• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.355-364
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• 2011

In this study, the details of WSA(wavelet series analysis) have been demonstrated to solve the 4th-order elliptic differential equation. It is clear to solve the 2nd-order elliptic differential equation with the basis function of Hat wavelet series that is used in the previous study existed in $H^1$-space. However, it is difficult to solve the 4th order differential equation with same basis function of Hat wavelet series because of insufficient differentiability and integrability. To overcome this problem, the linear equations in terms of moment and deflection have been formulated and solved sequentially that are similar to extension of Elastic Load Method and Moment Area Method in some senses. Also, the differences and common points between the proposed method and the meshless method are discussed in the procedure of WSA formulation. As we expect, it is easy to ascertain that the more terms of Hat wavelet series are used, the better numerical solutions are improved. Also the solutions obtained by WSA have been compared with the conventional FEM solutions in case of Euler beam problems with stress singularity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.423-434
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• 2001

In this paper, a three-span continuous box girder is analysed by using elastic equation based on energy method, concerning the behaviour with the effects of bending and pure torsional moment. The statically indeterminate forces of a three-span continuous curved box girder are calculated by applying the principle of least work to this elastic equation. The influence line of shear force, bending moment, pure torsion, displacement and angle of rotation due to unit vortical load and unit torque for curved box girder are obtained. The internal forces of the curved box girder which the actual load is applied can be calculated using the influence line obtained from this study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.420-427
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• 2008

For simulation of a fin unfolding motion for the various aerodynamic conditions, equations and moments applying to the unfolding fin were modelled. Aerodynamic roll moment consists of the static roll moment and the damping moment, which were obtained through wind tunnel tests and numerical analyses respectively. Panel method was used to compute the roll damping coefficient with deflected fin, whose angle was equivalent to angle of attack due to the deployment motion. Roll damping coefficient is a function of angle of attack, sideslip angle, and deployment angle but not of angular velocity of deployment. Simulation with aerodynamic damping model gave more similar deployment time compared to fin deployment test results.

• Journal of Korea Water Resources Association
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• v.32 no.2
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• pp.99-110
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• 1999

The method of moments, a Lagrangian scheme, considers the zeroth, first, and second moments of the grid cell spatial distributions of the concentration and then advects the concentration by maintaining conservation of the moments. The reasonable inital description of the first and second moments as well as the mean concentration, the zeroth moments, in grid element is important in the method of moments. In this study, the description methods of each initial moment are reviewed, and the method of moments is extended to overcome the restrictions of Courant number. Its performance is compared with those of available Eulerian and Lagrangian schemes. As the results, the method is successfully extended to overcome the stability restriction and is an accurate scheme for the advection simulation of concentration distribution, especially of which the gradient is steep. In addition, the method is very promising scheme in terms of computational efficiency when the mixing is confined in a relatively small region to the entire domain in two-dimensional problem.

• Journal of the KSME
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• v.29 no.3
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• pp.231-243
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• 1989

복합재료의 탄성 문제를 정리하면 다음과 같다. 복합재료와 등방성 재료의 탄성학적 차이는 재료의 탄성계수에 기인하며 이것은 각각 다른 형태의 응력-변형률관계를 갖게 한다. 한편 응 력-변형률 관계식을 제외한 탄성학의 지배방정식은 재료의 종류에 관계없이 성립한다. 복합적 층판의 Stiffness와 응력 등은 Lamination 이론을 사용하여 구할 수 있다. 판이론은 평형식을 z방향으로 적분한 식, 즉 합력(resultant force)와 모멘트로 나타낸 평형식을 사용하는데 이 때 처짐 방정식을 구하기 위해 합력. 모멘트-곡률. 변형률 관계식을 이용하는데 이 관계식이 복합 재료와 등방성재료가 상이하다. 결과로 복합재료는 커플링 효과를 갖게 되며, 복합적층판을 대 칭으로 쌓으면 이 효과를 상쇄시킬 수 있다. 복합적층 보의 이론은 유효 굽힘 계수를 도입하면 등방체 보 이론을 사용하여 보의 처짐을 해석할 수 있다. 복합적층 보의 경우 굽힘 응력의 최 대치는 등방체와는 달리 보의 표면에서만 일어나지 않고 내부에서도 일어날 수 있다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.35-36
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• 2011

