• Geomechanics and Engineering
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• v.11 no.1
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• pp.161-175
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• 2016

A series of experimental studies are conducted on the deformation and shear strength property of compacted loess. The results reveal that the relationships of both the initial moisture content (w) and the initial degree of compaction (K) of compacted loess with cohesion (w) and the angle of internal friction (${\varphi}$) are linear. The relationship between the secant modulus ($E_{soi}$) and K is also linear. The relationship between $E_{soi}$ and w can be fitted well by a second-order polynomial. Further, when the influences of w and K are ignored, the relationship between the confined compression strain (${\varepsilon}$) and vertical pressure (p) can be expressed by a formula. A correction formula for the deformation of compacted loess caused by a change in w and K is derived on the basis of the study results.

• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.17-30
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• 2004

In this study, a new formula of settlement at the head of IGM was suggested and the applicability of suggested formula was verified with field test results. This suggested formula was the function of the settlement at the shaft head and the elastic compression of shaft. The applicability of suggested formula was verified with the result of in-situ load test. Also, the bearing capacity of drilled shaft with the IGM's theory was compared with those of classical theories. The results showed that classical method showed smaller values of bearing capacity than those of field load test data. The results of analysis also showed that the suggested formula and IGM's theory were applicable for the estimation of bearing capacity with the increase of shaft settlement. Especially, settlement correction factor($k_m$), which reflects ground condition and load transfer characteristics, increases as the applying load and shaft deformation increase. This suggested formula was applicable for medium density or higher density of soil condition and $k_m=1$ means yielding load for firm soil condition.

• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.87-93
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• 2012

Many longitudinally-arranged pipes in ships are equipped with loops as a measure to reduce stresses caused by displacement loads conveyed from the hull girder bending and/or thermal loads of carried fluid of non-ambient temperature. But as the loops have some negative effects such as causing extra manufacturing cost and occupying extra space, the number and the dimensions of the loops need to be minimized. In the meanwhile, a design formula for pipe loops has been developed by modeling them as a spring element of which stresses and axial stiffness are calculated based on the beam theory. But as the beam theory turns out to be inappropriate to deal with the complex structural behavior in the curved corner portion of the loop, this paper aims at improving the previously developed design formula by adopting correction factors which can allow for the gap between the results of beam theory and a more accurate analysis. This paper adopts a finite element analysis with two-dimensional shell elements with some validation work for it. The paper ends with a sample application of the proposed formulas showing their accuracy and efficiency.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.379-384
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• 2018

This study showed the development process of structural design method of BHB(Blast Hardened Bulkhead) which are applicable in preliminary design stage. In the previous 1st report, the simplified structural scantling equations of BHB were formulated theoretically using the modified plastic hinge method supplemented by considering the membrane effects due to large plastic deformation. And the scantling methodology of plate thickness and section area of stiffeners of the curtain plate type BHB was dealt with. In the present 2nd report, derivation process of the correction factors which can adjust the developed scantling equations considering the uncertainties contained in the design parameters was introduced. Considering the actual BHB structures of 3 warship, the correction factors for the developed scantling equations for curtain plate type BHB were derived. Finally the applicability, validity of them and the strategy of future improvement were considered.

• Journal of Korean Society for Geospatial Information Science
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• v.11 no.3 s.26
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• pp.23-34
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• 2003

Currently, the efficiency of GPS has been increased in the various precise survey like as the control survey and the navigation etc. Also, it is widely used in the deformation analysis of the structure, the measurement of the marine tides, the measurement of the river level and the topographic monitoring of seabed or riverbed by combined the measurement equipment for depth. In this study, we intend to increase in efficiency of the topographic monitoring of seabed or riverbed by combined with DGPS, RTK GPS and echo sounder. For this study, we defined the error correction of the echo sounder with the experiment of water tank which is considered the characteristic of estuary riverbed and then we developed the s/w for 3-dimensional monitoring of estuary riverbed and applied the s/w to field test and improved the various problems. On analyzing topography of estuary riverbed by combined GPS with echo sounder, the draught error which is yielded to change of length from the water surface by the movement of survey vessel to the end of the transducer was eliminated by geometrical rearrangement and we defined the correction formula $z=BM+SAH-DBR_{(i)}-DRT-ED$. The sounding error about the echo sounder and characteristic of estuary riverbed was found by understanding the relation of average diameter ind residual error and we defined correction formula, $Y=0.00474{\ast}ln(X)-0.0045$ by the regression analysis. and then we verified applicability of correction formula.

