• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 1989년도 봄 학술발표회 논문집
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• pp.38-43
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• 1989

An improved model for predicting the reinforced concrete element behavior under dynamic strain rates was developed using the layer modeling technique. The developed strain rate sensitive model for axial/flexural analysis of reinforced concrete elements was uses to predict the test results, performed at different loading rates, and the predictions were reasonable. The developed analysis technique was used to study the loading rate sensitivity of reinforced concrete beams and columns with different geometry and material properties. Two design formulas for computing the loading rate dependent axial and flexural strengths of reinforced concrete sections were also suggested.

• Journal of Korean Society of Steel Construction
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• 제22권6호
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• pp.609-616
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• 2010

The objective of this study is to investigate the structural character of the buckling strength of 600MPa-class high-strength steel compression members. The buckling strength of circular hollow-section columns is evaluated by a numerical analysis of the stress-strain curves of the tension test results. The numerical analysis was based on the beam-column theory and the tangent modulus theory. It was considered possible to enlarge the nominal yield strength of the 600MPa-class steel.

• Journal of Korean Association for Spatial Structures
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• 제7권4호
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• pp.63-72
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• 2007

As business of steel consuming industries is freshly booming in domestic and foreign countries especially in China, the price of steel plates comes to very high compare with the other materials. The HR Plates made from hot rolled coils is lower steel plates in price. In this study, material characteristics of HR Plates is investigated and availabilities of HR Plates for steel bridges as sub member or a main member is discussed. No difference between steel plates and HR Plates with thickness up to 22mm is found in most characters such as cutting operation, fabrication and even welding. As sub member in steel box girders, the application ratio and the loss ratio of HR Plate is investigated as about $10{\sim}15%$, average $10{\sim}15%$ respectively.

• Korean Journal of Materials Research
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• 제6권9호
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• pp.905-918
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• 1996

초전도 마그네트 구조용 부재로 최근 개발된 오스테나이트계 스테인레스강 JN1 모재, GTA 용접부 및 열처리재에 대한 기계적 성질을 조사하기 위해 실온(293K)에서 극저온(4K)까지의 온도에서 소형펀치(Small Punch)시험을 실시하였다. GTA 용접부의 용융선 근방의 극저온 기계적 성질은 모재와 용접금속에 비해 크게 저하하였다. 4K에서 실험된 용융선 시험편으로 얻어진 하중-변위곡선상에서 부하의 초기 단계에 보통의 서레이션과 다른 pop-in이 관찰되었고, 이때 시험편 표면의 용융선 근처에서 약 0.1-1mm 정도의 크랙이 발생하였다. 열처리재의 기계적 성질은 열처리 시간과 온도의 증가 또는 시험온도의 저하에 따라 크게 저하되었다. 위의 결과에 기초하여 본 연구에서 실시한 소형 시험편을 사용하는 SP 시험법은 극저온에서 JN1 강의 모재와 열처리재뿐 만 아니라 GTA 용접부의 기계적 성질을 평가할 수 있는 유용한 시험법이었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제27권2호
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• pp.113-117
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• 2015

This study presents a 3-dimensional flow-structure interaction analysis of subsea risers in water flows. Two structural connectors (flat and circular couplers) were intentionally devised and numerically tested using ANSYS CFX to investigate how these couplers behave under the water flows. In the flow analysis, the water field was constructed with an inlet, outlet, and symmetric boundary conditions. As a result, the responses (drag coefficients and pressure fields) were obtained and the pressure fields were applied for the structural analysis. Finally, the structural responses (displacements and equivalent stresses) of the risers were measured to demonstrate the efficiency of the riser connectors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제41권12호
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• pp.967-974
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• 2013

Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin's material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제25권4호
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• pp.279-285
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• 2012

In this paper a computational method for a homogenized peridynamics description of unidirectional fiber-reinforced composites is presented. For these materials, dynamic brittle fracture and damage are simulated with the proposed peridynamic model. Compared with observations from dynamic experiments by Coker et al.(2001), the peridynamic computational model can reproduce various characteristics of dynamic fracture and supersonic or intersonic crack growth in asymmetrically loaded unidirectional fiber-reinforced composite plates. Also we analyze the same model in the symmetric loading condition and figure out that the asymmetric loading leads to a much higher propagation speed. Consistent results have been reported in the experiments.

• Journal of the Korea institute for structural maintenance and inspection
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• 제25권6호
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• pp.41-49
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• 2021

Cement-mixed polymer-based waterproofing materials are generally used in the form of application by mixing in the field, and it is necessary to supplement the construction ability for air bubbles and uneven coating thickness due to irregularities during construction. The final purpose of this study is to improve the waterproofing performance by adding a sheet attaching process to the composite construction rather than the single process of painting and applying the construction method when applying the polymer waterproofing material to the field. In this regard, the applicability was evaluated by examining the material, environment, and manufacturing method.

• Composites Research
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• 제31권6호
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• pp.340-346
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• 2018

This paper addresses the stress analysis and design of composite double lead spiral which is boarded in 20mm universal ammunition drum by finite element method. The spiral system is very important to transfer the ammunition in stable and reliable manners for aircraft. Some verifications are done to check the possibility of composite application in spiral system. The design variables, stacking sequence and fiber orientation angles, are investigated for reliable design for practical design. The Tsai-Wu failure theory is applied to see the safety of the spiral structure. The design result is suggested to manufacture the double lead spiral part.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제47권1호
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• pp.35-40
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• 2019

The objective of this paper is to identify the fatigue properties of carbon-fiber composite which is widely applied for the development of aircraft structures and obtain data for full-scale fatigue test. The durability and damage tolerance evaluation of composite structures is achieved by fatigue tests and parameters such as fatigue life factor and load enhancement factor. The specimens are made with carbon-fiber/epoxy UD tape and fabric prepreg. Fatigue tests are performed with several stress ratios and lay-up patterns. The Weibull shape parameters are analyzed by Sendeckyj model and individual fatigue lives with Weibull distribution. And the fatigue life factor and load enhancement factor considering reliability are evaluated.