• The Journal of Advanced Prosthodontics
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• 제8권4호
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• pp.251-258
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• 2016

PURPOSE. This study was undertaken to investigate whether use of an adhesive penetration enhancer, dimethyl sulfoxide (DMSO), improves bond stability of fiber posts to root dentin using two two-step etch-and-rinse resin cements. MATERIALS AND METHODS. Forty human maxillary central incisor roots were randomly divided into 4 groups after endodontic treatment and post space preparation, based on the fiber post/cement used with and without DMSO pretreatment. Acid-etched root dentin was treated with 5% DMSO aqueous solution for 60 seconds or with distilled water (control) prior to the application of Excite DSC/Variolink II or One-Step Plus/Duolink for post cementation. After micro-slicing the bonded root dentin, push-out bond strength (P-OBS) test was performed immediately or after 1-year of water storage in each group. Data were analyzed using three-way ANOVA and Student's t-test (${\alpha}$=.05). RESULTS. A significant effect of time, DMSO treatment, and treatment${\times}$time interaction were observed (P<.001). DMSO did not affect immediate bonding of the two cements. Aging significantly reduced P-OBS in control groups (P<.001), while in DMSO-treated groups, no difference in P-OBS was observed after aging (P>.05). CONCLUSION. DMSO-wet bonding might be a beneficial method in preserving the stability of resin-dentin bond strength over time when fiber post is cemented with the tested etch-and-rinse adhesive cements.

• 한국구조물진단유지관리공학회 논문집
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• 제22권2호
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• pp.43-50
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• 2018

본 연구에서는 강주형과 바닥판의 합성에 사용되는 전단연결재에 대한 연구를 위해 세계 각국에서 사용되는 설계기준과 연구사례를 분석하고 교량 바닥판에 작용하는 각종 수직하중으로 인해 강주형과 콘크리트 슬래브의 접촉면에 발생하는 수평방향의 전단력을 전달하는 이 연결재를 설치한 밀어내기 시험체에 대하여 전단실험을 수행하였으며, 이 시험을 통하여 철근 대신 FRP 철근이 배치된 Steel strap 바닥판의 전단열재 평가식을 제안하였다. 본 연구에서의 제안식은 도로교설계기준의 전단연결재 허용강도 대비 약 3배의 안전율을 가지고 있으며, 기존의 DIN 기준과 Viest 평가식과 비교하면 5%정도의 오차로 유사한 결과를 보여주었다.

• Restorative Dentistry and Endodontics
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• 제44권2호
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• pp.21.1-21.8
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• 2019

Objectives: The purpose of the present study was to evaluate the effect of calcium hydroxide with 2% chlorhexidine gel (HCX) or distilled water (HCA) compared to triple antibiotic paste (TAP) on push-out bond strength and the cement/dentin interface in canals sealed with White MTA Angelus (WMTA) or Biodentine (BD). Materials and Methods: A total of 70 extracted human lower premolars were endodontically prepared and randomly divided into 4 groups according to the intracanal medication, as follows: group 1, HCX; group 2, TAP; group 3, HCA; and group 4, control (without intracanal medication). After 7 days, the medications were removed and the cervical third of the specimens was sectioned into five 1-mm sections. The sections were then sealed with WMTA or BD as a reparative material. After 7 days in 100% humidity, a push-out bond strength test was performed. Elemental analysis was performed at the interface, using energy-dispersive spectroscopy. The data were statistically analyzed using analysis of variance and the Tukey test (p < 0.05). Results: BD presented a higher bond strength than WMTA (p < 0.05). BD or WMTA in canals treated with calcium hydroxide intracanal medications had the highest bond strength values, with a statistically significant difference compared to TAP in the WMTA group (p < 0.05). There were small amounts of phosphorus in samples exposed to triple antibiotic paste, regardless of the coronal sealing. Conclusions: The use of intracanal medications did not affect the bond strength of WMTA and BD, except when TAP was used with WMTA.

