• 한국전산구조공학회논문집
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• 제13권2호
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• pp.209-220
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• 2000

보강된 판 및 쉘구조의 기하학적 비선형해석을 수행하기 위하여, total lagrangian formulation에 근거한 증분 평형방정식을 적용하고, 강도행렬 산정시 회전각의 2차항을 포함시켜 기하학적 비선형 해석시 해의 수렴성을 향상시켰으며, 보강된 쉘 구조의 해석시 보강재를 쉘 요소로 모델링하고 주부재와 보강재의 연결점에서 일반적인 변환관계를 이용하였다. 등매개 쉘 유한요소의 단점인 locking 현상을 극복하기 위하여 가정 변형률장을 적용하여 감차적분 또는 선택적분시 나타날 수 있는 제로 에너지 모드를 제거하였다. 수치해석 예제를 통하여 가정 변형률장에 근거한 쉘유한요소에 대한 효율성 및 적용성을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.574-582
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• 1999

This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 토목섬유기술위원회 학술세미나 논문집
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• pp.1-11
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• 2001

This Paper presents the result of a parametric study on the behavior of stiffened grid reinforced segmental wall resting on non-yielding foundation. The parametric study was conducted using the nonlinear finite element analysis. In the finite element analysis, the step by step construction of the wall such as backfill, block reinforcement, block/backfill and soil/reinforcement interfaces were carefully modeled. The mechanical behavior of stiffened grid reinforced segmental walls was then investigated based on the result of analysis with emphasis on the effect of reinforcement stiffness on the behavior of the wall. The results of analysis indicate that the horizontal wall displacement decrease; with increasing the reinforcement stiffness at a decreasing rate, and that the horizontal stress at the back of the reinforced soil block does not much vary with the reinforcement stiffness. It is also revealed that the calculated maximum vertical stress at the base of the reinforced soil block agrees well with that based on the Meyerhof distribution and that the reinforcement and the connection force are considerably smaller than what might be expected based on the current design assumptions. The implications of the findings from this study to current design approaches were discussed in detail.

• 한국해양공학회지
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• 제26권2호
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• pp.79-84
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• 2012

This study aimed to analyze the nonlinear buckling of ring-stiffened circular cylinders under uniform external pressure, e.g. hydrostatic pressure, considering material nonlinearity and initial imperfection. In the present study, we analyzed the collapse pressure of pressure vessels using ANSYS Workbench, which is a framework of finite element methods. First, linear buckling analysis is performed to find collapse modes of the model. Second, scaling the first mode shape with small factor, geometric model is pre-deformed. And then, by analyzing the nonlinear buckling of the pre-deformed shape, the collapse pressure is estimated. To verify the validity of the analyses, we compared the results with Ross' experimental results. Finally, we applied it to ring-stiffened circular cylindrical shell of the pressure hull of a small submarine.

• Structural Engineering and Mechanics
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• 제48권3호
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• pp.395-414
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• 2013

The present study fundamentally investigated the mechanical performance of the rib-stiffened super-wide bridge deck with twin box girders in concrete, which is a very popular application to efficiently widen the bridges with normal span. The shear lag effects of the specific cross-sections were firstly studied. The spatial stress distribution and local stiffness of the bridge deck with twin box girders were then investigated under several typical wheel load conditions. Meanwhile, a comparative study for the bridge deck with and without stiffening ribs was also carried out during the investigation; thereby, a design optimization for the stiffening ribs was further suggested. Finally, aiming at the preliminary design, an approximate methodology to manually calculate the bending moments of the rib-stiffened bridge deck was analytically proposed for engineers to quickly assess its performance. This rib-stiffened bridge deck with twin box girders can be widely applied for concrete (especially concrete cable-stayed) bridges with normal span, however, requiring a super-wide bridge width due to the traffic flow.

• 한국소음진동공학회논문집
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• 제21권7호
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• pp.622-628
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• 2011

The purpose of this study was to analyze the vibro-acoustic characteristics of a stiffened rectangular plate at high frequencies. The stiffeners attached along the plate surface were assumed to have rotational and translational stiffness and inertia. The harmonic response of the stiffened plate were predicted and compared using the Rayleigh-Ritz method with two different trial functions - polynomial and beam functions. The variation of the spatially averaged mean square velocity and the modal characteristics with the number of stiffeners were obtained. The use of the beam function ensured fast convergence which was essential for analyzing the high frequency vibration responses. Using the calculated modal characteristics and the Rayleigh-integral, the radiated sound power was predicted, and the effects of stiffeners were investigated. The proposed model can be applied to study optimal layout of stiffeners for minimal noise generation of the stiffened structures.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.431-443
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• 2019

