• Geomechanics and Engineering
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• v.4 no.3
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• pp.209-218
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• 2012

This paper presents the derivation of an analytical expression for the dynamic active thrust from c-${\phi}$ (c = cohesion, ${\phi}$ = angle of shearing resistance) soil backfill on rigid retaining walls with wall friction and adhesion. The derivation uses the pseudo-static approach considering tension cracks in the backfill, a uniform surcharge on the backfill, and horizontal and vertical seismic loadings. The development of an explicit analytical expression for the critical inclination of the failure plane within the soil backfill is described. It is shown that the analytical expression gives the same results for simpler special cases previously reported in the literature.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.263-277
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• 2014

In the conventional design of retaining structures in a seismic zone, seismic inertia forces are commonly assumed to act upwards and towards the wall facing to cause a maximum active thrust or act upwards and towards the backfill to cause a minimum passive resistance. However, under certain circumstances this design approach might underestimate the dynamic active thrust or overestimate the dynamic passive resistance acting on a rigid retaining structure. In this study, a new analytical method for dynamic active and passive forces in c-${\phi}$ soils with an infinite slope was proposed based on the Rankine earth pressure theory and the Mohr-Coulomb yield criterion, to investigate the influence of seismic inertia force directions on the total active and passive forces. Four combinations of seismic acceleration with both vertical (upwards or downwards) and horizontal (towards the wall or backfill) directions, were considered. A series of dimensionless dynamic active and passive force charts were developed to evaluate the key influence factors, such as backfill inclination ${\beta}$, dimensionless cohesion $c/{\gamma}H$, friction angle ${\phi}$, horizontal and vertical seismic coefficients, $k _h$ and $k_v$. A comparative study shows that a combination of downward and towards-the-wall seismic inertia forces causes a maximum active thrust while a combination of upward and towards-the-wall seismic inertia forces causes a minimum passive resistance. This finding is recommended for use in the design of retaining structures in a seismic zone.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.5
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• pp.193-202
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• 2023

In this paper, a dynamic centrifuge model test was conducted on a 24.8-meter-deep excavation consisting of a 20 m sand layer and 4.8 m bedrock, classified as S3 by Korean seismic design code KDS 17 10 00. A braced excavation wall supports the hole. From the results, the mechanism of seismically induced earth pressure was investigated, and their distribution and loading points were analyzed. During earthquake loadings, active seismic earth pressure decreases from the at-rest earth pressure since the backfill laterally expands at the movement of the wall toward the active direction. Yet, the passive seismic earth pressure increases from the at-rest earth pressure since the backfill pushes to the wall and laterally compresses at it, moving toward a passive direction and returning to the initial position. The seismic earth pressure distribution shows a half-diamond distribution in the dense sand and a uniform distribution in loose sand. The loading point of dynamic thrust corresponding with seismic earth pressure is at the center of the soil backfill. The dynamic thrust increased differently depending on the backfill's relative density and input motion type. Still, in general, the dynamic thrust increased rapidly when the maximum horizontal displacement of the wall exceeded 0.05 H%.

• Journal of Magnetics
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• v.14 no.4
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• pp.175-180
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• 2009

This paper describes the design and analysis of a tubular linear actuator for intelligent AAP (Active Accelerate Pedal) system. In a driving emergency, the electromagnetic actuator produces an additional pedal force such as the active pedal force and vibration force to release the driver's foot on accelerator pedal. A prior study found that the linear actuator with a ferromagnetic core had a problem in transferring the additional force naturally to a driver due to the cogging force. To reduce the cogging force and obtain higher performance of the AAP system, a coreless tubular linear actuator is suggested. Electromagnetic finite element analysis is executed to analyze and design the coreless tubular actuator, and dynamic analysis is performed to characterize the dynamic performance of the AAP system with the suggested tubular actuator for two types of thrust force.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.963-967
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• 2007

Flywheel energy storage systems (FESS) have advantages over other types of energy storage methods due to their infinite charge/discharge cycles and environmental friendliness. The system has two radial bearings and one hybrid-thrust bearing. Thrust hybrid-type bearing use permanent magnet to relieve gravity load. The radial bearings were designed to provide sufficient force slew rate considering the unbalance disturbance at the operating speeds. In this paper, we will derive dynamic model of hybrid-type bearing using permanent magnet for thrust bearing and present simulation and stability of the model.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.136-138
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• 1999

Linear Induction Motors (LIMs) with the long secondary conductor often have joints between the segmented secondary, which are specially used for magnetically levitated high-speed vehicle and elevators. In this paper, the dynamic characteristics of the LIM with joints in the secondary are investigated using the time-stepping finite element analysis. It is supposed that both aluminium conductor and back-iron have joint in the active zone during the analysis. As a result, thrust and normal force ripple which have effects on the motor dynamics and vibration are examined.

