• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.53-66
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• 2007

A series of model tests were performed to investigate the soil arching effect in embankments supported by piles with geosynthetics. In the model tests, model piles with isolated cap were inserted through the holes in a steel plate, which could be operated up and down. Then geosynthetics was laid on the pile caps below sand fills. The settlement of soft ground was simulated by lowering the plate. As the plate was lowered, the soil arching was mobilized in the embankments. The deformation of both the sand fills and geosynthetics were captured by camera. Also the loads acting on pile cap and the tensile strain of geosynthetics were monitored by data logging system. Model tests showed that the embankment loads transferred on pile cap by soil arching Increased rapidly with settlement of the soft ground. In case of the absence of geosynthetics, the loads acting on pile caps dropped to residual value after peak value, whereas loads on pile caps gradually increased until constant value in case of geosynthetic-reinforced. This illustrated that reinforcing with the geosynthetics has a good effect to restrain the settlement of embankments. Also, the deformation shape of geosynthetics between pile caps was circular. The embankment loads transferred on pile caps can be estimated by considering both soil arching and tensile strain of geosynthetics in embankments supported by piles with geosynthetics.

• Earthquakes and Structures
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• v.14 no.4
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• pp.323-336
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• 2018

Machine foundations with impact loads are common powerful sources of industrial vibrations. These foundations are generally transferring vertical dynamic loads to the soil and generate ground vibrations which may harmfully affect the surrounding structures or buildings. Dynamic effects range from severe trouble of working conditions for some sensitive instruments or devices to visible structural damage. This work includes an experimental study on the behavior of dry dense sand under the action of a single impulsive load. The objective of this research is to predict the dry sand response under impact loads. Emphasis will be made on attenuation of waves induced by impact loads through the soil. The research also includes studying the effect of footing embedment, and footing area on the soil behavior and its dynamic response. Different falling masses from different heights were conducted using the falling weight deflectometer (FWD) to provide the single pulse energy. The responses of different soils were evaluated at different locations (vertically below the impact plate and horizontally away from it). These responses include; displacements, velocities, and accelerations that are developed due to the impact acting at top and different depths within the soil using the falling weight deflectometer (FWD) and accelerometers (ARH-500A Waterproof, and Low capacity Acceleration Transducer) that are embedded in the soil in addition to soil pressure gauges. It was concluded that increasing the footing embedment depth results in increase in the amplitude of the force-time history by about 10-30% due to increase in the degree of confinement. This is accompanied by a decrease in the displacement response of the soil by about 40-50% due to increase in the overburden pressure when the embedment depth increased which leads to increasing the stiffness of sandy soil. There is also increase in the natural frequency of the soil-foundation system by about 20-45%. For surface foundation, the foundation is free to oscillate in vertical, horizontal and rocking modes. But, when embedding a footing, the surrounding soil restricts oscillation due to confinement which leads to increasing the natural frequency. Moreover, the soil density increases with depth because of compaction, which makes the soil behave as a solid medium. Increasing the footing embedment depth results in an increase in the damping ratio by about 50-150% due to the increase of soil density as D/B increases, hence the soil tends to behave as a solid medium which activates both viscous and strain damping.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.1-13
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• 1982

Transition process of plastic region. displacements, stresses and strains ahead the flaw tips were analysed by the finite element method on the steel plate with the circular hole and the one with the elliptical hole under completely alternating load (repetition of tensile loading, unloading and compressive loading). As the results, the followings were obtained. Transition process of elastic failure (yielding) region was estimated. From this the tendency was confirmed that the fracture would be initiated from ahead the flaw tip, and propagated along the $45^{\circ}$ direction. The fundamental data available in estimating the stress intensity factor that was considered as the core in analysing the fracture mechanism of steel plates were obtained. It was indicated that when unloading after tension the effect of compressive loading, and even the compressive reyield, was occured ahead the flaw tip. Similarly it was indicated that when unloading after compression the effect of tensile loading, and even the tensile reyield, was occured ahead the flaw tip. It was considered that these phenomena were occured because the unloading effect was constrained by the residual strains when unloading. It was considered that the fatigue phenomenon was occured ahead, the flaw tip by repetition of tensile yield, the above compressive reyield, compressive yeild and the above tensile reyield. In addition, the tendency was confirmed that the fracture ahead the flaw tip was occured as the flaw was changed from the circular hole to the elliptical hole and became to be the crack lastly.

