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Matsumoto Koji

Faculty of Engineering　Civil Engineering　Infrastructure and ManagementAssociate Professor

Researcher basic information

■ Degree
  • 博士（工学）, 北海道大学
■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
  • 10573660
J-Global ID■ Research Keywords and Fields
Research Keyword
  • Maintenance Engineering
  • Structural Engineering
  • Concrete Engineering
Research Field
  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention), Structure engineering and earthquake engineering
  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention), Civil engineering material, execution and construction management
■ Educational Organization

Career

■ Career
Career
  • Apr. 2019 - Present
    Hokkaido University, Faculty of Engineering, Associate Professor, Japan
  • Jan. 2015 - Mar. 2019
    The University of Tokyo, Institute of Industrial Science, Project Assistant Professor, Japan
  • Apr. 2010 - Jan. 2015
    Tokyo Institute of Technology, 大学院理工学研究科, Assistant Professor, Japan

Research activity information

■ Papers
  • Equilibrium-based analysis of diagonal tension failure from a re-entrant corner of an RC half-joint
    Takeru Kanazawa; Kohei Nagai; Koji Matsumoto
    Structures, 59, Jan. 2024
    Scientific journal
  • Estimation of Construction Year of Medium to Long Road Bridges in Zambia using Satellite Imagery
    Bennie Hamunzala; Koji Matsumoto
    IABSE Symposium Manchester 2024: Construction's Role for a World in Emergency, 319, 327, 2024
    International conference proceedings
  • Polymer cement mortar strengthened RC beams with/without silica fume as repair material
    Mahmudul Hasan Mizan; Koji Matsumoto
    Construction and Building Materials, 409, 15 Dec. 2023
    Scientific journal
  • Investigating the fracture behavior of structural concrete shear key in prefabricated walls by discrete modeling
    Saeid Mehrpay; Koji Matsumoto; Miaochang Zhu; Zhao Wang; Tamon Ueda
    Construction and Building Materials, 397, 15 Sep. 2023
    Scientific journal
  • Improved Method for Estimating Construction Year of Road Bridges by Analyzing Landsat Normalized Difference Water Index 2.
    Bennie Hamunzala; Koji Matsumoto; Kohei Nagai
    Remote Sensing, 15, 14, 3488, 3488, Jul. 2023
    Scientific journal
  • Durability Enhancement Effect of Silica Fume on the Bond Behavior of Concrete–PCM Composites under Environmental Conditions
    Mahmudul Hasan Mizan; Koji Matsumoto
    Polymers, 15, 9, 2061, MDPI AG, May 2023
    Scientific journal
  • Contractor's Controlling Factors Contributing to Effective Construction Waste Management in Building Construction
    Vuthea Min; Kriengsak Panuwatwanich; Koji Matsumoto
    International Conference on Construction in the 21st Century, 2023-May, 2023
    International conference proceedings
  • Field investigation and finite element analysis on expansion and shrinkage strains of expansive concrete structures
    Hakas Prayuda; Ganchai Tanapornraweekit; Somnuk Tangtermsirikul; Koji Matsumoto; Passarin Jongvisuttisun; Chalermwut Snguanyat
    Construction and Building Materials, 360, 19 Dec. 2022
    Scientific journal
  • Degradation behavior of multifunctional carbon fabric-reinforced cementitious matrix composites under anodic polarization
    Miaochang Zhu; Ji Hua Zhu; Tamon Ueda; Koji Matsumoto
    Construction and Building Materials, 341, 25 Jul. 2022
    Scientific journal
  • Material comparative analysis of crack-bridging degradation of SFRC structural beams under flexural fatigue loading
    Mohamed Adel; Koji Matsumoto; Tamon Ueda; Kohei Nagai
    Construction and Building Materials, 339, 11 Jul. 2022
    Scientific journal
  • Estimation of restrained expansion strain of reinforced expansive concrete considering mixture and curing conditions
    Hakas Prayuda; Rasla Dumaru; Ganchai Tanapornraweekit; Somnuk Tangtermsirikul; Warangkana Saengsoy; Koji Matsumoto
    Construction and Building Materials, 322, 07 Mar. 2022
    Scientific journal
  • Studying the Influence of Silica Fume on Bond Strength of the PCM-Concrete Interface under Shear Stress Condition
    Mahmudul Hasan Mizan; Koji Matsumoto
    Materials, 15, 4, 1473, MDPI AG, Feb. 2022
    Scientific journal
  • Performance of FRCM composites and FRCM-strengthened RC beams subjected to anodic polarization and cyclic loading
    Liangliang Wei; Ji Hua Zhu; Tamon Ueda; Koji Matsumoto
    Engineering Structures, 250, 113475, Elsevier BV, 01 Jan. 2022
    Scientific journal
  • INFLUENCE OF SILICA FUME ON THE PCM-CONCRETE INTERFACIAL BOND STRENGTH UNDER TENSILE AND SHEAR STRESS CONDITIONS
    Mahmudul Hasan Mizan; Koji Matsumoto
    fib Symposium, 2276, 2285, 2022
    International conference proceedings
  • Experimental and analytical study on the behavior of RC beams with externally bonded carbon-FRCM composites
    Koji Matsumoto; Liangliang Wei; Tamon Ueda; Ji-Hua Zhu
    Composite Structures, 273, 114291, Elsevier BV, 01 Oct. 2021
    Abstract This paper presents both experimental and analytical study results for predicting the flexural capacity of reinforced concrete (RC) beams with externally bonded carbon fabric reinforced cementitious matrix (carbon-FRCM). Firstly, the available prediction approaches for FRCM-strengthened RC in flexure were summarized. The prediction formulas were deficient in the fabric slippage failure. Nine carbon-FRCM specimens with different layers of carbon fabric (CF) were tested under uniaxial tensile loading. Four RC beams were strengthened in flexure with carbon-FRCM having different layers of CF, which were tested under four-point bending. From the tensile test results, the apparent strain of CF was derived from the global strain of carbon-FRCM, and the two-layer carbon-FRCM was an optimized selection in the design of multilayer carbon-FRCM. From the bending test results, the utilization efficiency of CF was slightly higher in the fabric slippage failure than that in the peeling-off of concrete cover, and the failure mode was differentiated as the layers of CF increased. Additionally, a new procedure of prediction formulas in flexure for carbon-FRCM-strengthened beams was proposed, using the apparent strain of CF to assess the strengthening performance of beams at different load-carrying scenarios. The prediction of the proposed formulas agreed well with the experimental results.
