• Journal of the KSME
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• v.54 no.1
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• pp.32-37
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• 2014

에너지 파이프라인 건설의 경제성을 확보하기 위한 최신 설계기법인 변형률기반 설계기법과 그 원리를 소개하고, 전통적인 응력기반 설계기법과 대비하여 변형률기반 설계기법을 도입하기 위한 필요사항과 현 단계의 변형률 기반설계기법의 발전현황을 정리하여 실무 기술자의 이해를 돕고자 하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.700-703
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• 2010

일반적으로 구조부재의 안전성 평가는 계측된 센서의 변형률로부터 부재의 최대응력 또는 부재력 수준을 결정하고 설계기준에 의한 부재의 허용응력 또는 설계 강도와의 비교에 의해서 이루어진다. 그러나 이러한 설계기준은 건물의 설계단계에서 미리 가정된 하중 및 부재의 강도에 대한 여러 확률분포 또는 안전율을 반영하여 작성된 것으로 실질적으로 센서로부터 측정한 데이터를 직접 설계기준에 반영하는 것은 합리적이지 못하다. 본 연구에서는 실제 센서로부터 측정되는 변형률을 이용하여 합리적으로 구조부재의 안전성 평가를 수행하기 위한 방법을 모색하고자 한다. 설계기준을 고려한 변형률 제한치, 저감계수가 도입되었으며 이에 추가적으로 센서와 관련한 계수를 도입하여 구조부재의 안전성 평가를 위한 방향을 제시한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.265-275
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• 2010

Concrete filled steel tube and concrete encased steel tube columns are expected to have confined effects of concrete by steel and reinforced effects of local buckling by concrete. On the basis of confined state concrete models of previous researches, stress-strain and load-displacement relations of RC, CFT and CET columns are analyzed by steel ratio. After comparing analysis results with experimental results, Modified stress-strain relations are derived through evaluation the influence upon confined effects of concrete in each cases. Also, the modified stress-strain models are carried out to be compared with specified strength of various countries.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.93-96
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• 2009

바퀴동력계는 차량에 지면으로부터 전달되는 힘과 모멘트를 측정하는 로드셀이다. 본 연구에서 개발한 바퀴동력계는 스트레인 게이지식 로드셀로써 이러한 로드셀을 설계하는데 있어서 몇가지 고려해야 하는 사항이 있다. 우선 스트레인 게이지를 부착하기 쉬운 구조가 되어야 하고 조립시의 오차를 줄이기 위하여 한 몸체로 제작되어야 한다. 이와 동시에 가장 중요하게 고려되어야 하는 인자로 감도를 위해 재료가 허용하는 응력내에서 되도록 큰 변형률이 발생해야 하고 상호 간섭 오차가 발생하지 말아야 한다. 본 연구에서는 수식을 이용하여 이론적으로 상호 간섭 오차를 0으로 만들 수 있었다. 또한 설계 변수 및 재료 물성치의 산포를 고려한 신뢰성 기반 최적설계 기법을 사용하였으며, 이를 통해 허용 응력하에서 최대의 변형률이 발생하는 바퀴동력계를 설계하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.67-80
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• 2009

The basic concept of seismic design is to attain the ductility required in a design earthquake. This ductility can be obtained by providing sufficient lateral confinements to the plastic hinge regions of columns. The most cost-effective design might be derived by determining the proper amount of lateral confinement using a stress-strain relationship for confined concrete. Korean bridge design code requires the same amount of lateral confinement regardless of target ductility, but Japanese design code provides the stress-strain relationship of the confined concrete to determine the amount of lateral confinement accordingly. While design based on material characteristics tends to make the design process more involved, it makes it possible to achieve cost-effectiveness, which is also compatible with the concept of performance-based design. In this study, specimens with different numbers of lateral confinements have been tested to investigate the characteristics of the stress-strain relationship. Test results were evaluated, using several empirical equations to quantify the effects.

