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김지상 ( Kim Jee-sang ),오병환 ( Oh Byung-hwan ) 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.9 No.1
This paper deals with an assessment of health monitoring of normal and high strength concrete structures using rebound hammer test and ultrasonic pulse velocity method. There are also few experimental results on the NDT of deteriorated concrete. In this paper, some on-going experimental results are summarized, in which the variables are compressive strength of concrete, age, degree of deterioration and load histories and correcting the surface-opening crack depth by ultrasonic pulse velocity in reinforcement concrete structures. These results are expected to use basic technique of concrete structure maintaining
초음파 펄스를 이용한 철근콘크리트 구조물의 균열 깊이 측정에 관한 연구
오병환 ( Oh Byung-hwan ),김지상 ( Kim Zi-sang ),김세훈 ( Kim Se-hoon ),백낙승 ( Paek Nak-seung ) 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.9 No.1
Ultrasonic pulse velocity method is employed for evaluation of crack depth in concrete structures. Due to the heterogeneous nature of concrete and the indirect transmission arrangement for the transit time measurement through the surface-opening cracks in concrete structures, ultrasonic pulse velocity has so many variations as crack depths and transmission length vary. In this study, ultrasonic pulse velocity method is investigated to evaluate the surface-opening crack depth of concrete slabs, reinforced concrete slabs, reinforced concrete flexural members. A resonable method is presented to detect the crack depth of concrete structures.
오병환 ( Oh Byung Hwan ),김세훈 ( Kim Se Hoon ),김지상 ( Kim Ji Sang ) 한국구조물진단유지관리공학회 2004 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.8 No.1
Presented is a method which can predict accurately the crack width in reinforced concrete beams under repeated loading. It is known that the crack widths increase with the increase of the number of load cycles. To evaluate the crack widths realistically, the bond stress-slip relation and the variation of transfer length under repeated loading have been modeled and incorporated in the analysis model for crack width. The present study indicates that the transfer length decreases according to the increase of load cycles, which is due to the increase of residual slip. The calculated crack widths from proposed method agree very well with test data available in the literature, while the existing method shows large deviation from the test data. The proposed method also allows to calculate the residual crack width after repeated loading. The present study provides a realistic base for the prediction of crack width, which is important for the serviceability of reinforced concrete structures subjected to repeated loads.
Propofol에 의한 전신마취 후 회복 시 발생한 근경련 -증례 보고-
김병환,정성수,Kim, Byung-Hwan,Chung, Sung-Su 대한치과마취과학회 2010 Journal of Dental Anesthesia and Pain Medicine Vol.10 No.1
There are a few case reports describing persistent seizure following propofol. A 45-year-old female underwent operation of mastoidectomy and tympanoplasty. She had no personal or family history of epilepsy. Anesthesia was induced with propofol and rocuronium, and maintained with sevoflurane-remifentanil after tracheal intubation. Any event was not noted during surgery. Seizure-like movement and shivering were developed after surgery in recovery room. Symptom was relieved by benzodiazepines, especially lorazepam. She was discharged in the 9th postoperative days without any sequelae.
김지상 ( Kim Jee-sang ),오병환 ( Oh Byung-hwan ),백낙승 ( Paek Nak-seung ) 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.9 No.1
This paper deals with an assessment of compressive strength of normal and high strength concrete using rebound hammer test and ultrasonic wave method. Most existing formulas for strength evaluation using NDT have been obtained on the experimental results of normal strength concrete. There are also few experimental results on the NDT of deteriorated concrete. In this paper, some on-going experimental results are summarized, in which the variables are compressive strength of concrete, age, degree of deterioration and load histories. It is found that some refinements are required assessment of compressive strength in existing concrete structures when rebound hammer and ultrasonic wave method are applied.
[제4분과/구조거동/재료Ⅱ] 반복하중을 받는 철근콘크리트의 부착슬립 모델
오병환(Oh Byung Hwan),김세훈(Kim Se Hoon),김지상(Kim Ji Sang) 한국구조물진단유지관리학회 2004 한국구조물진단학회 학술발표회논문집 Vol.- No.-
The crack widths of reinforced concrete flexural members are influenced by repetitive fatigue loadings. The bond stress-slip relation is necessary to estimate these crack widths realistically. The purpose of the present study is, therefore, to propose a realistic model for bond stress-slip relation under repeated loading. To this end, several series of tests were conducted to explore the bond-slip behavior under repeated loadings. Three different bond stress levels with various number of load cycles were considered in the tests. The present tests indicate that the bond strength and the slip at peak bond stress are not influenced much by repeated loading if bond failure docs not occur. However, the values of loaded slip and residual slip increase with the increase of load cycles. The bond stress after repeated loading approaches the ultimate bond stress under monotonic loading and the increase of bond stress after repeated loading becomes sharper as the number of repeated loads increases. The bond stress-slip relation after repeated loading was derived as a function of residual slip, bond stress level. and the number of load cycles. The models for slip and residual slip were also derived from the present test data.