• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.481-487
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• 2009

On the paved track, the railway ballast is used as aggregate for the filling layer using the pre-packed concrete method. The condition of ballast as the paved track aggregate ensure that the compressive strength, particle distribution size for the pouring and surface clearance to increase the adhesive strength with mortar. It is profitable to recycle the existing railway ballast as a economical supply. In order to increase recycling characteristic, it is necessary to apply the similar criterion which does not exceed the conventional railway ballast criterion. Consequently, this paper was to investigate physical characteristics of existing ballast, particle size distribution, compressive and flexural strength, bearing capacity and filling capacity to prepare the aggregate's recycling. As a result, optimized aggregate criterion is suggested.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.775-778
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• 2008

기초의 지지방식 중 깊은 기초로 분류되는 말뚝기초는 일반적으로 고강도의 기성강관(Spiral Steel Pipe)을 재료로 한 말뚝을 사용하는 것이 설계 및 시공측면에서 유리하나, 현재 국내 외의 치솟는 건설원자재 비용 및 고유가에 따른 장거리 운반비용의 증가와 더불어 건설현장에서의 경제적 부담이 상당부분 증가되고 있는 실정이다. 특히, 개발후진국을 비롯한 건설 산업의 국제적 진출에 대한 활기와 더불어 해외현장 변동상황(원자재의 수급 문제에 따른 공기지연 및 경제성) 등을 고려하면 이에 대한 능동적인 대처가 절실할 수 있다. 본 사례는 중동지역 $\bigcirc\bigcirc$조선소의 이러한 현장여건을 고려하여 중 소하중 규모의 크레인 기초에 적용된 말뚝의 구조 해석적 검토와 지역 지반조건을 반영하여 안정하고 현지조달이 가능한 말뚝 재료의 변경을 제안한 경우이다. 본 검토에서는 기초 말뚝의 정역학적 허용지지력과 기초지반 조건을 고려한 항타관입 분석 및 크레인 이동하중을 고려한 응력해석을 실시하여 최대연직력, 모멘트, 전단력, 응력비 등을 비교하였으며, 동일한 검토조건하에서 결과를 바탕으로 변경 가능한 말뚝을 선정하였다. 기초지반에 대한 적정안전율을 갖는 허용지지력 및 구조적 안정성의 확보가 가능한 콘크리트 말뚝으로의 변경이 가능하며 상부하중 규모에 따라 설치간격에 따른 파일본수의 증 감이 발생되었다.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.43-51
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• 2008

This study examines shear capacity performance and structural characteristics of reinforced concrete beam using carbon fiber sheet(CFS), g)ass fiber sheet(GFS), glass fiber steel plate(GSP) and carbon fiber bar CB) which are reinforcing materials for reinforced concrete beam in order to produce similar condition to repair and reinforce actual structure and aims to provide data available In designing and constructing reinforced concrete structures under the structural damage. This study obtains the following conclusions. After considering the shear experiment results. it was indicated that the CB reinforced test object was the best in the shear capacity improvement and ductility capacity as it was contained in the concrete and was all operated, Also, GFS reinforced test object indicated the reduced flexural capacity but good shear capacity. GSP reinforced test object had bigger reinforcing strength than other reinforcing test objects. On the other hand, it showed the lowest reinforcement effect as compared section thickness of reinforced material because it showed the bigger relativity a section thickness of reinforced material. If the adherence to the concrete is improved, it will seem to show bigger reinforcement effect.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.7
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• pp.748-751
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• 2013

We perform a wideband radiated pulse coupling analysis of simple building structures using the finite-deference time-domain(FDTD) method. Toward this purpose, the building structures composed of concrete and window materials are assumed and we numerically model the electrical properties of each material. In this work, we apply a dispersive FDTD algorithm for the electromagnetic analysis of building structures and investigate their shielding effectiveness in the frequency range of 50 MHz to 1 GHz.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.716-716
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• 2012