• Composites Research
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• v.31 no.5
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• pp.221-226
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• 2018

The Split Hopkinson Pressure Bar(SHPB) has been the most widely used apparatus to characterize dynamic mechanical behavior of materials at high strain rates between $100s^{-1}$ and $10,000s^{-1}$. The SHPB test is based on the wave propagation theory which was developed to give the stress, strain and strain rate in the specimen using the strains measured in the incident and transmission bars. In this study, the SHPB was directly designed and fabricated for the dynamic mechanical properties of fiber reinforced plastic (FRP) composites. In addition, this apparatus was verified for the validity by comparing the strain data obtained through the high speed camera and Digital Image Correlation(DIC) during the high strain rate compression test of the self-reinforced polypropylene composite (SRPP) specimen.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.383-389
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• 2010

The concrete structural design provisions in Korea are based on ultimate strength design. Up to service load stage, it is assumed a linear stress-strain relation, but there is no stress-strain relationship for a concrete material from service load stage to limat state. According to the current provisions, an independent method is provided for the each calculation of deflection and crack width. In EC2 provisions based on limit state design, however, a stress-strain relationship of concrete is provided. Thereby, it is able to calculate a strength as well as a deflection directly from concrete stress-strain relationship. In this paper the moment-curvature relationship is directly calculated from a material law using equilibrium and compatibility conditions. Then strength and deflection are formulated. These results are compared with the values from the current provisions in Korea. From the results, the deflection based on a moment-curvature relationship is well agreed with experimental results and it is appeared that the deflection after the yielding of steel is also possible.

• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.34-40
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• 2008

Using the finite element method and Taguchi's design technique, the displacement in vertical direction, von Mises stress, and strain energy of the corrugation damper have been analyzed as functions of the extruded length and the thickness of the corrugation damper, and the upper and lower corner radii of the damper. The optimized profile design elements of a corrugation damper are very important for increasing a strain energy absorption capacity of a helmet structure, which is attacked by impulsive external forces. In this study, the optimized design data based on the Taguchi's method was computed as a corrugation damper length of L = 20 mm, a damper thickness of t = 2 mm, the upper corner radius of $R_1=4\;mm$, and the lower corner radius of $R_2=3\;mm$. The optimized design parameters of a corrugation damper indicated that the thickness and extruded length of a corrugation damper may affect to increase the strain energy, which absorbs the impact forces of the helmet.

• Journal of Aerospace System Engineering
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• v.18 no.2
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• pp.12-20
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• 2024

The application of reinforcement design to ensure the structural safety of electronics in small satellites is limited by the spatial constraints of the satellite structure during launch vibrations. Additionally, a reliable evaluation approach is needed for mounting highly integrated devices that are susceptible to fatigue failure. Although the Steinberg fatigue failure theory has been used to assess the structural integrity of electronic devices, recent studies have highlighted its theoretical limitations. In this paper, we propose a structural methodology based on the critical strain theory to design the digital control unit (DCU) of the X-band SAR payload component for the small SAR technology experimental project (S-STEP), a small satellite constellation. To validate the design, we conducted modal and random analyses using simplified modeling techniques. Based on our methodology, we ultimately demonstrated the structural safety of the electronics through analysis results, safety margin derivation, and functional tests conducted both before and after the launch test.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.191-196
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• 2022

In this study, the anisotropic mechanical property of fused deposition modeling three-dimensional (3D) printing based on lamination direction was verified by a tensile test. Moreover, the property was applied to solid isotropic materials with penalization-based topology optimization. The case of the lower control arm, one of the automotive suspension components, was considered as a benchmark problem. The optimal topological results varied depending on the external load and anisotropic property. Based on these results, two test specimens were fabricated by varying the lamination direction of 3D printing; a tensile test utilizing 3D non-contact strain gauge was also conducted. The measured strain was compared with that obtained by computer-aided engineering response analysis. Quantitatively, the measurement and analysis results are found to have good agreement. The effectiveness of topology optimization considering the lamination direction of 3D printing was confirmed by the experimental result.