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Featured researches published by Toshiyuki Kanakubo.


Aci Structural Journal | 2001

BOND BEHAVIOR BETWEEN FIBER-REINFORCED POLYMER LAMINATES AND CONCRETE

Kasumassa Nakaba; Toshiyuki Kanakubo; Tomoki Furuta; Hiroyuki Yoshizawa

This paper studies the bond behavior between fiber-reinforced polymer laminates and concrete. In order to obtain the local bond stress (LBS) vs. slippage relationship, a double-face shear type bond test was conducted. Primary test variables were the types of fiber and concrete. Test results show that fiber stiffness influences both bond strength and shape of stress distribution. However, the LBS-slip relationships are not influenced by the type of fiber. Only the maximum LBS increases as concrete compressive strength also increases. A new model representing the LBS vs. slippage relationship is offered using Popovics formula, which has been adapted to present the concrete compressive stress-strain relationship. A numerical analysis was performed to confirm the model, and experimental results are presented. The analytical results show good agreement with the bond strength and strain distribution found in the experimental results.


Aci Structural Journal | 2012

Shear-Peeling Bond Strength between Continuous Fiber Sheet and Concrete

M. S. Alam; Toshiyuki Kanakubo; Akira Yasojima

Fiber-reinforced polymer (FRP) sheets can be externally bonded to reinforced concrete structural members to increase strength. However, the bond between the FRP sheet and concrete may adversely affect the performance of flexurally strengthened members when there are diagonal tension cracks in the members. This study investigates the bond strength between the FRP sheet and concrete interface for both shear bond and peeling conditions. In the experiment, 27 rectangular specimens with FRP sheets bonded on two sides were tested in uniaxial tensile loading. The specimens were designed for different step angles at the middle to ensure that the interface acts for both shear and peeling conditions. Three types of woven composite sheets made of aramid and carbon were used to allow the study of various sheet stiffnesses and strengths. The results showed that the bond strength decreases considerably due to the peeling effect. Step angle and fiber stiffness greatly influence the bond strength between the FRP sheet and concrete interface for combined shear and peeling conditions. The highest bond strength was observed for the lowest axial stiffness of the laminate. Based on the test results, a modification to an existing bond strength model is proposed that improves the prediction of the bond strength between FRP laminate and concrete for shear-peeling conditions.


Journal of Asian Architecture and Building Engineering | 2006

Full Scale Processing Investigation for ECC Pre-cast Structural Element

Tetsushi Kanda; Shiro Tomoe; Satoru Nagai; Makoto Maruta; Toshiyuki Kanakubo; Katsuyuki Shimizu

Abstract ECC is a pseudo-strain-hardening, highly ductile cementitious composite. However, the major studies on this material have been limited to laboratory scale without experience in full-scale plants. Thus, practical applications of ECC have not been previously investigated. In the current study, full-scale processing experiments were executed, and mechanical and fresh properties were tested, where emphasis was placed on two types of tensile test. It was thus proven that ECC can provide excellent fresh and mechanical properties in full scale production, and a statistical basis for determining tensile property specifications was provided. Furthermore, it was found that flexural tests can be utilized for inspecting tensile properties in daily production. These experimental data were reflected in an actual building construction project that was designed to utilize ECC structural elements. As a result, ECC element production was successfully achieved with the required quality in this project.


Aci Materials Journal | 2016

Influence of Fiber Orientation on Bridging Performance of Polyvinyl Alcohol Fiber-Reinforced Cementitious Composite

Toshiyuki Kanakubo; Masaru Miyaguchi; Kohei Asano

Crack bridging performance of fibers strongly affects the tensile characteristics of fiber-reinforced cementitious composites (FRCCs) after first cracking. The fiber orientation distribution is likely to be affected by factors that include fresh-state properties, casting method, formwork geometry, and others. The objective of this study is to investigate the influence of the fiber orientation on the bridging performance in polyvinyl alcohol (PVA) FRCCs through a visualization simulation using a water glass solution and a calculation of the bridging law. The main parameter of the investigations in the present study is the casting direction. To evaluate the fiber orientation distribution quantitatively, an approximation methodology using an elliptic function is newly introduced. The bridging stress versus crack width relationship is calculated considering the elliptic distribution, the snubbing effect, and the fiber strength degradation. The calculated stress-crack width curves can express the uniaxial tension test results after first cracking well.


Archive | 2012

Study on Size Effect in Bond Splitting Behavior of ECC

Kohei Asano; Toshiyuki Kanakubo

This paper describes the test results of the pullout test in order to obtain the local bond behavior between Engineered Cementitious Composites (ECC) and steel reinforcing bar. There is a possibility that the size of cover thickness of ECC around reinforcing bar affects the orientation of fiber, so bridging performance of fiber is influenced by specimen size. To evaluate size effect, the main parameters of specimens are reinforcing bar diameter and cover thickness. The shape of specimen is a similarity shape based on reinforcing bar diameter. From the test results, bond strength tends to increasing with cover thickness. Moreover, bond strength decreases with increasing reinforcing bar diameter. To evaluate size effect, cylindrical volume around reinforcing bar is defined as highly-stressed volume. As for specimen of each cover thickness, the normalized bond strength decreases with increasing of highly-stressed volume.


