• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.23-31
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• 2003

Over the past half century, borehole seismic surveys have been diversified into the three techniques such as crosshole, downhole, and suspension logging according to their devices and testing configurations. These field techniques have been improved, in terms of equipment and testing procedures, and are very valuable in the evaluation of ground characteristics for geotechnical and earthquake engineering problems. Yet, despite the importance and significance of the techniques as engineering tools, the techniques are not much used as standard penetration test (SPT) by practicing engineers. The possible explanations are cost and operational difficulties of the surveys as well as sophistication and complexity of the devices. An in-hole seismic method has been developed to meet the requirement of economical testing cost and practicality in engineering practice to measure dynamic soil properties. The prototype in-hole probe developed herein is small and light enough to be fit in three-inch boreholes and to be handled with bare hands. The performance of the source has been evaluated through extensive crosshole tests at various sites. The in-hole seismic method was adopted at three test sites and verified by comparing with crosshole results.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.281-293
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• 2002

Empiricism has characterized the traditional methods of pile design; in essence, pile design recommendations are based on the accumulated knowledge of pile behaviour based on the construction and subsequent load testing of piles in soil and rock. In this paper, the traditional approaches to design of piles in rock will be briefly reviewed. It will be shown that the unrelated empirical relationships developed fur rock lead to considerable uncertainty in the design of piles. A new method for predicting the shaft resistance of piles socketed into rock, and based on fundamental principles is outlined. It is shown that the shaft resistance predictions of this method agree well with the field test data for rock and hard soil. It is demonstrated by way of a limited parametric study that shaft roughness and socket diameter are critical factors in the performance of piles constructed in these materials. The application of the method to piles socketed into the granites and gneisses of Korea is discussed by way of a case study and by reference to recent direct shear tests on these rocks.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.25-34
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• 2011

In general, many instrumentations of slope rely on theory or experience because on-site accessibility and long term instrumentation are difficult to conduct the instrumentation of slopes. Also the prediction of disaster is very difficult. Therefore experimental research was conducted about an effective method to predict collapse of slope and on-site applicability in this study. The collapse of slope was able to be predicted by applying AE sensor which we call WEAD to the failure criteria. The parameters of AE generated during the collapse of slope were secured through bending shear test. Test construction was applied to the slope with a history and a possibility of collapse. As a result, it is shown that AE parameters do not exceed the failure criterion and is found to be stable slopes. As the real symptoms of collapse did not appear, AE was found to have excellent applicability.

• Journal of the Korean Geotechnical Society
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• v.33 no.7
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• pp.29-41
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• 2017

There are uncertainties about the seismic load caused by seismic waves, which cannot be predicted due to the characteristics of the earthquake occurrence. Therefore, it is necessary to consider these uncertainties by probabilistic analysis. In this paper, procedures to develop a fragility curve that is a representative method to evaluate the safety of a structure by stochastic analysis were proposed for cut slopes. Fragility curve that considers uncertainties of soil shear strength parameters was prepared by Monte Carlo Simulation using pseudo static analysis. The fragility curve considering the uncertainty of the input ground motion was developed by performing time-history seismic analysis using selected 30 real ground input motions and the Newmark type displacement evaluation analysis. Fragility curves are represented as the cumulative probability distribution function with lognormal distribution by using the maximum likelihood estimation method.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.83-91
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• 2002

A common form of construction for apartment buildings consists of walls and coupling elements. But, the structural behavior of coupling elements are very complex and affected by the properties of coupling elements. The objective of this study is to estimate the behavior of coupling elements in wall-dominant systems. For the purpose of this study, two wall-slab specimens and two wall-beam specimens were tested. The specimens with different reinforcement layouts were subjected to reversed cyclic loading, consistent with coupling action, with increasing imposed inelastic deformations. From the results of this study, 1) in coupling slabs, the stresses were not uniform across the width, 2) the effective width of coupling slabs was found smaller than that of predicted from previous studies, 3) diagonally reinforced coupling beam with slab showed larger ductility and more amount of energy dissipation to be attained compared with conventionally reinforced coupling beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.121-127
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• 2010

An experimental study of composite beam with perforated fiber reinforced polymer(FRP) plank as a permanent formwork and the tensile reinforcement was performed. A combined formwork and reinforcement system can facilitate rapid construction of concrete members since no conventional formwork is needed, which requires time consuming assembly and dismantling. In order for a smooth FRP plank to act compositely with the concrete, the surface of the FRP needs to be treated to increase its bond properties. Aggregates were bonded to the FRP plank using a commercially available epoxy and perforated web of plank. No additional flexural or shear reinforcement was provided in the beams. For comparison, two control specimens were tested. One control had no perforated hole in the web of FRP plank and the other had internal steel reinforcing bars instead of the FRP plank. The beams were loaded by central patch load to their ultimate capacity. This study demonstrates that the perforated FRP plank has the potential to serve as a permanent formwork and reinforcing for concrete beam.

