• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.209-216
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• 2007

This study reports on the structural characteristics of slab-column connections using fiber-reinforced ultra-high-strength concrete (UHSC). Compression tests were performed on two slab-column and four isolated column specimens. In the column load tests, slab loads were also applied on the slab-column specimens so that the actual confinement condition at the slab-column joint was considered. The main parameter investigated was the "puddling" of fiber-reinforced UHSC. This paper also investigates the effects of some parameters, such as confinement of slab concrete, steel fibers, and concrete strength of the joint, related to the ability of the slab-column specimens and isolated column specimens without the surrounding slab to transmit axial loads from the UHSC columns through slab-column connections. Furthermore, the ACI Code (2005) and the CSA Standard (2004) are compared to the experimental results. The beneficial effects of the puddling of fiber-reinforced UHSC on the transmission of column loads through slab-column connections are demonstrated.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.133-144
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• 2003

The resonant column testing is a laboratory testing method to determine the shear modulus and material damping factor of soils. The method has been widely used for many applications and its importance has increased. Since the first use of the testing method in 1960's, the low-technology electronic devices fir testing and data acquisition have limited the measurement only to the amplitude of the linear spectrum. The limitations of the testing method are also attributed to the assumption of linear-elastic material in the theory of the resonant column testing and also to the incomplete understanding of the dynamic behaviour of the resonant column testing device. Recently, Joh et al. proposed a theory to overcome the limitations of the resonant column testing by deriving the equation of motion and providing its solution for the resonant column testing device. This study proposed the improved data reduction and analysis method for the resonant column testing, thanks to the advanced data acquisition system and the new theoretical solution for the resonant column testing system. For the verification of the proposed data reduction and analysis method, the numerical simulation of the resonant column testing was performed by the finite element analysis. Also, a series of resonant column testing were performed fir Joomunjin sand, which verified the feasibility of the proposed method and revealed the limitations of the conventional data reduction and analysis method.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.31-38
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• 2008

A column test was performed far a new-type column with a quasi static test. An internally confined hollow reinforced concrete column with a corrugated steel tube (ICH RC-CT column) was tested to evaluate its seismic performance. And also, a general solid RC column was tested fur the comparison. The test was performed as planned drift levels. The lateral displacements and the lateral loads of column specimens were measured during tests. From the test results, the ICH RC-CT column showed smaller energy absorbing capacity than a solid RC column but showed the almost equal energy ductility and equivalent viscous damping ratio to those of the solid RC column.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.145-153
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• 2003

The resonant column testing determines the shear modulus and material damping factor dependent on the shear strain magnitude, based on the wave-propagation theory. The determination of the dynamic soil properties requires the theoretical formulation of the dynamic behavior of the resonant column testing system. One of the theoretical formulations is the use of the wave equation for the soil specimen in the resonant column testing device. Wood, Richart and Hall derived the wave equation by assuming the linear elastic soil, and didn't take the material damping into consideration. Hardin incorporated the viscoelastic damping of soil in the wave equation, but he had to assume the material damping factor for the determination of the shear modulus. For the better theoretical formulation of the resonant column testing, this study derived a new wave equation to include the viscosity of soil, and proposed an approach for the solution. Also, in this study, the equation of motion for the testing system, which is another approach of the theoretical formulation of the resonant column testing, was also derived. The equation of motion leads to the better understanding of the resonant column testing, which includes the dynamic magnification factor and the phase angle of the response. For the verification of the proposed equation of motion for the resonant column testing, the finite element analysis was performed for the resonant column testing. The comparison of the dynamic magnification factors and the phase angles far the system response were performed.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.369-376
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• 2003

One of the most complex reinforcement location in the precast building frame is the beam-column joint in a prefabricated construction. It is generally resulted from the vortical bars of column, anchorage bars of beam, and bars of hoop. Particularly the hooked anchorage bars of beam are confronted with hoop and main column bars. The headed reinforcement is considered to place them easily and to reduce the anchorage length in a precast construction. Reversed cyclic loading tests are performed on four beam-column specimens to evaluate the strength and behavior of beam to column and column to column connections. The result of test shows that the headed reinforcement has a similar performance than that of hooked reinforcement in a precast specimen with strong column and weak beam joints. The splice column joints which are used frequently in the domestic fields also show reliable behaviors in those tests with strong column and weak beam joints.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.17-24
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• 2005

