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Evaluation of slip coefficient of slip critical joints with high strength bolts
Nah, Hwan-Seon,Lee, Hyeon-Ju,Kim, Kang-Seok,Kim, Woo-Bum Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.4
A slip critical joint has various values to adopt the proper slip coefficient in various conditions of faying surfaces in the following codes: AISC, AIJ and Eurocode 3. However, the Korean Building Code still regulates the unique slip coefficient, 0.45, regardless of the diverse faying conditions. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The faying surfaces were comprised of a clean mill, rust, red lead paint, zinc primer, and shot blast treatment. The candidates for high strength bolts were torque-shear bolts, torque-shear bolts with zinc coating, and ASTM A490 bolts. Based on the test results, the specimens with a shot blasted surface and rusted surface exhibited $k_s$, 0.61, and 0.5, respectively. It is recommended that the specimens with zinc primer exhibit $k_s{\geq}0.40$. The clean mill treated surface had prominently lower values, 0.27. For red lead painted treatment, the thickness of the coating affects the determinant of slip coefficient, so it is necessary to establish a minimum $k_s$ of 0.2, with a coating thickness of 65 ${\mu}m$. During 1,000 hours of relaxation, the uncoated surfaces exhibited the loss of clamping force behind 3%, while the coated surfaces within a certain limited thickness exhibited the loss of clamping within a range of 4.71% and 8.37%.
Evaluating long-term relaxation of high strength bolts considering coating on slip faying surface
Nah, Hwan-Seon,Lee, Hyeon-Ju,Choi, Sung-Mo 테크노프레스 2014 Steel and Composite Structures, An International J Vol.16 No.6
The initial clamping forces of high strength bolts subjected to different faying surface conditions drop within 500 hours regardless of loading, any other external force or loosening of the nut. This study develops a mathematical model for relaxation confined to creep on a coated faying surface after initial clamping. The quantitative model for estimating relaxation was derived from a regression analysis for the relation between the creep strain of the coated surface and the elapsed time for 744 hours. This study establishes an expected model for estimating the relaxation of bolted joints with diverse coated surfaces. The candidate bolts are dacro-coated tension control bolts, ASTM A490 bolt, and plain tension control bolts. The test parameters were coating thickness, species of coating. As for 96, 128, 168, and $226{\mu}m$ thick inorganic zinc, when the coating thickness was increased, relaxation after the initial clamping rose to a much higher range from 10% to 18% due to creep of the coating. The amount of relaxation up to 7 days exceeded 85% of the entire relaxation. From this result, the equation for creep strain can be derived from a statistical regression analysis. Based on the acquired creep behavior, it is expected that the clamping force reflecting relaxation after the elapse of constant time can be calculated from the initial clamping force. The manufacturer's recommendation of inorganic zinc on faying surface as $75{\mu}m$, appears to be reasonable.
이현주 ( Hyeon Ju Lee ),나환선 ( Hwan Seon Nah ),조혜진 ( Hye Jin Jo ),최성모 ( Sung Mo Choi ) 한국복합신소재구조학회 2013 복합신소재학회논문집 Vol.4 No.2
This project is mainly related to evaluation of total energy consumption of low energy house, the exterior envelope of which was wholly composed of structural insulated panels(SIP). The U-value of applied SIP was in the range of 0.189 to 0.269W/㎡·K and the U-value of pair glass from 0.78 to 1.298W/㎡·K was applied for window dependent to its function respectively. For comparison of total energy performance, the energy simulation for pilot house was performed to compare with the control house having insulation criteria of Korean building regulation in 2009. Based on simulation of dynamic energy performance, the pilot house saved 48.3% of annual energy consumption while the control house in 2009 consumed as 85.7GJ/y. In case of heating, the result showed that the energy saving ratio amounted to 76.7%. For CO2 emission, the pilot house diminished approximately 35.4% from 6,208.4kgCO2 to 4,009.2kgCO₂. In payback period to early investment, it was analyzed the pilot house took 7.8 years, when the low energy house built by other insulation method with same thermal perfusion took 11.5 years. From this result, it is considered that the SIP is more effective, economic to Green Home application.
