• 한국해양공학회지
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• 제12권3호통권29호
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• pp.19-30
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• 1998

In this paper, the dynamic analysis of a dolphin system for mooring a floating structure such as barge mounted plant is studied. The characteristics of the soil-pile system are simplified by a set of equivalent spring elements at the mudline. To evaluate the equivalent spring constants, the finite difference method is used. Since the characteristics of the soil-pile system are nonlinear in case of soft foundation, the nonlinear dynamic analysis technique is needed. The Newmark $beta$ method incorporating the modified Newton-Raphson method(initial stiffness method) is used. A numerical analysis is performed on two mooring dolphin systems on soft foundation and rock foundation. In case of the rock foundation, the characteristics are found to be nearly linear, so the linear dynamic analysis may be sufficient to consider the foundation effect. But in case of soft foundation, the non-linearity of the foundation appears to be very signigicant, so the nonlinear dynamic analysis si needed.

• Structural Engineering and Mechanics
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• 제8권1호
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• pp.27-38
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• 1999

Cables are used in many applications such as cable-stayed bridges, suspension bridges, transmission lines, telephone lines, etc. Generally, the linear relationship is inadequate to present the behavior of cable structure. In finite element analysis, cables have always been modeled as truss elements. For these types of model, the nonlinear behavior of cables has been always ignored. In order to investigate the importance of the nonlinear effect on the structural system, the effect of cable stiffness has been studied. The nonlinear behavior of cable is due to its sag. Therefore, the cable pretension provides a large portion of the inherent stiffness. Since a cable-stayed bridge has numerous degrees of freedom, analytical methods at present are not convenient to solve this type of structures but numerical methods may be feasible. It is necessary to provide a different and more representative analytical model in order to present the effect of cable stiffness on cable-stayed bridges in numerical analysis. The characteristics of cable deformation have also been well addressed. A formulation of modified modulus of elasticity has been proposed using a numerical parametric study. In order to investigate realistic bridges, a cable-stayed bridge having the geometry similar to that of Quincy Bayview Bridge is considered. The numerical results indicate that the characteristics of the cable stiffness are strongly nonlinear. It also significantly affects the structural behaviors of cable-stayed bridge systems.

• Earthquakes and Structures
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• 제7권1호
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• pp.57-82
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• 2014

The heritage value of the mixed wood-masonry 18th century Pombalino buildings of downtown Lisbon is recognized both nationally and internationally. The present paper focuses on the seismic assessment of global response and retrofitting of a typical Pombalino building by nonlinear static analyses, performed by the research software Tremuri, which is able to model 3D configurations. The structure is modelled using nonlinear beams for masonry panels, while in case of the internal walls (frontal walls) an original formulation has been developed in order to take into account their specific seismic behaviour. Floors are modelled as orthotropic membrane finite elements: this feature allows to simulate the presence of both flexible and rigid diaphragms, being the first ones more representative of the original state while the second ones of retrofitted configurations. Seismic assessment has been evaluated by applying nonlinear static procedure and comparing the performance of different configurations (by considering various retrofitting strategies). Finally, assuming a lognormal cumulative distribution, fragility curves are obtained to be representative of Pombalino buildings: the most important application of such curves is for seismic risk and loss estimation analyses.

• 대한조선학회논문집
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• 제28권2호
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• pp.307-317
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• 1991

선체구조 및 해양구조물의 기본 구조요소로 사용되는 편심으로 보강된 평판이나 쉘 수조물의 기하하적 비선형 해석에 관한 논문으로서 사용된 유한요소는 격하 쉘요소와 편심된 격하보요소이며 total Lagrange(T.L.)수식과 updated Lagrange(U.L.)수식으로 정식화 하였다. 편심된 보강평판의 비선형 해석에서 사용된 모델은 보강재의 이상화 방법에 따라 평판과 보강재를 격하 쉘요소로 이상화한 모델과 평판은 격하 쉘요소로하고 보강재는 편심된 격하 보요소로 이상화한 모델로 각각 구분하여 비선형 해석을 수행하였으며 해석과정에서 편심 보강평판의 임계하중을 구하고 좌굴 후 비선형 거동을 조사하였다. 해석된 임계 좌굴하중은 선급에서 규정하고 있는 방식의 오일러의 좌굴하중값 보다는 낮게 조사되었다.

