• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.159-168
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• 2005

This study carries out a finite difference nonlinear analysis of anisotropic advanced composite plate structures with various layer sequences. In the numerical analysis of various mechanical problems involving complex partial differential equations, the finite difference method (FDM) developed in this study has an advantage over the finite element method in its ability to avoid mesh generation and numerical integration. Many studies in FDM have been made on clamped or simple boundary conditions using merely an energy approach. These approaches cannot be satisfied, however, with pivotal points along the free boundary. Therefore, this study addresses the nonlinear problem of anisotropic plates by adopting a finite difference modeling elimination of pivotal difference points in the case of a free boundary condition. Complex nonlinear behaviors of composite plate structures for various parameters, especially for layer sequences, are analyzed using the proposed approach.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.141-147
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• 2017

Recently, lots of researches on concrete with high volume mineral admixtures such as ground granulated blast-furnace slag(GGBS) have been carried out to reduce greenhouse gas. The high volume GGBS concrete has advantages such as low heat, high durability, but it has a limitation in practical field application, especially low strength development in early ages. This study investigated the compressive strength and hydration characteristics of high performanc and volume GGBS cement pastes with low water to binder ratio. The effects of fineness($4,330cm^2/g$, $5,320cm^2/g$, $6,450cm^2/g$, $7650cm^2/g$) and replacement(35%, 50%, 65%, 80%) of GGBS on the compressive strength, setting and heat of hydration were analyzed. Experimental results show that the combination of high volume slag cement paste with low water to binder ratio and high fineness GGBS powder can improve the compressive strength at early ages.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.5
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• pp.78-88
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• 2002

본 연구는 울산월드컵경기장의 조경현황을 분석함과 동시에 경기가 끝난 후에도 이곳을 찾는 이용자들의 요구를 수렴함으로써, 향후 경기장조경시에 적용할 수 있는 교훈을 얻기 위한 목적을 두고 진행되었다. 조경현황에 대한 분석 자료는 월드컵경기장 조경을 위한 시공보고서와 도면 및 사진 그리고 현장에서 수집한 제반 자료이며, 이용자요구는 현장에서 조사한 이용행태이다. 연구결과 2002월드컵대회에 대비해서 만들어진 울산월드컵경기장은 건축공간을 확보하는 과정에 서 대규모의 정지작업을 실시하여 과다한 지형변화가 발생하였으나, 친환경적인 법면의 처리와 향토식생의 도입 및 대형목 등의 이식을 통해서 자연과 친화될 수 있는 경관을 조성하고 있었다. 특히 기존의 옥동저수지를 보전.활용하여 친수공간을 확보한 것은 울산월드컵경기장조경에서 주목할만한 특징으로써, 기회요소를 지혜롭게 활용한 좋은 사례가 되고 있다. 한편, 울산월드컵경기장은 시민들이 부담 없이 여가공간으로 활용할 수 있는 공원적 기능이 체육시설에 접목됨으로써 기존의 경기장과는 달기 체육, 문화, 교육기능이 복합적으로 기능하는 세계적 수준의 체육공원으로 개발되었다. 또한, 울산이 가진 역사 문화적 요소를 상징적인 설계언어로 도입한 것은 역사적 장소성을 중시한 설계방법으로서 이것 역시 울산월드컵경기장조경의 특징으로 손꼽을 수 있는 것이다. 특히 울산월드컵경기장은 경기가 종료된 이후에도 시민들에게 적극적으로 개방되고 있으며, 시민공원의 성격으로 이용될 수 있는 다원적 기능을 가지고 있어서 주목되는 바가 컸다 이와 같은 경기장 건설의 개념은 공간의 이용을 시간적으로 확장하는 것으로서 향후 보다 적극적으로 도입되어야 할 현대적 개념의 공간이용으로 볼 수 있다. 연구결과 향후 울산월드컵경기장이 시민의 휴식과 문화공간으로서 보다 적극적으로 기능하기 위해서는 경기장은 물론 공원으로 이용되는 공간에 대한 철저한 유지관리와 운영관리에 대한 노력이 필요할 것으로 생각된다. 특히 자연환경이 훼손된 부분에 대해서는 원래의 생태적 질서가 회복될 수 있도록 더욱 노력하여야 할 것이다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.84-89
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• 2018

Recently, study on self-healing materials have been performed to increase the life by repairing the damage of structures themselves, which are difficult to repair or require high maintenance costs. A water permeability test has been widely used for the evaluation of self-healing performance. However, in the self-healing performance test method, the initial crack width of the concrete greatly affects on the self-healing performance but it does not have a consistent standard. Therefore, in this study, the correlation between crack and permeability and that between time and permeability were analyzed based on crack width and permeability. In addition, since the initial crack width measured by optical microscope is not reliable, the value is derived from the Poiseuille flow and the tendency of time-permeability and time-crack width are analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.90-96
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• 2018

