than common distance attenuation model. Severe wooden house damage in Mukawa town was due to amplified seismic waves due to site effects. Sounding and boring investigation revealed filled low-density volcanic ash and higher groundwater level in liquefaction area. Electricity blackout caused severe damage in social and economic activities of Hokkaido. These scientific outcomes were explained to residents at public briefing session.
  Japan Society for the Promotion of Science, Grant-in-Aid for Special Purposes, Hokkaido University, 18K19952
• Substructure Shaking Table Test for Collapse Process of Reinforced Concrete Building
  Grants-in-Aid for Scientific Research
  01 Apr. 2016 - 31 Mar. 2019
  Nagae Takuya, Yenidogan Cem, Takahashi Noriyuki, Matsumiya Tomohiro, Maruyama Ippei, Kajiwara Koichi, Mikoshiba Tadashi, Nakazawa Hiroshi
  A method of substructure test was developed by using a shaking table facility. Deformation time histories occurring in prototype buildings were applied to the substructure specimen equivalent to their critical portions. The force-deformation hysteresis was evaluated in the large deformation level significantly exceeding design limit, and compared with a promising numerical model, Krawinkler model. This model was developed in Stanford University, and is now recommended in the newest high-rise building design guideline of the United States. The ultimate energy capacity and other main parameters were tuned according to the test results. The numerical models, which represented substructure test results, were incorporated in the model of a full-scale frame test structure. The adopted method of static cyclic loading frame analysis indicated a new design procedure based on a reasonable performance assessment format.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Nagoya University, 16K06568
• Evaluate collapse margin of medium-low-rise steel buildings
  Grants-in-Aid for Scientific Research
  01 Apr. 2014 - 31 Mar. 2017
  MATSUMIYA Tomohiro
  For beam-to-column connection of the steel building, the gradual increase amplitude cyclic loading experiment which assumed loading speed (period 1Hz and 0.01Hz) were carried out. This experiment is fundamental researches for the performance evaluation technique construction that can evaluate the influence that the fracture property of the member end and the yield mechanism of the frame give to the ultimate state of the building. The conclusions obtained from this experiment are (1) The difference in loading speed produced differences of some behavior.(2) In the dynamic loading, beam-to-column connection fracture occur in comparison with static loading earlier, and plastic deformation capacity was inferior. For sliding in the high-strength bolt friction joint, the possibility that it hastened the crack spread started from the welding defect is thought about.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Kindai University, 26420570
• Structural Performance and Seismic Design of Steel Building Structures without Base Anchorage
  Grants-in-Aid for Scientific Research
  01 Apr. 2013 - 31 Mar. 2017
  NAKASHIMA, Masayoshi
  Japan and many regions in the world keep suffering from large earthquakes, and building collapse is considered to be most responsible for both the human and material losses. Advancement of building technologies for better collapse prevention is a critical societal need. This study proposes a new system in which the base of the super-structure is detached from the foundation, by which shear forces exerted onto the super-structure can be capped to a specified level. A series of dynamic loading test indicates that placing carbon graphite on the surface of foundation RC/mortar beam is found to ensure a friction coefficient of about 0.2 despite the number of sliding cycles. Theoretical equations are formulated to represent the sliding structure, and extensive time-history analyses are implemented for sliding structures subjected to pulse-type ground motions. The results verified that the maximum shear force applied to the super-structure is approximately twice the friction coefficient.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Kyoto University, 25249078
• Seismic Performance of Rocking Frames with Column Mid-height Uplift Mechanism at the First Story
  Grants-in-Aid for Scientific Research
  01 Apr. 2013 - 31 Mar. 2016
  Midorikawa Mitsumasa, ASARI Tetsuhiro, AZUHATA Tatsuya, ISHIHARA Tadashi, OKAZAKI Taichiro