Journal of Structural and Construction Engineering (transactions of Aij) | 2009

PREDICTION METHOD OF CRACK WIDTH IN REINFORCED CONCRETE MEMBERS

Nobuyuki Yamato; Toshiyuki Kanakubo

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International Conference on Strain-Hardening Cement-Based Composites | 2017

Evaluation of Shear and Tensile Bridging Characteristics of PVA Fibers Based on Bridging Law

Yuriko Ozu; Hiroshi Yamada; Akira Yasojima; Toshiyuki Kanakubo

Strain-Hardening Cementitious Composites (SHCC), in which short fibers are mixed in mortar, show improved tensile performance and ductility of the cementitious material because fibers bridging the crack transfer tensile forces after first cracking. It is considered that the stress field at the shear crack surface in the structural element under the shear force is a biaxial stress field in which tensile and shear stresses exist concurrently. In fiber-reinforced cementitious composites, both tensile and shear stresses are transmitted via fibers that bridge shear cracks. It is necessary that the effect of fibers bridging a shear crack under tensile and shear stresses is investigated. In this study, uniaxial tension tests were carried out for specimens which have a square cross-section and an inclined notch. The biaxial stress field can be expressed by the inclined crack surface produced by the tensile loading. From the test results, it was confirmed that the tensile stress decreased with increasing notch angle in the tension tests. A calculation method for the bridging law with an inclined crack was introduced and the calculation results were compared with the test results. Though the maximum tensile stress in the tests was smaller than that in the calculation results, the curves after the maximum stress show good agreements with the calculations. The maximum stress reached in the tests tends to decrease with increasing crack angle (notch angle) as in the calculation results.


International Conference on Strain-Hardening Cement-Based Composites | 2017

Simulation of Scattering of Bending Characteristics of FRCC Based on Bridging Law Considering Fiber Distribution

Toshiyuki Kanakubo; Keisuke Watanabe; Yuriko Ozu

It is well known that tensile and bending characteristics of fiber-reinforced cementitious composite (FRCC) are influenced by fiber orientation and distribution. In this study, a visualization simulation is conducted using sodium silicate solution (known as water glass) to observe the flow patterns of the fibers in the beam specimen. The results of the visualization simulation are discussed mainly for the distribution of the position of each single fiber. In this study, based on the visualization results, Poisson distribution for expressing the position of fibers is adopted to calculate the bridging law (tensile stress – crack width relationship), in which the pullout properties of the single fiber are considered. The influence of fiber orientation is also considered in the calculation using the elliptic function characterized by the principal orientation angle and the orientation intensity. The scattering of maximum tensile stress (bridging strength) can be confirmed by Monte Carlo simulation (MCS), in which the fiber distribution following Poisson distribution is considered. The calculated bridging law is modeled by trilinear model, and section analysis is conducted to compare with the bending test results using polyvinyl alcohol (PVA) fiber. The possibility to evaluate the variation of bending strength can be found out by considering fiber distribution.


International Conference on Strain-Hardening Cement-Based Composites | 2017

Influence of Fiber Orientation on Structural Performance of Beam-Column Joints Using PVA FRCC

Yu Mu; Mai Ando; Akira Yasojima; Toshiyuki Kanakubo

In recent years, many studies on fiber-reinforced cementitious composite (FRCC) has been conducted actively to improve brittle behavior of cementitious materials. FRCC shows the improved tensile performance and ductility because fibers across the crack can transfer tensile force after first cracking. When fibers tent to orient perpendicularly to crack surface, higher bridging effect of fibers is observed. When fibers tend to orient parallel to crack, however, bridging performance of fibers becomes poor. As one of the examples, the authors have already conducted that the casting direction of FRCC influences the tensile performance of FRCC. The objective of this study is to investigate the influence of fiber orientation on structural performance of PVA FRCC beam-column joint by using two types of casting method. Horizontal and vertical casting beam-column joint specimens are tested by reversed cyclic load simulating earthquake force. A vibrator rod is also applied during the casting. The applied load on beams and the story drift angle of two specimens are obtained directly from the experiment. According to the experimental results, specimens of horizontal casting and vertical casting show almost the same shear capacities. Using a vibrator rod during casting has an influence on shear capacity of PVA FRCC beam-column joint.


Aij Journal of Technology and Design | 2011

BOND SPLITTING TEST OF REINFORCED STRAIN-HARDENING CEMENTITIOUS COMPOSITE BEAMS

Hiroshi Hosoya; Toshiyuki Kanakubo; Masaaki Yano; Norihiro Shigemizu

Recently, RC buildings with core wall structures have been constructed. The coupling beams connecting core walls are possible to be failed by bond splitting during an earthquake. Short span beams using SHCC (Strain Hardening Cementitious Composites) with PVA fibers have been developed to improve brittle behavior. In this study, cantilever-shaped specimens were subjected to bond splitting tests to investigate bond characteristics of SHCC beams. The experimental bond strength shows higher value than calculated strength by conventional formulas for RC beams. The effect of SHCC can be expressed by modifying the term of lateral reinforcement ratio in these formulas.

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Jun Orita

University of Tsukuba

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Keisuke Watanabe

Central Japan Railway Company

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