• 대한정형도수물리치료학회지
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• 제28권3호
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• pp.9-19
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• 2022

Background: The study objectives were to investigate the effect of Kinesio taping, Mulligan taping on push-off-test and maximum grip strength in elite men's artistic gymnast with wrist impingement syndromes. Methods: The subjects of this study were 18 wrist impingement syndromes men's artistic gymnast and randomly assigned to a Kinesio taping group, Mulligan taping group. Weight-bearing wrist pain and Muscle strength were assessed with push-off-test (POT) and the maximum grip strength (MGS). Results: As a result of the research, there were no significant difference in POT in pre and post group in the Kinesio taping (p>.05). But Mulligan taping group were significant difference in POT (p<.05). In comparison after intervention between each other groups, there was a no significant difference on (p<.05), but no significant difference on post (p>.05). there were significant difference in MGS in both pre and post group in the Kinesio taping and Maximum Grip Strength (p<.05). In comparison after intervention between each other groups, there was a no significant difference on pre (p<.05), but no significant difference on post (p>.05). Conclusion: This results suggests that Mulligan taping are encouraged due to effects on pain, Muscle strength increase in elite men's artistic gymnast with wrist impingement syndromes.

• Steel and Composite Structures
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• 제44권5호
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• pp.741-752
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• 2022

Earlier works have shown that excessive shear stiffness at the steel-concrete interface causes a non-uniform distribution of shear force in composite structures. When the shear studs are wrapped at the fixed end with flexible materials with a low elastic modulus, the shear stiffness at the interface is reduced. The objective of this study was to investigate the effect of silicone rubber-sleeve mounted on shear studs on the shear stiffness of steel-concrete composite structures. Eighteen push-out tests were conducted to investigate the mechanical behavior of silicone rubber-sleeved shear stud groups (SRS-SSG). The dimension and arrangement of silicon rubber-sleeves (SRS) were taken into consideration. Test results showed that the shear strength of SRS-SSG was higher than that of a shear stud group (SSG), without SRS. For SRS-SSG with SRS heights of 50 mm, 100 mm, 150 mm, the shear strengths were improved by 13%, 20% and 9%, respectively, compared to the SSG alone. The shear strengths of SRS-SSG with the SRS thickness of 2 mm and 4 mm were almost the same. The shear stiffness of the SRS-SSG specimens with SRS heights of 50 mm, 100 mm and 150 mm were 77%, 67% and 66% of the SSG specimens, respectively. Test results of specimens SSG-1 and predicted values based on the three design specifications were compared. The nominal single stud shear strength of SSG-1 specimens was closest to that calculated by the Chinese Code for Design of Steel Structures (GB50017-2017). An equation is proposed to consider the effects of SRS for GB50017-2017, and the predicted values based on the proposed equation agree well with the tested results of SRS-SSG.

• 대한토목학회논문집
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• 제38권2호
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• pp.349-356
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• 2018

본 논문은 국내에서 연구가 미진한 적재설비의 지진 취약도 평가에 적용할 수 있는 FE 해석 기반의 연결부 모델을 개발하는데 목적이 있다. 이러한 목표를 달성하기 위하여, 적재설비 거동을 파악하기 위한 진동대 실험과 Modal Test, 그리고 구성 부재를 대상으로 한 다양한 부재실험(8가지 Push-over Test)을 진행하였다. 실험결과를 바탕으로 지진취약도 평가에 적용하기 위한 적재설비의 연결부 모델을 개발하기 위하여, NX-Nastran 프로그램을 활용하여 연결부의 상세 모델링을 진행하였다. 특히, 단순 걸쇠 방식으로 연결되는 기둥 부재와 보 부재의 연결을 모사하기 위하여 면대면 표면접촉 요소와 스프링 요소를 적용하였으며, 스프링 요소의 모델은 ARX (Auto Regressive eXogenous) 기반의 수학적 모델을 개발하여 적용하였다. FE 모델 기반의 simulation 결과는 부재 실험 결과와 비교하였을 때, 상호 오차율 8% 미만의 우수한 신뢰도를 보여주었다. 결과적으로 연구에서 개발한 FE해석 기반의 연결부 모델은 적재설비의 지진 취약도 평가를 위한 해석 모델에 활용될 수 있음을 확인하였다.