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.1 s.160
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• pp.68-76
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• 2007

The purpose of this study is to investigate change of mechanical and physical properties, shape behavior and hand value in weft knit when rib stitch and milan stitch are combined. The knit stitches used in this study are plain stitch, half milan rib stitch, milan rib stitch, $2{\times}1$ rib stitch, $2{\times}1$ half milan rib stitch and $2{\times}1$ milan rib stitch. We analyzed physical and mechanical properties(tensile, bending, shear, compression, surface properties, thickness and weight) of the knit stitches and calculated their primary hand value and total hand value through translational formulas using the KES(Kawabata Evaluation System). The results are as follows; In evaluation of mechanical properties and hand values of knit stitches, plain stitch had the highest flexibility and the lowest T.H.V. as women's winter knit wear. Since $2{\times}1$ rib stitch had too high elongation in one direction, although it had the highest T.H.V, it needs to be careful when plain stitch and $2{\times}1$ rib stitch are applied for women's winter knit wear. Since Milan rib stitch and $2{\times}1$ milan rib stitch had high T.H.V. similarly, it is considered that they are suitable for women's winter knit wear. Specially, when Milan stitch is combined with $2{\times}1$ rib stitch, its shape stability and fullness are contained and flexibility is added on it. Therefore, $2{\times}1$ milan rib stitch can be also applied for women's winter knit wear.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.2
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• pp.97-105
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• 1984

We have, at present, found some studies on the optimum design of reinforced concrete about the simple slab but very few about the multi-story and multi-span slab. The aim of this study is to make a optimum design of coalesced beam and column slab constructure. Some results of the evaluation by using the optimalized algorithm that was developed in this study are as follows. 1. Slab was mainly restricted by the constraint of effective depth, bending moment, and minimum steel ratio; especially the effective depth was the preceding crifical constraint. In the optimum design of slab, therefore, the constraint about the minimum thickness should be surely considered. 2. This optimum design is good economy as much as some 3.4&~6.2% compared with the conventional design method. 3. In most case, it was converged by 3 to 6 iteratin regardless of the highest or lowest value and only in case of N=1 and case 1, there is a little oscillation after the 3rd iteration but it makes no difference in taking either the highest or lowest value because the range of oscillation is low as much as about 1.2% of the total construction cost. 4. In this study the result seeking for constraints that make no difference in the least cost design shows that shear stress and maximum steel ration may not be considered in it. 5. Bending moment was converged by one time iteration regardless of the initial value, while steel ratio, in most case, by two times because both bending moment and steel ratio are the fuction of effective depth.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.147-155
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• 2010

A prediction model of resilient modulus($E_R$) was developed for recycled crushed-rock-soil mixtures. The evaluation of $E_R$, using the "orthodox" repeated loading tri-axial test, is not feasible for such a large-size gravelly material. An alternative method was proposed hereby using the subtle different modulus called nonlinear dynamic modulus. The prediction model was developed by utilizing in-situ measured shear modulus($G_{max}$) and its reduction curves of modeled materials using the large free-free resonant column test. A pilot evaluation of the model parameters was carried out for recycled crushed-rock-soil-mixture at a highway construction site near Gimcheon, Korea. The values of the model parameters($A_E,\;n_E,\;{\varepsilon}_r\;and\;{\alpha}$) were proposed as 9618, 0.47, 0.0135, and 0.8, respectively.

• Land and Housing Review
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• v.2 no.4
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• pp.553-558
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• 2011

Existing method protruding strands that are embedded in PHC pile to connect pile head and foundation slab shows poor constructibility. As this causes crack and damage in pile head and casualties often occurs in construction site during the work, alternative method called one-cutting method, in which pile above the ground surface and strands embedded in pile are completely cut and pile head is reinforced with rebar for connection with foundation slab, is currently adopted. However, the capacity of details for these methods are not mechanically proved. In this study, in order to suggest proper details of reinforcement for one-cutting method, failures due to lack of shear resistance between infilled concrete and PHC pile are analyzed through experiments and embedded depth with infilled concrete inside PHC pile is suggested. Assuming that slip failure strength is 0.4MPa, which is obtained from experiment conservatively, to have rebar yielded before slip failure, minimum depth of infilled concrete for PHC 450 and PHC 500, need to be 600mm above, and for PHC 600, 1,000mm above.