시간영역 신호의 FFT를 이용한 2차 LC네트워크 모델링
배현주(Hyeon-ju Bae),하정래(Jungrae Ha),김병기(Byung-Ki Kim),나완수(Wansoo Nah) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
본 논문에서는 시스템의 입출력 신호를 FFT(Fast Fourier Transformation)하였고, 이를 ABCD 매트릭스를 이용하여 전달함수를 구하였다. 또한 구해진 전달함수를 바탕으로 최소자승법을 사용하여 2차 LC 네트워크의 파라미터(parameter)를 추출하였다. 추출된 2차 LC 네트워크의 파라미터 값의 정확성을 검증하기 위하여 circuit simulator인 Agilent사의 ADS를 사용하여 등가회로를 모델링하였고, 출력된 파형을 실제 측정파형과 비교 검증하였다. 설계된 등가회로 모델이 시스템의 출력파형과 100㎒ ~500㎒까지 일치하는 것을 확인하였다.
나환선 ( Nah Hwan-seon ),이현주 ( Lee Hyeon-ju ),권기주 ( Kwon Ki-joo ) 한국구조물진단유지관리공학회 2006 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.10 No.1
The purpose of this study is focused on evaluating the flexural behavior of concrete beam, which are arranged by mechanically spliced reinforcing bar. This splicing method related to parallel threaded coupler is registered newly on KEPIC 2005. To compare the existent lapping method with newly registered splicing method, four cases of concrete beam are tested to be failed flexurally by monotonic loading. The co-relation between load and displacement, ductility, maximum load and max. displacement were comparatively analyzed. Based on test results, ductility of specimen mechanically all spliced by parallel threaded coupler is approximately 4 times better than those of other specimens.
구조단열패널의 저에너지주택 적용을 위한 내화 및 단열성능 평가
이현주 ( Hyeon Ju Lee ),나환선 ( Hwan Seon Nah ),이철희 ( Cheol Hee Lee ),최성모 ( Sung Mo Choi ) 한국복합신소재구조학회 2012 복합신소재학회논문집 Vol.3 No.2
Structure Insulated Panel (SIP) is an wooden structure material with which structure and insulation functions are satisfied. Hence, it would be a cost-effective model to implement low energy house which has higher insulation and structure performance and which the wall thickness is able to be reduced. In this study, performance of thermal insulation and fire resistance were evaluated in order to verify applicability to low energy house. Fire resistance test is performed on vertical load bearing members for partitions, and the test results satisfy one hour of fire resistance condition according to KS F 2257. The members include two layers of fireproof gypsum board with thicknesses of 12.5mm attached to SIP. Thermal insulation performance is satisfied with the 2012 standard (0.225W/㎡·K). As the performance of resistance and thermal insulation are satisfied, SIP is expected to be applied to low energy building materials. In the future, the structural safety will be confirmed by structural performance and seismic performance test and the guidelines for distribution will be drawn up.
나환선(Nah Hwan-Seon),이현주(Lee Hyeon-Ju),권기주(Kwon Ki-Joo) 한국구조물진단유지관리학회 2006 한국구조물진단학회 학술발표회논문집 Vol.10 No.1
The purpose of this study is focused on evaluating the flexural behavior of concrete beam, which are arranged by mechanically spliced reinforcing bar. This splicing method related to parallel threaded coupler is registered newly on KEPIC 2005. To compare the existent lapping method with newly registered splicing method, four cases of concrete beam are tested to be failed flexurally by monotonic loading. The co-relation between load and displacement, ductility, maximum load and max. displacement were comparatively analyzed. Based on test results, ductility of specimen mechanically all spliced by parallel threaded coupler is approximately 4 times better than those of other specimens.