• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.3
• /
• pp.21-30
• /
• 1989

In this study, the dynamic behavior of a continuous bridge under moving load is studied considering roughness of the road surface. Vehicle model includes the spring effects of axes, and due to these effects, equations of motions for the vehicle and bridge are derived in coupled form. And then iteration method is used to solve the equations. In experimental study a bridge model is constructed considering the similarity rule in order that the model exhibits dynamic behavior similar to that of prototype. Three types of roughness such as uneven random roughness, uplift on the approach and piece-wise constant roughness are used to describe road roughness. Through the numerical analysis and experiments, the effects of surface roughness, sprung mass, and velocity on the dynamic behavior of the bridge are examined.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.2
• /
• pp.91-96
• /
• 2010

The combination of a bolt and nut is the element most widely used for connecting machines and structures. When a load is repetitively applied in the direction right angle to the bolt axis after the bolt and nut is fastened, the nut gradually becomes loose. To solve this problem, in this study, a new type of the loose-proof nut, called a lock nut, is developed. The lock nut is equipped with a spring, and the spring increases the axial force of the bolt. Then, the connection force between the bolt and nut is also augmented. Three dimensional finite element models for the bolt and spring are generated, and the change of the axial force of the bolt while the bolt is being inserted into the spring is analyzed using MSC/Marc, a commercial finite element program. Finally, the optimum shape of the spring is found according to the response surface analysis methodology. The optimization result is verified by comparing the variation of the axial force of the bolt when the bolt is inserted to the initial and optimized spring.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.7
• /
• pp.29-35
• /
• 2002

Aeroelastic characteristics of a deployable missile control fin have been investigated. A deployable missile control fin is modeled by a 2-dimensional typical section. Supersonic Doublet-Point method is used for the computation of supersonic unsteady aerodynamic forces and Karpel's Minimum-State approximation is used for the aerodynamic approximation. Root-locus method and time-integration method are used for the linear and nonlinear flutter analyses. For the nonlinear flutter analysis the deployable hinge is represented by a asymmetric bilinear spring and is linearized by using the describing function method. From the flutter analyses, the effects of nonlinear parameters on the aeroelastic characteristics are investigated.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.2 s.35
• /
• pp.253-261
• /
• 1998

The buckling length of exterior beam-columns of the first floor in moment resisting steel frames with weak beams is uncertain when plastic hinges occur at the ends of weak beams due to seismic loads. The objective of this study is to investigate the buckling strength of concrete-filled tubular beam-columns and to suggest the reduced buckling length of them to apply to the beam-column design code. The exterior beam-columns are modelized with horizontal displacement restraint springs. Their strength and reduced buckling length are evaluated by numerical analysis.

• Journal of KSNVE
• /
• v.5 no.1
• /
• pp.107-115
• /
• 1995

An analytical model for drillstring axial vibration is proposed. The drillstring is modelled as an equivalent stepwise uniform bar, and the bottom boundary is modelled asa spring and a damper which depend on WOB(weight on bit). The effect of tool joints and the effect of surrounding layers, such as mud and formation, are evaluated theoretically. To investigate the bottom boundary condition, a forced axial vibration testing technique was developed and the tests with a typical drillstring were performed at various WOB's. The results show good agreement with theoretical results. An important conclusion is that the flexibility of the bottom rock must be included in order to predict resonant frequencies of the drillstring axial vibration.

• Journal of the Korean Magnetics Society
• /
• v.6 no.5
• /
• pp.281-286
• /
• 1996

For the accurate analysis of motional characteristics of electrical machines, it is needed to solve the motion equations together with the electromagnetic field equations. In this paper the sequential coupling of systems, the spring mass system and the electromagnetic system, is adopted. The induced current and the magnetic fields are calculated by finite element method(FEM) with given speed. And then, with the computed elec-tromagnetic force, the mechanical equations are solved by the Runge-Kutta method. The above two processes are repeated sequentially to obtain the time domain solutions. The resultant values are applied to the energy conservation law to prove the usefulness of the proposed sequential method.

• Computational Structural Engineering
• /
• v.9 no.3
• /
• pp.209-216
• /
• 1996

The primary objective of this paper is to grasp many characteristics of buckling behavior of latticed spherical domes under various conditions. The Arc-Length Method proposed by E.Riks is used for the computation and evaluation of geometrically nonlinear fundamental equilibrium paths and bifurcation points. And the direction of the path after the bifurcation point is decided by means of Hosono's concept. Three different nonlinear stiffness matrices of the Slope-Deflection Method are derived for the system with rigid nodes and results of the numerical analysis are examined in regard to geometrical parameters such as slenderness ratio, half-open angle, boundary conditions, and various loading types. But in case of analytical model 2 (rigid node), the post-buckling path could not be surveyed because of Newton-Raphson iteration process being diversed on the critical point since many eigenvalues become zero simultaneously.

