• 대한기계학회논문집
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• 제17권8호
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• pp.2051-2060
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• 1993

A finite element program using degenerated shell element was developed to solve the geometric, material and combined nonlinear behaviors of composite laminated shell. The total Lagrangian method was implemented for geometric nonlinear analysis. The material nonlinear behavior was analyzed by considering the matrix degradation due to the progressive failure in the matrix and matrix-fiber interface after initial failure. The result of the geometric nonlinear analysis showed good agreement with the other exact and numerical solutions. The results of the combined analyses considered both geometric and material nonlinear analyses were compared with the experiments in which internal pressure was applied to the filament wound antisymmetric tubes.

• 대한토목학회논문집
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• 제30권1A호
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• pp.1-13
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• 2010

본 연구에서는 사장교의 기하학적 비선형 거동을 기하학적 비선형 유한요소 해석을 통해 분석한다. 사장교의 주탑 및 거더는 휨 모멘트 뿐만 아니라 케이블의 장력에 의해 축력이 작용한다. 즉, 거더와 주탑은 보-기둥 부재와 같이 휨모멘트와 축력의 상호작용에 의한 대변위 거동을 일으킬 수 있다. 본 연구에서는 기하학적 비선형 해석을 통해 완성계 사장교의 대변위 효과, 주탑 및 거더의 보-기둥 효과 그리고 케이블의 새그효과가 모두 고려된 비선형 거동을 검토하였다. 거더 및 주탑은 6자유도 프레임 요소로 모사하고 사장교 케이블은 새그효과를 효율적으로 고려하기 위해 3자유도 등가 트러스 요소를 사용하여 모사하였다. 해석은 먼저 사하중에 대한 초기 형상 해석을 통해 사하중을 고려하고, 이 후 각기 다른 형태의 활하중에 대한 기하학적 비선형 해석을 수행하였다. 해석 후 각 모델의 변형형상, 각 주요 지점의 하중-변위곡선, 케이블 장력의 변화등의 정량적 수치를 분석하여 고려한 활하중 형태 및 사장교 형식에 대한 주요 기하학적 비선형 거동을 규명하였다.

• 대한기계학회논문집
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• 제17권12호
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• pp.2915-2925
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• 1993

A finite element program using degenerated shell element was developed to solve the geometric, material and combined nonlinear behaviors of composite laminated plates. The total Lagrangian method was implemented for geometric nonlinear analysis. The material nonlinear behavior was analyzed by considering the matrix degradation due to the progressive failure in the matrix and matrix-fiber interface after initial failure. The results of the geometric nonlinear analyses showed good agreements with the other exact and numerical solutions. The results of the combined nonlinear analyses considered both geometric and material nonlinear behaviors were compared to the experiments in which a concentrated force was applied to the center of the square laminated plate with clamped four edges.

• 수산해양기술연구
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• 제28권1호
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• pp.79-92
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• 1992

This is analyzed using the finite element method which is appling excellent isoparametric curve element in the aspect of large usages of dynamic responses in which is regarding geometric and material nonlinear of a large scale shell structure of an airplane, a submarine, a ship, and an ocean structure. The solution of dynamic equations is got by direct integration method using time-stepping procedure and regarding Central Difference Method of the both solutions. But because formal matrix factorization is not necessary in each time step and it does not take less time to compute relatively, this method must be regarded very few time steps on the condition. Axisymmatric shell problems are inspected using 8 node Isoparametric element in this paper. Partial axisymmatric spherical shell is used as a model to analyze axisymmatric nonlinear dynamic behavior regarding. Total Lagrangian formulation in geometric nonlinear behavior and elastio-viscoplastic in material nonlinear behavior.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.321-326
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• 2007

The joined-wing is a new concept of the airplane wing. The fore-wing and the aft-wing arc joined together in the joined-wing. The range and loiter are longer than those of a conventional wing. The joined-wing can lead to increased aerodynamic performances and reduction of the structural weight. The structural behavior of the joined-wing has a high geometric nonlinearity according to the external loads. The gust loads are the most critical loading conditions in the structural design of the joined-wing. The nonlinear behavior should be considered in the optimization of the joined-wing. It is well known that conventional nonlinear response optimization is extremely expensive: therefore, the conventional method is almost impossible to use in large scale structures such as the joined-wing. In this research, geometric nonlinear response structural optimization is carried out using equivalent loads. Equivalent loads are the load sets which generate the same response field in linear analysis as that from nonlinear analysis. In the equivalent loads method, the external loads are transformed to the equivalent loads (EL) for linear static analysis, and linear response optimization is carried out based on the EL.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.341-344
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• 2006

A study for the nonlinear analysis of segmentally erected curved PSC(prestressed concrete) cable-stayed bridge considering the effects due to large deflections is presented. Various case studies regarding the effects of the material nonlinearities and the geometric nonlinearities on the behavior of segmentally erected curved PSC cable-stayed bridge are conducted. The numerical results on the bridge which has relatively low stress profile through the bridge deck section like the example herein show that the geometric nonlinearities has more significant effects on the structural behavior than the material nonlinearities.

