• Earthquakes and Structures
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• v.23 no.4
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• pp.353-361
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• 2022

The dynamic behavior of a single pile was investigated by using analytical and numerical studies. The focus of this study was to develop the dynamic p-y curve of a pile for pseudo-static analysis considering the shear wave velocity of the soil by using three-dimensional numerical analyses. Numerical analyses were conducted for a single pile in dry sand under changing conditions such as the shear wave velocity of the soil and the acceleration amplitudes. The proposed dynamic p-y curve is a shape of hyperbolic function that was developed to take into account the influence of the shear wave velocity of soil. The applicability of pseudo-static analysis using the proposed dynamic p-y curve shows good agreement with the general trends observed by dynamic analysis. Therefore, the proposed dynamic p-y curve represents practical improvements for the seismic design of piles.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.107-116
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• 2022

The steady state of unsaturated soil takes a long time to achieve. The soil seepage behaviours and hydraulic properties depend highly on the wetting/drying rate. It is observed that the soil-water characteristic curve (SWCC) is dependent on the wetting/drying rate, which is known as the dynamic effect. The dynamic effect apparently influences the scanning curves and will substantially affect the seepage behavior. However, the previous models commonly ignore the dynamic effect and cannot quantitatively describe the hysteresis scanning loops under dynamic conditions. In this study, a dynamic hysteresis model for SWCC is proposed considering the dynamic change of contact angle and the moving of the contact line. The drying contact angle under dynamic condition is smaller than that under static condition, while the wetting contact angle under dynamic condition is larger than that under static condition. The dynamic contact angle is expressed as a function of the saturation rate according to the Laplace equation. The model is given by a differential equation, in which the slope of the scanning curve is related to the slope of the boundary curve by means of contact angle. Empirical models can simulate the boundary curves. Given the two boundary curves, the scanning curve can be well predicted. In this model, only two parameters are introduced to describe the dynamic effect. They can be easily obtained from the experiment, which facilitates the calibration of the model. The proposed model is verified by the experimental data recorded in the literature and is proved to be more convenient and effective.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.572-581
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• 2006

This study is to investigate dynamic response of concrete buried pipelines with various end boundary conditions and develop a curve fitted equation to ensure practicality and convenience for the use at the actual field for the test of resistance of earthquake. Dynamic response under the various end boundary conditions is calculated with analysis on values and computing programs. However, such a method of analysis requires skillfulness in using computing programs for dynamic movement of buried pipelines with dynamic analysis formula and has lower efficiency and practicality because, in the nature of analysis program of values, it needs much time to conduct repeated calculations. Therefore, the study is intended to develop a curve fitted equation to ensure more efficient and practical analysis. This paper tests various degrees of equation with non-linear least square method and developments a curve fitted equation based on the transmission speed with the best results. In the use of curve fitted equation, degree of polynomial and determining coefficient are influenced by the speed of transmission.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.877-883
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• 2009

Shaking table tests are performed to evaluate the dynamic group pile effect in fine sand. Single pile tests and $2{\times}4$ group pile tests are performed on 3D pile spacing. Dynamic p-y backbone curves are obtained to evaluate dynamic group pile effect by using dynamic p-y curve of single pile. And dynamic group pile p-multiplier is estimated by dynamic p-y backbone curve. Dynamic p-multiplier can be calculated by using subground reaction ratio of dynamic p-y backbone curve which is the same displacement of p-y curve peak point As the result, dynamic group pile effects are evaluated in terms of a shaking frequency, a shaking acceleration, and a relative density. Dynamic group pile p-multiplier is the largest at lead pile, and the value decrease at middle pile and trail pile. p multiplier increases as increasing input acceleration and decreasing relative density. This results coincide with NCHRP's research which suggest p multiplier increases as increasing pile cap displacement.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.188-193
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• 1998

This paper describes static and dynamic weak point analysis of spindle systems to eliminate high concentrated bending point on spindle and improve total stiffness of spindle systems. The weak point analysis is based on the evaluation of bending curves of spindles. For static weak point analysis the bending curve is derived from static deflection curve and for dynamic weak point analysis it is derived from the mode shape curves in consideration of the transfer function at exciting point. The validity of the weak point search methodology is verified by comparison of the static deflection, the natural frequency and the dynamic compliance between the original and the improved spindle.

