http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
이차돈 ( Lee¸ Chadon ),정상모 ( Chung¸ Sang-mo ),원종필 ( Won¸ Jong-pil ),이승환 ( Lee¸ Seung-hwan ),방정환 ( Bang¸ Jeong-hwan ) 한국구조물진단유지관리공학회 2002 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.6 No.2
Experiments were performed in order to examine the effectiveness of strengthening the reinforced concrete beams by the method of Near Surface Mounted(NSM) fiber reinforced plastic rebars(FRP rebars). Test results showed that NSM strengthening method with FRP rebars inserted directly into the grooves adequately increased the flexural strength. Using the theoretical model, parametric studies were performed. It was theoretically observed that identical flexural behavior of strengthened beams can be obtained if the concept of equivalent sectional areas based on the ratio of moduli of elasticity between different FRP rods is used.
Modeling of Bond Stress-Slip Relationships of a Strand in Concrete during Steam Curing
Chadon Lee,Sangmin Shin,Songhee Lee,Jeongha Oh 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.3
The restrained thermal expansion of a pretensioned strand causes thermal prestress loss during steam curing until sufficient bond strength develops. The amount of thermal prestress loss is directly related to the characteristics of the interfacial bond stress-slip relationship at different maturity phases of concrete. For a rational assessment, the bond stress-slip relationship needs to be investigated experimentally at different maturity phases. In this study, a total of 12 pull-out tests were performed using seven-wire strand of 12.7 mm diameter, at different concrete equivalent ages of 7.8, 23.5, 53.8 and 85.2 h. Based on the test results, an empirical model of the bond stress-slip relationship was developed. The model comprised four segments: a curvilinear ascending region, a constant maximum region, a linearly descending region, and a region of constant frictional bond stress. The characteristic values in the model were expressed as functions of equivalent age. The model was able to predict the test results with reasonable accuracy.
Chadon Lee,Songhee Lee,Ngocchien Nguyen 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.2
High-early-strength-concrete (HESC) made of Type Ⅲ cement reaches approximately 50–70 % of its design compressive strength in a day in ambient conditions. Experimental investigations were made in this study to observe the effects of temperature, curing time and concrete strength on the accelerated development of compressive strength in HESC. A total of 210 HESC cylinders of 100 9 200 ㎜ were tested for different compressive strengths (30, 40 and 50 ㎫) and different curing regimes (with maximum temperatures of 20, 30, 40, 50 and 60 ℃) at different equivalent ages (9, 12, 18, 24, 36, 100 and 168 h). From a series of regression analyses, a generalized rate-constant model was presented for the prediction of the compressive strength of HESC at an early age for its future application in precast prestressed units with savings in steam supply. The average and standard deviation of the ratios of the predictions to the test results were 0.97 and 0.22, respectively.
이차돈 ( Chadon Lee ),김현 ( Hyun Kim ),최충현 ( Chung-hyun Choi ) 한국구조물진단유지관리공학회 2010 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.14 No.2
The research performed in this study aimed to experimentally and theoretically investigate the responses and structural behavior of the bearing walls with both sides being exposed to the fire. From the experiments, it was found that the walls with both sides being exposed to the fire could be severely damaged and led to a complete collapse. The developed model, which could reasonably simulate the wall behavior in fire, predicted that wall thickness and the ratio of the axial load to the nominal strength of the wall section are the most influential factors affecting the fire resistance rate.
Lee, Chadon,Lee, Songhee,Nguyen, Ngocchien Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.2
High-early-strength-concrete (HESC) made of Type III cement reaches approximately 50-70 % of its design compressive strength in a day in ambient conditions. Experimental investigations were made in this study to observe the effects of temperature, curing time and concrete strength on the accelerated development of compressive strength in HESC. A total of 210 HESC cylinders of $100{\times}200mm$ were tested for different compressive strengths (30, 40 and 50 MPa) and different curing regimes (with maximum temperatures of 20, 30, 40, 50 and $60^{\circ}C$) at different equivalent ages (9, 12, 18, 24, 36, 100 and 168 h) From a series of regression analyses, a generalized rate-constant model was presented for the prediction of the compressive strength of HESC at an early age for its future application in precast prestressed units with savings in steam supply. The average and standard deviation of the ratios of the predictions to the test results were 0.97 and 0.22, respectively.