HASHIMOTO Kunitaro | ![]() |
Graduate School of Engineering / Department of Civil Engineering | |
Associate Professor | |
Civil Engineering / Architecutre and planning / Building Engineering |
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The stress state around a rib-to-deck (RD) joint in an orthotropic steel bridge deck is extremely sensitive to wheel-load location in the transverse direction. Fatigue cracks of various types can occur around the RD joint. In this study, a bending fatigue-test system was used to simulate an RD joint under the critical-load case. The fatigue tests for two groups of RD joint specimens with weld-penetration ratios of 15 and 75% were conducted to assess the influence of the penetration ratio on the fatigue-crack type and its fatigue resistance. Fatigue-test results suggest that the fatigue resistances of the RD joint specimens with 75 and 15% penetration ratios were approximately Class B and between Class C and Class D, respectively, per Japanese standards. Furthermore, results show that increasing the weld-penetration ratio can prevent root-to-throat fatigue cracks and enhance the fatigue resistance RD joints.
American Society of Civil Engineers (ASCE), 01 Feb. 2018, Journal of Bridge Engineering, 23 (2), English[Refereed]
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Pultruded Fiber Reinforced Polymers (FRPs) have been increasingly used in civil infrastructure applications due to advanced properties such as high specific strength, lightweight and especially high corrosion resistance. In highly corrosive environment such as chemical and acid environment where metallic by-products are prone to corrosion, the use of adhesive bonding in addition to FRP bolts not only decreases the structure's weight, limits the impacts of aggressive environment but also increases the ultimate strength of the connection and improves the connection stiffness. In this paper, mechanical behavior of pultruded FRP double-lap specimens combined by only FRP bolt as well as both FRP bolt and adhesive under tension tests was investigated by finite element method and experimental data. Two kinds of used adhesive were high strength adhesive and low elastic one. Results show that comparing with bolt-only specimens, connections with both FRP bolt and adhesive had the higher joint strength. Specimens with high strength adhesive had the highest joint strength but the shear out failure and delamination at FRP plates happened suddenly while the low elastic adhesive specimens witnessed the debonding failure and shear out failure alternately in the both sides of connections. Moreover, the stress distributions in the GFRP plates were also investigated and there were good agreements between finite element analysis (FEA) and experimental data achieved in this paper.
AMER INST PHYSICS, 2017, PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF GLOBAL NETWORK FOR INNOVATIVE TECHNOLOGY AND AWAM INTERNATIONAL CONFERENCE IN CIVIL ENGINEERING (IGNITE-AICCE'17): SUSTAINABLE TECHNOLOGY AND PRACTICE FOR INFRASTRUCTURE AND COMMUNITY RESILIENCE, 1892, (10pages,CD - R), English[Refereed]
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Clustering stud shear connectors with minimized spacing based on specifications to form group studs are useful for concrete slab prefabrication and prestress installation efficiency in steel-concrete composite bridges. To date, many long-span composite bridge girders have been designed with wide transverse cantilevers and web spacing, and most of these girders use group studs. The concrete's self-weight and the weight of moving loads result in a significant transverse bending-induced effect generally consisting of bending stresses and tensile concrete cracks. In this sense, the studs are actually under longitudinal interlayer shear force that is influenced by the transverse bending-induced effect. This biaxial loading effect has not been investigated experimentally. Thus, standard and newly designed push-out tests and corresponding analyses were carried out. In addition, the stud arrangement effect also was of concern. In this study, the ratio of stud height to shank diameter was approximately 6.2. This study found that steel-concrete interlayer friction and biaxial concrete compression around the stud roots contribute to a favorable effect of biaxial loading on stud performance. However, the residual tensile concrete cracks are unfavorable. Engineers should note the tendency toward mechanical degradation of studs when such a situation occurs. Moreover, arranging studs in clusters to form group studs may lead to comparatively more severe concrete damage at the ultimate stage. The specification-based evaluations of stud strength were found to be more or less conservative based on related test results. (C) 2014 American Society of Civil Engineers.
