• Journal of the Korean GEO-environmental Society
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• v.20 no.3
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• pp.31-38
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• 2019

To determine the optimum dynamic load test analysis for PCFT (Prestressed Concrete Filled steel Tube) hybrid composite piles that PCFT piles are connected to the top of PHC piles, the dynamic load tests and CAPWAP analyses were performed on two hybrid composite piles with steel pipe and PCFT piles as upper piles. The results of the dynamic load tests and CAPWAP analyses showed that the particle velocity measured in PCFT hybrid composite piles was equal to the wave speed of PHC piles when the strain gauges and accelerometers are attached to the surface of inner composite PHC pile after removing the steel pipe in the upper PCFT pile. In addition, when assuming that the material of that upper PCFT pile was the same as that of the lower PHC pile and the cross-sectional area of the steel pipe in upper PCFT pile was converted to that for concrete through the pile model (PM) in CAPWAP analysis, the accuracy of the CAPWAP analysis result for PCFT hybrid composite piles was very high.

• Geomechanics and Engineering
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• v.36 no.4
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• pp.317-328
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• 2024

Adopting a rational engineering methodology for building structures on sandy-clay soil layers has become increasingly important since it is crucial when structures erected on them often face seismic and cyclic wave loads. Such loads can cause a reduction in the stiffness, strength, and stability of the structure, particularly under un-drained conditions. Hence, this study aims to investigate how the dynamic properties of sand-clay mixtures are affected by loading frequency and clay content. Cyclic triaxial tests were performed on a total of 36 samples, comprising pure sand with a relative density of 60% and sand with varying percentages of clay. The tests were conducted under confining pressures of 50 and 100 kPa, and the samples' dynamic behavior was analyzed at loading frequencies of 0.1, 1, and 4 Hz. The findings indicate that an increase in confining pressure leads to greater inter-particle interaction and a reduced void ratio, which results in an increase in the soil's shear modulus. An increase in the shear strength and confinement of the samples led to a decrease in energy dissipation and damping ratio. Changes in loading frequency showed that as the frequency increased, the damping ratio decreased, and the strength of the samples increased. Increasing the loading frequency not only reflects changes in frequency but also reduces the relative permeability and enhances the resistance of samples. An analysis of the dynamic properties of sand and sand-clay mixtures indicates that the introduction of clay to a sand sample reduces the shear modulus and permeability properties.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.49-54
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• 2016

An active layer distributed on surface of an extreme cold region causes a frost heave by repeating the freezing and thawing according to the seasonal temperature change. Since the height of frost heave is greatly affected by the thickness of active layer, an accurate evaluation of the thickness of active layer is necessary for the safe design and construction of the infrastructure in the extreme cold region. In this study, dynamic cone penetrometer, which is miniaturized in-situ penetration device, is applied for the evaluation of active layer depth distribution. As the application tests, two dynamic cone penetration tests were conducted on the study sites located in Solomon and Alaska. In addition, ground temperature variations were obtained. As the results of the application tests, the depth of interface between the active layer and the permafrost was evaluated from the difference in dynamic cone penetration indexes of the active layer and the permafrost, and a layer was detected around the interface considered as an ice lens layer. Also, the interface depths between the above zero and the below zero temperature determined from the ground temperature variations correspond with the interface depths evaluated from the dynamic cone penetration tests. This study demonstrates that the dynamic cone penetrometer may be a useful tool for the evaluation of the active layer in the extreme cold region.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.229-235
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• 1996

The tapered leaf spring is regarded as the adequate tool to improve ride quality and to reduce vehicle weight of commercial vehicles. These effects are due to minimizing the contact area of each leaf by reducing the number of leaves and by optimizing the thickness profile of each leaf. But in adapting the tapered leaf spring to improve ride quality, we often have some problems of bad pitching and bouncing motion. This paper shows the basic properties of tapered leaf spring by rig tests and how to improve ride quality of a vehicle with tapered leaf springs, compared with multi-leaf spring. From the results of vehicle tests and rig tests it is concluded that the ride quality was effected by the dynamic spring rate and the friction of the tapered leaf spring.