  The steel frames with column mid-height uplift (CMU) mechanism at the first story are implemented as response-control structural systems that reduce the seismic effects by exploiting the gravity effect generally deteriorating the seismic performance of ordinary structures. In the previous studies, the reduction effect on the seismic response of the column-base uplift (CBU) rocking systems with columns allowed to uplift has been evaluated and examined. The advantages and disadvantages of the systems have also been discussed. This study presents the seismic performance of CMU rocking frames with emphasis on the fundamental mechanical properties of CMU frames based on the simplified analytical models, performance evaluation of CMU mechanism resulted from the cyclically static loading tests and the seismic response behavior of CMU frames. Finally, some suggestions and recommendations are made on the seismic design of the rocking systems.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 25289177
• Design and Seismic Performance of Steel Braced Frames
  Grants for Research and Education in Steel Structures
  Apr. 2014 - Mar. 2016
  岡崎太一郎
  The Japan Iron and Steel Federation, Principal investigator, Competitive research funding
• Economic beam-to-column moment connections in steel structures
  Grants-in-Aid for Scientific Research
  Apr. 2012 - Mar. 2015
  OKAZAKI TAICHIRO
  Steel systems using I-shaped columns instead of box-shaped columns was examined to increase the economy of steel building construction. Two full-scale beam-to-column moment connections were tested in the laboratory. One specimen connected the beam to the column flange, while in the second specimen connected the beam to the column web. Both specimens exhibited similar performance to standard connections of a I-shaped beam to a box-shaped column. However, the connections to the web resulted in a 10% loss in stiffness. Out-of-plane deformation of the column web and in-plane deformation of the continuity plates was notable in the post-yield response. The experimental behavior was reproduced successfully by a detailed, nonlinear finite element simulation. Both the experiment and simulation indicated that the connection to the column web is susceptible to fracture in the weld between the beam flange and continuity plate.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 24560676
• Development and Application oSfeismically Response-control
  Grants-in-Aid for Scientific Research
  2010 - 2012
  MIDORIKAWA Mitsumasa, ASARI Tetsuhiro, AZUHATA Tatsuya, ISHIHARA Tadashi, OKAZAKI Taichiro
  The steel frames with uplift column-bases are implemented as response-control structural systems that reduce the seismic effects by exploiting the gravity effect generally deteriorating the seismic performance of ordinary structures. The reduction effect on the seismic response of the base-plate-yielding (BPY) rocking systems with columns allowed to uplift has been evaluated and examined. The advantages and disadvantages of the systems have also been discussed. This study presents the seismic response characteristics with emphasis on the torsional behavior of the BPY systems and proposes the advanced rocking systems resolving the disadvantage of the BPY systems towards developing and applying widely the rocking structural systems. Finally, some suggestions and recommendations are made on the seismic design of the rocking systems.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 22360219
• Steel Connections using Structural Adhesives
  Grants-in-Aid for Scientific Research
  2010 - 2011
  OKAZAKI Taichiro
  In order to examine how structural adhesives could be utilized in steel construction, a total of 65 double-splice tension coupons were constructed from two types of adhesives and with various splice proportions. With one of the adhesives, the coupon strength increased with splice length to the point where the splice strength exceeded the yield strength of steel. Three out of 50 specimens exhibited a 25% lower strength owing to the fact that they were governed by interfacial failure rather than cohesive failure. In contrast, with the other adhesive, the coupon strength did not change significantly with splice length and coupon failure was governed entirely by interfacial failure.
  Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 22760430
• International hybrid simulation of tomorrow's braced frame systems　　　　　　　　　　　　　　　
  NEESR-SG
  2006 - 2011
  Taichiro OKAZAKI
  National Science Foundation, Principal investigator, Competitive research funding
• Damage investigation and data collection for collapsed I-35WBridge　　　　　　　　　　　　　　　
  SGER
  2007 - 2009
  Taichiro OKAZAKI
  National Science Foundation, Principal investigator, Competitive research funding