• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.697-705
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• 1997

The purpose of this study was to evaluate the effects of two metal adhesive primers on the shear bond strengths of self-curing resin to Ni-Cr a]toy and the effects of 1000 thermal cycling on the durability of the bond. The two selected metal adhesive primers were Metal Primer II(G-C corp., Japan) and MR Bond(Tokuyama corp., Japan) and no treatment groups were used as control. All specimens were divided into two groups according to thermal cycling. In the group without thermal cycling, the specimens were stored in water for 24 hours. In the group with thermal cycling, the specimens were thermocycled 1000 times at temperature of $5^{\circ}C\;and\;55^{\circ}C$. Shear bond strengths were measured using the Universal testing machine(Zwick 145641, Germany) with a crosshead speed of 0.5 mm/min. The results were as follows: 1. MR Bond significantly improved the shear bond strength of resin to Ni-Cr alloy before and after thermal cycling. 2. There were no difference in the shear bond strength of resin to Ni-Cr alloy between Metal Primer II treated group and no treatment group. 3. Regardless of the type and the use of adhesive primers, there were tendency of decrease in shear bond strength with 1000 thermal cycling.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.63-71
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• 1989

Four series of reinforced concrete beams were tested to determine their shear cracking strengths and ultimate shear capacities. All beams were singly reinforced without shear reinforcement. The concrete strength was the prime variable which was varied from 247 to $708kg/cm^2$(8500 to 10000 psi). Within each series the shear span-to-depth ratio was varied from 2 to 5, while concrete strength was held constant. Test results indicate that the effect of concrete strength on shear capacities is varied as the shear span-to-depth ratio is changed. Furthermore, the current shear design provisions do not provide a consistency with respect to estimating shear capacities of reinforced concrete beams. By introducing the shear failure mode index, a new equation is proposed to predict ultimate shear strengths of reinforced concrete beams without web reinforcement.

• Steel and Composite Structures
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• v.43 no.6
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• pp.785-796
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• 2022

Concrete-encased steel (CES) beam, in which structural steel is encased in a reinforced concrete (RC) section, is widely applied in high-rise buildings as transfer beams due to its high load-carrying capacity, great stiffness, and good durability. However, these CES beams are prone to shear failure because of the low shear span-to-depth ratio and the heavy load. Due to the high load-carrying capacity and the brittle failure process of the shear failure, the accurate strength prediction of CES beams significantly influences the assessment of structural safety. In current design codes, design formulas for predicting the shear strength of CES beams are based on the so-called "superposition method". This method indicates that the shear strength of CES beams can be obtained by superposing the shear strengths of the RC part and the steel shape. Nevertheless, in some cases, this method yields errors on the unsafe side because the shear strengths of these two parts cannot be achieved simultaneously. This paper clarifies the conditions at which the superposition method does not hold true, and the shear strength of CES beams is investigated using a compatible truss-arch model. Considering the deformation compatibility between the steel shape and the RC part, the method to obtain the shear strength of CES beams is proposed. Finally, the proposed model is compared with other calculation methods from codes AISC 360 (USA, North America), Eurocode 4 (Europe), YB 9082 (China, Asia), JGJ 138 (China, Asia), and AS/NZS 2327 (Australia/New Zealand, Oceania) using the available test data consisting of 45 CES beams. The results indicate that the proposed model can predict the shear strength of CES beams with sufficient accuracy and safety. Without considering the deformation compatibility, the calculation methods from the codes AISC 360, Eurocode 4, YB 9082, JGJ 138, and AS/NZS 2327 lead to excessively conservative or unsafe predictions.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.69-75
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• 2017

Structural safety evaluation for static strength of thin plate RC member with high strength concrete is conducted in this study. Static strengths were predicted and compared with the experimental values. Predicted values were calculated by the evaluation formula based on the punching shear behavior and the yield line theory which can appear in the plate members. Static load tests were carried out for the specimens with high strength concrete and the test results were compared with the required performance in design. The comparison results show that the specimens with high strength concrete have sufficient structural safety for flexural and punching shear performance required in design. High strength concrete specimens exhibited excellent strength despite their small thickness. The range of concrete strengths applied in this study was about 60 MPa to 100 MPa.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.156-165
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• 1999