ASCE-AMER SOC CIVIL ENGINEERS, Oct. 2015, JOURNAL OF BRIDGE ENGINEERING, 20 (10), English[Refereed]
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Numerous fatigue cracks were observed recently in orthotropic steel bridge decks that have been in service for a long period of time. A fatigue crack initiating from the rib-to-deck (RD) joint may especially produce asphalt surfacing damage, and hence have an impact on traffic safety. In fatigue evaluation of RD joints, in most current design specifications the asphalt surfacing is just treated as a layer dispersing wheel loads, in which the wheel loads are uniformly distributed on the deck plate and the effect of the composite stiffness of the deck plate and asphalt surfacing is neglected. In this study, comprehensive finite-element and load models were used to investigate the asphalt surfacing influence on the wheel load dispersal and composite stiffness. The analysis result shows that wheel loads are not uniformly distributed on deck plates but are concentrated on the weld joints, the asphalt surfacing could significantly decrease the stress magnitude around the RD joints, and this decrease may mainly result from composite stiffness rather than load dispersal. The effective stresses of RD joints, and their fatigue evaluation indicate that the fatigue life of RD joints could be drastically improved by asphalt surfacing. However, on the other hand, the fatigue life is shortened considerably by the effects of temperature. Moreover, the type of fatigue crack initiating from the weld root may also be influenced by the asphalt surfacing. (C) 2014 American Society of Civil Engineers.
ASCE-AMER SOC CIVIL ENGINEERS, Oct. 2014, JOURNAL OF BRIDGE ENGINEERING, 19 (10), English[Refereed]
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In this study, to investigate frictional behavior and maximum strength of GFRP members connected by high strength bolts and splice plates made of stainless or GFRP plates, slip test and bolt relaxation test are carried out. And FE analysis is executed to study on mechanism of stress concentration. From the slip test, slip coefficient of the specimen with stainless splice plates is lager than 0.4 and it is found that the slip coefficient can calculate by toribology theory. From the FE analysis, the maximum strength of the GFRP firictional bolted joint can estimate based on consideration of stress concentration. Relaxation test for one year provides the amount of decrements of the bolt axial forces of each connection.
土木学会, Mar. 2012, 構造工学論文集, 58A, 935 - 945, Japanese[Refereed]
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Many steel structures have been faced to the problem of superannuation in Japan. Severe damages will be caused in these structures subjected to huge earthquakes. It is necessary to secure safety of these structures to such earthquakes. Two-dimensional horizontal behavior of seismic response of structures with damages by corrosion has been hardly researched. Therefore, in this study experiments and numerical analyses intended for rectangular steel bridge piers with damages in the corners were conducted in order to evaluate two-dimensional behavior. As a result, it was clarified that the decrease of strength of steel piers with damages by corrosion was remarkable.
土木学会, Mar. 2012, 構造工学論文集, 58A, 299 - 309, Japanese[Refereed]
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In this paper, in order to study on bending behaviors of a riveted steel girder with corrosion damage at heads of some rivets, bending loading tests are carried out. The steel girders used as specimens were cut out from the bridge that had been used for 55 years. Considering the results of the bending experiment, it is found that the initial rigidity of the specimen with the rivet heads corroded is decreased a little. But the effect of corrosion damage at rivet heads of riveted steel I shaped girder for ultimate load is nothing.
土木学会, Mar. 2012, 構造工学論文集, 58A, 701 - 709, Japanese[Refereed]
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CFT (Concrete Filled Steel Tubular members) has attracted much attention because of its structural superiority. However, the increase of weight by filling with concrete inside is one of problem associated with CFT. Thus in this study, to reduce the self-weight of CFT, CFDT (Concrete Filled Double-Skin Steel Tubular members) is proposed particularly for higher bridge piers. The purpose of this study is to clarify the influence of the thickness of outer and inner steel tubes on the bending characteristics by the cyclic loading test and the analysis. As a result, it is shown by the cyclic loading test that CFDT has higher bending strength and energy absorption than CFT of the same weight. CFDT without inner tube has sufficient bending strength, but after the crush of the concrete, its ductility declines like only outer tube. By the constraint effect of concrete, buckling of inner tube is prevented, so the thickness of inner tube can be thin. For reasonable structure, it is effective to make the outer tube thicker than inner tube.
土木学会, Mar. 2009, 構造工学論文集, 55A, 670 - 679, Japanese[Refereed]
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