• Journal of the Korean Society of Hazard Mitigation
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• v.1 no.2 s.2
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• pp.93-101
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• 2001

The objective of this study is to derive a shrinkage correction formula that considers temperature effect and to develop a methodology for the improved prediction of the long-term behavior of the FCM bridges by considering seasonal temperature variations in-situ. Thereby, current formulation were performed by using the actual experimental shrinkage data including seasonal temperature variation. The investigation of the long-term behavior of the FCM bridge was performed on the construction site in order to decide applicability of the shrinkage formula Numerical results by the general method indicates inaccurate values of total strain when considering real strain, whereas the applied method demonstrates a good agreement in the resultant strain. In consequently, the applied method will improve the prediction of the long-term deformation of the FCM Bridges.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.3
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• pp.148-156
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• 2015

Deck plates of ships or offshore structures would make out-of-plane distortion for their thin thickness. These distortions are usually straightened by thermal straightening such as flame heating method. After thermal straightening, the blocks are lifted and moved by cranes to assemble it at dry-dock stage. After this lifting process, out-of-plane deformation again happens frequently. And then, they continuously cause quality and accuracy problems in the final dry-dock process. So, it takes more time for repair and correction working. According to preceding research, the lifting process by cranes would offset the effect on thermal straightening. The target of this study is to develop a methodology analyzing the remaining efficiency of thermal straightening after block lifting. The development was based on the assumption of yield state at straightening region. Therefore the remaining efficiency was obtained by different stiffness slope while lifting & relieving. The efficiency formula was designed using inherent strain, and we made a table of zero-efficiency by cooling speed and class rule's steels. As a result, if the stress orthogonal to straightened line is calculated during lifting analysis by FEA, the efficiency can be obtained linearly to the values in the table. Finally, even optimized carling position can be designed by considering the regional data from series project and welding region on deck.

• Smart Structures and Systems
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• v.30 no.4
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• pp.353-369
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• 2022

In this paper, a new sensor chip with frequency reconstruction range of 2.252 GHz ~ 2.450 GHz is designed and fabricated. On this basis, a self-designed "T-shaped" shell is added to overcome the disadvantage of uneven deformation of the traditional steel shell, and the range of the sensor chip is expanded to 0 kN ~ 96 kN. The liquid metal antenna is used to carry out a step-by-step loading test, and the relationship between the antenna resonance frequency and the pressure load is analyzed. The results show that there is a good linear relationship between the pressure load and the resonant frequency. Therefore, the liquid metal antenna can be regarded as a pressure sensor. The cyclic loading and unloading experiments of the sensor are carried out, and different loading rates are used to explore the influence on the performance of the sensor. The loading and unloading characteristic curves and the influence characteristic curves of loading rate are plotted. The experimental results show that the sensor has no residual deformation during the cycle of loading and unloading. Moreover, the influence of temperature on the performance of the sensor is studied, and the temperature correction formula is derived.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.3
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• pp.249-258
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• 2012

In this study, the epoch adjustment model was developed to correct GPS precise point positioning result to be suitable for the current geodetic datum of Korea which is tied at past epoch statically. The model is based on the formula describing crustal movements, and the formula is composed of several parameters. To determine the parameters, the data gathered at 14 permanent GPS stations for 10 years, from 2000 to 2011, were processed using GIPSY-OASIS II. It was possible to determine the position of permanent GPS stations with an error range of 16mm and the position of check points with an error range of 12mm by appling the model to GPS precise point positioning result. It is considered that more precise model could be calculated by using GPS data of more permanent GPS stations.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.410-414
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• 2014

In this study, the behavior of urban subway tunnels is measured using instrumentation sensors installed in the lining concrete inside subway tunnels in order to analyze their behavior according to temperature variations. It is observed that the stresses of the concrete lining, tunnel convergence, and cracks change according to the temperature variations. However, the crack deformation differs depending on the size and status of the crack. In addition, this study proposes a correction formula for the lining stress and tunnel convergence through numerical analyses of the concrete lining according to the temperature variations. The results of this research can be used in the tunnel maintenance considering the tunnel behavior depending on the temperature variations in the tunnel.