• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.647-652
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centro(NS, 1942) ground motion histories with different Peak Ground Acceleration(PGA) ranging from 0.06g to 0.50g. For model updating, flexural stiffness values of structural members(walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions(i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of inputs for updating(i.e. transfer function and natural frequencies). The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters(i.e. flexural stiffness values).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.725-731
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centre (NS, 1942) ground motion histories with different peak ground acceleration (PGA) ranging from 0.06 g to 0.50 g. For model updating, flexural stiffness values of structural members (walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions (i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of Inputs for updating (j.e. transfer function and natural frequencies) The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters (i.e. flexural stiffness values).

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.87-94
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• 1999

Sand drain as a vertical drainage is widely used in soft ground improvement. Recently, sand, the principal source of sand drain, is running out. A laboratory model test was carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. D is the diameter of the column. The transient process of pore water pressure with loading and the characteristics of consolidation were studied with the data gained from the measuring instrument place on the surface of the container. The parameter study was performed for the marine clayey soil before and after the test in order to check the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. According to the test, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. As a result, it is assumed that gravel is relatively acceptable as a drainage material.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.47-54
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• 2011

A piled raft foundation is one of the systems used to reduce the settlement of structures. However, the general design method for a piled raft foundation system assumes that the piles only support external loads, which exclude the bearing capacity of the raft itself. In this study, an experimental model test was performed to evaluate the raft capacity for the external load on the sand. Additionally, a part of the sandy ground under the raft was replaced with a gravel mat to reinforce the piled raft foundation system and increase the bearing capacity. Then, parametric studies of the reinforced ground were performed to determine the displacement and load-sharing ratio of the piled raft foundation system.

• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.33-39
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• 2008

VDL Mode 2 is one of air-to-ground VHF digital data link technologies. The VDL Mode 2 system is designed to be an air-to-ground subnetwork of the Aeronautical Telecommunication Network (ATN) using the AM(R)S band and it is organized according to the Open System Interconnection (OSI) model (defined by ISO). It can be used in ATS Applications especially for ATC communication such as CPDLC and ADS as well. And It is expected VDL Mode 2 replaces ACARS(Aircraft Communications Addressing and Reporting System) which has broadly been used for over 20 years. This paper presents the result of design of operational test equipments for the validation of VDL Mode 2 system under development in KARI.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.551-558
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• 2001

The horizontal drain method is one of methods improving reclamation ground. This method reduces consolidation time by using drained installed horizontally, and negative pressure is applied on end of these drains by vacuum pump. But, effective negative pressure still wasn't evaluated in applying this method to reclamation ground. To estimate optimum negative pressure, soil box test that make a model the in-situ by installing horizontal drains in the center is performed pressing different vacuum pressure In the laboratory, and the variations in settlement and volume of drained water through the drains during consolidation process were measured. Also, water content with distance from drain and with depth is measured after the test.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.51-51
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• 2003

인공위성의 개발 단계는 Prototype Model(PM), Engineering Model(EM), Qualification Model(QM) 그리고 Flight Model(FM)로 구분된다. 이때, Prototype 개발을 제외한 EM, QM, FM 개발단계는 반드시 종합조립시험(AIT)을 통하여 System Integration Test를 수행한다. 이 중에서 위성발사 전 최종 종합조립시험단계인 FM AIT는 위성의 최종시험단계이므로 Scenario Test를 포함한 지상에서 수행하여야 할 모든 시험을 수행한다. 이때, EM, QM 단계와는 다르게 FM AIT는 전기적 및 기계적 시험을 수행하나, 본 논문에서는 전기적 시험 과정과, Control Center 구성도 등을 포함하고 있는 Hardware 부분과, 관련 시험을 수행하게 될 Simulator를 포함한 Software 부분으로 나누어 소개하며, 기타 FM AIT 수행에 필요한 Electrical Ground Support System (EGSE) 전체 구성을 소개한다.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.549-560
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• 1998

The dynamic model of a tractor-trailer system developed in the first part of this paper was verified in this article by comparing the simulated acceleration responses of the system with actually measured ones. A commercially available tractor and a trailer were used for the verification test. Values of the model parameters were measured or theoretically derived if the measurement was practically impossible. The tractor-trailer system was operated with different forward speeds over three equally spaced half-sine bumps on the flat concrete surface. Results of the verification tests showed that autospectra of the measured and simulated accelerations of the tractor-trailer system agreed well up to the frequencies slightly feater than the fundamental frequencies of the ground excitations and at the frequencies of engine excitations. The mean of normalized errors of the simulated responses to the measured ones was estimated to be less than 10% for all the test runs. The peak responses in the autospectra also coincided well both in the frequency and magnitude.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.121-130
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• 2007

Centrifuge model tests were performed to find appropriate equations proposed previously of estimating the bearing capacity of the composite clayey soil reinforced with sand compaction pile. Model tests were carried out with changing the replacement ratio of SCP (20%, 40%, 70%), contents of fine materials (5%, 10%, 15%) and ratio of treated width to loading width (1B, 2B, 3B). Test results about bearing capacity of the composite ground were obtained by performing the surcharge load tests with measurements of applied loads and vertical displacement. Bearing capacities against bulging and shear failures were estimated by the existing equations. As results of comparing the estimated bearing capacity with experimental values the bearing capacities estimated by Greenwood's equation (1970) for bulging failure mode were similar to the test results.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.49-56
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• 2013

The use of geothermal energy has been increased for economic and environmental friendly utilization. Ground thermal conductivity and borehole thermal resistance are very important parameters in the design of geothermal heat pump system. This paper presents an experimental study of heat exchange rate of U and W type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). U and W type GHEs were installed in a partially saturated dredged soil deposit, and TPTs were conducted to evaluate heat exchange rates under 100-hr continuous operation condition. The heat exchange rates were also calculated by analytical models to estimate borehole thermal resistances and were compared with experimental results. It comes out that multi-pole and equivalent diameter (EQD) models resulted in more accurate agreement than shape factor (SF) model which is currently more often used.