  • Crack-bridging degradation and evolution in SFRC structural beams under variable amplitude flexural cyclic loading
    Mohamed Adel; Koji Matsumoto; Kohei Nagai
    Composite Structures, 272, 114176, Elsevier BV, 15 Sep. 2021
    Scientific journal
  • Bond behavior of carbon fabric reinforced cementitious matrix (FRCM) composites considering matrix impregnation
    Miaochang Zhu; Ji Hua Zhu; Tamon Ueda; Koji Matsumoto; Meini Su
    Composite Structures, 262, 15 Apr. 2021
    Scientific journal
  • Exploring the transfer of knowledge by Japanese engineers after participation in infrastructure maintenance training programs
    M. Henry; K. Matsumoto; H. Yokota; K. Nagai
    Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations - Proceedings of the 10th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2020, 4084, 4088, 2021
    International conference proceedings
  • Enhancement of the concrete-PCM interfacial bonding strength using silica fume
    Mahmudul Hasan Mizan; Tamon Ueda; Koji Matsumoto
    Construction and Building Materials, 259, 119774, 30 Oct. 2020
    English, Scientific journal
  • Evaluation of crack-bridging strength degradation in SFRC structural beams under flexural fatigue
    Mohamed Adel; Punyawut Jiradilok; Koji Matsumoto; Kohei Nagai
    Composite Structures, 244, 112267, Elsevier BV, 15 Jul. 2020
    Scientific journal
  • Investigation on local bond behavior in concrete and cement paste around a deformed bar by using DIC technique
    Ahmed Okeil; Koji Matsumoto; Kohei Nagai
    Cement and Concrete Composites, 109, 103540, Elsevier BV, May 2020
    Abstract This study is an effort to gain a better understanding of local bond behavior between a reinforcing bar and concrete or cement paste. Axial tension tests were applied to deformed steel bars that had been embedded in specimens of concrete and cement paste. The specimens were formed with openings to allow for full and continuous observation. The results of digital image correlation (DIC) analysis unveiled differences in the phenomena of crack propagation from the surface of the steel rebar inside concrete and cement paste. In concrete, large deformations tend to concentrate around the interface between mortar and aggregate particles, especially big particles. The results also show that a similar interface zone of almost 1–2 mm around the deformed bar is present in both concrete and cement paste. Finally, it is shown that there are deformations normal to the surface of the steel bar in concrete and cement paste which result in opening, not only sliding, at the concrete-steel interface.
  • Analytical investigation of the role of reinforcement in perpendicular beams of beam-column knee joints by 3D meso-scale model
    Liyanto Eddy; Punyawut Jiradilok; Koji Matsumoto; Kohei Nagai
    Engineering Structures, 210, 01 May 2020
    Scientific journal
  • Evaluating Expectations for Training Transfer: Exploratory Study on a Capacity Development Project for Road and Bridge Technology in Myanmar
    Michael Henry; Kohei Nagai; Koji Matsumoto; Hiroshi Yokota
    Journal of Disaster Research, 15, 3, 368, 376, Fuji Technology Press Ltd., 30 Mar. 2020, [Peer-reviewed]
    Scientific journal, To ensure the long-term performance of bridges in Myanmar, the Japan International Cooperation Agency (JICA) initiated a capacity development project to enhance the quality control capabilities of engineers in the Myanmar government. Such expertise will be transferred to a group of “core trainers,” who will be responsible for sharing their acquired skills and knowledge with other engineers in Myanmar. The effective transfer of Japanese expertise is thus crucial for realizing the project’s goal of improving the quality of bridges and structures managed by the government of Myanmar. This research aims to explore the perspectives and expectations of the core trainers’ for training transfer after the project using the results of a survey questionnaire and to evaluate the effect of various factors on their expectations for transfer using partial least squares path modeling. It was found that the core trainers had positive expectations regarding the benefits of training transfer as well as generally positive perspectives on the factors affecting such transfer. The results of statistical modeling, however, failed to reveal any significant relationships between the modeled factors and the expectations for training transfer. This may be attributable to the sample size, which is limited by the scope of the capacity development project; a mixed method approach is therefore proposed as a more appropriate method in this context. Nonetheless, the results generally suggest that the work environment is fundamental in facilitating effective training transfer, and further research is necessary.
  • Development of discrete meso-scale bond model for corrosion damage at steel-concrete interface based on tests with/without concrete damage
    Punyawut Jiradilok; Yi Wang; Kohei Nagai; Koji Matsumoto
    Construction and Building Materials, 236, 117615, Elsevier BV, Mar. 2020
    Abstract Rebar corrosion can lead to significant deterioration in bond strength between steel and concrete. However, since confinement is lost as the concrete cracks, the changes in frictional bonding and mechanical bonding resulting from corrosion remain unclear and there is a need for an efficient tool that can evaluate the bond performance of corroded concrete structures. In this study, an innovative pull-out test is used to study changes in bonding in reinforced concrete after rebar corrosion, then a discrete meso-scale model based on the Rigid Body Spring Model (RBSM) is developed to simulate the observed bond behavior. To isolate the effects of concrete cracking, after an initial pull-out test, the corroded rebars are obtained and used as the reinforcement in newly cast sound specimens that are subject to a further pull-out test. A corrosion acceleration method is used to obtain corroded rebars. Different types of reinforcement (round rebars and deformed rebars) are studied. The results are used to study changes in frictional bonding and mechanical bonding at different degrees of corrosion. It is found that, without concrete cracking, the frictional bond in specimens with both round and deformed rebars significantly increases with the amount of corrosion, while total bond strength of specimens with deformed bar is almost unchanged because mechanical bonding is weakened. In the presence of concrete cracking, for specimens reinforced with a corroded round rebar, bond capacity increases initially (up to 3% corrosion) and then falls as corrosion increases, while bonding in those with a corroded deformed rebar shows a consistent decrease. In the RBSM-based simulations, the effect of corrosion is modeled by adjusting springs at the corroded interface. Constitutive models of shear and normal springs are developed to simulate corrosion and reflect the changes on frictional and mechanical bonding. Simulated results for load-displacement relationship, pull-out capacity and crack pattern are in good agreement with the experimental results. The numerical simulation is used to visualize internal stress development and strain distribution along the rebar as the degree of corrosion increases, a result that cannot be obtained by experimental methods. The results demonstrate that RBSM is a useful tool for evaluating the mechanical performance of corroded reinforced concrete structures.