The present paper illustrates a numerical investigation on the failure behaviour of ring-stiffened cylinder subjected to external hydrostatic pressure. The published test data of steel welded ring-stiffened cylinder are surveyed and collected. Eight test models are chosen for the verification of the modelling and FE analyses procedures. The imperfection as the consequences of the fabrication processes, such as initial geometric deformation and residual stresses due to welding and cold forming, which reduced the ultimate strength, are simulated. The results show that the collapse pressure and failure mode predicted by the nonlinear FE analyses agree acceptably with the experimental results. In addition, the failure mode parameter obtained from the characteristic pressure such as interframe buckling pressure known as local buckling pressure, overall buckling pressure, and yield pressure are also examined through the collected data and shows a good correlation. A parametric study is then conducted to confirm the failure progression as the basic parameters such as the shell radius, thickness, overall length of the compartment, and stiffener spacing are varied.

• 국제강구조저널
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• 제18권4호
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• pp.1397-1409
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• 2018

Stiffened plates with high slenderness parameters show large out-of-plane deflections, due to elastic buckling, which may occur before the plates reach their ultimate strength. From a serviceability point of view, restriction of out-of-plane deflections exceeding the fabrication tolerance is of primary importance. Compressive strength at the serviceability limit state (SLS) for slender stiffened plates under uniaxial stress was investigated through nonlinear elasto-plastic finite element analysis, considering both geometric and material nonlinearity. Both normal and high-performance steel were considered in the study. The SLS was defined based on a deflection limit and an elastic buckling strength. Probabilistic distributions of the SLS strengths were obtained through Monte Carlo simulations, in association with the response surface method. On the basis of the obtained statistical distributions, partial safety factors were proposed for SLS. Comparisons with the ultimate strength of different design codes e.g. Japanese Code, AASHTO, and Canadian Code indicate that AASHTO and Canadian Code provide significantly conservative design, while Japanese Code matches well with a 5% non-exceedance probability for compressive strength at SLS.

• Advances in Computational Design
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• 제6권1호
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• pp.15-30
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• 2021

With improvement in innovative manufacturing technologies, it became possible to fabricate any complex shaped structural design for practical applications. This allows for the fabrication of curvilinearly stiffened pressure vessels and pipes. Compared to straight stiffeners, curvilinear stiffeners have shown to have better structural performance and weight savings under certain loading conditions. In this paper, an optimization framework for designing curvilinearly stiffened composite pressure vessels and pipes is presented. NURBS are utilized to define curvilinear stiffeners over the surface of the pipe. An integrated tool using Python, Rhinoceros 3D, MSC.PATRAN and MSC.NASTRAN is implemented for performing the optimization. Rhinoceros 3D is used for creating the geometry, which later is exported to MSC.PATRAN for finite element model generation. Finally, MSC.NASTRAN is used for structural analysis. A Bi-Level Programming (BLP) optimization technique, consisting of Particle Swarm Optimization (PSO) and Gradient-Based Optimization (GBO), is used to find optimal locations of stiffeners, geometric dimensions for stiffener cross-sections and layer thickness for the composite skin. A cylindrical pipe stiffened by orthogonal and curvilinear stiffeners under torsional and bending load cases is studied. It is seen that curvilinear stiffeners can lead to a potential 10.8% weight saving in the structure as compared to the case of using straight stiffeners.

• 한국강구조학회 논문집
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• 제24권4호
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• pp.383-398
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• 2012

본 연구의 목적은 리브 보강된 강관 접합부의 유한요소 해석을 통하여 접합부의 극한강도를 추정하고 그 거동을 파악하는 것이다. 가셋트 강관 접합부의 강도는 관벽 모멘트에 의한 국부적인 응력집중 및 국부 소성화에 의해 크게 저하된다. 이러한 국부적인 응력분포를 재분배 시킬 목적으로 가셋트 상하 단부에 보강플레이트를 부착하고 있다. 이러한 접합부의 거동은 보강된 리브의 형상 및 보강 방법등에 따라 보강하지 않은 경우와 상당히 다르지만 현행 강관구조 설계식은 제한적인 부분만 다루고 있다. 따라서 본 연구에서는 ABAQUS 6.5.1을 사용하여 리브로 보강된 가셋트-강관 접합부의 거동과 구조적 성능을 파악하고 기존 접합부 내력식과 비교하여 리브 보강된 플레이트 원형 강관 X형 접합부에 적합한 내력식을 제안하고자 한다.