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요소 연결 매개법을 이용한 선형 구조물의 동적 컴플라이언스 최적화
윤길호,Yoon, Gil-Ho 한국전산구조공학회 2009 한국전산구조공학회논문집 Vol.22 No.3
본 연구 논문에서는 요소 연결 매개법(Element Connectivity Parameterization Method)을 이용하여 선형 구조물의 동적 컴플라이언스(Dynamic compliance)를 최소화하는 위상을 설계하는 기법을 연구한다. 기존의 밀도를 기반으로 한 위상최적화기법은 각 유한 요소의 탄성계수를 각 요소에 정의되어 있는 설계변수(Design Variable)를 이용하여 위상최적화를 수행한다. 이 방법은 현재까지 많은 선형구조문제에 적용되었지만 비선형 문제와 멀티피직스 시스템에서 수치적인 문제점이 보고되었다. 이런 문제점을 근본적으로 해결하기 위하여 최근에 요소 연결 매개법(Element Connectivity Parameterization Method)이란 새로운 최적화 기법이 개발되었다. 이 새로운 설계 방법은 요소의 강성을 설계하는 것이 아니라 요소의 연결성을 설계하는 기법으로 이를 이용하여 비선형 구조물이나 멀티피직스 시스템의 위상최적화를 효과적으로 수행할 수 있다. 하지만, 아직까지 질량 행렬의 정의에 대한 모호함으로 인하여 동적인 구조물의 최적화에 대한 연구가 많이 이루어지지 않았다. 이런 문제점을 해결하기 위하여 요소 연결 매개법에서 질량행렬을 정의하는 방법을 연구하며, 이를 이용하여 선형 구조물의 동적 컴플라이언스(Dynamic Compliance)를 고려한 위상최적화 문제에 적용하여 제안된 방법을 검증하였다. This paper studies the Element Connectivity Parameterization Method(ECP method) for topology optimization considering dynamic compliance. The previous element density based topology optimization method interpolates Young's modulus with respect to design variables defined in each element for topology optimization. Despite its various applications, these element density based methods suffer from numerical instabilities for nonlinear structure and multiphysics systems. To resolve these instabilities, recently a new numerical method called the Element Connectivity Parameterization(ECP) Method was proposed. Unlike the existing design methods, the ECP method optimizes the connectivities among plane or solid elements and it shows some advantages in topology optimization for both nonlinear structure and multiphysics systems. In this study, the method was expanded for topology optimization for the dynamic compliance by developing a way to model the mass matrix in the framework of the ECP method.
윤길호,모준수,김기현,윤충희,임남훈 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9
To qualitatively understand the deformation processes and damages in the human body caused by high-speed impact, we conductedexperimental and computational investigations for bullet penetration into viscoelastic ballistic gelatin blocks. Because it is difficult tomeasure the strain rate-dependent material properties of viscoelastic gelatin blocks during high-speed impact, the material properties thatare indirectly defined by the stress relaxation test were used for the computational simulation. We also conducted some firing experimentsand analyzed the deformation processes of the structures. In particular, the passing through times and the shapes of the temporaryand permanent cavities inside the ballistic gelatin blocks were analyzed and compared. This data reveals that the employed material models,with some modifications for the FE simulation, are sufficient for predicting the high-speed impact behaviors. To investigate theshapes of the permanent cavities and fragments made by bullets inside the gelatin blocks, two-dimensional sectional images were takenby an industrial CT scanner and a three-dimensional CAD model was constructed based on these images.
현장타설 끼움 전단벽 및 철골가새를 활용한 기존 학교 건물의 내진보강
윤길호,김성호,김용철,윤현도,Youn, Gil-Ho,Kim, Sung-Ho,Kim, Yong-Cheol,Yun, Hyun-Do 한국교육시설학회 2012 敎育施設 Vol.19 No.4
This study proposes a procedure for evaluating the seismic performance and retrofit of a typical reinforced building (R/C) school buildings contructed in the 1980s. The procedure is derived from the Japanese Standard for Evaluation of Seismic Capacity of Existing Reinforced Concrete Buildings and Nonlinear Static Procedure (NSP) specified in Federal Emergency Management Agency (FEMA 356). In this study, the Japanese Standard was applied for evaluating the additionally required seismic performance in the existing school building. Cast-in-place (CIP) reinforced concrete infill walls and steel braces were used to seismically retrofit the existing school building located in the region of Hongsung in Chungnam. In the pushover analysis, i.e NSP, the hinge properties of columns, beams, infill walls and steel braces were carefully calibrated based on the existing experiment results in the available literatures. The predicted seismic performance for the retrofitted building was compared to that for the virgin building. Based on the seismic evaluation with the Japanese Standard and the FEMA 356 criteria, the addition of CIP reinforced concrete infill walls and steel braces have superior constructablility and can improve effectively the seismic performance of the existing school buildings constructed in 1980s.