• Advances in concrete construction
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• 제10권2호
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• pp.113-125
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• 2020

This paper presents experimental results on bond-slip behavior of steel reinforced high-strength concrete (SRHC) after exposure to elevated temperatures. Three parameters were considered in this test: (a) high temperatures (i.e., 20℃, 200℃, 400℃, 600℃, 800℃); (b) concrete strength (i.e., C60, C70, C80); (c) anchorage length (i.e., 250 mm, 400 mm). A total of 17 SRHC specimens subjected to high temperatures were designed for push out test. The load-slip curves at the loading end and free end were obtained, the influence of various variation parameters on the ultimate bond strength and residual bond strength was analyzed, in addition, the influence of elevated temperatures on the invalidation mechanism was researched in details. Test results show that the shapes of load-slip curves at loading ends and free ends are similar. The ultimate bond strength and residual bond strength of SRHC decrease first and then recover partly with the temperature increasing. The bond strength is proportional to the concrete strength, and the bond strength is proportional to the anchoring length when the temperature is low, while the opposite situation occurs when the temperature is high. What's more, the bond damage of specimens with lower temperature develops earlier and faster than the specimens with higher temperature. From these experimental findings, the bond-slip constitutive formula of SRHC subjected to elevated temperatures is proposed, which fills well with test data.

• Steel and Composite Structures
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• 제25권6호
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• pp.705-716
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• 2017

The objective of this study is to investigate the actual behavior of studs in structures under earthquake load through laboratory tests and numerical simulation. A test program including eighteen specimens was devised with consideration of different concrete strengths and stud diameters. Six of specimens were subjected to monotonically increasing loading while the others were subjected to cyclic loading. Mechanical behavior including the failure mechanism, load-slip relationship, stiffness degradation, energy dissipation and the damage accumulation was obtained from the test results. An accurate numerical model based on the ABAQUS software was developed and validated against the test results. The results obtained from the finite element (FE) model matched well with the experimental results. Furthermore, based on the experimental and numerical data, the design formulas for expressing the skeleton curve were proposed and the simplified hysteretic model of load versus displacement was then established. It is demonstrated that the proposed formulas and simplified hysteretic model have a good match with the test results.

• 한국산업융합학회 논문집
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• 제22권2호
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• pp.155-161
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• 2019

Recently, increases in major disasters such as fires, earthquakes and typhoons have raised public expectations for safety. In addition to this increase in expectations of safety, the government continues to push for more manpower and better treatment for firefighters who are operating in the disaster scene. Despite the improvement of working conditions and increased welfare for firefighters, however, the incidence and turnover of various mental diseases continues to increase. It is reported that many of the diseases such as post-traumatic stress disorder and the turnover of firefighters are due to a mismatch in individual's personality and work environment. In this study, 108 firefighters were evaluated for their vocational aptitude in the new curriculum. Based on the analysis results, new firefighters were proposed to provide employment and education training improvements, and to provide job security suitable for the individual's personality type through the introduction of the vocational aptitude test for firefighters who are working in the fire service. In addition, we would like to use the vocational aptitude test as a material for reducing post-traumatic stress disorder and increasing turnover through long-term tracking and observation, rather than from a one-off perspective.

• 한국지진공학회논문집
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• 제26권6호
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• pp.255-265
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• 2022

In order to determine fragility curves, the limit state of piers for each damage level is suggested in this paper based on the previous test results in Korea, including our test results. In previous studies, the quantitative measures for damage levels of piers have been represented by curvature ductility, lateral drift ratio, or displacement ductility. These measures are transformed to lateral drift ratios of piers for consistency, and the transformed values are compared and verified with our push-over test results for flexural RC piers with a circular cross-section. The test specimens are categorized concerning the number of lap-splices in the plastic hinge region and whether seismic design codes are satisfied or not. Based on the collected test results in Korea, including ours, the lateral drift ratio for each pier damage level is suggested.