  • Expansive cracking and compressive failure simulations of ASR and DEF damaged concrete using a mesoscale discrete model
    Yi Wang; Yushi Meng; Punyawut Jiradilok; Koji Matsumoto; Kohei Nagai; Shingo Asamoto
    Cement and Concrete Composites, 104, 103404, Elsevier BV, Nov. 2019
    Abstract Internal stresses induced by the alkali silica reaction (ASR) and delayed ettringite formation (DEF) can cause cracking and degrade the mechanical properties of concrete, but the relationship between these phenomena remains unclear. In this study, crack patterns and the loss of compressive strength and elastic modulus of concrete after ASR and DEF expansion are simulated at the mesoscale using a three-dimensional Rigid Body Spring Model (3D RBSM). Concrete expansions induced by ASR and DEF are introduced in the model by applying initial strain on the springs of interfacial transition zone (ITZ) and mortar elements as damage history respectively. After verifying the model with single aggregate, further analysis of differences in concrete cracking due to ASR and DEF damage is carried out. The effect of the percentage of reactive aggregate is studied in the cases of ASR damage, while different intensified expansion areas are considered in the case of DEF. The simulated losses of mechanical properties of the concrete are compared with the experimental results and good agreement is obtained. It is found that the loss of mechanical properties is dominated by internal cracks rather than the surface crack pattern. Compressive strength is highly dependent on the development of large cracks while elastic modulus is closely related to the total number of cracked faces. More importantly, regardless of the intensified expansion area, the mechanical properties are consistent with expansive cracking damage.
  • Fatigue pull-out failure of deformed bars in concrete under the effect of liquid water
    Kohei Nagai; Hirofumi Yamaguchi; Koji Matsumoto
    Cement and Concrete Composites, 91, 198, 208, Elsevier BV, 01 Aug. 2018
    Abstract To investigate the pull-out behavior of deformed bars subjected fatigue loading in the simultaneous presence of liquid water, fatigue pull-out tests were carried out. Experimental parameters were the presence/absence of liquid water, matrix type, loading pattern, and the presence of a mechanical anchorage. It was found that the matrix in the vicinity of the deformed bar was converted into sludge by the complex interaction of liquid water and fatigue, and pull-out failure of the deformed bar occurred without accompanying macro cracks, resulting in significantly reduced fatigue life. Pull-out failure associated with the formation of sludge occurred at a comparatively low load level, and tended to occur when the water-cement ratio was high and under reversal loading. A further finding is that mechanical anchorages have the effect of reducing the conversion to sludge and have the beneficial effect of preventing pull-out failure.
  • Visual Investigation Method and Structural Performance Evaluation for DEF Induced Damaged Indian Railway PC Sleepers
    松本 浩嗣
    Journal of Asian Concrete Federation, Vol. 4, No. 2, 103, 115, 2018, [Peer-reviewed], ［Internationally co-authored］
    Scientific journal
  • Investigation on possible causes of expansion damages in concrete – a case study of sleepers in Indian Railways
    Anupam Awasthi; Koji Matsumoto; Kohei Nagai; Shingo Asamoto; Seishi Goto
    Journal of Asian Concrete Federation, 3, 1, 49, 66, Asian Concrete Federation, 05 Jul. 2017
    Indian Railways uses factory made pre-tensioned pre-stressed concrete sleepers for its track. These sleepers start cracking after 6-9 years of their manufacturing in many areas of the Indian Railways. For the investigation of the premature cracking of sleepers, different categories of samples namely “Severely damaged”, “Moderately damaged”, and “Undamaged” are collected from different locations of Indian Rail- ways. These samples are analyzed under Scanning Electron Microscope (SEM) and Energy Dispersive Spec- troscopy (EDS). SEM images reveal that there is large ettringite deposition at the interfaces of aggregate and paste in case of “Severely damaged” and “Moderately damaged” sleepers, which could be a cause of delete- rious expansion and subsequent cracking, whereas the interfaces of “Undamaged” sleepers were found to be intact. High temperature experienced by these sleepers in form of steam curing during their production in factories may lead to Delayed Ettringite Formation (DEF) and subsequent expansion and cracking. Tempera- ture recorded in the concrete sleeper plant during steaming of the sleepers reveals that the temperature inside concrete exceeds 80°C, which is a critical temperature for the occurrence of damage due to DEF in future. Also, stress bench method of production of concrete sleepers, used in Indian Railways for older concrete sleeper plant, poses some structural deficiency which adversely affects the temperature of curing. Thus, DEF could be the possible cause of premature cracking of sleepers in Indian Railways.
  • REPLACEMENT OF CONVENTIONAL STEEL STIRRUPS BY INTERNAL REINFORCING CFRP GRIDS IN SHEAR OF CONCRETE BEAMS
    SUWANPANJASIL Sirapong; NAKAMURA Takuro; MATSUMOTO Koji; NIWA Junichiro
    Journal of JSCE, 5, 1, 377, 391, Japan Society of Civil Engineers, 2017
    English, This study proposes an innovative idea of shear reinforcement in concrete beam by replacing the conventional steel stirrups with CFRP grids at the shear span inside concrete cover. The compatibility between the internal grids and the surrounded concrete was investigated first in the elementary test. Flexural performances of two concrete elements reinforced by different spacing of internal grids were compared and discussed. After that, a concrete beam test was conducted with a total of eight RC beams varied in the number of grid strips in the shear span and the spacing of reinforcing grids. The experimental results showed that the shear capacity and the shear carried by internal CFRP grids significantly improved with a higher amount of grid strips; however, the increasing ratio of shear capacity was not proportional to the shear reinforcement ratio. Moreover, the location of internal grid in the shear span was an important part of the shear-resisting effectiveness in this study since the more number of grid strips located near the center of the shear span was much more effective to resist the propagation of diagonal shear crack than the grids at the edge. Finally, a model for evaluating shear carried by internal CFRP grids was introduced. Validity of the proposed model was explained by comparing with the experimental results and also other sets of experimental results.
  • Experimental study on shear behavior of the interface between old and new deck slabs
    Junichiro Niwa; Fakhruddin; Koji Matsumoto; Yuji Sato; Masahiko Yamada; Takahiro Yamauchi
    Engineering Structures, 126, 278, 291, Elsevier BV, Nov. 2016
    Abstract An experimental study of the interface shear transfer between differently aged concrete (old and new deck slabs) has been performed. The old and new deck slabs parts were crossed by steel bars and subjected to the external prestressing force. The tests were carried out to be representative of a proposed technique used for widening prestressed concrete (PC) highway decks. The experimental program comprised nine specimens tested under double-shear test by taking the initial prestressing levels, connection methods between steel bars, reinforcement ratio and surface roughness as parameters. The experimental results indicated that the failure behavior of the interface was greatly affected by the initial prestressing level, reinforcement ratio and surface roughness of the interface. Finally, a comparison of the experimental shear strength with those given by JSCE Standard Specification, AASHTO and fib Model Code 2010 showed a conservative result for low and high prestressing levels, low reinforcement ratio and smooth surface.