• 대한토목학회논문집
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• 제10권1호
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• pp.57-69
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• 1990

본(本) 연구(硏究)에서는 기하학적(幾何學的) 비선형성(非線形性)을 고려(考慮)하여 해저(海底)파이프라인을 설치(設置)하는 동안의 정적(靜的) 해석방법(解析方法)을 제시(提示)하였다. 해석(解析)방법(方法)으로는 유한요소법(有限要所法)을 사용(使用)하였으며, 기본방정식(基本方程式)은 최소위치(最少位置)에너지의 원리(原理)를 사용(使用)하여 유도(誘導)하였다. 평형방정식(平衡方程式)의 해(解)는 modified Newton-Raphson방법(方法)을 사용(使用)하여 구(求)하였다. 파이프라인요소(要素)의 유한변위(有限變位) 및 회전(回轉)과 축방향력(軸方向力)의 영향(影響)이 고려(考慮)되었고 경계조건(境界條件)은 스프링요소(要素)를 사용(使用)하여 모델화(化)하였다. 해석(解析) 적용례(適用例)에서는 다이아몬드형(形) 프레임, 곡선(曲線)외팔보와 해저(海底)파이프라인을 설치(設置)하는 동안의 정적(靜的) 해석례(解析例)를 다루었으며 다른 방법(方法)에 의(依)한 해석결과(解析結果)와 비교(比較)하여 본(本) 연구(硏究)의 정당성(正當性)을 입증(立證)하였다.

• Structural Engineering and Mechanics
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• 제74권1호
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• pp.1-18
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• 2020

For the large deformation of shear walls under vertical and horizontal loads, there are difficulties in obtaining accurate simulation results using the response analysis method, even with fine mesh elements. Furthermore, concrete material nonlinearity, stiffness degradation, concrete cracking and crushing, and steel bar damage may occur during the large deformation of reinforced concrete (RC) shear walls. Matrix operations that are involved in nonlinear analysis using the traditional finite-element method (FEM) may also result in flaws, and may thus lead to serious errors. To solve these problems, a planar four-node element was developed based on vector mechanics. Owing to particle-based formulation along the path element, the method does not require repeated constructions of a global stiffness matrix for the nonlinear behavior of the structure. The nonlinear concrete constitutive model and bilinear steel material model are integrated with the developed element, to ensure that large deformation and damage behavior can be addressed. For verification, simulation analyses were performed to obtain experimental results on an RC shear wall subjected to a monotonically increasing lateral load with a constant vertical load. To appropriately evaluate the parameters, investigations were conducted on the loading speed, meshing dimension, and the damping factor, because vector mechanics is based on the equation of motion. The static problem was then verified to obtain a stable solution by employing a balanced equation of motion. Using the parameters obtained, the simulated pushover response, including the bearing capacity, deformation ability, curvature development, and energy dissipation, were found to be in accordance with the experimental observation. This study demonstrated the potential of the developed planar element for simulating the entire process of large deformation and damage behavior in RC shear walls.

• 한국정밀공학회지
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• 제17권4호
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• pp.220-225
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• 2000

This paper develops a finite element model for studying occupant behavior of a mid-size truck equipped with a driver side airbag. The developed model simulates an occupant behavior using PAM-CRASH/PAM-SAFE in super computer SP2. The model is developed based on a sled test. A 50% hybrid dummy III is used for measuring head and chest accelerations and femur loads, and major injury coefficients such as HIC, CA and femur load. Inferior components such as foot rest, seat, kneebolster, crash pad, etc. are roughly modeled and defined by a rigid material model. And contact type II is used for detecting a contact with dummy. Contact type II definition uses force-deflection relationship of each body Such components as steering column which directly affect on the occupant injuy are modeled in detail and defined by an elastic-plastic material model. Airbag cushion is modeled using rivet elements. Airbag cover groove is modeled using rivet elements. Airbag tether is modeled as nonlinear bar elements. Airbag model has two vent holes to ventilating the exploded gas. Airbag is folded close to the real airbag folding procedure, and folded cautiously in order not to have initial penetration. A vehicle pulse acquired from 31mph frontal barrier test is used as input signal for the simulation. The simulation conditions are tuned to the sled test ones. The measured dummy accelerations and major injury coefficients, and filmed dummy behavior and airbag inflation process using high speed camera are compared to the simulation results to verify the developed finite element model.