Response of reinforced concrete (RC) column-bent piers subjected to bidirectional seismic loadings was experimentally investigated. RC column-bent piers represent one of the most popular shapes of piers used in Korea highway bridges. Four column-bent piers were constructed in 400 mm diameter and 2,000 mm height. Each pier has two circular supporting columns. These piers were tested under bidirectional lateral load reversals with an axial load of $0.1f_{ck}A_g$. The test parameters included : different transverse reinforcement contents and lap-spliced longitudinal reinforcing steels. Test results indicate that the lap splice of longitudinal reinforcing steels have significantly influenced on hysteretic response of column-bent piers similar to previous test results for single columns with corresponding test parameters. Column capacity was changed with the level of transverse confinement. From the comparison of test result for single column under unidirectional loading, the damage of single column was concentrated on lower plastic hinge region but the damage of column-bent piers was scattered to upper and lower plastic hinge region.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.53-65
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• 2007

Column tests were performed for a new type of column, the internally confined hollow concrete filled tube column (ICH CFT column), to evaluate its seismic performance. The seismic performances for two types of ICH CFT columns and a general solid RC column were evaluated and compared by quasi-static tests. The displacements and the lateral loads of column specimens were measured during tests. Ductilities, absorbed energy, equivalent damping ratios, damage indices were calculated from recorded data. From the test results, the ICH CFT column shows superior seismic performances with double moment capacity and larger energy absorbing capacity over that of a solid RC column.

• Journal of the Korean GEO-environmental Society
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• v.18 no.2
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• pp.59-65
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• 2017

The costal reclamation construction is for making reclaimed land by dredging marine clay with seawater, and then bringing the dredged soil into the reclaimed land. During the process, the dredged soil in the reclaimed land undergoes the sedimentation-consolidation process. Among the processes, the consolidation is a very critical factor when planning reclaimed land because of its requiring time and settlement. In order to predict the requiring time and settlement, the Column test, which was suggested by Yano, has been usually used in the nation. However, the test method needs a very long time to identify the characteristic of sedimentation-consolidation of dredged soil. Therefore, in this study, in order to supplement the weakness of the Column test which needs such a long time, and in order to identify the characteristic of the sedimentation-consolidation for dredged soil in a short time, the Geo-centrifuge test was examined as an alternative method. The result considered that Geo-centrifuge test would be useful to identify the characteristic of sedimentation-consolidation for dredged soil efficiently.

• Journal of Korean Society of Steel Construction
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• v.25 no.6
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• pp.635-647
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• 2013

PSRC composite column is a concrete encased steel angle column. In the PSRC composite column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. In the present study, using the performance criteria in KBC 2009, cyclic lateral loading test was performed for PSRC columns to verify the seismic performance. The test parameters were the column type, the use of continuous hoop, and the use of studs for steel angle. 2/3 scale specimens of a conventional composite column and three PSRC columns were tested. The test results showed that the load-carrying capacity predicted by KBC 2009 correlated well with the test results. The specimens also exhibited good deformation and energy dissipation capacities. After concrete cover spalling under cyclic loading, the load-carrying capacity were decreased by buckling of longitudinal bars and steel angles. When continuous hoop was used, the deformability of the PSRC column was improved, preventing early buckling of the steel angles.

• Journal of Korean Society of Steel Construction
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• v.29 no.6
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• pp.411-422
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• 2017

In this study, to investigate the seismic performance of beam-column joints using concrete-encased and -filled circular steel tube(CEFT) columns, two types of tests were performed: (1) column - flange tension test and (2) beam - column joint cyclic load test. In column - flange tension test, test parameters were concrete encasement and connection details: flange width and strengthening rebar. Five specimens were tested to investigate the load-carrying capacity and the failure mode. Test results showed that increase of flange width from 200mm to 350mm result in increase of connection strength and stiffness by 61% and 56%, respectively. Structural performances were further improved with addition of tensile rebars by 35% and 92%, respectively. In cyclic loading test, three exterior beam-column joints were prepared. Test parameters were strengthening details including additional tensile rebars, thickened steel tube, and vertical plate connection. In all joint specimens, flexural yielding of beam was occurred with limited damages in the connection regions. In particular, flexural capacity of beam-column joint was increased due to additional load transfer through tube - beam web connection. Also, connection details such as increase of tube thickness and using vertical plate connection were effective in improving the resistance of panel zone.