• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.583-588
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• 2005

In this study, a concrete faced rockfill dam constructed by stages was numerically analyzed, and the numerical results were compared with in situ measurements. The simple incremental elastic and isotropic hyperbolic model was employed to characterize the nonlinear deformation behavior of rockfill material and computational procedure followed construction sequence. A series of large triaxial tests for rockfill material were carried out to obtain mechanical input parameters. According to the analysis results, relative great additional deformation was introduced at the surface of stage-I dam body due to the loading by stage-II construction. The results reveal that numerical analysis can effectively simulate the construction processes, and some meaningful insights about the behavior of CFRD during construction were gained.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.836-841
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• 2008

CFRD (Concrete Faced Rockfill Dam) has been world-widely constructed due to a lot of advantages compared with rockfill dam and recently, sand/gravel materials, instead of crushed rock materials, are also utilized as a main rockfill material to overcome geological and environmental problems. In this paper, the process of water infiltration into the originally unsaturated sand/gravel-fill dam is studied using two-dimensional saturated-unsaturated seepage theory. According to the results of seepage analysis, if the effective drainage zone is installed in the dam, the reservoir water infiltrate into the dam along a downward flow path towards the lower drainage area. The main body constructed with sand/gravel materials, therefore, remains unsaturated.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.367-374
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• 2010

The transfer slab system is a structural system that transfers the loads from the upper shear wall structure to the lower columns. This is a costly system due to a very thick slab, and the relatively high cost can be mitigated by introducing voids in the slab. However, this system of flat plate containing voids is vulnerable to brittle failure caused by punching shear in vicinity of slab-column connection. Thus, the punching shear capacity of the void system is very important. However, the current code doesn't provide a clear design provision for the strength of slabs with a void section. In this study, experimental study was conducted to investigate the punching shear strength of the void slab system. The shear strength of the specimens was predicted by current code and previous researches. In result, the punching shear strength of the void system is determined as the least value calculated at critical section located a distance d/2 from the face of the column and the center of the void section using the effective area at critical section.

• Steel and Composite Structures
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• v.22 no.1
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• pp.141-159
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• 2016

Commonly in steel frames, steel beam and concrete slab are connected together by shear keys to work as a unit member which is called composite beam. When a composite beam is subjected to positive bending, flexural strength and stiffness of the beam can be increased due to "composite action". At the same time despite these advantages, composite action increases the strain at the beam bottom flange and it might affect beam plastic rotation capacity. This paper presents results of study on the rotation capacity of composite beam connected to Rectangular Hollow Section (RHS) column in the steel moment resisting frame buildings. Due to out-of-plane deformation of column flange, moment transfer efficiency of web connection is reduced and this results in reduction of beam plastic rotation capacity. In order to investigate the effects of width-to-thickness ratio (B/t) of RHS column on the rotation capacity of composite beam, cyclic loading tests were conducted on three full scale beam-to-column subassemblies. Detailed study on the different steel beam damages and concrete slab damages are presented. Experimental data showed the importance of this parameter of RHS column on the seismic behavior of composite beams. It is found that occurrence of severe concrete bearing crush at the face of RHS column of specimen with smaller width-to-thickness ratio resulted in considerable reduction on the rate of strain increase in the bottom flange. This behavior resulted in considerable improvement of rotation capacity of this specimen compared with composite and even bare steel beam connected to the RHS column with larger width-to-thickness ratio.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.109-119
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• 2007

As the number of CFRD constructions increases, the necessity of an accurate assessment on its behavior also has been increasing. The performance of concrete faced rockfill dam (CFRD) under different water levels is a great concern of dam engineers and designers in the world. However, domestic research on CFRD design and construction has not been performed sufficiently. This study deals with three centrifuge model tests, mainly investigates quantitatively the deformation of the concrete faced slabs and settlements on the crest with different face slab stiffness. The prototype of a centrifugal model dam is half size of domestic CFRD dam. Detailed material preparation, model design, model set-up, model instrumentation and testing procedures are presented. In order to simulate the prototype concrete faced slab, three kinds of thin fiberglass plates with different thickness were adopted in three model tests. Finally, the centrifuge test results were compared with field measurements of domestic dams, which showed that the centrifuge tests were performed successfully.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.400-413
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• 2016