• Computational Structural Engineering
• /
• v.11 no.1
• /
• pp.38-45
• /
• 1998

최근 국내외에서 활발히 개발되고 있는 지진격리 시스템은 원자력 발전소, 교량, 중요한 공공건물 등의 지진피해를 최소화하기 이하여 널리 적용되고 있다. 그리고 다른 방법에 비하여 경제성 및 효율성이 우수하기 때문에 관련 연구 및 응용이 활발히 진행되고 있다. 이에 따라 국내외에서 격리시스템의 비선형성과 구조물의 불연속성을 고려한 지진격리 구조물의 해석을 통한 거동을 규명하는 연구가 과거 수년간 활발히 진행되어 왔다. 당사(금호건설)는 상부하중 지지능력과 감쇠능력이 우수한 지진격리장치를 개발하였으며 지진격리장치를 설치한 교량의 지진해석을 수행하여 본 지진격리 시스템의 이론적 성능을 파악하였다. 본 수치해석은 CrayC94에 탑재된 비선형 해석에 뛰어난 것으로 알려진 ABAQU를 이용하였다. 본 지진격리 시스템은 적층고무받침(Laminated Rubber Bearing)과 PTFE 미끄럼받침으로 구성되어 있으며, 적층고무받침은 주로 복원력을 제공하며 PTFE 미끄럼받침은 상부하중을 지지하며 마찰감쇠를 제공하여 에너지를 소산하는 역할을 한다. 본 수치해석에서는 선형스프링과 마찰요소를 이용하여 각각을 모형화하였다. 개발된 지진격리 시스템이 주로 사용될 상판자중이 무거운 다경간 연속 PC Box Girder교를 모델교량으로 선택하여 해석을 수행하였으며 수치해석에 사용된 격리시스템의 사전에 수행된 동특성 실험결과를 활용하였다. 이러한 해석을 통하여 이론적 효율성을 파악할 수 있었다.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.2266-2268
• /
• 2000

본 논문에서는 스캐닝 미러의 일종으로, 광저장 장치의 픽업헤드용으로 미세회전을 하면서 레이저 빔을 편향시키는 용도로 사용되는 미러를 제작하고 구동실험을 하였다. 제작된 미러의 크기는 $2400{\times}2400{\times}64{\mu}m^3$이고, 빔 스프링은 $500{\times}9.6{\times}64{\mu}m^3$이다. 니켈 전해 도금으로 29${\mu}m$ 높이의 구동 전극을 제작하였고(세가지 모델: 공기통로가 없는 전극, 공기통로와 간격이 각각 200${\mu}m$인 전극, 공기통로와 간격이 각각 100${\mu}m$인 전극), 미러판과 전극을 조립하여(미러판과 전극 사이의 간격은 각각 29${\mu}m$, 26${\mu}m$, 26${\mu}m$) 구동실험을 하였다. 공진 주파수의 계산간은 576Hz, 측정값은 3개의 미러에서 모두 568Hz이었다. 전극과 미러판의 간격이 최대 접근거리 18${\mu}m$가 되도록 미세 회전을 시켰을 때, 공기통로가 없는 전극에서는 공진 주파수가 524Hz, 공기통로가 200${\mu}m$인 전극에서는 544Hz로 각각 감쇠되었고, 공기통로가 100${\mu}m$인 전극에서는 그대로 568Hz이었다.

• Journal of the Society of Naval Architects of Korea
• /
• v.45 no.6
• /
• pp.703-709
• /
• 2008

In the shipyard, line heating and triangle heating are two major processes for forming curved plates in various shapes. While there have been many studies on line heating, triangle heating has been rarely studied due to its complicated heating process with irregular multi-heating paths and highly concentrated heat input. As the triangle heating process is one of the most labor-consuming jobs in shipyards, it is essential to study the automation as well as improvement of triangle heating process in order to increase hull forming productivity. In this study, a pioneering attempt to simulate triangle heating was made. A circular disk-spring model was proposed for elasto-plastic analysis procedure of triangle heating and the inherent strain method was also used to analyze the deformation of plates. Simulation results were compared with those of experiments and showed good agreement. It is shown that the present approach including analysis model used in this study is effective to simulate the triangle heating for plate forming process in shipbuilding.