• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.629-638
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• 1999

본 연구에서는 고속철도에서 차량·교량 구조물의 상호작용을 가능한 정밀하게 취급할 수 있는 3차원 해석모형을 개발하였다. 경부고속철도 교량형식인 PSC 박스거더 교량을 40m 단순 와 25-40-25m 3경간 연속 에 대해 뼈대요소를 사용하여 3차원으로 모형 하였으며, 궤도의 불규칙성은 정상확률과정으로 가정하고, 지수 스펙트럼 밀도함수를 사용하여 궤도의 형상을 생성시켰다. 열차는 경부고속철도 차량 하중효과가 가장 큰 동력차 만을 대상으로 17 자유도 모형과 38 자유도 모형으로 분리하여 개발하였다. 다양한 조건에 대한 분석결과를 검토하면 여러 가지 상황에서 38 자유도 모형의 필수 성이 보여지고 있다. 특히 교량의 솟음 및 장기 처짐에 의한 궤도형상변화가 있는 경우에는 반드시 38 자유도 모형이 적용되어야 하는 것으로 분석되었다. 또한 제동하중이 작용할 때 쏠림 효과에 의한 영향이 큰 것으로 평가되어, 제동에 의한 교량의 동적 거동은 종변 위에 대한 자유 도를 고려할 수 있는 주행차량모형으로 해석되어야 함이 규명되었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.259-262
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• 2010

최근 건물형상의 다양화로 인하여 수직부재의 불규칙성이 빈번하게 발생하면서 전통적인 보-기둥 형식의 골조에서 변형된 보와 기둥의 특징을 공유하고 있는 경사기둥의 사용빈도가 높아지고 있다. 현재 국내에서 사용하고 있는 내진설계방법은 강도에 근거를 둔 설계법으로서 구조물이 탄성상태에서 저항해야 하는 부재력에 근거하고 있다. 그러나 기준에서 규정하고 있는 또는 그 이상의 지진하중이 구조물에 가해지는 경우에 구조물은 비선형 거동을 하게 되는데 구조물이 비선형 거동을 할 때에는 탄성상태와는 다른 힘의 흐름을 나타내게 된다. 본 논문에서는 12층 철골 모멘트 골조 구조물에 대하여 횡력에 저항하는 정형화된 골조와 경사기둥을 이용한 골조의 내진성능 및 비선형 거동을 조사하였다. 그 결과 강기둥-약보로 설계된 정형화된 구조물에서는 보의 소성힌지가 계속적으로 발달하면서 구조물이 저항하는데 반하여 경사기둥을 가진 구조물은 비탄성 상태에서 경사기둥에 인접한 기둥부재로 하중이 집중되면서 정형골조에 비하여 붕괴 메카니즘이 훨씬 작은 변위에서 발생하는 것을 볼 수 있었다.

• Journal of Korean Society of Disaster and Security
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• v.6 no.3
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• pp.1-8
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• 2013

Based on random vibration theory, a procedure for calculating the dynamic response of the tall building to time-dependent random excitation is developed. In this paper, the fluctuating along- wind load is assumed as time-dependent random process described by the time-independent random process with deterministic function during a short duration of time. By deterministic function A(t)=1-exp($-{\beta}t$), the absolute value square of oscillatory function is represented from author's studies. The time-dependent random response spectral density is represented by using the absolute value square of oscillatory function and equivalent wind load spectrum of Solari. Especially, dynamic mean square response of the tall building subjected to fluctuating wind loads was derived as analysis function by the Cauchy's Integral Formula and Residue Theorem. As analysis examples, there were compared the numerical integral analytic results with the analysis fun. results by dynamic properties of the tall uilding.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.116-125
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• 1995

Higher order nonlinear transfer functions are applied to model the nonlinear responses obtained Inn dynamic analysis of single degree of freedom systems (SDOF) subjected to wave and current loadings. The structural systems are subjected to single harmonic, two wave combination and irregular wave loading. Three different sources of nonlinearities are examined for each of the wave loading condition and it is shown that the nonlinear response appear at the resonance frequencies of the SDOF even when virtually no wave energy exists at those resonance frequencies. Higher order nonlinear transfer functions based on Volterra series representation are used to model the nonlinear responses mainly f3r the flexible systems and clearly shows the degrees of nonlinearity either as quadratic or cubic.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.2
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• pp.92-99
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• 1991

