• Advances in concrete construction
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• v.15 no.6
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• pp.377-389
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• 2023

In this study, an improved modular arch system with the lower arch space composed of a precast arch block and an outrigger was proposed as an underground culvert, and its applicability and structural behaviors were confirmed. This modular arch culvert structure with vertical walls was designed using precast blocks and by adjusting the placement spacing of concrete blocks to the upper part form an arch shape and the lower part form a vertical wall shape, based on previously researched modular arch systems. Owing to the vertical wall of the proposed modular arch system, it is possible to secure a load-carrying capacity and an arch space that can sufficiently resist the earth pressure generated from the backfill soil and loading on the arch system. To verify the structural characteristics, and applicability of the proposed modular precast arch culvert structure, a full-scale modular culvert specimen was fabricated, and a loading test was conducted. By examining its construction process and loading test results, the applicability and constructability of the proposed structure were analyzed along with its structural characteristics. In addition, its the structural predictability and safety for the applicability were evaluated by comparing the construction process and loading test results with the FE analysis results.

• Wind and Structures
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• v.6 no.3
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• pp.221-248
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• 2003

The design of high-rise building is often influenced by wind-induced motions such as accelerations and lateral deflections. Consequently, the building's structural stiffness and dynamic (vibration periods and damping) properties become important parameters in the determination of such motions. The approximate methods and empirical expressions used to quantify these parameters at the design phase tend to yield values significantly different from each other. In view of this, there is a need to examine how actual buildings in the field respond to dynamic wind loading in order to ascertain a more realistic model for the dynamic behavior of buildings. This paper describes the findings from full-scale measurements of the wind-induced response of typical high-rise buildings in Singapore, and recommends an empirical forecast model for periods of vibration of typical buildings in Singapore, an appropriate computer model for determining the periods of vibration, and appropriate expressions which relate the wind speed to accelerations in buildings based on wind tunnel force balance model test and field results.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.147-149
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• 2000

Samsung Superconducting Test Facility (SSTF) will be built at SAIT, Taejeon. The superconducting cables to be used for KSTAR magnets are going to be tested in SSTF. The background magnet in SSTF is needed to simulate harsh magnetic environment for testing short CICC samples as well as full-scale magnets. The main coils can make central magnetic field of up to 8 Tesla and the blip coils can maintain fast ramping rate of 20T/s. The cancellation coils reduce the disturbance of main coils due to blip coils. The magnetic field distribution of these coils has been obtained with finite element method as well as the direct integration method.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1046-1050
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• 2010

During construction of a sea-crossing bridge grouting was used to fill densely the space between the bottom of caisson and the ground. This grout mixture was mixed with an anti-washout admixture after locating accurately the pre-cast caisson on three concrete landing pads. This method differs significantly from the costly conventional method, for bridge foundations offshore, where concrete is placed in situ after excavating inside of a temporary concrete coffering wall. To verify the grouting method in advance, the full-scale field tests were performed twice on land. After identifying the fluidity of the grout material to be filled, finding some possible problems with the main construction and revising the original design, the main construction has been continuing successfully with 20 caissons completed to date. The purpose of this paper is to introduce for the first time in Korea the grouting method including the automatic and the manual monitoring system based on the main construction of the caisson foundation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.375-381
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• 2017

A full-scale field test was conducted to investigate the arching effect of an embankment pile. The arching effect calculated from the test results was compared with theoretical values. Measurements obtained from a load cell and an earth pressure cell during the field test reflected the arching effect of the embankment pile well. The arching effect measured by load cells for an embankment height of 3m or less was smaller than the theoretical value with the assumption of plain strain.The measured effect for a height of 4 m or more was larger than the theoretical value. In contrast to the consistent decrease of the theoretical arching effect, the arching effect obtained from the field test shows continually increasing trends. The arching effects calculated from the earth pressure cells were greater than those from the theory under the plain strain assumption, but the trend was similar to the theoretical one. The arching effects measured by the earth pressure cells an embankment heights of 2, 3, 4, 5, and 6 m were 1.05, 1.23, 1.29, 1.28, and 1.29 times greater than those from the theory under the assumption of plain strain. The arching effects from the field test were much greater than those from the theory under the installation of a pile grid.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.329-336
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• 2007