  • Investigation on the Pull-out Behavior of Deformed Bars in Cracked Reinforced Concrete
    Matsumoto Koji; Wang Tao; Hayashi Daisuke; Nagai Kohei
    Journal of Advanced Concrete Technology, 14, 9, 573, 589, Japan Concrete Institute, 21 Sep. 2016
    English, Scientific journal, Pull-out tests and numerical analyses for deformed bar were performed on test specimens having cracks in concrete along the axial direction of the bar. The parameters for the experiment and analysis were: the maximum width of the initial crack, the presence or absence of a mechanical anchorage, the presence or absence of bond on either side of the deformed bar, and the presence or absence of a transverse bar. In both the experiments and the analyses, the pull-out load was applied at the end of the deformed bar after introducing the initial cracking by means of preloading. The results showed that the pull-out performance was greatly reduced by cracking along the axial direction of the bar. Also, it was seen that cracking along the deformed bar tended to occur only on one side of the bar. In the particular case of mechanical anchorage it was found that bending stresses occurred near the anchorage due to eccentric loading. The transverse bar increases the residual crack width when the same initial crack width was generated before unloading and also inducing spalling of the concrete cover due to cracking of the bond, resulting the reduction in pull-out strength.
  • Effect of perpendicular beams on failure of beam-column knee joints with mechanical anchorages by 3D RBSM
    Liyanto Eddy; Koji Matsumoto; Kohei Nagai
    Journal of Asian Concrete Federation, 2, 1, 56, 66, Asian Concrete Federation, 05 Jul. 2016
    When mechanical anchorages are placed near the surface of a beam-column knee joint, anchorage failure may occur because of local stresses from anchorage plates. Perpendicular beams placed on both sides of the joint can be a way to avoid the occurrence of this failure. In this study, a meso-scale discrete analysis using 3D RBSM is conducted to investigate the effect of perpendicular beams on the behavior of a beamcolumn knee joint with mechanical anchorages and their effect on failure mode. By studying the internalstresses and cracks in a beam-column knee joint with mechanical anchorages, perpendicular beams can improve its performance in terms of loading capacity and failure behavior. Perpendicular beams are known to have two effects. The perpendicular beams increase bond performance along the development length of anchorages and resist the opening of the diagonal cracks. It has the same failure mode as in the case without perpendicular beams which is an anchorage failure, but the occurrence of the anchorage failure is delayed in this case. It is also inferred by simulation that the effective length of the perpendicular beams is determined by approximately 45 degrees inclination to the longitudinal beam, measured from the original position of anchorage plates.
  • FLEXURAL STRENGTHENING EFFECT OF PRE-TENSIONED UFC PANEL ON REINFORCED CONCRETE BEAMS
    LIMPANINLACHAT Pornpen; MATSUMOTO Koji; NAKAMURA Takuro; KONO Katsuya; NIWA Junichiro
    Journal of JSCE, 4, 1, 181, 196, Japan Society of Civil Engineers, 2016
    English, Recently, various strengthening methods have been utilized to enhance the structural performance and extend the life cycle of RC structures. However, the existing strengthening methods still have some drawbacks especially in the durability aspect. In this study, with the outstanding properties of UFC (i.e., high strength, ductility, and durability), a new flexural strengthening method using precast UFC panels was used to strengthen the RC beams. However, to obtain greater strengthening effect and durability, PC strands were pre-tensioned to the panel and this panel was subjected to a heat curing procedure to supplement a hydration procedure and eliminate the effect of shrinkage. Using this novel technology, this research was conducted to investigate the flexural enhancement and corresponding behavior of RC beams strengthened by pre-tensioned UFC panel. Five pre-tensioned UFC panels and eight strengthened RC beams were prepared and investigated using the bending test. Two different experimental parameters, i.e., prestressing level and amount of PC strands, were used. The undercut anchor bolts were applied for sufficient bonding between interfaces. The bending results of panels were investigated to compute the exact prestressing level in order to determine the calculation of prestressing losses. The results of the strengthened beams revealed that the pre-tensioned UFC panel drastically enhanced the loading capacity of RC beams, and each variable parameter affected the different structural characteristics. To ensure compatibility along a cross-section of the strengthening system, the compatibility along panel specimens and strengthened RC beams was investigated. Finally, the strain compatibility was satisfied at the mid-span of beams where the calculation of load-carrying capacity in strengthened beams could be carried out by using conventional flexural section analysis.
  • SHEAR-RESISTING MECHANISMS OF PRE-TENSIONED PC BEAMS WITHOUT SHEAR REINFORCEMENT STRENGTHENED BY CFRP SHEETS
    Thi Thu Dung NGUYEN; MATSUMOTO Koji; SATO Yuji; YAMADA Masahiko; NIWA Junichiro
    Journal of JSCE, 4, 1, 59, 71, Japan Society of Civil Engineers, 2016
    English, Although externally bonded carbon fiber-reinforced polymer (CFRP) sheets have been used more commonly for the strengthening of existing reinforced concrete (RC) structures, the effects of this strengthening method on prestressed concrete (PC) beams have not been well clarified. In this study, an experiment was conducted to investigate the behaviors of pre-tensioned PC beams without shear reinforcement strengthened in shear using externally bonded CFRP sheets with the consideration of CFRP reinforcement ratio, stiffness and prestressing level in strands. The results implied that the shear resistance in the strengthened PC beams depended on maintaining the combination of beam action, arch action, and the bonded sheets. The failures and the increase in shear capacity of the strengthened PC beams were strongly affected by the amount, thickness of the CFRP sheets, and the effective prestress in the strands. The higher effectiveness of strengthening could be obtained in the beams strengthened with a higher CFRP reinforcement ratio of the same thickness, higher elastic modulus sheets or having higher prestressing level. Nevertheless, the increase in the thickness of the sheets did not provide a better performance. Moreover, the high inaccuracy in the calculations using the equations stipulated in the recent design guidelines compared to the increment of the shear strength obtained by the experiment was explained by the shear-resisting mechanisms.
