• The Journal of Engineering Geology
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• v.2 no.1
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• pp.19-35
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• 1992

aThe elastic properties of the fault zone (width; 3~12m), the shattered zone (width; over 40m) and the fresh rock zone distributed under the core foundation of fill dam in granitic gneiss have widely different range. The deformation moduli of the fresh rock zone, the fault zone and the shattered zone obtained from in situ rock tests - Plate Load Test and Bore Hole Deformation Test - show a range of $42,000~168,000kg/\textrm{cm}^2,{\;}963~2,204kg/\textrm{cm}^2{\;}and{\;}1,238~2,098kg/\textrm{cm}^2$, respectively. The differential settlements hetween the fault zone and the fresh rock zone are expected after the dam construction. Therefore, the displacement of foundation and concrete fill are evaluated using FEADAM 84 program of finite element analysis. The geometric distribution of discontinuifies obtained from the site mapping and drilling is considered in the finite element analysis. The analysis shows that the differential settlements between the fault zone and the fresh rock zone is about 6cm, while that of concrete fill is within 0.5cm.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.3-10
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• 2005

In this study, 1-g shaking table tests on the model of CFR(Concrete-Face Rockfill) type "D" dam in operation and the model of virtual ECRD(Earth Core Rockfill Dam) of which static stability is about the same compared to the model of CFRD were carried out. The purpose of this study is to compare the seismic performance of CFRD and ECRD from the analysis of model test results. Displacement response behavior of the dam was examined through the measurement of vertical and horizontal displacement of model dam crest. Also, amplification characteristics of accelerometers installed with dam height were examined through the measurement of acceleration with dam height. Also, in the case of ECRD, patterns of excess pore pressure generation with dam height were examined. From the test results, it was found that accelerations of dam crest of CFRD and ECRD were amplified about 1.52 times and 2 times compared to the accelerations of dam bottom, respectively. amplification was outstanding at three quarters of dam height from the bottom of dam. This phenomenon was outstanding in case of ECRD. And it was estimated that vertical and horizontal displacement of prototype dam of CFRD were 6.8cm (0.1% of dam height) and 12.3cm (0.2% of dam height), respectively. Also, it was estimated that vertical and horizontal displacement of prototype dam of ECRD were 4.3cm (0.1% of dam height) and 5.5cm (0.11% of dam height), respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1833-1843
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• 2011

Recently, Our society socioeconomically has faced the sudden changes. The retirement of the baby-boom generation is expected to become mainstream amid the falling birth rate and the aging society at the fastest rate in the world. As such a baby-boom generation is a core pillar of our economic development in the 1970s and 1980s, the rehiring difficulties after retirement, the insignificant old age preparation and their welfare and medical problem has become national issue. The government has implemented the policy for promoting the senior entrepreneur to participate productive economic activity by actively utilizing the senior's strength from this year. However, in spite of the importance of such a senior entrepreneur, the research to study the senior's desire and the concrete characteristics of the senior entrepreneur is nonexistence. Therefore, this paper empirically analysed the senior's concrete nature, entrepreneurial intention and the impact on the senior entrepreneurship, which is the core of the success entrepreneur and provided stimulating measure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.131-142
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• 2021

For old piers constructed when seismic design code had not been developed, lap splices usually exist in plastic hinge region. Corrosion of rebars causes decreasement in cross-sectional area of rebar and deterioration of lap-splice behaviour, thereby reducing the seismic performance of the old piers. In this research, according to these characteristics of old piers, test specimens are designed and manufactured considering rebar corrosion, lap splice, seismic design details, and seismic reinforcement. These effects are investigated through experiments. As a result of these experiment, rebar corrosion as well as lap splice reduces displacement ductility. When seismic design details or steel-plate reinforcement are applied, sufficient displacement ductility is expressed. For non-seismically designed specimens, loosening of the lap splice of transverse rebars caused buckling of longitudinal rebars and crushing of core concrete in plastic hinge region . For seismically designed specimen, area-reducing and untying of transverse rebars due to corrosion of rebars caused buckling of longitudinal rebars and crushing of core concrete.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.385-397
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• 2023

This study presents an experiment and analysis to compare the seismic behavior of full-scale reinforced concrete beam-column joint strengthened by prestressed steel strips, externally bonded steel plate, and CFRP sheets. For experimental investigation, five specimens, including one joint without any retrofitting, one joint retrofitted by externally bonded steel plate, one joint retrofitted by CFRP sheets, and two joints retrofitted by prestressed steel strips, were tested under cyclic-reserve loading. The failure mode, strain response, shear deformation, hysteresis behavior, energy dissipation capacity, stiffness degradation and damage indexes of all specimens were analyzed according to experimental study. It was found that prestressed steel strips, steel plate and CFRP sheets improved shear resistance, energy dissipation capacity, stiffness degradation behavior and reduced the shear deformation of the joint core area, as well as changed the failure pattern of the specimen, which led to the failure mode changed from the combination of flexural failure of beams and shear failure of joints core to the flexural failure of beams. In addition, the beam-column joint retrofitted by steel plate exhibited a high bearing capacity, energy consumption capacity and low damage index compared with the joint strengthened by prestressed steel strip, and the prestressed steel strips reinforced joint showed a high strength, energy dissipation capacity and low shear deformation, stirrups strains and damage index compared to the CFRP reinforced joint, which indicated that the frame joints strengthened with steel plate exhibited the most excellent seismic behavior, followed by the prestressed steel strips.