In this study, the mechanical and micro-structural change of cement pastes incorporating Stainless-Steel Slag Argon Oxygen Decarburization Slag (STS-A) containing ${\gamma}-C_2S$ as a carbon capture materials were investigated with carbonation curing condition. ${\gamma}-C_2S$ is non-hydraulic, therefore does not react with water. But ${\gamma}-C_2S$ has a reactivity under carbonation curing condition with water. The reaction products fill up the pore in pastes. The microstructure of STS-A blended cement pastes could be densified by this reaction. The pore structure of cement pastes incorporating STS-A was measured using mercury intrusion porosimetry (MIP) after carbonation curing ($CO_2$ concentration is about 5%). Also the fractal characteristics were investigated for the effect of carbonation curing on the micro-structural change of paste specimens. From the results, the compressive strength of carbonated specimens incorporating STS-A increased and pore-structure of carbonated paste is more complicated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.60-67
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• 2020

Recently, many studies have been conducted on the structural behavior of HPFRCC, but most of the studies focused on the flexural behavior while studies on the shear behavior are limited. In this study, a model has been developed to reasonably predict the shear strength of a HPFRCC beam without stirrups. To develop the model, a HPFRCC beam was simply idealized with upper & lower chords resisting bending moment and a web shear element resisting shear forces. Then, taking into the account of the tensile behavior of HPFRCC, the main diagonal compressive strut angle and shear stress of the web shear element were evaluated on shear failure. Then, the shear strength of the HPFRCC beam could be evaluated. For the verification of the proposed model, the predictions by the proposed model were compared with the test results of 48 HPFRCC beams exhibiting shear failure. The results showed that the proposed model reasonably predicted the actual shear strength with an average of 1.045 and CoV of 0.125. This study are expected to be useful for related researches and design of members or structures to which HPFRCC is applied.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.78-87
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• 2012

This study is for developing a system for electro-deposition utilizing sea water containing various ions like calcium and magnesium. This is the first step research for the final goal which is a development of anti-corrosive steel for RC structure, so that this paper is mainly focused on the development for electro-deposition system. Optimum conditions for steel coating is obtained through various tests considering anode type, temperature, duration time, and current density. The composition of electro-deposition is analyzed through SEM, EDS, and XRD and it is evaluated to be $CaCO_3$ and $Mg(OH)_2$. Through measuring polarization potential and current density in the coated steel, the coating layer from the developed system is evaluated to have high resistance to steel corrosion. Additional tests and discussions on durability and structural performance in the coated steel from this work will be performed for the second step research.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.127-132
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• 2018

The amount of generated Circulating Fluidized Bed Combustion ash (CFBC ash) is annually increasing, but most CFBC ash has been landfilled and discarded due to the limited utilization. The major chemical compositions of CFBC ash are $SiO_2$, CaO and $CaSO_4$, which could form hydration products by reacting with water as self-cementing property such as cement. The purpose of the this study is to derive the optimal mix proportions to improve polymer-modified mortar with the use of CFBC ash which has the self-cementing property. In order to develop polymer-modified mortar, three mix proportions were determined, and fundamental properties for the mixtures were obtained. As a result, the optimal mixture containing 10 percent of silica fume, 1.0 percent of polymer and 3.5 percent of expansive additives were proposed in this study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.119-126
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• 2018

Recently, the production of circulating fluidized bed combustion ash has been increased in thermal power plants. The addition of limestone for the desulfurizing effect of circulating fluidized bed boiler ash increases the content of CaO and $SO_3$ contained in ash, which is higher than the free fly ash in general fly ash. Unlike conventional fly ash, the circulating fluidized bed combustion ash has a high reactivity when it comes into contact with water due to its hydraulic properties and high free-CaO content. The aim of this study is to investigate the possibility of non-sintered binder by using self-cementing properties of circulating fluidized bed combustion ash. The mechanical and hydration characteristics were investigated according to the content of CFBC ash. In addition, the effects of gymsum type and content on the compressive strength and micro-structure of non-sintered binder pastes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.190-198
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• 2011

The precast production has many advantages by fast construction period, labor-saving and high quality. In recent years, the application of the precast product has been increased in the earth retaining wall field. This paper presents the results of the numerical analysis that was carried out to evaluate the dynamic stability of precast and prestressed earth retaining wall under moving train load. The two-dimensional FEM analysis was used to the numerical analyses. The train load to act on trackbed is combined by the real measured roughness phase angle and quasi-static load. The dynamic stability is analysed by the displacement, acceleration and stress under moving train load at each specified location. The results of the analysis show that the precast and prestressed retaining wall has very stable capability for the railway.