  • Application of PP-ECC in beam–column joint connections of rigid-framed railway bridges to reduce transverse reinforcements
    Rui Zhang; Koji Matsumoto; Takayoshi Hirata; Yoshikazu Ishizeki; Junichiro Niwa
    Engineering Structures, 86, 146, 156, Elsevier BV, Mar. 2015
    Abstract In the rigid-famed railway bridges, due to extensive amount of transverse reinforcements in the joint connections, the over congestion at the connection brings the difficulties in fabricating and casting. With the objective of avoiding the congestion, Polypropylene Fiber Reinforced Engineered Cementitious Composite (PP-ECC), as one kind of Engineered Cementitious Composites, was implemented to reduce the extensive amount of transverse reinforcements in the beam–column joint connection of rigid-framed railway bridges. The basic mechanical properties of PP-ECC were confirmed by compression and uniaxial tensile tests. The effects of reducing stirrup ratio in PP-ECC beams were investigated by four-point beam tests, including two normal reinforced concrete (RC) beams and five PP-ECC beams with stirrup ratios ranging from zero to 0.42%. Having confirmed the shear reinforcing effect of PP-ECC, three one-sixth scale beam–column joint connections were constructed and tested by applying a cyclic load. A specimen was prepared following the structural design of existing railway bridges in Japan but without transverse reinforcements in the joint. Further, two more specimens were prepared with reduced stirrups and ties in the beam and column, respectively. The experimental results reveal that the PP-ECC is effective in replacing transverse reinforcements in the beam–column joints of railway rigid-framed bridges.
  • A NEW ALTERNATIVE SHEAR IMPROVEMENT OF CONCRETE BEAMS BY INTERNALLY REINFORCING PBO FIBER MESH
    SUWANPANJASIL Sirapong; MATSUMOTO Koji; NIWA Junichiro
    Journal of JSCE, 3, 1, 67, 80, Japan Society of Civil Engineers, 2015
    English, This paper aims to develop a new method for shear reinforcing concrete beams by using the ultrahigh performance PBO fiber mesh as a replacement for conventional stirrups inside a concrete structural member. The elementary test was performed first to investigate the general behavior of the internal reinforcing PBO fiber mesh as a fundamental objective of this study. Then, nine RC beams with and without internal PBO fiber mesh were conducted in the RC beam test. The parameters in the RC beam test were the number of internal PBO mesh layers, the width of internal PBO mesh in the shear span, and the reinforcing configuration of the internal PBO mesh. The experimental results showed that the shear capacity and the shear carried by internal PBO fiber mesh increased significantly with a higher number of the internal mesh layers; however, the shear capacity decreased when the width of internal mesh in the shear span was expanded. Besides, the difference in reinforcing configuration of the internal PBO mesh showed a great impact on the shear capacity of concrete beams reinforced with internal PBO fiber mesh. Furthermore, an empirical method for evaluating shear carried by internal PBO fiber mesh was modeled and a moderate agreement between values from the model and values from the experiment was obtained.
  • SHEAR FAILURE MECHANISM OF REINFORCED CONCRETE HAUNCHED BEAMS
    HOU Chenwei; MATSUMOTO Koji; NIWA Junichiro
    Journal of JSCE, 3, 1, 230, 245, Japan Society of Civil Engineers, 2015
    English, This study aims to clarify the shear resistance mechanism of reinforced concrete haunched beams (RCHBs). Four series of ten RCHBs with different parameters (positions of haunched portions, thickness of the concrete cover, presence of stirrups and the arrangement of the tensile rebar) were tested. The results demonstrated that the bending position of the tensile rebar as well as the different arrangement of the tensile rebar highly influenced the crack propagations which caused the variation in the shear capacities due to different contributions of the arch action. Different diagonal crack angles also resulted in different contributions by stirrups in RCHBs with stirrups. The thicker concrete cover at the mid span affected the crack propagation but had almost no effect on the shear capacity. Nonlinear FEM analyses were also conducted to complement the experiments and verify the results, which showed a good agreement including load-deflection curves, load capacities and crack patterns. The shape of the compression zone, which dominates the arch action in RC beams, was also evaluated by the analyses.
  • EFFECTS OF EXTERNALLY BONDED CFRP SHEETS ON FLEXURAL STRENGTHENING OF PRETENSIONED PRESTRESSED CONCRETE BEAMS HAVING RUPTURED STRANDS
    NGUYEN Thi Thu Dung; MATSUMOTO Koji; SATO Yuji; IWASAKI Asami; TSUTSUMI Tadahiko; NIWA Junichiro
    Journal of JSCE, 2, 1, 25, 38, Japan Society of Civil Engineers, 2014
    English, The paper represents the experimental work of strengthening prestressed concrete (PC) beams having strands ruptured at the midspan using externally bonded carbon fiber reinforced polymer (CFRP) sheets. The effects of different parameters as the sheet lengths, number of the bonded sheets and attaching schemes on the flexural performance were investigated. The flexural capacity of the strengthened beam having 50% ruptured strands was enhanced up to 167.3% compared to that of the undamaged PC beam. The outcomes exhibited that both the number of layers and the lengths of CFRP sheets affected the failure behaviors as well as the flexural capacity of the strengthened PC beams. The increase in the number of sheets resulted in the reduction of tensile stress resisted by the remaining prestressing strands. However, the increase in the number of sheets with insufficient sheet lengths did not provide a higher flexural strength because the failure mode was transformed from the debonding induced by the flexural cracks in the constant moment region to the debonding from the sheet ends. The increase in the sheet lengths not only prevented the latter failure but also significantly improved the beam stiffness. More importantly, the debonding of the sheets was avoided by wrapping the transverse sheets for the whole beam span. The prediction of the flexural strength of the strengthened PC beams based on the guidelines of ACI, JSCE and fib exhibited a good agreement with small total thickness of the bonded sheets. However, the equations in the guidelines were conservative when the total thickness of the bonded sheets was large.
  • EXPERIMENTAL STUDY ON SHEAR BEHAVIOR OF RC BEAMS USING U-SHAPED UFC PERMANENT FORMWORK WITH SHEAR KEYS AND BOLTS
    WIROJJANAPIROM Puvanai; MATSUMOTO Koji; KONO Katsuya; NIWA Junichiro
    Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 69, 1, 67, 81, Japan Society of Civil Engineers, 2013
    English, UFC is one of the cementitious materials which have outstanding properties such as more than 200 MPa compressive strength, high ductility and durability. The permanent formwork for RC structures is one of the promising applications of UFC. This research is aimed to investigate the shear behavior of RC beams using a U-shaped UFC permanent formwork. Eight RC beams using a U-shaped UFC permanent formwork were tested by four-point bending test. The experimental parameters were the presence of shear keys at the internal surface of a UFC U-shaped permanent formwork, presence of screws and bolts, thickness of formwork, shear span to effective depth ratio and presence of stirrups. The experimental results indicated that a U-shaped UFC permanent formwork enhanced the shear capacity of RC beams more than twice compared to normal RC beams. In addition, the shear resistance mechanisms were investigated. By using a UFC formwork with shear keys and screwed bolts, the UFC formwork intercepted widening of diagonal cracks inside a RC part. Finally, the shear carried by a UFC permanent formwork was investigated. The proposed calculation method can provide a good agreement with the experimental values.
