• Journal of Welding and Joining
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• v.13 no.4
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• pp.36-45
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• 1995

우리나라의 용접 기능 인력의 검정제도는 국제적 수준에 비교하여 그 질이 현격히 떨어지고 있다. 따라서 현재 우리나라의 용접사의 기량이 국제적으로 공인을 받지 못함으로 해서, 일본 강구조물 건설 시장에 참여하고자하는 우리나라 건설업체 의 용접기능공의 자격증이 전혀 인정을 받지 못하고 일본용접 협회에서 우리나라에와 기량 검정을 일본공업규격에 맞춘 새로운 기량 검정 시험을 치루고 자격증을 발급하고 있는 실정이다. 앞에서 언급한 바와 같이 도시가스관 용접부의 절반이 가스 누설된다 는 사실은 단순히 건설제도의 문제를 떠나서 용접사의 수준을 증명하는 일이기 때문 이다. 이러한 모든 문제점은 전문성이 전적으로 결여되고, 각 산업 분야의 특성을 무시한 패키지식 기능 인력의 공급을 담당하고 있는 한국산업인력공단과 이를 뒷받침 하는 현행 국가기술자격법에 기인하고 있다. 현재 운용되고 있는 국가기술자격법은 1973년도 처음 제정되어 지금까지 20여년 넘게 지속되어 오고 있으나 적어도 용접분야 의 자격증 효용은 아직까지도 산업 현장에서 뿌리내리고 있지 못한 실정이다. 뒤늦게 나마 정부가 국가기술 자격법의 폐해를 인정하고 이의 개정을 발표하였으나 용접계의 결연한 의지로 새롭게 국제적으로 인정받을 수 있는 용접사 기량 검정 제도를 개발하 여 이의 시행 의지를 밝혀야 제대로 된 용접사의 배출이 가능할 것이다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.281-287
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• 2004

In this paper, the refined plastic-hinge analysis accounting for gradual yielding with fibers on a section is developed. Geometric nonlinearities of member(P-δ) and frame(P-Δ) are accounted for by using stability functions. Residual stresses are considered by assigning initial stresses to the fiber on the section. The elastic core in a section is investigated at every loading step to determine the axial and bending stiffness reduction. The strain reversal effect is captured by investigating the stress change of each fiber. The proposed analysis proves to be useful in applying for practical analysis and design of three-dimensional steel frames.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.270-277
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• 2004

In this paper, path-independent values of the J-integral in the fininte element context for arbitrary two-dimensional and three-dimensional crack configurations in welds are presented. For the fracture mechanics analysis of cracks in welds, residual stress analysis and fracture analysis must be performed simultaneously. In the analysis of cracked bodies containing residual stress, the usual domain integral formulation results in path-dependent values of the J-integral. This paper discusses modifications of the conventional J-integral that yield path independence in the presence of residual stress generated by welding. The residual stress problem is treated as an initial strain problem and the J-integral modified for this class of problem is used. And a finite element program which can evaluate the J-integral for cracks in two-dimensional and three-dimensional residual stress bearing bodies is developed using the modified J-integral definition. The situation when residual stress only is present is examed as is the case when mechanical stresses are applied in conjunction with a residual stress field.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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• pp.192-197
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• 2015

In many fields, the importance of reducing weight is increasing. A product should be designed such that it is profitable, by lowering costs and exhibiting better performance than other similar products. In this study, the mass and deflection of steel structures have to be reduced as objective functions under constraint conditions. To reduce computational analysis time, central composite design(CCD) and D-Optimal are used in design of experiments(DOE). The accuracy of approximate models is evaluated using the $R^2$ value. In this study, the objective functions are multiple, so the non-dominant sorting genetic algorithm(NSGA-II), which is highly efficient, is used for such a problem. In order to verify the validity of Pareto solutions, CAE results and Pareto solutions are compared.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.192-199
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• 2006

