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Experimental Study on Ultimate Strength of Concrete Filled Double Tubular Steel with Shear Connector
Masaru Shimizu,Fumihito Tatsumi,Toshiyuki Ishikawa,Atsushi Hattori,Hirotaka Kawano 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.1
Concrete Filled Tubular steel (CFT) member, which represents a superb deformability due to well-known confined effectbetween steel tube and concrete, has been used mainly as bridge pier. As a progressive composite member, Concrete FilledDouble tubular steel (CFDT), which is consist of double skin steel tubes and filled concrete between them, has been proposed. Although a lot of reports on mechanical characteristics of the CFDT member are presently published, the necessity of shearconnector for the CFDT member has not been addressed. In this research, the shear connector was installed at the interfacebetween tubes and concrete in the CFDT member. To investigate the effect of the shear connector on the bending characteristics,the four points bending test were carried out. The results show that integrating the steel tubes and concrete enhances its bearingcapacity. Furthermore, the strains of outer and inner tubes were also discussed in this paper.
Effect of caspases and RANKL induced by heavy force in orthodontic root resorption
Yukari Minato,Masaru Yamaguchi,Mami Shimizu,Jun Kikuta,Takuji Hikida,Momoko Hikida,Masaaki Suemitsu,Kayo Kuyama,Kazutaka Kasai 대한치과교정학회 2018 대한치과교정학회지 Vol.48 No.4
Objective: Orthodontic root resorption (ORR) due to orthodontic tooth movement is a difficult treatment-related adverse event. Caspases are important effector molecules for apoptosis. At present, little is known about the mechanisms underlying ORR and apoptosis in the cementum. The aim of the present in vivo study was to investigate the expression of tartrate-resistant acid phosphatase (TRAP), caspase 3, caspase 8, and receptor activator of nuclear factor kappa-B ligand (RANKL) in the cementum in response to a heavy or an optimum orthodontic force. Methods: The maxillary molars of male Wistar rats were subjected to an orthodontic force of 10 g or 50 g using a closed coil spring. The rats were sacrificed each experimental period on days 1, 3, 5, and 7 after orthodontic force application. And the rats were subjected to histopathological and immunohistochemical analyses. Results: On day 7 for the 50-g group, hematoxylin and eosin staining revealed numerous root resorption lacunae with odontoclasts on the root, while immunohistochemistry showed increased TRAP- and RANKL-positive cells. Caspase 3- and caspase 8-positive cells were increased on the cementum surfaces in the 50-g group on days 3 and 5. Moreover, the number of caspase 3- and caspase 8-positive cells and RANKL-positive cells was significantly higher in the 50-g group than in the 10-g group. Conclusions: In our rat model, ORR occurred after apoptosis was induced in the cementum by a heavy orthodontic force. These findings suggest that apoptosis of cementoblasts is involved in ORR.[Korean J Orthod 2018;48(4):253-261]
Takuji Hikida,Masaru Yamaguchi,Mami Shimizu,Jun Kikuta,Tomokazu Yoshino,Kazutaka Kasai 대한치과교정학회 2016 대한치과교정학회지 Vol.46 No.4
Objective: Root mobility due to reciprocating movement of the tooth (jiggling) may exacerbate orthodontic root resorption (ORR). “Jiggling” describes mesiodistal or buccolingual movement of the roots of the teeth during orthodontic treatment. In the present study, buccolingual movement is described as “jiggling.” We aimed to investigate the relationship between ORR and jiggling and to test for positive cell expression in odontoclasts in resorbed roots during experimental tooth movement (jiggling) in vivo. Methods: Male Wistar rats were divided into control, heavy force (HF), optimal force (OF), and jiggling force (JF) groups. The expression levels of cathepsin K, matrix metalloproteinase (MMP)-9 protein, interleukin (IL)-6, cytokine-induced neutrophil chemoattractant 1 (CINC-1; an IL-8-related protein in rodents), receptor activator of nuclear factor κB ligand (RANKL), and osteoprotegerin protein in the dental root were determined using immunohistochemistry. Results: On day 21, a greater number of root resorption lacunae, which contained multinucleated odontoclasts, were observed in the palatal roots of rats in the JF group than in rats from other groups. Furthermore, there was a significant increase in the numbers of cathepsin K-positive and MMP-9-positive odontoclasts in the JF group on day 21. Immunoreactivities for IL-6, CINC-1, and RANKL were stronger in resorbed roots exposed to jiggling than in the other groups on day 21. Negative reactivity was observed in the controls. Conclusions: These results suggest that jiggling may induce ORR via inflammatory cytokine production during orthodontic tooth movement, and that jiggling may be a risk factor for ORR.