  • SHEAR CAPACITY OF FIBER REINFORCED CONCRETE BEAMS WITH VARIOUS TYPES AND COMBINATIONS OF FIBERS
    JONGVIVATSAKUL Pitcha; MATSUMOTO Koji; NIWA Junichiro
    Journal of JSCE, 1, 1, 228, 241, Japan Society of Civil Engineers, 2013
    English, This paper presents an investigation of the shear carried by fibers of fiber reinforced concrete (FRC) beams consisting of various types and combinations of fibers, and a proposal of the predictive equation for their shear capacity. Eight FRC beams with stirrups were tested by four-point bending. The testing program employed five fiber types (30-mm steel, 60-mm steel, polypropylene, polyvinyl alcohol and polyethylene terephthalate) and three combinations of hybrid fibers. The stress transferred across a diagonal crack was investigated using crack surface displacement and tension softening curve. The stress was significantly affected by the material types and combinations of fibers. The stress and the angle of the diagonal crack increased with the increase in fracture energy, whereas the diagonal crack length decreased. On the other hand, the angle of principal tensile strain did not significantly vary in the range of study. The shear carried by fibers was investigated from the stress and area of the crack surface. Good correlation between test results and calculated results was observed. In addition, a simplified equation of shear carried by fibers, involving fracture energy, stirrup ratio and effective depth, was formulated. Finally, a predictive equation for shear capacity of FRC beams was proposed and validated with 43 FRC beams. The proposed equation gave good prediction for FRC beams with various types and combinations of fibers.
  • DIAGONAL COMPRESSIVE CAPACITY OF REINFORCED CONCRETE BEAMS WITH WIDE STIRRUP SPACING
    TANTIPIDOK Patarapol; MATSUMOTO Koji; NIWA Junichiro
    Journal of JSCE, 1, 1, 298, 306, Japan Society of Civil Engineers, 2013
    English, To promote more widespread use of high-strength concrete (HSC) for the efficient design of reinforced concrete (RC) beams, an experimental investigation on the effect of wide stirrup spacing on the diagonal compressive capacity of HSC beams was performed. The predictive equation for the diagonal compressive capacity of RC beams proposed by the authors was modified to cover the application to RC beams with wide stirrup spacing. Four 590-mm deep I-beams with wide stirrup spacing were tested by three-point bending. The influence of stirrup spacing, stirrup diameter, and the number of stirrup legs was discussed. The results show that the diagonal compressive capac ity linearly decreased with wider stirrup spacing regardless of its diameters when stirrup spacing was narrower than 140 mm; however, the effect of spacing became negligible when stirrup spacing was wider than 140 mm. Even when wide stirrup spacing was used, the diagonal compressive stress did not concentrate on the local area of the specimens and a sufficient confinement effect was achieved by providing two-legged stirrups; the localization of compressive stress on the struts was likewise prevented. Finally, the predictive equation by the authors was modified on the basis of the experimental findings. The modified equation covers the application to RC beams with wide stirrup spacing while maintaining adequate simplicity and precise prediction of the diagonal compressive capacity of RC beams.
  • Experimental Study on the Possibility of Using Steel Fiber–Reinforced Concrete to Reduce Conventional Rebars in Beam-Column Joints
    NIWA, JUNICHIRO; KABIR, SHAKYA; Shakya, Kabir; Matsumoto, Koji; Watanabe, Ken
    Journal of Materials in Civil Engineering, 24, 1461, 1473, American Society of Civil Engineers (ASCE), 01 Dec. 2012
    AbstractIn rigid-framed railway bridges, because of excessive amounts of rebar in beams and columns, overcongestion at the beam-column joints of rigid-framed railway bridges was investigated in this paper. The experiments were conducted on eight one-sixth scaled specimens that include four T-joint and four knee-joint specimens. In the control specimens, the amount of steel rebars and their arrangements and detailings resembled the as-built configuration of the rigid-framed railway bridge in Japan. In the other specimens, the amount of steel rebars was reduced and steel fibers were varied as 0, 1.0, and 1.5% by volume. The experimental results of the specimens were compared in terms of crack patterns, load-displacement relationships, ductility, energy dissipation capacity, and stiffness degradation and found that the performance of the control specimens and specimens with 1.5% of steel fibers and reduced steel rebars was comparable.
  • Application of steel fibers in beam–column joints of rigid-framed railway bridges to reduce longitudinal and shear rebars
    KABIR, SHAKYA; Shakya, Kabir; Matsumoto, Koji; Watanabe, Ken; NIWA, JUNICHIRO
    Construction and Building Materials, 27, 482, 489, Elsevier BV, 01 Feb. 2012
    Abstract The effects of reducing steel rebars in beam–column joints and use of steel fiber reinforced concrete (SFRC) were investigated in this study. A control specimen was prepared following the structural design of existing railway bridges in Japan. Further, three more specimens were prepared with reduced longitudinal rebars and hoops in columns. In these three specimens amount of steel fibers were varied by 0%, 1% and 1.5%, respectively. Based on the comparison of observed responses, it is found that the addition of 1.5% of steel fibers is effective in reducing amount of steel rebars in the beam–column joints of railway bridges.
  • EVALUATION OF SHEAR CARRIED BY STEEL FIBERS OF REINFORCED CONCRETE BEAMS USING TENSION SOFTENING CURVES
    JONGVIVATSAKUL Pitcha; WATANABE Ken; MATSUMOTO Koji; NIWA Junichiro
    Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 67, 4, 493, 507, Japan Society of Civil Engineers, 2011
    English, The aim of this paper is to propose the method for evaluating the shear carried by steel fibers of reinforced concrete with steel fibers (RSF) beams. Ten RSF beams with various steel fiber volume fraction, stirrup ratio and specimen size were tested by a four-point bending test. The crack surface displacement was examined by the image analysis. Length of the diagonal crack was measured. The tension softening curves were used to calculate the stress transferred across the diagonal crack. The contribution of steel fibers on the shear resistance of RSF beams has been investigated based on the fracture mechanics. The shear carried by steel fibers calculated from the proposed method showed good agreement with experimental values.
  • SHEAR CARRYING CAPACITY OF SEGMENTAL CONCRETE BEAMS WITH DRAPED EXTERNAL TENDONS
    NGUYEN Dinh Hung; MATSUMOTO Koji; WATANABE Ken; HASEGAWA Tsuyoshi; NIWA Junichiro
    Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 67, 4, 564, 577, Japan Society of Civil Engineers, 2011
    English, This study presents an investigation of the shear be havior of segmental concrete beams with draped external tendons. Deviator force and transfer mechanism of prestressing force from an anchorage that affect the shear failure mechanism have been examined base d on the results of experimental procedure and FEM with different location of deviator and inclined angle of draped tendons. The modified model proposed by authors has been extended for segmental concrete beam s with draped external tendons with considering the effect of deviator force and transfer mechanism of prestressing force from the anchorage. The results from the extended modified model for draped external tendons had a good agreement with experimental results.