• Steel and Composite Structures
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• v.52 no.4
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• pp.405-418
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• 2024

To study the influence of different reduced beam section (RBS) on the mechanical performance of modular boltedwelded hybrid connection joints (MHCJs), this article uses ABAQUS to establish and verify the finite element model (FEM) of the test specimens on the basis of quasi-static test research. Based on, 14 joint models featuring different RBS are devised to evaluate their influence on seismic behavior, such as joint failure mode, bending moment (M)-rotation angle (θ) curve, ductility, and energy consumption. The results indicate that when the flange and web are individually weakened, they alleviate to some extent the concentrated stress of the core module (CM) and column end steel skeleton in the joint core area, but both increase the stress on the flange connecting plate (FCP). At the same time, the impact of both on seismic performance such as bearing capacity, stiffness, and energy consumption is relatively small. When simultaneously weakening the flange and web of the steel beam, forming plastic hinges at the weakened position of the beam end, significantly alleviated the stress concentration of the CM and the damage at the FCP, improving the overall deformation and energy consumption capacity of joints. But as the weakening size of the web increases, the overall bearing capacity of the joint shows a decreasing trend.

• Magazine of the Korea Concrete Institute
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• v.6 no.6
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• pp.159-172
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• 1994

The relmund hammer test and ultrasonic pulse velocity test methods are commonly used to determine the in-situ compressive strength of concrete. One of the special feature of these methods is that they cannot give consistent and reliable results for variety of structures. In particular, very old existing structures have been generally received sreious environmental affectsand thus the strength prediction will be different from normal structures. The purpose of the present study is, therefore, to propose realistic equations to predict the in-situ strengths of actual old concrete structures. The rebound hammer and ultrasonic pulse velocity tests, carbonation depth measurments and core compressive strength measurements have been carried out for very old hydraulic and seacoast concrete structures spanning from one to about seventy years in age. From these test results, the strength-rebound number relations, the strength-pluse velocity relatinns and the strength-rebound number-pluse velocity relations have been obtained through multiple regression analysis. The present study indicates that the existing equations by nondestructive tests give quite different results from the present data. The proposed equations reasonably well predict the measured data for old concrete structures, especially for low strength concrete. The prediction equations proposed here can be efficiently used in determining the in-situ strength of old concrete structures.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.785-794
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• 2004

This paper describes a new refined truss modeling technique derived based on the well-known relationship of V=dM/dx=zdT/dx+Tdz/dx in a reinforced concrete beam subjected to combined shear and moment loads. The core of the model is that a new perspective on the shear behavior can be gained by considering the variation of the internal arm length along the span, so that the shear resistance mechanism can be expressed by the sum of two base components; arch action and beam action. The sharing ratio of these two actions is determined by accounting for the compatibility of deformation associated to the two actions. Modified Compression Field Theory and the tension-stiffening effect formula in CEB/FIP MC-90 are employed in calculating the deformations. Then the base equation of V=dM/dx has been numerically duplicated to form a new refined truss model.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.11-17
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• 2011

A major source of durability problems in concrete structures is the corrosion of steel by the damage of passivity layer around steel bars. As chloride ion penetration is major cause of the destruction of passivity layer, evaluation of depth and concentration profile of chloride ion is the essential factor for the service-life estimation of concrete structure. To estimate chloride ion penetration characteristics, this paper on the basis of in-situ experimental data investigated the depth and concentration profile of chloride ion penetration. The core specimens are obtained at air-zone, splash zone, and tidal zone in Wando, Masan, Incheon, Gwangyang, and donghae harbors. Colorimentric method measured the chloride ion penetration depth and ASTM C 114 evaluated the concentration profile of chloride ion. Based on experimental data, the influence of harbor location and exposure condition on chloride ion penetration is evaluated.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.39-46
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• 2010

Concrete strength relationship between various strength properties was presented through experimental data from concretes made from different sources of coarse aggregates and fine aggregates, and different amount of cement contents. In the strength relationship were included compression-flexure, compression-split tension, compression-modulus and flexure-split tension. A total of 61~81 data sets were analyzed while each data set is composed of 3 to 4 experimental test data. Using the proposed strength relations, a procedure to reliably estimate modulus values from the LTPP field test section was suggested. Core specimens were taken from 10 LTPP sections on the expressway as well as 4 sections on the national road. Then compressive strengths and modulus were determined in the lab. Finally concrete modulus was averaged with the estimated values by using the derived relationship and experimental values.