• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.3
• /
• pp.83-91
• /
• 2015

Porous concrete consists of cement, water and coarse aggregate and has been used for the purpose of decreasing the earth environmental load such as air and water permeability, sound absorption, etc. However, the physical and mechanical properties of porous concrete changes due to compaction load during construction. For such a reason, the purpose of this study is to investigate the physical and mechanical properties of porous concrete according to the kinds of binder, the ratio of water to binder and target void ratio. In particular, this study has been carried out to investigate the influence of compaction load on the void ratio, strength and coefficient of permeability. Aggregate used in this study are by-products generated during production of crushed gravel with a maximum size of 13mm. The results of this study showed that the target void ratio, the coefficient of permeability and compressive strength of porous concrete had a close relationship with the void ratio, and it will be possible that the void ratio is suggested by the mix design of porous concrete. The compressive strength of porous concrete was the highest at the content of the expansive admixture of 5% and compared to non-mixture, 10% mixture of silica fume improved compressive strength about 32%. And in the result of the study to change the compaction load, the compressive strength increased from the load of 15kN, the void ratio decreased from the load of 0.8kN, the coefficient of permeability decreased from the load 35kN, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.15-20
• /
• 2019

This paper evaluated the construction costs of 11 design cases to decrease the horizontal forces applied to the abutment. They include two abutment types, which are to improve backfill materials for a reversed T-shaped abutment and geosynthetic Reinforced Abutment for Railways (RAR). The first type of economic analysis was that the internal friction angles of backfill materials were increased from Φ=35° to Φ=40° and 50° for a reversed T-shaped abutment. In addition, the second type was the cases with the design of geosynthetic RAR. When friction angles of 40° or 50° were applied through the improvement of the backfill material, the decrease in construction cost of the abutment was not large (2.0~3.9%), even though the horizontal forces applied to the abutment had decreased to 18~48%. In the case of applying the RAR, however, a maximum 30% cost reduction was evaluated by the decrease in horizontal force to "0" theoretically. The cost reduction resulted from the decrease in wall thickness, base slab size, and number and material change of pile foundation for the abutment.

• Elastomers and Composites
• /
• v.35 no.2
• /
• pp.138-148
• /
• 2000

In order to investigate the possibility of EPDM micro cellular pad (MCP) as an impact sound insulation product, we studied static/dynamic properties and vibration transfer characteristics of EPDM MCP depending on shape, thickness, degrees of foaming by using material test system (MTS) and lab scale mock-up test apparatus. Static/dynamic rigidity is increased when shape is simple. thickness and degrees of foaming low. We could see that dynamic stiffness is proportional to the transmissibility of EPDM MCP. When dynamic stiffness is increased, characteristic peak at transmissibility curve moves high frequency range or snows increase of maximum value of transmissibility. For lab scale mock-up test and finite element method, EPDM MCP shows low vibration velocity and superior mode shape to just concrete plus slab structure. We could confirm that possibility of EPDM MCP as a impact sound insulation product is high.

• Explosives and Blasting
• /
• v.37 no.1
• /
• pp.1-13
• /
• 2019

The repeated blasting vibration, which is induced commonly in NATM excavation site, can cause a severe damage to the nearby facilities. It is known that the most effective method for reducing blasting vibration includes the use of electronic detonator, deck charge and change of cut method, and so forth. In order to analyze the effect of blasting vibration reduction, in this study, three-dimensional FDM (Finite Difference Method) program FLAC3D has been used for reflecting the blasting hole, delayed time and charging amount. Also the numerical analysis has been performed by applying a dynamic load to each blasting hole. The cut method has been applied with several methods, such as V-cut and Double-drilled parallel cut, which are common in tunnel construction sites. Also, the field test blasting has been carried out in order to compare the measured data with results of numerical analysis. It was shown that the numerical analysis and the field measurement coincide well.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.1
• /
• pp.100-108
• /
• 2021

The purpose of this study is to analyze the reliability index of a design by applying the reduction factor of the recently developed fiber reinforced high strength concrete design guideline(draft). By collecting material and member test data performed for the development of the design guideline(draft), statistical characteristics of material strength and member strength analysis equations are obtained. A simul ation that appl ies the material statistical characteristics and the member anal ysis equation of the design guidel ine(draft) is performed, and the statistical characteristics of the section strength are calculated by combining the statistical characteristics of the analysis equation. Reliability analysis was performed by applying the load combination of the domestic highway bridge design code and concrete structural code, and it was confirmed that the design that applies the reduction factor for materials and members suggested in the design guideline(draft) satisfies the target reliability index.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.272-272
• /
• 2020