The horizontal shear capacity when the flange of a steel girder is replaced with 80 MPa concrete is important for its structural safety. In this study, 6 specimens with different interface conditions were designed and fabricated based on the Limit State Design Code on Korean Highway Bridges and static tests were performed to measure the horizontal shear capacity. Not only the resistance factors of the stud shear connector, concrete and reinforcement, but also the surface conditions of the casing concrete and spacing of the horizontal shear reinforcements were used as the experimental variables. The experiments showed that the interfaces between the steel girder and the concrete flange have stronger joint performance than those between the concrete flange and deck slab. To ensure the composite action in the plastic zone, the conservative horizontal shear reinforcement is more important than the roughness in the concrete face.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.105-116
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• 2009

Reinforced concrete (RC) structures have been most widely used because of their good economic efficiency. However, it is very weak in tensile stresses and difficult to control deflection due to the heavy self-weight of concrete. On the other hand, it is generally known that prestressed concrete structures can be the most effective to overcome the demerits of RC structures by using various tendon lay-out and its amount. In the prestressed concrete members, the inflection points of tendons should be placed effectively for the deflection control and the moment reduction. Therefore, in this study, the equations of tendon profiles are derived in terms of polynomials that satisfy essential conditions of tendon geometries such as inflection points and natural curved shapes of tendons placed in continuous members, from which vertical components of prestressing forces can be also calculated. The derived high order polynomial expression for the distributed shape of the upward and downward forces was transformed to an simplified equivalent uniform vertical force in order to improve the applicability in the calculation of member deflection. The influences of vertical forces by tendons to deflection and moment in a continuous slab were also considered depending on the distance from column face to the location of tendons. The applicability of the proposed method was examined by an example of deflection calculation for the cases of slabs with and without tendons, and the efficiency of deflection control by tendons was also quantitatively estimated.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.349-354
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• 2005

In this study, settlement characteristics of 23 CFRD was investigated from monitoring data and the method to estimate the crest settlements considering internal settlement during constructions was proposed. Moreover, crest settlement smaller than 20cm and deflection of face slab smaller than 20cm are not considered to be critical to the stability of large dam whose height is over 40m. Therefore, we assigned the region as safe zone that can be used as a guideline of maintenance of dam. These estimated data can be used in the design, construction and long-term maintenance in domestic CFRD hereafter.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.668-676
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• 2002

Especially, when orthotropic material such as uni-dierectionally woven Carbon Fiber Sheet, resisting only the unidirectional tension, is used to strengthening bridge deck, the direction and width of the strengthening material should be considered very carefully. Thus, analysis of the failure characteristics and the premature failure mechanism of the strengthened decks based on the test results are required. In this study, the premature failure due to the interface debonding of strengthening material of the strengthened deck slab are inquired into failure mechanism through both experiments results and analyses with prototype strengthened deck specimens using carbon fiber sheet. From the test results, interface debonding of strengthening material is occured at the crack face

• Magazine of the Korea Concrete Institute
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• v.4 no.1
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• pp.119-126
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• 1992

AC] 318-H9 Recommended that when the specified compressive strength of concrete in a column is greater than 1. 4 times that specified for a floor system, top surface of the colurrm concrete shall extend 2ftU;OOrrun) into the slab from the face of colUlml to avoid unexpected brittle failure. The purpose of this investigation is to suggest the basic information for the structural safety, The major variables are com preSSlve strength of concrete, shear confinement ratio, and loading types. The test results showed that the load capaCIty of speCImen subjected to monotOI1lC loading had more than that of specimen subjected to one way cyclic loading. The failure modes of specimens under cyclic loading were concentrated at 5-20cm apart region from beam-column joint face and ductility index are increased with increasing of shear confinement ratio. Keywords: ACI 318-89, High and Low Strength Concrete, Beam-Column Joint, Shear Confinement Ratio, Loading Type, Ductility Index, Extension Distance.