For scaling of the gradient of misfit function, we develop a new pseudo-Hessian matrix constructed by combining amplitude field and pseudo-Hessian matrix. Since pseudo- Hessian matrix neglects the calculation of the zero-lag auto-correlation of impulse responses in the approximate Hessian matrix, the pseudo-Hessian matrix has a limitation to scale the gradient of misfit function compared to the approximate Hessian matrix. To validate the new pseudo- Hessian matrix, we perform frequency-domain elastic full waveform inversion using this Hessian matrix. By synthetic experiments, we show that the new pseudo-Hessian matrix can give better convergence to the true model than the old one does. Furthermore, since the amplitude fields are intrinsically obtained in forward modeling procedure, we do not have to pay any extra cost to compute the new pseudo-Hessian. We think that the new pseudo-Hessian matrix can be used as an alternative of the approximate Hessian matrix of the Gauss-Newton method.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1319-1327
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• 2001

The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed 1:1 scale. The model experiments were executed at a lower pressure than that in a real gas turbine. Combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure and NOx emission were measured at partial and full loads for both model and on-site testing. The comparison of these items in the stand and field test results led to has the development of a method of calculation and the improvement of gas turbine combustors.

• Earthquakes and Structures
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• v.19 no.3
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• pp.157-174
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• 2020

The in-situ pushover test differs from the shake-table test because it is performed outdoors and thus its size is not restricted by space, which allows us to test a full-size building. However, to build a new full-size building for the test is not economical, consequently scholars around the world usually make scale structures or full-scale component units to be tested in the laboratory. However, if in-situ pushover tests can be performed on full-size structures, then the seismic behaviors of buildings during earthquakes can be grasped. In view of this, this study conducts two in-situ pushover tests of reinforced concrete (RC) buildings. One is a masonry-infilled RC building with openings (the openings ratio of masonry infill wall is between 24% and 51%) and the other is an RC building without masonry infill. These two in-situ pushover tests adopt obsolescent RC buildings, which will be demolished, to conduct experiment and successfully obtain seismic capacity curves of the buildings. The test results are available for the development or verification of a seismic evaluation model. This paper uses ASCE 41-17 as the main evaluation model and is accompanied by a simplified pushover analysis, which can predict the seismic capacity curves of low-rise buildings in Taiwan. The predicted maximum base shear values for masonry-infilled RC buildings with openings and for RC buildings without masonry infill are, respectively, 69.69% and 87.33% of the test values. The predicted initial stiffness values are 41.04% and 100.49% of the test values, respectively. It can be seen that the ASCE 41-17 evaluation model is reasonable for the RC building without masonry infill walls. In contrast, the analysis result for the masonry infilled RC building with openings is more conservative than the test value because the ASCE 41-17 evaluation model is limited to masonry infill walls with an openings ratio not exceeding 40%. This study suggests using ASCE 41-17's unreinforced masonry wall evaluation model to simulate a masonry infill wall with an openings ratio greater than 40%. After correction, the predicted maximum base shear values of the masonry infilled RC building with openings is 82.60% of the test values and the predicted initial stiffness value is 67.13% of the test value. Therefore, the proposed method in this study can predict the seismic behavior of a masonry infilled RC frame with large openings.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1343-1344
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• 2006

There have been numerous accelerated aging laboratory tests for evaluating suitability of polymeric materials and devices. Aging test for materials and its full scale device has been conducted. Service experience plays a key role in the utility section of composite insulators. A meaningful and reliable accelerated aging test is needed for evaluating composite insulator. During the service these insulators are subjected to aging stress such as humidity, pollution, and electrical field, and erosion and tracking of the weathershed occurs. This paper presents the criteria of reliability evaluation and evaluation facilities for 22.9 kV suspension composite insulator. We adopt the criteria of reliability evaluation consist of two test methods. One is CEA tracking wheel test for examining the tracking and erosion performance of composite insulator. The other is multi-stress aging test for examining effects of environmental factors such as UV, temperature, humidity, etc on composite insulator.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.99-107
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• 2008

This paper presents the prediction of the actual strength of shear reinforcement on the basis of the concept of effective stirrups. The prediction method incorporating the shear cracking angle was proposed with the estimation by the Modified Compression Field Theory (MCFT). To check the validity of the method, discussion of the current ACI 318-05 and comparison of 39 test results from the literature including author's retrospective test data were made. The influencing factors of compressive concrete strength and type of shear-reinforcement were also investigated. Furthermore, two full-scale beam specimens shear-reinforced with headed bars were tested to demonstrate the applicability of the proposed method.