최근 항만구조물을 설계함에 있어 대수심 및 고파랑 지역에 설치되는 외곽시설의 상당수는 직립식 케이슨 혼성제 단면을 채택하고 있다. 이는 상대적으로 수심이 깊고, 설계파와 같은 외력 조건이 크기 때문에 경사제에 비하여 경제성 및 시공성이 유리하기 때문으로 판단된다. 그렇지만 아직까지 소규모 항만 및 어항시설에 있어 경사제를 채택하고 있다. 본 연구에서는 이와 같은 경사식 구조물을 설계함에 있어 월파에 의한 방파제 배후 경사면에 피복된 피복재의 안정성을 검토하며, 실험사례를 통하여 최적 설계안 및 설계방향을 제시하고자 한다. 경사식 구조물 배후 사면 피복재의 안정 중량에 대해서는 우리나라의 항만 구조물의 설계기준(항만 및 어항설계기준, 2005) 뿐만 아니라 국외의 설계기준(CEM, Coastal engineering manual, 2005 등)에서도 아직까지 설계법을 제시하고 있지 않고 있다. 본 연구에서 수행한 단면 수리모형실험에서는 1/50의 실험축척을 적용하여 대상 외곽 구조물에 대하여 수리특성과 안정성을 검토하였다. 특히 경사제 배후의 안정성 확보를 위하려 동일 구간에 대하여 설계파 조건 등을 중심으로 총 9개의 실험안을 설정하여 안정성을 검토하였다. 아래 그림은 이중 초기 설계안과 최종적으로 제안된 제시안에 대한 완성모형, 실험장면 및 결과이다. 일반적으로 접안시설과 외곽시설이 어느 정도 이격되어 있어 적정량의 월파를 허용할 수 있는 경우 상치콘크리트의 형상 및 마루높이을 변경하여 월파의 낙하 및 도달거리를 배후면의 안정성을 확보할 수 있을 정도로 유도함으로써 안정적인 구조물 설계가 가능할 것으로 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.199-204
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• 1999

A recent application of advanced composite materials, primarily fiber-reinforced plastic (FRP) composites, in structures is the reinforcement of conventional structural materials, such as concrete and glued-laminated timber (glulam), to increase their performance. In particular, the construction of large-scale glulam structures usually requires members with large depths and to significantly increase the stiffness and strength of glulam, the members can be reinforced with FRP at top and bottom surfaces. In this paper, glulam beams reinforced with GFRP strip are tested under 2-point bending and results are compared with numerical solution using layer-wise beam theory.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.33-40
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• 2013

The cement industry brought very severe environment problems with massive carbon dioxide during its production. To solve this problem, attempts on Alkali-Activated Slag (AAS) concrete that perfectly substitutes industrial by-products such as ground granulated blast furnace slag (GGBFS) for cement are being actively made. AAS concrete is possible to have high strength development at room temperature, however, it is difficult to ensure the working time due to the fast setting time and the loss of workabillity because of the alkali reaction. In this study, the early age properties of alkali activated slag mortar are investigated to obtain the fundamental data for AAS concrete application to structural members. The water-binder ratio (W/B) was fixed at 0.35 and sodium hydroxide and waterglass as alkali activator was used. The compressive strength, the flow and the ultrasonic pulse velocity were measured according to the type of superplasticisers, which were naphthalene(N), lignin(L), melamine(M) and PC(P), up to a maximum of 2 percent by the mass of GGBFS. The results showed that adding melamine type of superplasticizer improved the fluidity of AAS mortar without decreasing the compressive strength, while naphthalene and polycarbonate type of superplasticizer had little effect on the fluidity of AAS mortar.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.271-282
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• 2008

Specific joint devices composed of end-plates and through bolts are under development to assemble steel beams to PC columns efficiently by dry construction method for the PCS structural system, of which major structural components are precast concrete columns and steel beams. Seismic performance of the joint devices had been evaluated by experimental tests in the previous studies and it was showed that all the performance requirements regarding to strength deterioration, stiffness degradation and energy dissipation capacity were satisfied to the criteria of ACI requirements, but the initial stiffness was not. In order to find out possible causes of the insufficient rigidity of the joint devices and provide the proper measures to improve the performance of the joint accordingly, numerical analyses were carried out by using ABAQUS. Parameters, such as thickness of neoprene pad, conditions of surface between PC column and end-plate, magnitude of pretension forces of through bolts, stiffness of end-plate were taken into consideration. As the result, it was found that the rigidity of the PCS system was negatively affected by the magnitude of initial gaps between PC columns and end-plates, and insufficient stiffness of neoprene fillers and end plates. In order to improve the initial stiffness performance of the joints, measures such as increase of the magnitude of pretension forces on through bolts and increase of the stiffness of end-plate by reducing the bolt pitch and providing adequate stiffeners are recommended.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.118-125
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• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.1-9
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• 2014

In this paper, $CO_2$ amount is evaluated considering repairing timing and unit $CO_2$ amount per repair method including various stage of material manufacturing, moving, and construction. Four mix proportions with mineral admixture are considered and repairing timing/numbers are simulated based on the results from Life 365 which can handle chloride penetration. Furthermore two repair methods (simple cover concrete replacement and replacement with electro-chemical method for removing chloride content) are considered and the related $CO_2$ emissions are evaluated. From the study, the case with high W/B (water to binder ratio) ratio shows smaller $CO_2$ emission in construction stage but it increases more rapidly with increasing number of repair. $CO_2$ emission considering electro-chemical method greatly increases with the increasing unit $CO_2$ for the repairing method. The numbers of jumping step (repairing number) are evaluated to be 9 for WB37-OPC, 18 for WB50-OPC, 4 for WB40-SG, and 7 for WB47-SG respectively. RC structures with the longer maintenance free period are evaluated to be advantageous for saving $CO_2$ emission.