• Progress in Superconductivity
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• v.13 no.3
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• pp.195-202
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• 2012

In this paper, we designed Active Magnetic Bearing (AMB) for large scale Superconductor Flywheel Energy Storage System (SFESS) and PD controller for AMB. And we experimentally evaluated SFESS including hybrid type AMB. The radial AMB was designed to provide force slew rate that was sufficient for the unbalance disturbances at the maximum operating speed. The thrust AMB is a hybrid type where a permanent magnet carries the weight of the flywheel and an electromagnetic actuator generates the dynamic control force. We evaluated the design performance of the manufactured AMB through comparison of FEM analysis and the results of experimental force measurement. In order to obtain gains of PD controller and design a notch filter, the system identification was performed through measuring frequency response including dynamics for the AMBs, a power amp and a sensor using a sine swept test method after levitating the flywheel. Through measuring the current input of the AMBs and the orbit of a flywheel according to rotational speed, we verified excellent control performance of the AMBs with small amount current for the large scale SFESS.

• Physical Therapy Korea
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• v.3 no.2
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• pp.95-105
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• 1996

Type I, II, III are regarded as "true" joint receptors, type IV is considered a class of pain receptor. Type I, II and III mechanoreceptors, via static and dynamic input, signal joint position, intraarticular pressure changes, and the direction, amplitude, and velocity of joint movements. Type I mechanoreceptor subserve both static and dynamic physiologic functions. Type I are found primarily in the stratum fibrosum of the joint capsule and ligaments. Type I receptors have a low threshold for activation and are allow to adapt to changes altering their firing frequency. Type II receptors have a low threshold for activation. These dynamic receptors respond to joint movement. Type II receptors are thus termed rapidly adapting. Type II joint receptors are located at the junction of the synovial membrane and fibrosum of the joint capsule and intraarticular and extraarticular fat pads. Type III receptors have been found in collateral ligaments of the joints of the extremities. Morphologically similar to Golgi tendon organ. These dynamic receptors have a high threshold to stimulation and are slowly adating. Type IV receptors possess free nerve ending that have been found in joint capsule and fat pads. They are not normally active, but respond to extreme mechanical deformation of the joint as well as to direct chemical or mechanical irritation. Small amplitude oscillatory and distraction movements(joint mobilization) techniques are used to stimulate the mechanoreceptors that may inhibit the transmission of nociceptors stimuli at the spinal cord or brain stem levels.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.2 no.1
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• pp.9-19
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• 1996

Type I, II, III are regarded as "true" joint receptors, type IV is considered a class of pain receptor. Type I, II and III mechanoreceptors, via static and dynamic input, signal joint position, intraarticular pressure changes, and the direction, amplitude, and velocity of joint movements. Type I mechanoreceptor subserve both static and dynamic physiologic functions. Type I are found primarily in the stratum fibrosum of the joint capsule and ligaments. Type I receptors have a low threshold for activation and are allow to adapt to changes altering their firing frequency. Type II receptors have a low threshold for activation. These dynamic receptors respond to joint movement. Type II receptors are thus termed rapidly adapting. Type II joint receptors are located at the junction of the synovial membrane and fibrosum of the joint capsule and intraarticular and extraarticular fat pads. Type III receptors have been found in collateral ligaments of the joints of the extremities. Morphologically similar to Golgi tendon organ. These dynamic receptors have a high threshold to stimulation and are slowly adating. Type IV receptors possess free nerve ending that have been found in joint capsule and fat pads. They are not normally active, but respond to extreme mechanical deformation of the joint as well as to direct chemical or mechanical irritation. Small amplitude oscillatory and distraction movements(joint mobilization) techniques are used to stimulate the mechanoreceptors that may inhibit the transmission of nociceptors stimuli at the spinal cord or brain stem levels.