• 한국지진공학회논문집
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• 제28권1호
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• pp.59-65
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• 2024

This paper describes the seismic performance evaluation of reinforced concrete bridge columns under constant and varying axial forces. For this purpose, nine identical circular reinforced concrete columns were designed seismically by KIBSE (2021) and KCI (2021). A comparison of lateral forces with theoretical strength shows that the safety factor for columns under varying axial forces is less marginal than those under constant axial forces. In addition, columns under varying axial forces exhibit significant fluctuations in the hysteretic response due to continuously varying axial forces. This is particularly prominent when many varying axial force cycles within a specific lateral loading cycle increase. Moreover, the displacement ductility of columns under varying axial forces does not meet the code-specified required ductility in the range of varying axial forces. All varying axial forces affect columns' strength, stiffness, and displacement ductility. Therefore, axial force variation needs to be considered in the lateral strength evaluation of reinforced concrete bridge columns.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2012년도 추계학술대회
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• pp.160-161
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• 2012

The traditional theory regarding the pivot point of a ship during maneuvering, so called apparent pivot point, is located nearly at 1/3 ship's length from the bow when the ship is moving ahead, and between 1/4 ship's length from the stern and the rudder post when going astern. The pivot point is sometimes considered to be the centre of leverage for forces acting on the ship. However, the pivot point is located out of ship due to strong lateral force, such as current and it is very inconvenient to use during maneuvering a ship. In this paper firstly, pivot points due to ship's condition are investigated carefully. And then the center of lateral resistance used at the present are determined. While a new lateral force is added, we can compare the pivot point with the center of lateral forces. Finally, we will suggest the center of all lateral forces for maneuvering instead of pivot point. Especially, it will be very helpful for pilots to handle ships in simulation.

• 한국항해항만학회지
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• 제27권6호
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• pp.625-630
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• 2003

In order to keep the safety of maneuverability under the lateral berthing, it is necessary to estimate the magnitudes and properties of the hydrodynamic forces acting on ship hull quantitatively. In this paper, CFD technique is used to calculate the steady lateral force according to the water depth for Wigley model under the unsteady lateral berthing. The numerical results are analysed into the steady lateral force and the transitional lateral force, and some of reviews for the safety of maneuverability relating to the lateral berthing are discussed based on the computed hydrodynamic forces.

• 대한조선학회지
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• 제20권2호
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• pp.37-42
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• 1983

This paper presents a procedure within the framework of linear potential theory for predicting the lateral drifting forces on a cylinder floating on the free surface of a finite depth water. The disturbance of a regular incident wave caused by the presence of the floating body is represented by the sum of the diffracted and radiated wave potentials, which are determined by using Green's theorem. The lateral drifting forces are calculated by use of momentum theorem, and the scattered waves are expressed in their asymptotic forms. The computed lateral drifting forces on a Lewis form cylinder(b/T=1.25, $\sigma$=0.95) for water depth to draft ratio of 5.0 are compared with the Kyozuka's experimental results for a deep water, and found to be in good agreement. The water depth effects on drifting forces of the same model are also calculated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.311-314
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• 1996

In contactless disk handling systems based on electrostatic suspension in which the stator is to be transferred, the limited stiffness in lateral direction severely restricts the achievable translational acceleration. In existing stator electrode pattern designs, the magnitude of the lateral force is determined by the magnitude of the control voltages which are applied to the individual electrodes to levitate the disk stably. As a result, the lateral force cannot be set arbitrarily. A new stator electrode pattern is presented for the electrostatic levitation of disk-shaped objects, in particular silicon wafers and aluminum hard disks, which allows the lateral forces to be controlled independently from the levitation voltages. Therefore, greater lateral forces can be obtained, compared with the existing stator designs. Experimental results will be presented for a 4-inch silicon wafer that clearly reveal the increased lateral stiffness by using the proposed stator electrode compared to the conventional electrode pattern.

