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하상수,Ha, Sang-Su 한국구조물진단유지관리공학회 2017 한국구조물진단유지관리공학회 논문집 Vol.21 No.5
Although the strength of polyethylene terephthalate (PET) fibers which are generally used to make plastic bottles is low, the deformability of PET fibers is substantially high. Due to these material characteristics, a PET fiber can be used as a reliable strengthening material to resist a large deformation caused by earthquake and research pertinent to application of PET fibers is actively conducted in Japan. Therefore, in this study, experiments have been carried out to investigate the lateral confinement effect of PET fibers and to assess the applicability of PET fibers to construction fields by comparing the strengthening effect of PET fibers to that of carbon and glass fiber sheets. For this purpose, concrete cylinder specimens with parameters of different concrete strength and strengthening layers of carbon fiber sheets, glass fiber sheets, and PET fibers were respectively tested using two sets of cylinders for each parameter. As a result, specimens strengthened with carbon fiber sheets and glass fiber sheets failed due to sudden decrease of strength as with existing studies. However, specimens with PET fibers reached their maximum strength and then failed after gradual decrease strength without failure of PET fibers. In addition, although the strength of specimens with PET fibers did not significantly increase in comparison with that of specimens with carbon fiber sheets and glass fiber sheets, specimens with PET fibers indicated considerable deformability. Thus, a PET fiber can be considered as an effective strengthening material. 비닐용기 등에 주로 사용되는 PET 섬유는 강도는 아주 작은 반면, 변형성능에는 아주 우수하기 때문에 지진 발생시 구조물의 대변형에 효과적으로 저항할 수 있는 보강재료로 사용가능하며, 일본에서는 이미 PET 섬유를 이용한 연구를 진행하고 있는 실정이다. 따라서 본 연구에서는 PET(polyethylene terephthalate) 섬유의 횡구속 효과를 파악하고, PET 섬유의 보강효과와 기존에 사용해왔던 탄소섬유시트 및 유리섬유시트의 보강효과를 비교함으로써 PET 섬유의 현장적용성 여부를 파악하기 위한 것이다. 이를 위해 무근 콘크리트 공시체에 탄소섬유시트와 유리섬유시트 및 PET 섬유 등으로 구분하고 각각에 대해 콘크리트 강도와 보강겹수를 달리하여 실험체 별로 각각 2개씩 동일하게 제작하여 실험을 실시하였다. 실험결과, 탄소섬유시트 및 유리섬유시트로 보강된 실험체는 기존연구결과들과 마찬가지로 시트가 파단된 후 급격한 내력저하로 최종파괴 되었다. 그러나 PET로 보강한 실험체들은 PET 섬유가 파단되지 않고 최대 강도 이후 급격한 내력저하 없이 서서히 감소되면서 최종파괴 되었다. 또한, 탄소섬유시트 및 유리섬유시트로 보강한 실험체에 비해 강도증진 효과는 크지 않았으나, 연성측면에서는 매우 우수하게 나타나 향후 보강재료로 사용할 수 있을 것으로 판단된다.
무연 솔더가 적용된 자동차 전장부품 접합부의 열적.기계적 신뢰성 평가
하상수,김종웅,채종혁,문원철,홍태환,유충식,문정훈,정승부,Ha, Sang-Su,Kim, Jong-Woong,Chae, Jong-Hyuck,Moon, Won-Chul,Hong, Tae-Hwan,Yoo, Choong-Sik,Moon, Jeong-Hoon,Jung, Seung-Boo 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.6
This study was focused on the evaluation of the thermo-mechanical board-level reliability of Pb-bearing and Pb-free surface mount assemblies. The composition of Pb-bearing solder was a typical Sn-37Pb and that of Pb-free solder used in this study was a representative Sn-3.0Ag-0.5Cu in mass %. Thermal shock test was chosen for the reliability evaluation of the solder joints. Typical $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed between both solders and Cu lead frame at the as-reflowed state, while a layer of $Cu_3Sn$ was additionally formed between the $Cu_6Sn_5$ and Cu lead frame during the thermal shock testing. Thickness of the IMC layers increased with increasing thermal shock cycles, and this is very similar result with that of isothermal aging study of solder joints. Shear test of the multi layer ceramic capacitor(MLCC) joints was also performed to investigate the degradation of mechanical bonding strength of solder joints during the thermal shock testing. Failure mode of the joints after shear testing revealed that the degradation was mainly due to the excessive growth of the IMC layers during the thermal shock testing.
하상수 ( Ha Sang-su ) 한국건축시공학회 2020 한국건축시공학회지 Vol.20 No.5
Due to the improvement of living standards and avoidance of the 3D industry, it is difficult to find young and competent domestic workers at construction sites, and most foreign workers are contributing to the replacement, but the quality is still deteriorating due to lack of skilled workers and aging. Precast method is a method that make members in factory and assembles them on site, which can be expected to improve labor force and quality. This study is intended to provide basic data for the development of hang-type PC beams that can be applied to the determination of the field application of developed PC beams. The U-type connecting material is installed on both ends of the hang-up PC beam, and the role of the U-type connecting material is very important because it is a simple construction method through the U-type connecting material. In addition, the performance of the U-type connecting material will determine the performance of the hang-type PC beam as the final destruction occurs in the hang-type PC beam. The material properties of U-type connecting material were identified through structural experiments, and the end test corresponding to the partial experiment was conducted based on the material test results identified. Finally, the final design value of PC beams was proposed through structural experiments for application to the site.
하상수 ( Ha¸ Sang-su ),김태수 ( Kim¸ Tae-soo ),이성찬 ( Lee¸ Sung-chan ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.2
슬래브의 강성을 높이고 바닥진동을 저감하기 위해 나사식 브레이스 시스템을 개발하였다. 나사식 브레이스 시스템은 양단부가 회전단으로 되어 있고 중앙부는 길이조정이 가능하도록 나사식 이음장치가 설치되어 있는 다. 본 연구는 연결재를을 위해 천장에 강성보강을 실시하여 바닥진동을 줄이고 을 천장 강성보강으로 바닥 지반굴착 흙막이공사 특성상 해석변수인 지형, 조사시기와 방법 등이 현장여건 변화에 따른 토질정수, 적용 토압방법, 구조모델링 등이 불확실함에 따라, 시공 중에 구조적 거동파악과 현장 주변 영향을 감시하는 계측관리시스템을 도입하여 시공하고 있다. 그러나 종래 계측관리시스템은 현장여건 변화에 따른 설계 관리치와 계측치와의 차이를 토압 및 구조거동 예측이 불가능하여, 시공 중 측정된 계측자료를 경험적 판단으로 정성적 구조거동을 분석하여 현장에 대한 안전성을 확인하는 등 정성적으로 평가함으로서, 설계 절대기준치 관리 및 현상파악 정도의 시공관리 목적 수준에 머물러 있는 실정이다.