• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.157-160
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• 2008

The confined concrete subjected multi-axil stresses have been known as the strength of concrete increases significantly. Many researchers have studied in confining effect of concrete, and now are studying in many fields. Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. But sudden brittle failure of lap splices may occur under loading. This study introduces a new method to retrofit RC bridge columns with lap splice which do not have enough ductility during an earthquake. The new method use mechanical external pressure and steel plates around RC columns. The jacketing built following the new method shows good results of increasing the compressive strength and ductility of concrete cylinders. The thicker steel jacket shows larger compressive strength, however, the ductility at failure depends on the welding quality of steel jackets. In this study, The effect of the new method is verified through comparing the results of the compressive tests and analysis results.

• Magazine of the Korea Concrete Institute
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• v.9 no.5
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• pp.233-244
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• 1997

구조적으로 손상을 입은 구조물들에 대한 보강방법으로 강판, 카본쉬트, 아라미드섬유쉬트 등을 이용한 접착공법이 최근 들어 많이 사용되고 있으며 그 중 가장 널리 Tm이는 방법은 강판접착공법이다. 강판접착공법에 대해서는 많은 연구가 진행되어 오고 있으나, 보의 구조적 거동에 영향을 미치는 다양한 인자들의 영향이나 강성, 파괴양상등에 미치는 영향들에 대해서는 체계적인 평가가 이루어지지 않은 실정이며 특히 강판접착공법에서 파괴에 큰 영향을 미치는 박리하중에 대한 연구는 미흡한 실정이다. 따라서 본 연구에서는 일련의 철근콘크리트보부재를 대상으로 하여 주요실험변수로 선행하중의 크기, 강판의길이, 강판의 두께, 앵커볼트의 간격과 유무, 강판의 층수, 측면보강높이를 실험변수로 하여, 휨인장에 대해 강판잡착공법을 적용하여 포괄적인 실험을 수행하였다. 3등분점하중법의 실험결과를 이용하여 처짐, 인장 및 압축 철근의 변형도, 콘크리트와 강판의 변형도를 분석하였고, 이를 토대로 파괴양상과 파괴하중을 분석하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.601-606
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• 1998

In recent years, strengthening by steel plate, carbon fiber sheets, and carbon fiber laminate in spotlighted in order to repair and rehabilitation of R/C slabs. In this study, 3 method of rehabilitation are analyzed from the tests. Test parameters are the width of cracks, the method of repair and rehabilitation, the magnitude of pre-load. Deflection, failure load, strains of reinforcing bar, strains of sheet and plates are measured during tests. The failure mode and separption load analyzed from these measured data.

• KCI Concrete Journal
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• v.13 no.2
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• pp.49-57
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• 2001

Flat-plate buildings are commonly modeled as two-dimensional frames to calculate unbalanced moments, lateral drift and shear at slab-column connections. The slab-column frames under lateral loads are analyzed using effective beam width models, which is convenient for computer analysis. In this case, the accuracy of this approach depends on the exact values of effective beam width to account for the actual behavior of slab-column connections. In this parametric study, effective beam width coefficients for wide range of the variations are calculated on the several types of slab-column connections, and the results are compared with those of other researches. Also the formulas for effective beam width coefficients are proposed and verified by finite element analysis. The proposed formulas are founded to be more suitable than others for analyzing flat-plate buildings subjected to lateral loading.

• Computers and Concrete
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• v.10 no.5
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• pp.489-505
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• 2012

This paper presents a simplified grid beam model for simulating the nonlinear response of reinforced concrete flat-plate structures. The beam elements are defined with nonlinear behavior for bending moment and torsion. The flexural stiffness and torsional strength of the beam elements are defined based on experimental data to implicitly account for slab two-way bending effects. A failure criterion that considers the interaction between the punching strength and slab flexural behavior is incorporated in the model. The effects of bond-slip of slab reinforcement on connection stiffness are examined. The proposed grid beam model is validated by simulating large-scale tests of slab-column connections subjected to concentric gravity loading and unbalanced moment. This study also determines the critical parameters for a hysteretic model used to simulate flat-plates subjected to cyclic lateral loading.

• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.455-470
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• 2013

RC flat plates that have no flexural stiffness by boundary beams may be governed by a serviceability as well as a strength condition. A construction sequence and its impact on the distributions of construction loads among slabs tied by shores are decisive factors influencing immediate and long term performances of flat plate. Over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction. A reshoring work may be helpful in reducing slab deflections by controlling the vertical distributions of construction loads in a multi-shored flat plate system. In this study, a change of construction loads by reshoring works and its effects on deflections of flat plate systems under construction are analyzed. The slab construction loads with various reshoring schemes are defined by a simplified method, and the practical calculation of slab deflections with considering construction sequences and concrete cracking effects is applied. From parametric studies, the reshoring works are verified to reduce construction loads and slab deflections.

• Earthquakes and Structures
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• v.15 no.3
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• pp.285-294
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• 2018

In this study, nonlinear dynamic response of a concrete plate retrofit with Aluminium oxide ($Al_2O_3$) under seismic load and magnetic field is investigated. The plate is a composite reinforced by Aluminium oxide with characteristics of the equivalent composite being determined using Mori-Tanka model considering agglomeration effect. The plate is simulated with higher order shear deformation plate model. Employing nonlinear strains-displacements, stress-strain, the energy equations of column was obtained and using Hamilton's principal, the governing equations were derived. Differential quadrature method (DQM) in conjunction with Newark method is applied for obtaining the dynamic response of structure. The influences of magnetic field, volume percent of nanoparticles, geometrical parameters of column, agglomeration and boundary conditions on the dynamic response were investigated. Results showed that with increasing volume percent of nanoparticles, the dynamic deflection decreases.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.70-77
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• 2018

In this study, the reinforced methods of joints were proposed to improve the structural performance of the enhanced spun reinforced concrete piles with joints. To verify the proposed methods, flexure performance was validated by finite element analysis considering both material and contact nonlinearity. Based on the previous study and those results of the analysis, it is concluded that the structural performance of the current joints system for the enhanced spun RC piles can be enhanced by applying the reinforced joints composed of extended circular band plates and studs. This proposed method showed the nearest structural behavior to the enhanced spun RC piles without joints. This numerical study will be used to further experimental study on the enhanced spun RC piles with reinforced joints.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.234-237
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• 2006

A series of three shear wall specimens was tested under constant axial stress and reversed cyclic lateral loading in order to evaluate the seismic retrofit that had been proposed for the shear wall with the opening induced by remodeling. One of these specimens was tested in the as-built condition and the other two were retrofitted prior to testing. The retrofit involved the use of carbon fiber sheets and steel plates (thickness of 3mm) over the entire face of the wall. The test results show that the ultimate failure modes of the specimens were found to be shear fracture of the wall around the opening and two difference types of retrofitting strategy make the different effects of a rise in the strength of each specimen.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.161-162
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• 2009

In this study, the methodology of calculating the construction loads with considering effects of the shoring stiffness and slab cracks is proposed. Comparisons with the proposed method and the existing methods for construction load calculations were performed for measured shoring loads.