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Kishima T.,Public Works Res Institute | Watanabe T.,AGC Matex Co.
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2010

The failure loads of FRP bolted joints depend on the failure mechanisms reflected in the failure modes. The aim of this paper is to obtain the failure properties of bolted joints in pultruded CF/GFRP laminates based on the experimental results. The failure modes are divided into bearing, shear-out, tension, shear-tension and bearing-tension failures and the latter three modes are with the net-tension failure of outer layers. Bearing failure could be ductile due to continuity of the compressive failure decreasing the stress intensity and depend on both compressive failure progress and out-of-plane shear failure. Shear-out failure could be ductile due to both decrease in the shear stress intensity for outer layers and stress redistribution among layers during failure progress, and its load could increase with the ratio of width or edge distance to bolt diameter when the loading stress at failure is out of relation to them. Bearing and shear-out failure loads could depend on the volume fraction of outer layers, that is, they could decrease with decreasing volume of outer layers for compressive failure less concentrated on loading point and relatively linearly with for more concentrated. Tension failure load could depend on edge-side interlayer delamination, suggesting that it could appreciably decrease for the small volume of outer layers due to increasing compressive stress and not largely depend on that volume for the thorough delamination of unidirectional layer due to the extremely higher stress at loading point than around by non-restrictive interlayer shear deformation. Shear-tension failure load could increase with the volume fraction of outer layers and bearing-tension for the thorough delamination of unidirectional layer almost linearly with, due to the compressive stress depending on the interlayer property. © 2010 The Society of Materials Science, Japan. Source


Kohno T.,Public Works Res Institute | Nakatani S.,Public Works Res Institute | Yamamoto T.,Kyoto University | Miyagawa T.,Kyoto University
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2012

In these days, the footings degenerated due to Alkali Silica Reaction (ASR) have been discovered in Japan. To perform an appropriate diagnosis for those footings, a lot of knowledge for the footings degenerated due to ASR have to be obtained, such as the occurrence condition of ASR in footings, the internal degradation conditions. Accordingly, the road administrator can't maintenance them, and this is a big problem to carry on safe road network. So, the long term exposure test has been done under the actual condition up to now, and the crack and strain of the footings, temperature and water level of the exposure environmental have been measured to get those knowledge. At first, we analyzed the difference of the degradation of footings cased by environmental condition, in water, air and under the ground, from measured data, and we examined the reason of the difference. And we showed that the strain of steel is affected by reflection from temperature. Further out, we identified the internal degradation mechanism in footings. Finally, the characteristic value, for example temperature, needed for the occurrence of ASR and the evaluation of the degenerated condition in the footings are revealed. © 2012 The Society of Materials Science. Source


Kishima T.,Public Works Res Institute | Katsuno T.,S. F. Ene. Co. | Kobayashi K.,Kyushu University | Hino S.-I.,Kyushu University | Nishizaki I.,Public Works Res Institute
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2010

The relaxation behavior of clamping force in friction-type FRP bolted joints is one of the significant subjects in application of FRP to structures. The aim of this paper is to obtain the factors of relaxation behaviors in the GFRP bolted joints based on the experimental results. The relaxation behaviors are due to both steel bolt and GFRP laminate. Steel bolt dominates the relaxed force immediately after initial loading but not reloading. The relaxation factors of GFRP laminate except matrix polymer could be both laminate surface geometry and laminate bond, considering the variance of relaxed force and more relaxed force for bonded laminate than single laminate observed in the experimental results. Boltzmann superposition principle can be hardly applicable to the relaxed forces for initial loading and reloading, suggesting that less relaxed force for reloading could be obtained by the strain hardening of bolt threads through the decrease of cross section area due to shear plastic deformation and that surface geometry could be modified by plastic and irreversible viscous deformation considering the viscoplastic property of matrix polymer. More relaxed force could be obtained for the surface geometry farther from the flat surface and the surface geometries could be categorized into the surface with either equal height protuberances or random height ones. Laminate bond dominates the relaxed force and its lower viscosity could give relaxed force more. The viscosity of laminate bond could be more variable than matrix polymer and increase through the modification of structure by plastic and irreversible viscous deformation. The minimum elapsed time could be required to complete the relaxation behavior for the flat surface and the bond viscosity as high as matrix polymer. ©2010 The Society of Materials Science,. Source


Nakajima N.,JDC Corporation | Saito Y.,Public Works Res Institute | Takahashi I.,Public Works Res Institute | Yoshida N.,Public Works Res Institute | And 2 more authors.
Zairyo/Journal of the Society of Materials Science, Japan | Year: 2010

Short Fiber-reinforced soil is effective in enhancing strength, toughness and erosion resistance to rain and water currents. To bring such effectiveness to its full extent, it is important to disperse the bundled Fibers uniformly in the soil. In the conventional method, however, the technology of disentangling and dispersing the bundled Fibers has not yet been fully established. This study report refers to discussions on how to disentangle and disperse the bundled Fibers using the rotary crushing and mixing (Twister) method that does crushing and mixture at the same time and also refers to confirmation regarding the enhanced strength and toughness of the relevant short Fiber-reinforced soil when mixed with cement Consequently, it has been confirmed that the bundled Fibers, if combined with gravel, make it possible to uniformly mix with other soil materials through disentanglement and dispersion and that the strength and toughness of the relevant short Fiber-reinforced soil mixed with cement are better in mechanical characteristics than those of other improved soil not mixed with short Fibers. The mechanical characteristic of the short Fiber-reinforced soil when mixed with cement will be investigated in the future. And, the erosion resistances etc. are scheduled to examine it. © 2010 The Society of Materials Science. Source

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