BIM is a collaborative. model-based way to work. Structural BIM is one of the key elements in the building process where the majority of structural information is created. Open BIM interfaces make it possible for all design information to be produced and managed within a single 3D product model. To make structural BIM a reality between owners, general contractors, architects and engineers. the software used need to be open in their communication. We used to Tekla Structures to provide an open environment through standard interfaces and Tekla Open API collaboration. We have developed MCP(machine cutting plan) and PIM(product information management)to provide cutting plan and drawing and manage to B.O.M, Materials, Production, Shipping and Project.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.29-33
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• 1989

An extended model for the assessment of fatigue reliability of steel structures In the presence of residual stresses Is developed. The model explicitly Includes the uncertainties of the lean stress and residual stress in terms of the zero-mean equivalent stress-range. It Is assumed that the fatigue life of welded Joints follows the Weibull distribution. Based on the numerical illustrations, It Is shown that the probability of fatigue fat lure and the allowable stress-range for fatigue design could be significantly affected by the presence of residual stresses. This effect may be represented through the mean stress at the welded joints.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.331-342
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• 2005

This paper presents a non-destructive evaluation (NDE) technique for detecting damages on a jointed steel plate on the basis of the time of flight and wavelet coefficient, obtained from wavelet transforms of Lamb wave signals. Support vector machines (SVMs), which is a tool for pattern classification problems, was applied to the damage estimation. Two kinds of damages were artificially introduced by loosening bolts located in the path of the Lamb waves and those out of the path. The damage cases were used for the establishment of the optimal decision boundaries which divide each damage class's region from the intact class. In this study, the applicability of the SVMs was investigated for the damages in and out of the Lamb wave path. It has been found that the present methods are very efficient in detecting the damages simulated by loose bolts on the jointed steel plate.

• Proceeding of KASS Symposium
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• 2005.05a
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• pp.236-245
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• 2005

This paper was developed the discrete optimum design program by the refined fuzzy-genetic algorithms based on the genetic algorithms and fuzzy theory. The optimum design of this paper can perform both size and shape optimum design for planar and spacial steel structures. In this paper, the objective function is the weight of steel structures and the constraints are the design limits defined by design and buckling strengths, displacements and thicknesses. The design variables are dimensions and coordinates of steel sections. Design examples are given to show the applicability of the discrete optimum design program of this paper.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.18-25
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• 1994

최근 건축용 강구조물이 초대형화 및 초고층화됨에 따라 용접물량의 급증하고 있으나 3D 직종에 대한 회피현상으로 용접기능자의 감소 및 인건비의 급증 등으로 인하여 건축용 강 구조물 제작시 경쟁력이 갈수록 저하되고 있다. 이에 대한 자구책으로 강 구조물 제작업체에서는 생산 성을 한층 배가 시킬 수 잇는 용접시공 기술을 자체 개발하거나 외부로부터 도입하고 있다. 본 보에서는 당사를 비롯하여 여러 업체에서 최근 개발된 용접기술 특히 대전류 SAW 기법, SESNET 기법 등의 초대입열 용접기술, Metal cored wire나 TIME 기법에 의한 고능률 GMAW 기법 및 Robot 용접 등에 대하여 간략히 기술하였다. 이 용접기술들의 적용에는 대개 고가의 시설투자가 수반되나, 이는 생산성 증가에 따른 원가절감으로 충분히 상쇄될 수 있다. 그러나 상기된 용접기술들의 적용에 대한 성패는 용접장비의 특성, 용접조건의 확립, 모재의 특성 혹은 주변 자동화 기술 및 상호 종속적인 관계에 크게 의존된다. 따라서 가 강 구조물 제작업체에서는 세심한 주위환경 분석을 토대로 각 업체에 가장 합당한 용접기술을 선정 및 적용하여야 하겠다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.751-755
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• 2003

In this paper, floor impact noise reduction in a steel structure is studied. A mock-up is built by using 6t steel plate, and two identical cabins are made where 25t panel is used to construct wall and ceiling inside the steel structure. Various floating floor systems are tested for which normalized impact noise is measured according to ISO 140-7. In addition, floor SBN(Structure-borne Noise) and floor damping are measured to study the effect of floating floor. structure. It is shown that VL(Visco-elastic Layer) is more effective when hard plates are added above the VL.