• The Mathematical Education
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• v.47 no.1
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• pp.49-59
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• 2008

In this paper, we discuss two representations of a curve. One is a static representation as set of points, the other is a dynamic representation using time parameter. And we suggest needs of designing a computer microword where we can represent a curve both statically and dynamically. We also emphasize the importance of translation activity from a static representation to a dynamic representation. For this purpose, we first consider constructionism and 'computers and mathematics education' as a theoretical backgrounds. We focus the curve of a parabola in this paper since this is common in mathematics curriculum and is related to realistic situation such as throwing ball. And we survey the mathematics curriculum about parabola representation. And we introduce JavaMAL microworld that is integrated microworld between LOGO and DGS. In this microworld, we represent a parabola using a dynamic action, and connect this dynamic parabola action to recursive patterns. Finally, we remake a parabola for a realistic situation using this dynamic representation. And we discuss the educational meaning of dynamic representation and its computer microworld.

• Transactions of Materials Processing
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• v.5 no.4
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• pp.327-336
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• 1996

The effect of dynamic strain aging on high temperature deformation behaviour of the A-Mg alloy was investigated by strain rate change tests and stress relaxation tests between 20$0^{\circ}C$and 50$0^{\circ}C$. Yield point, short stress transient and periodic discontinuities on the stress-strain curve were considered as an evidence of the effect of dynamic strain aging. With this criterion two distinct strain rate-temperature regimes could be manifested. Dynamic strain aging was considered to be effective in the high temperature-low strain rate regime, whereas dynamic recovery was a dominant deformation mechanism in the low temperature-high strain rate regime. It was found that dynamic strain aging in the high temperature deformation was governed by the mechcanism of diffusion-controlled, viscous dislocation movement.

• Journal of the Korean Geotechnical Society
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• v.32 no.3
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• pp.39-47
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• 2016

In this study, dynamic centrifuge tests in dry sand were conducted in order to evaluate the effect of pile installation on the dynamic p-y curve. According to the result of the pile installation effect on the dynamic p-y backbone curves, the subgrade resistance of a jacked pile in 40 g was found to be greater than that of a jacked pile in 1 g and a preinstalled pile in 1 g. It was also found that differences of the subgrade resistance decrease with the depth of the pile. Applicability of dynamic p-y backbone curve for the bored pile proposed by preceded researcher was evaluated by comparing with the result of centrifuge tests. In addition, dynamic p-y backbone curve for jacking/driven pile was developed by modifying that for the bored pile.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.59-65
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• 1995

The cam is used to a main component in a variety of automatic machines and instruments. To meet the demand of a complicated operation and of reducing weight for automatic machine, Curve Blending Technology, in which each of the basic curves suitable for individual interval is connected, is used for the cam design. In the curve blending, it is necessary to select appropriate elementary curve for each interval and to confirm the dynamic continuity at connecting points between adjoining elementary curves. This paper represented the elementary curve selection method to select an appropriate curve for each interval, and executed computation for the follower displacement and angular displacement of each interval. The paper made an analysis and examine closely for elementary curves to synthesizing curve blending, and it performed dynamic conditions clearly at every points on the cam motions. Therefore the curve blending technology presented by the paper turned into easier work.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.97-103
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• 1999

The dynamic resistance monitoring in primary circuit is one of the important issues. Because in-process and real time quality assurance of resistance spot weld is needed to increase the product reliability. In this study, new dynamic resistance detecting method is proposed as a practical manner of weld quality assurance using instantaneous current and voltage measured at the primary circuit. and also, various patterns of primary dynamic resistance curve are characterized with the macro photograph and the weldability lobe curve. It is found that the primary dynamic resistance patterns are basically similar to those of the secondary, but there is evident advantage such as no extra devices are needed to obtain the quality information and eventually real time feedback control will be possible.