  • PROPOSED PREDICTIVE EQUATION FOR DIAGONAL COMPRESSIVE CAPACITY OF REINFORCED CONCRETE BEAMS
    TANTIPIDOK Patarapol; KOBAYASHI Chikaharu; MATSUMOTO Koji; WATANABE Ken; NIWA Junichiro
    Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 67, 4, 535, 548, Japan Society of Civil Engineers, 2011
    English, The current standard specifications of JSCE fo r the diagonal compressive capacity of RC beams only consider the effect of the compressive strength of conc rete and are not applicable to high strength concrete. This research aims to investigate the effect of vari ous parameters on the diagonal compressive capacity and propose a predictive equation. Twenty five I-beams were tested by three-point bending. The verification of the effects of concrete strength, stirrup ratio and spacing, shear span to effective depth ratio, flange width to web width ratio and effective depth was performed. The diagonal compressive capacity had a linear relationship to stirrup spacing regardless of its diameter. The effect of spacing became more significant with higher concrete strength. Thus, the effect of concrete strength and stirrup spacing was interrelated. On the other hand, there were slight effects of the other parameters on the diagonal compressive capacity. Finally, a simple empirical equation for predicting the diagonal compressive capacity of RC beams was proposed. The proposed equation had an adequate simplicity and can provide an accurate estimation of the diagonal compressive capacity than the existing equations.
  • Mesoscopic Analysis of Mortar under High-Stress Creep and Low-Cycle Fatigue Loading
    Matsumoto Koji; Sato Yasuhiko; Ueda Tamon; Wang Licheng
    Journal of Advanced Concrete Technology, 6, 2, 337, 352, Japan Concrete Institute, 2008
    English, Mesoscopic analyses of mortar failure under high-stress creep and low-cycle fatigue loading are presented using a newly developed time-dependent constitutive model for Rigid Body Spring Model, which is a discrete analysis method. The failure process over time was successfully expressed by adopting a four-component combined mechanical model as the time-dependent model of connected springs, and by developing a new method for determining the failure state for load-controlled analysis. The numerical model provides reasonable results not only for the stress-strain characteristics under cyclic loading but also for the inapplicability of Miner's law under varying stress levels. The mechanism of the time-dependent failure of mortar was clarified by investigating the local stress-strain behaviors.
■ Other Activities and Achievements
■ Syllabus
  • コンクリート構造工学特論, 2024年, 修士課程, 工学院
  • 大学院共通授業科目（教育プログラム）：JICA開発大学院連携プログラム, 2024年, 修士課程, 大学院共通科目
  • コンクリート構造工学特論, 2024年, 博士後期課程, 工学院
  • 国際交流Ⅱ, 2024年, 学士課程, 国際本部
  • 構造力学Ⅱ, 2024年, 学士課程, 工学部
  • 構造動力学, 2024年, 学士課程, 工学部
  • 耐震工学, 2024年, 学士課程, 工学部
  • 地震工学, 2024年, 学士課程, 工学部
  • 構造設計論, 2024年, 学士課程, 工学部
  • 構造・コンクリート工学実験, 2024年, 学士課程, 工学部
  • 土木工学創成実験Ⅰ, 2024年, 学士課程, 工学部
■ Research Themes
  • デジタルツインモデルと内部損傷逆推定解析を用いたRC構造性能予測システムの構築
    科学研究費助成事業
    01 Apr. 2026 - 31 Mar. 2029
    長井 宏平; 松本 浩嗣; 中村 拓郎; 橋本 勝文; 酒井 雄也; 浅本 晋吾
    日本学術振興会, 基盤研究(A), 北海道大学, 26H02151
  • 深層学習を実装した微細構造解析による鉄筋コンクリート内部損傷の逆推定と性能評価
    科学研究費助成事業
    Apr. 2022 - Mar. 2025
    長井 宏平; 松本 浩嗣; 酒井 雄也; 浅本 晋吾
    日本学術振興会, 基盤研究(A), 東京大学, 22H00224
  • 損傷後に補修したRC構造性能評価のための微細構造解析システムの構築
    科学研究費助成事業
    07 Oct. 2021 - 31 Mar. 2024
    長井 宏平; 松本 浩嗣; 鎌田 知久; 金澤 健
    海外共同研究者となる深セン大学の上田教授，カリフォルニア大学デイビス校のBolander教授と研究の進め方について確認した。
    研究のコアとなる微細構造解析プログラムに連続繊維シートのモデルを組み込み，引張試験による付着挙動の解析を行った。微細スケールにおいてはコンクリート側にもひび割れが進展し損傷が蓄積されることでマクロな付着挙動にも影響を与える。また，コンクリートには繊維軸方向から横方向にも応力が広がるが，これを3次元解析により再現可能である。解析により，局所の損傷と全体の応答を再現し，解析の妥当性の検討を続けている。
    水分移動のモデル化についても，既往の水分移動，物質移動モデルから，本解析システムに組み込むモデルの高度化を進めている。特に，水分供給初期にコンクリートの乾燥度が高い場合と湿潤状態では，条件により水分の浸透速度が異なるので，適切なモデル化が必要である。
    鉄筋腐食については，腐食後の付着挙動をより正確に再現するために，研究代表者が過去に行った試験の観察動画から画像相関法を用いて界面の挙動をより詳細に分析し，鉄筋からコンクリートへの応力伝達の変化と鉄筋表面の腐食生成物の影響について調査をしている。
    凍結融解作用については，水分の供給と温度の影響のモデル化の方法と，劣化後に材料力学特性がどのように低下していくかについて，既往の文献を参考に，モデル化の方法を検討している。特に温度履歴のモデルへの反映を，解析可能なものとして行うことが重要となる。
    日本学術振興会, 国際共同研究加速基金(国際共同研究強化(B)), 東京大学, 21KK0072
  • Radiation technology for new concrete material development that significantly increases productivity
    Grants-in-Aid for Scientific Research
    01 Apr. 2021 - 31 Mar. 2024
    杉山 隆文; 松本 浩嗣; 高橋 駿人
    コンクリート構造物の建設需要が経済的、社会的、環境側面において多様化する中で、コンクリートに要求される性能が大きく変化している。品質を確保しながら生産性を高めることが共通しているが、その上で過酷環境、長寿命化、環境負荷低減などの条件を満足するコンクリートを実現することが求められている。そして、これらを満足する素材や配合設計の自由度が拡大する中、新しい素材や設計手法の開発において、性能を迅速に評価する手法の研究開発を目的としている。特に、耐凍害性の向上が期待される新素材である中空微小球の導入による気泡構造の可視化や研究期間が長期に及ぶ浸食作用による抵抗性評価のために、X線CT法に代表される放射線の優れた非破壊透視技術を活用した。
    気泡構造はASTM法に代表されるリニアトラバース法が採用されるが、多くの労力を要していた。また、電子顕微鏡による断面観察によって中空微小球の分布の様子を観察していた。これら従来法は、いずれも平面観察であり空間分布を捉えることはできていなかった。そこで、X線CT法を用いることで、硬化体への特別な成型過程が不要で客観的な評価判定が可能となることを示した。さらに、直径3㎜で高さが5㎜の微小供試体を用いることで、マイクロメートルオーダーでの分析が可能なCT-XRD連成法を採用することで、コンクリートからのカルシウムイオンの溶出現象を可視化することが可能であることが推察された。
    このように、放射線による非破壊透視技術によって、ブラックスボックスである構造体内部を立体的に画像として把握することができて、さらに繰り返し同一供試体の測定が可能であり、測定前の試料準備も不要になることから、評価判定までの生産性を著しく向上することが示された。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 21H01402
  • Cracking mechanism and structural performances of concrete damaged by delayed ettringite formation
    Grants-in-Aid for Scientific Research
    01 Apr. 2018 - 31 Mar. 2021
    Matsumoto Koji
    Cracking mechanism of concrete damaged by delayed ettringite formation and its influence on the structural performance were investigated. Meso-scale discrete analyses considering volume changes revealed that expanded regions significantly affect cracking patterns caused by paste expansion. Contribution of interface expansive pressure and paste expansion was also investigated from ring type expansion tests using an artificial aggregate. As for the structural performances, the effect of delayed ettringite formation on flexural capacities and shear capacities of PC sleepers of Indian Railways were experimentally investigated as case examples. Furthermore, the calculation method for flexural capacity was considered.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), 18K04299