본 논문은 불안정한 비선형시스템의 대표적인 플랜트인 도립진자를 이용하여, 비선형시스템의 선형화된 모델링에서 PID제어기와 상태궤환제어기의 제어역할을 연구한다. 우선 선형화시스템에서의 제어기를 구성한 후 회전형 도립진자를 모델링한다. 회전형 도립진자의 모델링은 실린더의 관성모멘트와 진자의 회전중심에 대한 모멘트의 관계를 토크를 기준으로 비선형 동적방정식 형태로 정리한다. 정리된 방정식을 선형화하여 컴퓨터 시뮬레이션을 통해 PID제어기와 상태궤환제어기의 제어특징과 성능을 비교 및 연구한다. 테스트용 회전형 도립진자를 이용하여 위에서 구성된 제어기로 제어가능한지 실험한다. 테스트용 회전형도립진자는 RealSYS사의 리얼시스 DSP Inverted Pendulum 2005년 생산품으로 실험한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.12A
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• pp.1759-1765
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• 2000

공기 갭을 갖는 일축성 기판위에 마이크로 패치 안테나의 공진 주파수가 full-wave approach와 모멘트 계산법을 이용하여 연구되었다. 일축성 매질내의 구성관계식을 통하여 제안된 구조에서의 파수영역 다이애딕 그린 함수를 유도하였으며 이 결과로부터 전계 적분 방정식을 수식화하였다. 갤러킨 모멘트법을 사용하여 전계 적분 방정식을 이산화 하였으며 기저함수의 선택은 수치 해석적 수렴을 고려하여 패치 위의 실제 전류밀도와 가장 유사한 형태인 정현적 기저함수를 선택하였다. 전사모의 실험 결과의 타당성을 검증하기 위해서 기존의 결과와 비교하여 일치된 결과를 얻었다. 공기 갭의 두께와 패치 길이, 이방성 비의 변화에 따른 공진 주파수가 제시되고 분석되었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.317-327
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• 2001

In this paper, a relation to calculate design moments for reinforced concrete(RC) bridges constructed by movable scaffolding system(MSS) is introduced. Through the time-dependent analysis of RC bridges considering the construction sequence, the structural responses related to the member forces and deflections are reviewed, and a governing equation for determination of the design moment, which includes the creep deformation, is derived on the basis of the displacement-force condition at every constructuion stage. By using the relation, the design moment and its variation over time can easily be obtained only with the elastic analysis results without additional time-dependent analysis. In addition, correlation studies with the results by rigorous numerical analyses are conducts to verify the applicability of the introduced relation, and a more reasonable guideline for the determination of design moments is proposed on the basis of the obtained moment envelop.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.615-627
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• 1998

In order to determine the maximum shear force, the maximum bending moment, the maximum pure torsion. the maximum warping torsion, and the maximum bimoment for the curved girder grid bridges, it is important to find the location of live load applied to the curved girder grid bridges, so that the influence line can be estimated. The fundamental differential equation concerning the behaviour with warping effects for the curved girder is developed by Vlasov. In this paper, the influence line of shear force, bending moment, pure torsion, warping torsion, and bimoment due to unit vertical load and unit torsional moment for curved I-girder grid bridges with variable and constant cross section are obtained by using the finite difference method and compared with respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.1-8
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• 2014

The present study proposes a simple equation to straightforwardly determine the potential plastic hinge length in boundary element of reinforced concrete shear walls. From the idealized curvature distribution along the shear wall length, a basic formula was derived as a function of yielding moment, maximum moment, and additional moment owing to diagonal tensile crack. Yielding moment and maximum moment capacities of shear wall were calculated on the basis of compatability of strain and equilibrium equation of internal forces. The development of a diagonal tensile crack at web was examined from the shear transfer capacity of concrete specified in ACI 318-11 provision and then the additional moment was calculated using the truss mechanism along the crack proposed by Park and Paulay. The moment capacities were simplified from an extensive parametric study; as a result, the equivalent plastic hinge length of shear walls could be formulated using indices of longitudinal tensile reinforcement at the boundary element, vertical reinforcement at web, and applied axial load. The proposed equation predicted accurately the measured plastic hinge length, providing that the mean and standard deviation of ratios between predictions and experiments are 1.019 and 0.102, respectively.