• 대한토목학회논문집
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• 제26권4D호
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• pp.601-608
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• 2006

포장을 설계하고 설계 수명을 산정하거나 현재 공용중인 포장의 유지 관리를 위한 상태 평가를 수행해야하는 경우 포장의 거동 분석은 중요한 입력 변수로 작용하게 된다. 포장의 거동을 예측하기 위해서는 정확한 타이어의 접지면적과 타이어의 압력이 필요하다. 따라서 본 연구에서는 실제 측정된 타이어의 형상을 측정하여 PCA에서 제안한 타이어의 형상과 비교하고, 측정된 타이어의 접지면적과 타이어의 종류에 대한 타이어 압력분포를 사용하여 3차원 유한요소해석을 통하여 포장의 거동을 예측하고 예측된 포장의 거동과 실제 포장의 거동을 비교 분석하였다. 해석 결과 표층의 경우 타이어의 형상과 비선형 압력분포의 영향을 크게 받으며, 이러한 타이어의 특성을 고려함으로써 현장 거동을 보다 잘 설명할 수 있는 것으로 나타났다. 하지만 중간층의 경우 타이어의 영향이 크지 않은 것으로 나타났으며, 실제 현장 거동과 비교했을 때 타이어 하부에서는 큰 차이를 보여주어 실제 포장의 거동을 보다 정확하게 예측하기 위해서는 이 부분을 보다 명확하게 설명을 할 수 있어야 할 것으로 나타났다.

• Steel and Composite Structures
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• 제20권1호
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• pp.167-184
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• 2016

This paper presents the details of Finite Element (FE) analysis carried out to determine the limiting deformation capacity and failure mode of Laced Steel-Concrete Composite (LSCC) beam, which was proposed and experimentally studied by the authors earlier (Anandavalli et al. 2012). The present study attains significance due to the fact that LSCC beam is found to possess very high deformation capacity at which range, the conventional laboratory experiments are not capable to perform. FE model combining solid, shell and link elements is adopted for modeling the beam geometry and compatible nonlinear material models are employed in the analysis. Besides these, an interface model is also included to appropriately account for the interaction between concrete and steel elements. As the study aims to quantify the limiting deformation capacity and failure mode of the beam, a suitable damage model is made use of in the analysis. The FE model and results of nonlinear static analysis are validated by comparing with the load-deformation response available from experiment. After validation, the analysis is continued to establish the limiting deformation capacity of the beam, which is assumed to synchronise with tensile strain in bottom cover plate reaching the corresponding ultimate value. The results so found indicate about $20^{\circ}$ support rotation for LSCC beam with $45^{\circ}$ lacing. Results of parametric study indicate that the limiting capacity of the LSCC beam is more influenced by the lacing angle and thickness of the cover plate.

• Structural Engineering and Mechanics
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• 제67권6호
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• pp.629-641
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• 2018

The paper describes the development of a two-dimensional (2D) co-rotational nonlinear beam finite element that includes advanced path-following capabilities for detecting bifurcation instability in elasto-plasticity of steel elements subjected to fire without introducing imperfections. The advantage is twofold: i) no need to assume the magnitude of the imperfections and consequent reduction of the model complexity; ii) the presence of possible critical points is checked at each converged time step based on the actual load and stiffness distribution in the structure that is affected by the temperature field in the elements. In this way, the buckling modes at elevated temperature, that may be different from the ones at ambient temperature, can be properly taken into account. Moreover, an improved displacement predictor for estimating the displacement field allowed significant reduction of the computational cost. A co-rotational framework was exploited for describing the beam kinematic. In order to highlight the potential practical implications of the developed finite element, a parametric analysis was performed to investigate how the beam element compares both with the EN1993-1-2 buckling curve and with experimental tests on axially compressed steel members. Validation against experimental data and numerical outcomes obtained with commercial software is thoroughly described.