  • Development of evaluation method for durability of RC structures subjected to fatigue loading in chloride environment
    Grants-in-Aid for Scientific Research
    01 Apr. 2014 - 31 Mar. 2017
    Matsumoto Koji
    Numerical simulation system, in which the structural analysis and mass transfer analysis are combined, was developed to evaluate the durability of reinforced concrete structures subjected to fatigue loading in chloride environment. The existing two-dimensional analysis system was extended to three-dimensional analysis system and the truss network model was implemented to simulate the mass transfer behavior. In addition, the system which enables to simulate cracking behavior due to volume expansion of steel corrosion by introducing initial strains at the surface of steel reinforcement was newly developed. Pull-out loading tests of the specimens with steel corrosion induced by the electric corrosion test were also conducted in this research. The test data confirms the validity of the developed analysis system.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (A), The University of Tokyo, 26709032
  • New Strengthening Method for Existing Concrete Structures to Achieve the Upgrading of Infrastructures
    Grants-in-Aid for Scientific Research
    01 Apr. 2014 - 31 Mar. 2017
    Niwa Junichiro
    In this research, the simple, effective and new strengthening methods for existing concrete structures have been developed. First one is the method to attach the CFRP sheet to concrete structures. Second one is the method to attach the ultra high-strength fiber reinforced concrete (UFC) plate to concrete structures. Last one is the method to use the embedded form and PC strands in combination.
    In the first one, when 50% of PC strands are cut off at the span center, the flexural capacity of a PC beam can be recovered completely by attaching CFRP sheets adequately at the bottom of a PC beam. In the second one, the flexural and shear capacities of damaged reinforced concrete beams can be restored by attaching the UFC plate on the surface of damaged reinforced concrete beams. In the last one, the strengthening effect of embedded form with fine diameter stainless bars and PC strands in combination can increase the capacity of the original damaged concrete structures significantly.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo Institute of Technology, 26289142
  • Development of prediction method for cracking in early-age concrete considering damaging creep
    Grants-in-Aid for Scientific Research
    01 Apr. 2014 - 31 Mar. 2016
    Matsumoto Koji
    A numerical analysis system which enables to predict cracking, fracture and structural performances of concrete structures in early age under a combination of concrete hardening, cause of autogenous shrinkage and external loadings was developed. Conventional structural analysis system and initial stress problem were successfully coupled by giving histories of mechanical properties of concrete, shrinkage strain and external loads to the existing Rigid Body-Spring Model. In addition, to verify the reliability of the analysis system, tests for measuring time change of shrinkage strain and concrete properties, and loading tests of RC beams by using the material were carried out. As a result, it was confirmed that the analysis system developed in this study can simulate the fracture process of concrete structures in which shrinkage occurs during the early age of the concrete.
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, The University of Tokyo, 26630202
  • Evaluation of shear resistance mechanism of RC liner members based on image analysis and upgrading the design method
    Grants-in-Aid for Scientific Research
    2011 - 2013
    MATSUMOTO Koji
    To upgrade the shear design method of reinforced concrete liner members, which is important to ensure the safety of structures in seismic events, shear failure mechanism was investigated by using the image analysis technique and a new predictive equation for shear capacity was developed. The accuracy of the existing image analysis was improved, and then it was applied to measure the crack surface displacement along the shear crack of fiber reinforced concrete beams. The shear resistance of fibers at the crack was calculated by using the measured crack surface displacement and tensile stress-crack opening displacement relationships obtained from the separately-conducted elementary tests. By formulating the shear resistance of fibers respecting to each parameter, a new predictive equation for shear capacity which has higher accuracy than that of the existing equation, was developed.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Tokyo Institute of Technology, 23760419
  • Construction of the integrated technology for the extension of life ofexisting concrete structures
    Grants-in-Aid for Scientific Research
    2010 - 2012
    NIWA Junichiro; MATSUMOTO Koji; MIKI Tomohiro; WATANABE Ken
    The target of this research work is to build the integrated technology for the maintenance of deteriorating existing concrete structures and to extend the life of infrastructures. This integrated technology is comprised of three elemental technologies. Namely, they are (1) the deterioration diagnosis technology for materials of existing concrete structures, (2) the evaluation technology for remaining load carrying capacity of deteriorated structures, and (3) the development of various repairing or strengthening techniques using new materials. By integrating these three elemental technologies, we have proposed practical and usefulmeasures for the maintenance of infrastructures.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Tokyo Institute of Technology, 22246061