• International Journal of Fluid Machinery and Systems
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• v.10 no.1
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• pp.40-46
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• 2017

Small valves including ball valves, gate valves and butterfly valves have been adopted in the fields of steam power generation, petrochemical industry, carriers, and oil tankers. Butterfly valves have normally been applied to fields where in narrow places installing the existing valves such as gate valves and ball valves have proven difficult due to the surrounding area and the heavier of these valves. Butterfly valves are used to control the mass flow of the piping system under low pressure by rotating the circular disk installed inside. The butterfly valve is benefitted by having simpler structure in which the flow is controlled by rotating the disc circular plate along the center axis, whereas the weight of the valve is light compared to the gate valve and ball valve above-mentioned, as there is no additional bracket supporting the valve body. The manufacturing company needs to acquire the performance and life test equipment, in the case of adopting the improving factors to detect leakage and damage on the seat of the valve disc. However, small companies, which are manufacturing the industrial valves, normally sell their products without the life test, which is the reliability test and environment test, because of financial and manpower problems. Furthermore, the failure mode analysis of the products failed in the field is likewise problematic as there is no system collecting the failure data on sites for analyzing the failures of valves. The analyzing and researching process is not arranged systematically because of the financial problem. Therefore this study firstly tried to obtain information about the failure data from the sites, analyzed the failure mode based on the field data collected from the customers, and then obtained field data using measuring equipment. Secondly, we designed and manufactured the performance and life test equipment which also have the real time monitoring system with the naked eye for the butterfly valves. The concept of this equipment can also be adopted by other valves, such as the ball valve, gate valve, and various others. It can be applied to variously sized valves, ranging from 25 mm to large sized valves exceeding 3000 mm. Finally, this study carries out the life test with square wave pressure, using performance and life test equipment. The performance found out that the failures from the real time monitoring system were good. The results of this study can be expanded to the other valves like ball valves, gate valves, and control valves to find out the failure mode using the real time monitoring system for durability and performance tests.

• International Journal of Highway Engineering
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• v.9 no.3
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• pp.39-50
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• 2007

Barrier VII program is normally used for the design of flexible barrier, but if modelled properly it can be used for the analysis of vehicle impact to small sign posts. In this paper sign post is shown to be modelled as flexible barrier by combining beam and column elements at each beam node. Simulations with the Barrier VII program have been made for 7 impact cases composed of sign posts of circular and H section with rigidly connected support and breakaway support system. The impact speed used for the simulation ranged from 30km/h to 110km/h. The study shows that in the vehicle impacts to a circular sign post with high speed, the large deflection and high inertia force causes the sign plate to hit the windshield leading to a hazard to the occupants. It is also shown that impact to H section post results in small deflection of the post and abrupt velocity change and high deceleration of the impact vehicle causing severe damage to both the vehicle and occupants. Simulation study also shows that breakaway support system eliminates the potential danger of the vehicle impact to the rigidly connected small sign posts by reducing deflection of the post, abrupt change in velocity and deceleration level.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.581-586
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• 2018

Cast iron manhole lids cause environmental pollution during the manufacturing process, and the work environment is very poor. In addition, if the height of the manhole cover does not match the height of the road surface, it causes considerable inconvenience and safety problems. This study proposes a height - adjustable steel manhole cover that can replace cast iron manhole covers and easily match the road surface with the upper surface of the manhole cover. Structural analysis was performed to grasp the design variable of the structure of the manhole cover, satisfying the required quality performance. To fabricate a manhole cover that satisfies the required load capacity, the optimal design for the U-shaped reinforcement structure was made. The cylindrical shape of the height adjustment part and the low frame were formed by bending the steel sheet into a circular shape and then welding. Reinforcing bars were also made by bending a steel plate. The height adjustment groove was machined by a CNC milling machine. Four prototypes were fabricated and a load bearing test was carried out, and new manhole cover was made reflecting results of the test. In the load bearing test, there was no breakage of the welded part, and deformation occurred mainly at the contact area between the groove and gusset plate. Deformation of 1 to 2.7mm occurred due to a load of 450kN. On the other hand, after removing the load, there was almost no residual deformation, and the load bearing evaluation was judged to be satisfactory because the manhole cover could be disassembled and reassembled.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.117-123
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• 2001