• Structural Engineering and Mechanics
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• 제90권4호
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• pp.357-370
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• 2024

Due to the fact that the mechanism of the effects of temperature and initial geometric imperfection on low-velocity impact problem of axially moving plates is not yet clear, the present paper is to fill the gap. In the present paper, the nonlinear dynamic behavior of axially moving imperfect graphene platelet reinforced metal foams (GPLRMF) plates subjected to lowvelocity impact in thermal environment is analyzed. The equivalent physical parameters of GPLRMF plates are estimated based on the Halpin-Tsai equation and the mixing rule. Combining Kirchhoff plate theory and the modified nonlinear Hertz contact theory, the nonlinear governing equations of GPLRMF plates are derived. Under the condition of simply supported boundary, the nonlinear control equation is discretized with the help of Gallekin method. The correctness of the proposed model is verified by comparison with the existing results. Finally, the time history curves of contact force and transverse center displacement are obtained by using the fourth order Runge-Kutta method. Through detailed parameter research, the effects of graphene platelet (GPL) distribution mode, foam distribution mode, GPL weight fraction, foam coefficient, axial moving speed, prestressing force, temperature changes, damping coefficient, initial geometric defect, radius and initial velocity of the impactor on the nonlinear impact problem are explored. The results indicate that temperature changes and initial geometric imperfections have significant impacts.

• Advances in materials Research
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• 제8권3호
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• pp.219-235
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• 2019

This research is devoted to analyzing mechanical-thermal post-buckling behavior of a micro-size beam reinforced with graphene platelets (GPLs) based on geometric imperfection effects. Graphene platelets have three types of dispersion within the structure including uniform-type, linear-type and nonlinear-type. The micro-size beam is considered to be perfect (ideal) or imperfect. Buckling mode shape of the micro-size beam has been assumed as geometric imperfection. Modified couple stress theory has been used for describing scale-dependent character of the beam having micro dimension. Via an analytical procedure, post-buckling path of the micro-size beam has been derived. It will be demonstrated that nonlinear buckling characteristics of the micro-size beam are dependent on geometric imperfection amplitude, thermal loading, graphene distribution and couple stress effects.

• Steel and Composite Structures
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• 제47권6호
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• pp.795-811
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• 2023

When studying the resonance problem of nanoplates, the existing papers do not consider the influences of geometric nonlinearity and initial geometric imperfection, so this paper is to fill this gap. In this paper, based on the nonlocal strain gradient theory (NSGT), the nonlinear resonances of functionally graded (FG) nanoplates with initial geometric imperfection under different boundary conditions are established. In order to consider the small size effect of plates, nonlocal parameters and strain gradient parameters are introduced to expand the assumptions of the first-order shear deformation theory. Subsequently, the equations of motion are derived using the Euler-Lagrange principle and solved with the help of perturbation method. In addition, the effects of initial geometrical imperfection, functionally graded index, strain gradient parameter, nonlocal parameter and porosity on the nonlinear forced vibration behavior of nanoplates under different boundary conditions are discussed.

• Structural Engineering and Mechanics
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• 제27권4호
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• pp.477-499
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• 2007

The main purpose of this paper is to investigate the ultimate behavior of steel cable-stayed bridges with design variables and compare the validity and applicability of computational methods for evaluating ultimate load capacity of cable-stayed bridges. The methods considered in this paper are elastic buckling analysis, inelastic buckling analysis and nonlinear elasto-plastic analysis. Elastic buckling analysis uses a numerical eigenvalue calculation without considering geometric nonlinearities of cable-stayed bridges and the inelastic material behavior of main components. Inelastic buckling analysis uses an iterative eigenvalue calculation to consider inelastic material behavior, but cannot consider geometric nonlinearities of cable-stayed bridges. The tangent modulus concept with the column strength curve prescribed in AASHTO LRFD is used to consider inelastic buckling behavior. Detailed procedures of inelastic buckling analysis are presented and corresponding computer codes were developed. In contrast, nonlinear elasto-plastic analysis uses an incremental-iterative method and can consider both geometric nonlinearities and inelastic material behavior of a cable-stayed bridge. Proprietary software ABAQUS are used and user-subroutines are newly written to update equivalent modulus of cables to consider geometric nonlinearity due to cable sags at each increment step. Ultimate load capacities with the three analyses are evaluated for numerical models of cable-stayed bridges that have center spans of 600 m, 900 m and 1200 m with different girder depths and live load cases. The results show that inelastic buckling analysis is an effective approximation method, as a simple and fast alternative, to obtain ultimate load capacity of long span cable-stayed bridges, whereas elastic buckling analysis greatly overestimates the overall stability of cable-stayed bridges.