• International Journal of Automotive Technology
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• v.3 no.4
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• pp.129-135
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• 2002

Durability estimation of a prototype vehicle has traditionally relied heavily on accelerated durability tests using predefined proving grounds or rig tests using a road simulator. By use of those tests, it is very difficult to predict durability failures in actual service environments. This motivated the development of an integrated CAE (Computer Aided Engineering) methodology for the durability estimation of a prototype vehicle in actual service environments. Since expensive computational costs such as computation time and hardware resources are required for a full vehicle simulation in those environments with a very long span of event time, the conventional CAE methodologies have little feasibility. An efficient computational methodology for durability estimations is applied with theoretical developments. The effectiveness of the proposed methodology is shown by the comparison of results of the typical actual service environment such as the city mode with those of the typical accelerated durability test over the Belgian road.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.183-190
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• 2000

Effective range of Hydraulic Hammer Compaction was studied by numerical analysis instead of empirical method. Numerical analyses were carried out with commercial FEM code, ABAQUS, and verified by comparing the numerical results with field tests of Hydraulic Hammer Compaction. Most of material properties were evaluated by data from laboratory and in-situ tests. Vertical effective range was estimated by distribution curve of plastic strain energy dissipated through soil layers under dynamic load and these results were in good agreement with field tests. Based on verification, the effects of governing properties of Hydraulic Hammer Compaction such as number of hit can be determined by numerical analyses. In addition, vertical effective range can also be determined by Menard's empirical equation using the external work at converging time of plastic strain energy in numerical analysis. This implies that the minimum energy of Hydraulic Hammer Compaction for improvement can be determined by Menard's equation.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.321-324
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• 2002

To analyze the settlement characteristics of short-fiber reinforced soil(SFRS) under dynamic loading, a series of tests with loading condition of 5 Hz frequency and 500,000 cycles were performed. The materials used for tests are a soil of SM type and short-fibers with polypropylene and monofilament or fibrillated type. From the tests, average plastic settlement of SFRS at PPF38(0.3%), PPF38(0.5%), PPM60(0.2%) is low. Elastic settlement of SFRS is low at PPM60(0.2%) and is high at PPF60(0.5% ).

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.92-97
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• 2003

Roadbed failure due to the rainfall may bring out social and economic demage such as the loss of life and property, the consumption of time and cost for recovery, and the delay of logistics in railway. In this study, the method using Geotextile Container was applied to rehabilitation of the railway roadbed which was failed by rainfall. The real scale tests with the simulated train loading were performed in order to evaluate the dynamic performance at the railway roadbed using Geotextile Container. The results of these tests were compared with unreinforced and reinforced cases with Geotextile Container, respectively. The data gathered by various measurement devices from these real scale tests would be useful to evaluate and understand the roadbed with Geotextile Container. Furthermore, the results of this study would be useful to ensure the workability and to save much time for restoration and to be widely applied to practical use.

• Structural Monitoring and Maintenance
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• v.1 no.2
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• pp.231-247
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• 2014

This paper focuses on the dynamic behaviour of Mirandola City Hall (a XV century Renaissance Palace) that was severely damaged during May 2012 Emilia earthquake in Northern Italy. Experimental investigations have been carried out on this monumental building. Firstly, detailed investigations have been carried out to identify the identification of the geometry of the main constructional parts as well as the mechanical features of the constituting materials of the palace. Then, Ambient Vibration Tests (AVT) have been applied, for the detection of the main dynamic features. Three output-only identification methods have been compared: (i) the Frequency Domain Decomposition, (ii) the Random Decrement (RD) and the (iii) Eigensystem Realization Algorithm (ERA). The modal parameters of the Palace were difficult to be identified due to the severe structural damage; however the two bending modes in the perpendicular directions were identified. The comparison of the three experimental techniques showed a good agreement confirming the reliability of the three identification methods.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.34-41
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• 2001

This study is to investigate the energy absorption characteristics of CFRP(Carbon-Fiber Reinforced Plastics) tubes on static and dynamic tests. Axial static compression tests have been carried out using the static testing machine(Shin-gang buckling testing machine) and dynamic compression tests have been utilized using an vertical crushing testing machine. When such tubes are subjected to crushing loads, the response is complex and depends on the interaction between the different mechanisms that could control the crushing process. The collapse characteristics and energy absorption have been examined for various tubes. Energy absorption of the tubes are increased as changes in the lay-up which may increase the modulus of tubes. The results have been varied significantly as a function of ply orientation and interlaminar number.