Anchovy scoop nets, a kind of lift net have been used in the coastal area of Cheju and South sea of Korea. An incandescent lamp(AC 100V, 1kW) is being used as a fishing lamp for gathering anchovy. Fishing lamp was installed at 1m ahead of the prow and 1.5m higher than the water surface. The fishing lamp let fish school rise to the water surface and attract to bag net. Accordingly, a successful anchovy catching depends on controling of fishing lamp. On the study, the distribution of spectral irradiance illumination of incandescent lamp(1kw) and the irradiance efficiency of reflection plate were analyzed and discussed to investigate the ability of fishing lamp which can attract anchovy school effectively. The results obtained are summarized as follows : 1. Around 180% of irradiance efficiency of incandescent lamp was increased by using the reflection plate. The light of lamp was radiated into water with circular shape. 2. The irradiance illumination of incandescent lamp in air was a maximum in wave length of 994nm but it was 690nm at 0.5m and 1.0m of water depth. 3. The relationship between water depth(x) and water illumination(y) of vertical light is represented as follows : y=146.03e supper(-0.37x) 4. The light of incandescent lamp(1kW) pass through much better into vertical direction than horizontal but it was estimated that the light was not able to reach depth of 20m.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.199-202
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• 1996

Artificial hearts are intended for use in patients with severe forms of heart disease for which no surgical repair is possible. The moving-actuator pump was developed to decrease the overall volume size of the electromechanical total artificial heart (TAH) by eliminating the occupied space of the fixed-actuator in the conventional pusher-plate type pump. In our pump, the actuator moves back and forth for alternative ejections of left and right ventricles. The problem of fitting the TAH to atrial remnants and arterial vessels could also be improved by circular or penduluous mot ion of the actuator instead of linear mot ion of the pusher-plate in the conventional pumps. We have evaluated two types of moving- actuator pump; one is a rolling cylinder type, and the other a pendulum type pump. In the rolling cylinder pump, frictional energy loss exists between the pump housing's guide bars and the actuator's end caps, while the bottom rack under the cylindrical actuator increases the height of the pump, the pump is therefor not implantable inside the small chest of human-sized animals with a body weight of less than 70kg. The new human type pump has a penduluous mot ion actuator to correct the above problems while maintaining the advantage of the moving- actuator's small total volume. The totally implantable TAH is composed of a blood pump, a control system and pheriperal equipments. The blood pump, which is constructed by a moving actuator, a right and left blood sac, and four artificial valves, is implanted in the thoracic. In 1988, the first implantation of the rolling cylinder TAH was performed into a female calf weighing 100kg, and the cal f recovered to the degree of voluntary standing and eat ing and survived to 100 hrs. We then survived two female sheep weighing about 63kg with the new human type TAH for three days.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.2
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• pp.148-154
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• 2014

Photoelasticity is a useful technique for obtaining the differences and directions of principal stresses in a model. In conventional photoelasticity, the photoelastic parameters are measured manually point by point. Identifying and measuring photoelastic data is time-consuming and requires skill. The fringe phase shifting method was recently developed and has been found to be convenient for measuring and analyzing fringe data in photo-mechanics. This paper presents an experimental study on the stress distribution along a horizontal line that passes the central point of a rhombus plate made of Photoflex (i.e., type of urethane rubber). The isoclinic fringe and/or principal stress direction is constant on this horizontal line, so a four-bucket phase shifting method can be applied. The method requires four photoelastic fringes that are obtained from a circular polariscope by rotating the analyzer at $0^{\circ}C$, $45^{\circ}C$, $90^{\circ}C$ and $135^{\circ}C$. Experimental measurements using the method were quantitatively compared with the results from FEM analysis; the results from the two methods showed comparable agreement.

• Journal of IKEEE
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• v.15 no.1
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• pp.49-56
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• 2011

In this paper, a compact doppler sensor with oscillator type active antenna operating at 2.4GHz frequency band is proposed to measure the distance or speed of a moving object. The active antenna has been realized by oscillator using radiator, patch antenna, as its resonator. The oscillation frequency is shifted depending on approaching of the object, and a detection circuit discriminates the frequency deviation. The oscillator type active antenna has been designed and simulated. The prototype fabricated has a very small circular disk type of diameter 30mm and height 4.2mm. As for antenna performance, broadside radiation pattern with beamwidth of $130^{\circ}$ and oscillation frequency of 2.373GHz has been measured. Test results as a doppler sensor shows that doppler signal voltage of about 190mV has been obtained for conducting plate moving 1 meter away from the sensor. And, doppler signal voltage has been linearly increased to the ground from 4.5m height by free-falling the sensor.