• Tribology and Lubricants
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• 제28권6호
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• pp.289-296
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• 2012

Atomic force microscopy (AFM) has been used for imaging surfaces and measuring surface forces at the nano-scale. Force calibration is important for the quantitative measurement of forces at the nano-scale using AFM. Normal force calibration is relatively straightforward, whereas the lateral force calibration is more complicated since the lateral stiffness of the cantilever is often comparable to the contact stiffness. In this work, the lateral force calibrations of the rectangular cantilever were performed using torsional Sader's method, thermal noise method, and wedge calibration method. The lateral optical lever sensitivity for the thermal noise method was determined from the friction loop under various normal forces as well. Experimental results showed that the discrepancies among the results of the different methods were as large as 30% due to the effect of the contact stiffness on the lateral force calibration of the cantilever used in this work. After correction for the effect of contact stiffness, all the calibration results agreed with each other, within experimental uncertainties.

• 제어로봇시스템학회논문지
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• 제21권10호
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• pp.903-909
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• 2015

This article presents an integrated chassis control with electronic stability control (ESC) and active front steering (AFS) under saturation of front lateral tire force. Regardless of the use of AFS, the front lateral tire forces can be easily saturated. Under the saturated front lateral tire force, AFS cannot be effective to generate a control yaw moment needed for the integrated chassis control. In this paper, new integrated chassis control is proposed in order to limit the use of AFS in case the front lateral tire force is saturated. Weighed pseudo-inverse control allocation (WPCA) with variable weight is adopted to adaptively use the AFS. To check the effectiveness of the proposed scheme, simulation is performed on a vehicle simulation package, CarSim. From simulation, the proposed integrated chassis control is effective for vehicle stability control under saturated front lateral tire force.

• 한국강구조학회 논문집
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• 제11권1호통권38호
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• pp.69-78
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• 1999

구조물이 지진과 같은 수평력을 받으면 골조의 기둥은 횡이동을 하게 되고 이 횡이동이 크면 골조는 불안정 좌굴, 초기항복, 골조전체의 강성이 감소하게 된다. 본 연구에서는 이러한 골조의 기둥이 횡이동에 의해 수평력과 축력을 동시에 받는 강골조를 대상으로하여 골조강성의 저하, 보와 기둥의 상대적인 강성비, 세장비효과, 하중조건 등을 고려한 다양한 해석모델을 상정하여 수치해석을 실시했다. 그 해석결과를 분석하여 강골조의 최대수평내력을 평가하고, 기둥의 세장비 제한치를 구하는 절차에 대해서도 검토한다. 해석에 있어서는, 골조의 $P-{\Delta}$효과를 고려해서 기발표된 저자의 탄소성해석법을 이용하여 일정한 축력하에 점증의 수평력을 골조에 가했으며, 최대내력후의 해법으로서 일반역행렬을 응용했다.

• Tribology and Lubricants
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• 제8권2호
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• pp.44-49
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• 1992

Hydrodynamic lateral forces acting on circumferentially grooved and tapered pistons in hydraulic piston pumps are analyzed for the case where the axis of piston and cylinder are tilted with each other. The effects of grooves and tilting on lateral force and leakage flowrate are discussed from the analytical solution of one-dimensional Reynolds equation. The analytical solution is in accordance with the numerical solution of two-dimensional Reynolds equation as the number of grooves increases.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2003년도 춘계공동학술대회논문집
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• pp.132-138
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• 2003

대형 유조선 접이안시 발생하는 비정상 운동을 이해하기 위해서는 천수역에서 작용하는 유체력의 크기와 성질을 명학히 파악해야 한다. 본 논문에서는 수식선형인 wigley 선형을 대상으로 수심과 가속도에 따른 유체력 변화에 대해 CFD를 이용하여 직접 시간영역에서 수치 계산을 행하였다. 또한 계산 결과를 수조 실험결과와 비교하여 CFD의 타당성 및 유효성을 검증하였다. CFD의 계산 결과는 선박 접이안시 선체에 작용하는 유체력의 산출은 물론이고 선체 주위 물리적 현상이나 유장 등의 특징을 상세히 파악할 수 있었다. 또한 수심과 가속도를 변수로 행한 계산 결과를 바탕으로 최초 정지상태에서 등속운동까지의 과도 횡력을 선체 이동속도에 이동거리를 곱한 순환함수의 개념을 이용하여 모델화하였다.