Effect of Compression Overload on Fatigue Strength Improved by ICR Treatment
Toshiyuki Ishikawa,Masaru Shimizu,Hajime Tomo,Hirotaka Kawano,Kentaro Yamada 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.1
ICR (Impact Crack-closure Retrofit) treatment was developed for extending fatigue life of cracked steel structures by closing the fatigue crack opening. By applying the ICR treatment to as-welded condition, compressive stress remains at weld toe. Therefore, ICR treatment can be used for the improvement of fatigue strength of welded joint at the same level of the other fatigue strength improved techniques. If a compression overload is subjected after ICR treatment, however, the residual compressive stress at weld toe will shift the tensile stress region. Accordingly, improved fatigue strength of welded joints by ICR treatment will be reduced after the compression overloaded. In order to investigate the effect of the compression overload on fatigue strength improved by ICR treatment, fatigue tests of out-of-plane gusset specimens were carried out. As the results,fatigue strength improved by ICR treatment was hardly reduced under the compression overload condition of nominal stress of −190 MPa.
Seiji Nakashima,Hironori Fujisawa,Masaru Shimizu,Osami Sakata,Tomoaki Yamada,Hiroshi Funakubo,박정민,Takeshi Kanashima,Masanori Okuyama 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.31
An electric-field-induced strain at 80 K in a 350-nm-thick BiFeO_3 (BFO) thin film deposited by pulsed laser deposition has been investigated by a time-resolved x-ray diffraction under an electric field using a synchrotron radiation. A 300-nsec-width and 804.09-nsec-period voltage pulses were applied to the BFO thin film during the measurements. The time-resolved-x-ray diffraction profile around BFO (001) diffraction peak indicates that BFO (001) diffraction peak shifts to lower angle side during the voltage application. A strain estimated from the peak shift lineally increases with increasing the amplitude of the voltage pulses. A piezoelectric constant (d_(33)) of (001)-oriented domains in the polycrystalline BFO thin film at 80 K is 20.2 pm/V. The value is smaller than that measured at RT of 27.8 pm/V in our previous report.
Failure Probability for Fatigue Crack in Web Plate of Bridge Girder
Cut Atika Putri,Kazuo Tateishi,Masaru Shimizu,Takeshi Hanji 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.1
Out-of-plane gusset joints are commonly used in welded assembly structures such as bridges. The studies regarding outof- plane gusset joint often defi ne fatigue life of this joint as the condition when the crack has fully penetrated through the web plate. However, the time frame from crack initiation until reaching complete structural failure is unclear. In this study, extended fatigue crack propagation analysis of out-of-plane gusset joint is performed. The variation of infl uential parameters such as fl ank angle, weld toe radius, material constant, and the threshold value of stress intensity factor range was considered. The crack propagation analysis was done until the crack reaches 80% of the lower fl ange plate of the bridge girder. Since the crack propagation life is highly infl uenced by traffi c conditions, the probability distribution of the number of cycles and the crack width (2 b ) is presented in regards to the fatigue life ratio. In estimating the failure probability of the joint, the infl uence of human error to detect cracks during the inspection is considered. Five cases of the probability of crack detection are assumed to represent the capability of the inspector. It was found that bridge inspection and reparation of cracks are important in controlling the failure probability.
Effect of UHPFRC Overlay on Fatigue Cracks Propagating from U-rib Welds of Orthotropic Steel Decks
Masafumi Hattori,Kazuo Tateishi,Takeshi Hanji,Masaru Shimizu 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6
Over the last decade, fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel deck bridges in Japan. This paper focuses on fatigue cracks that initiate from a weld root of rib-to-deck welded joints and propagate to a deck plate. This study examines the eff ect of a countermeasure that uses overlaying Ultra-High Performance Fiber Reinforced cement-based Composites (UHPFRCs) on steel decks with cracks from U-rib welds, and confi rms the fatigue durability of this method. Specifi cally, the retardation of crack propagation and the fatigue durability of the UHPFRC itself as well as the interface between the UHPFRC and the deck plate were confi rmed by a wheel running test and fi nite element analysis. Based on the results, it was clarifi ed that this countermeasure has a positive eff ect on retarding further crack propagation compared with the method of overlaying steel fi ber reinforced concrete, which is generally adopted. In addition, it was revealed that the studied countermeasure has suffi cient fatigue durability.