A moored body in the sea is subjected to second-order wave forces as well as to linear oscillatory ones. The second-order farces contain slowly-varying components, of which the characteristic frequency can be as low as the natural frequency of horizontal motions of the moored body. As a consequence, the slowly-varying force can excite unexpectedly large horizontal excursion of the body, which may cause a serious damage on the mooring system. In design analysis of Turret-type mooring system which is one of the interesting mooring systems for a floating body. the slowly-varying drift forces and the transient motion of the system during weathervaning are very important. In this paper the slowly-varying drift forces were calculated by using the Quadratic Transfer Function with considering the second order free-wave contributions. Additionaly the transient surge motion of the moored body was simulated with including the roll of the time-memory effect. In this simulation the spring constant of the spread Turret mooring system is updated at every time step for considering the nonlinear effect.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.3
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• pp.133-140
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• 2012

In this study, 3 kinds of models about bike frame are simulated with static structural analysis, And fatigue life, damage and durability according to fatigue load are analyzed. A bike frame model with diamond type is compared with another model on the reinforced support with its type. In case of the reinforced support type, maximum equivalent stress or total deformation is shown with 10% or 20% more than the diamond type respectively. At both types of models, the trends of fatigue life and damage at both types are same. 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable among the cases of nonuniform fatigue loads. In case of 'Sample history' with the average stress of 0 to -1MPa and the amplitude stress of 0 to 1MPa, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE Bracket history' or 'SAE transmission'. In case of the reinforced support type, fatigue life becomes shorter and damage probability becomes larger at the right side installed with support than diamond type. The structural result of this study can be effectively utilized with the design on bike frame by investigating prevention and durability against its damage.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.623-628
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• 2007

The accurate peak response estimation of a seismically excited structure with frictional damping system(FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated that by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In the case that an earthquake load is defined with probabilistic characteristics, the corresponding response of the structure with FDS has probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake loads generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Finally, coefficients of the proposed PDF are obtained by regression analysis of the statistical distribution of the time history responses. Finally the correlation between PDFs and statistical response distribution is presented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.65-75
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• 1984

A comparative study between several methods for the marine drilling riser analysis is carried out. One static analysis method and four dynamic methods are studied. The dynamic analysis methods used are two time domain methods using regular and random waves, and two frequency domain methods using the conventional and an improved linearization techniques. Two different sizes of risers are investigated. The analysis model of the structure is based on the beam-column element with lateral wave/current loads in a vertical plane. The forces on the riser are calculated using a modified farm of the Morison's equation. The finite element method is used to solve the equation for several wave/current conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.27-33
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• 2016

A numerical analysis on deck wetness is carried out for a large caisson directly wet-towed by tugs in irregular waves. A constant panel method is used for linear analysis in frequency domain and a statistical post-processing for the deck wetness is presented. Hydrodynamic coefficients obtained from the frequency domain computation are imported for time domain analysis which enables complete modeling for towing equipment, environment, etc. Both frequency and time domain computations over two sea states are performed and comparison is made. In the time domain analysis, towing systems of various arrangements of tugs are investigated from short-term prediction for the largest deck wetness and the number of occurrences of deck wetness.

• Korean Journal of Agricultural Science
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• v.10 no.1
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• pp.110-117
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• 1983

This study was conducted to investigate the influence of load increment ratio on the secondary consolidation for the marine clay at Asan bay by the hyperbola method. The results were summarized as follow: 1. Calculated secondary consolidation by the hyperbola method was slightly less than the value of Casagrande's log t method, but the difference was very little, and the secondary consolidation could be easily calculated by the hyperbola method even if load increment ratio was small. 2. The secondary consolidation ratio was increased with the decrement of load increment ratio, and the creep phenomenon of the settlement curve occurred under the condition of small load increment ratio seemed to be caused by the secondary consolidation. 3. The secondary consolidation ratio occurred during the primary consolidation was irregular in the overconsolidated range, but it was increased with the decrement of load increment ratio in the normally consolidated range. 4. The coefficient of secondary consolidation was increased with the increment of the consolidation load, made a point of the inflection near preconsolidation. And the coefficient of secondary consolidation was decreased from consolidation load $2kg/cm^2$, showed independent of load increment ratio. 5. The coefficient of secondary consolidation was showed in proportion to compression index.