The purpose of this study was to evaluate the effect of surface treatments on the shear bond strength between new and old composites. Circular cavities prepared on the center of acrylic resin mold and the prepared cavities were filled with composite resin. They randomly assigned into control group and 8 groups according to the difference in surface treatments of old composites; Control group: no surface treatment, Group 1: surface treated with #120 SiC paper & bonding agent, Group 2: surface treated with #400 SiC paper & bonding agent, Group 3: surface treated with #120 SiC paper, 32% $H_3PO_4$ & bonding agent, Group 4: surface treated with #400 SiC paper, 32% $H_3PO_4$ & bonding agent, Group 5: surface treated with #120 SiC paper, primer & bonding agent, Group 6: surface treated with #400 SiC paper, primer & bonding agent, Group 7: surface treated with #120 SiC paper, 32% $H_3PO_4$, primer & bonding agent, Group 8: surface treated with #400 SiC paper, 32% $H_3PO_4$, primer & bonding agent. New composites were applicated on the old composites of experimental groups. The shear bond strengths for the experimental specimen were measured and the results were analyzed by using one way ANOVA. The observations of surface morphology after SiC paper roughening and debonded surface morphology after shear bond strength test were done by SEM. The results were as follows; 1. Shear bond strengths for specimens roughened with #120 SiC paper matching with the particle size of coarse diamond bur were significantly higher than those for the specimens with #400 SiC paper(P<0.05). By SEM, the surface of the specimens roughened with #120 SiC paper was more irregular than the specimens with #400 SiC paper. 2. Shear bond strengths for specimens treated with 32% $H_3PO_4$ etchant, primer, bonding resin were significantly higher than those for specimens treated with 32% $H_3PO_4$ and bonding resin(P<0.05). 3. Shear bond strengths for the specimens treated with 32% $H_3PO_4$ etchant and bonding resin were significantly higher than those for specimens treated with only bonding resin(P<0.05). There was no remarkable change of surface morphology after 32% $H_3PO_4$ etching. 4. It was possible to observe mixed fracture patterns (the cohesive fracture of old composite and the adhesive fracture between old and new composite) in the specimens roughened with #120 SiC paper, but almost adhesive fracture in the specimens roughened with #400 SiC paper.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.2
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• pp.293-299
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• 2005

It is important to reduce chair time and procedure in restorative treatment for children. Composite resin is not only used in esthetic restoration of anterior teeth but also posterior teeth by its improved physical property. The 7th generation dentin bonding system was recently developed in order to simplify three steps which is needed to bond composite resin to tooth surface-etchant, primer, adhesive. We compared shear bond strengths of 4, 5, 6, 7th generations dentin bonding systems. The primary dentin was pretreated with 4, 5, 6, 7th generation dentin bonding systems. Then composite resin was cured to the specimen using molds 2.5mm in diameter and 2mm in height. Thermocycling was performed and shear bond strength was finally measured. The results were as follow; 1. The mean values of shear bond strengths in 5th generation dentin bonding system(group 2) were greater than those of 4, 6, 7th generation dentin bonding system(group 1, 3, 4). The differences were statistically significant. 2. The mean values of shear bond strengths in 4th generation dentin bonding system(group 2) were greater than those of 6, 7th generation dentin bonding system(group 1, 3, 4). But, the differences were not statistically significant. 3. Between the mean values of shear bond strengths in 6, 7th generation dentin bonding system(group 3, 4) were similar.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.416-425
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• 1999

The purpose of this study was to evaluate shear bond strength of glass ionomer cements and compomer according to dentin surface treatment method. The materials used in this study were dentin conditioner and cavity conditioner for dentin treatment: Ketacfil, Fuji II LC, and Dyract for restoration. In this study, 90 sound bovine teeth were selected and then the teeth were embeded in improved stone and were grounded with 400 to 600 grit silicon carbide paper to create a flat dentin surfaces. The teeth were divided into nine groups as follows ; Group 1A : Samples bonded to dentin surface with Ketacfil after no treatment Group 1B : Samples bonded to dentin surface with Ketacfil after applicating dentin conditioner Group 1C : Samples bonded to dentin surface with Ketacfil after applicating cavity conditioner Group 2A : Samples bonded to dentin surface with Fuji II LC after no treatment Group 2B : Samples bonded to dentin surface with Fuji II LC after applicating dentin conditioner Group 2C : Samples bonded to dentin surface with Fuji II LC after applicating cavity conditioner Group 3A : Samples bonded to dentin surface with Dyract after no treatment Group 3B : Samples bonded to dentin surface with Dyract after applicating dentin conditioner Group 3C : Samples bonded to dentin surface with Dyract after applicating cavity conditioner Treated dentin surfaces were observed under SEM. After filling of each materials, shear bond strenth was evaluated and then debonded surfaces were observed under SEM. The following results were obtained; 1. The shear bond strengths obtained were decreased as Fuji II LC, Dyract, Ketacfil in that order and there was statistically significant difference(p<0.05). 2. About Group 1. the shear bond strengths were decreased as 1C, 1B and 1A in that order. But there was no significant difference between group 1B and 1C (p<0.05). 3. About Group 2, the shear bond strengths were decreased as group 2B, 2A and 2C in that order. And there was significant difference between group 2B and 2C (p<0.05). 4. About Group 3, the shear bond strengths were decreased as group 3A, 3C and 3B in that order. And there was signicant difference between group 3A and 3B (p<0.05). 5. As a result of observation under SEM, the fracture patterns of Fuji II LC and Dyract were adhesive failures, but those of Ketacfil were cohesive failure of material and mixture of cohesive and adhesive failure.

• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.394-398
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• 2019

In this paper, the joining characteristics of GDC-LSM ceramics with Crofer 22 APU metal alloys was investigated at different brazing temperatures and holding times by reactive air brazing. Brazing was performed using Ag-10 wt% CuO filler, at three different temperatures (1000, 1050, and 1100℃ for 30 minutes) as well as for three different holding times (10, 30, and 60 minutes at 1050℃). The interfacial microstructures were examined by scanning electron microscopy and the joining strengths were assessed by measuring shear strengths at room temperature. The results show that with increasing brazing temperature and holding time, joint microstructure changed obviously and shear strength was decreased. Shear strength varied from a maximum of 100±6 MPa to a minimum of 18±5 MPa, depending on the brazing conditions. These changes were attributed to an increase in the thickness of the oxide layer at the filler/metal alloy interface.

• Restorative Dentistry and Endodontics
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• v.29 no.4
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• pp.339-345
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• 2004

The aim of this study was to measure and compare the micro shear bond strengths of the following dentin bonding systems to the dentin surfaces under simulated pulpal pressure: All Bond $2^{\circledR},{\;}Second^{\circledR},{\;}AdheSE^{\circledR}$, Adper Prompt $L-Pop^{\circledR}$. The occlusal surfaces of 180 extracted human molars were prepared so the dentin bonding surfaces could be exposed. The teeth were randomly assigned to 3 equal groups of 60 each and subdivided. The dentin surfaces were treated with the above mentioned bonding system and resin composite cylinders were built up under a simulated pulpal pressure when saline (Group II) or diluted bovine serum (Group III) was used as the pulpal fluid. As a control. the same procedures were performed in the dried dentin surfaces (Group I). After one day of storage in water. the micro shear bond strengths were measured using an EZ tester. Group II and III showed significantly lower shear bond strength than Group I statistically (p < 0.05). $SEbond^{\circledR}{\;}and{\;}AdheSE^{\circledR}$ showed no difference among the different dentin condition. In the Adper Prompt $L-Pop^{\circledR}$. a simulated pulpal pressure were applied to the specimens using diluted bovine serum. which showed a higher strength than the specimens in which saline was used (p < 0.05).

• Steel and Composite Structures
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• v.20 no.2
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• pp.251-266
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• 2016

The paper combines two distinct parts. First the behavior of welded headed studs with small diameters of 10 and 13 mm acting as shear connectors (which are not embraced in current standards) is studied. Based on standard push tests the load-slip relationships and strengths are evaluated. While the current standard (Eurocode 4 and AISC) formulas used for such studs give reasonable but too conservative strengths, less conservative and full load-slip rigidities are evaluated and recommended for a subsequent investigation or design. In the second part of the paper the partially encased beams under bending are analyzed. Following former experiments showing rather indistinct role of studs used for shear connection in such beams their role is studied. Numerical model employing ANSYS software is presented and validated using former experimental data. Subsequent parametric studies investigate the longitudinal shear between steel and concrete parts of the beams with respect to friction at the steel and concrete interface and contribution of studs with small diameters required predominantly for assembly stages (concreting). Substantial influence of the friction and effect of concrete confinement was observed with rather less noticeable contribution of the studs. Distribution of the longitudinal shear and its sharing between friction and studs is presented with concluding remarks.