급격한 도시화와 기후변화로 인해 기존 물순환 체계가 왜곡됨에 따라 저영향개발(Low Impact Development) 기법의 필요성이 증가하고 있는 추세이다. LID 요소 중 하나인 옥상녹화는 국내에 도입이 많이 되었고 적정 설계인자를 설정하기 위해 지속적으로 연구를 수행하고 있다. 따라서 본 연구에서는 옥상녹화 설계인자의 설정과 수문·식생·토양을 고려한 시나리오 구축을 통해 국내 물순환 모형인 K-LIDM을 이용하여 옥상녹화의 정량적 물순환 효율성 분석을 수행하였다. 대상유역은 한국 그린인프라 저영향개발센터 내 옥상녹화 실험장으로 옥상녹화에서 계측하고 있는 측정값을 기반으로 K-LIDM 모형 검보정을 수행하고 옥상녹화의 설계인자에 따른 시나리오를 통해 수문학적 성능평가를 수행하였다. 단기강우 시나리오를 적용하였을 때 옥상녹화는 일반콘트리트 옥상에 비해 5.25 ~ 36.48%의 유출저감률이 산정되었으며, 유출저감 한계효율은 지속시간 60분, 120분, 180분 일 때 각각 8.93%, 6.17%, 5.25%로 산정되었다. 장기강우 시나리오를 적용하였을 때는 연평균 53.54%의 유출저감률이 산정되었다. 또한 토심의 증가에 따른 유출량 감소는 관목>교목>지피 식물 순으로 나타났으며, 토심이 1cm 증가할 때의 저감유출랴은 지피 식물의 경우 0.0002㎥/s, 교목의 경우 0.0005㎥/s, 관목의 경우 0.0008㎥/s로 나타났다. 옥상녹화는 건물 설계에 따른 적재하중과 환경조건, 식물선정, 생육에 많은 영향을 받는 기술요소이므로 다양한 시나리오를 통한 수문학적 성능평가가 필요시 된다. 본 연구결과는 정량적 옥상녹화시스템 효율성 검증을 실시하기 위한 옥상녹화 설계가이드라인에서 고려사항을 제시할 수 있는 기준이 될 것이라고 기대된다.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.4 no.1 s.12
• /
• pp.65-75
• /
• 2004

Roadbed failure due to the natural disaster may bring out social and economic damage such as the loss of life and property, the consumption of time and cost for recovery, and the delay of logistics in railway In this study, the method using geosynthetic soilbag was applied to rehabilitation of the railway roadbed which was failed by disaster. The full scale tests with the simulated train loading were performed in order to evaluate the static and dynamic performance at the railway roadbed using geosynthetic soilbag. The results of these tests were compared with unreinforced and reinforced cases with geosynthetic soilbag, respectively The data gathered by various measurement devices from these full scale tests would be useful to evaluate and understand the roadbed with geosynthetic soilbag. In conclusion, geosynthetic soilbag was evaluated as a permanent restoration method to reinforce the roadbed of railway.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.1
• /
• pp.109-120
• /
• 2013

This paper presents the results of a laboratory investigation into a study on undrained characteristics of a geogrid-encased stone column (GESC) installed in soft clay under cyclic load. In order to analyze behavior of settlement, pore water pressure, stress concentration ratio and strain of the GESC compared to a stone column, a series of reduced-scale laboratory tests were performed. The model tests show that GESC provides a simple and effective method of deformation resistance and settlement restraint when a short-term cyclic load is applied. The maximum strain of geogrid occurred at 1.2D and 1.5D from the top of the column. This paper highlights the importance of considering overlay effect and replacement ratio on cyclic load supporting GESC.

• Journal of the Korean Society of Safety
• /
• v.15 no.1
• /
• pp.140-145
• /
• 2000

This paper was composed with fatigue test of the cruciform specimens, as load carrying and non-load carrying type. It also has performed computational analyses for geometric condition of the fillet welding bead. As test results, the effect of stress ratio in the specimen was insignificant. Stress ranges were varied with R=0.1~0.2. The fatigue cracks that were found in the load carrying type specimens and most specimens welded with contact were developed at the end of welds. The fatigue strength of specimen that have fractured in maternal plate was found about ${\Delta}\sigma_c$=63.5MPa. It's about 24% less than that of the non-load carrying type specimens having about ${\Delta}\sigma_c$=83.8MPa. A category of the Fatigue design specifications which provide for cruciform details was defined grade C as a stress of the maternal member. And then, the fatigue strength to be transformed into the maternal stress was found about 78.27 MPa, it tends to be less than that of allowable fatigue strength.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.3
• /
• pp.125-132
• /
• 2014

Steel fiber is a effective composite for crack resistance and improve structural performance under tensile loading. This study presents an evaluation of crack resistance and structural performance in cement mortar with steel fiber and expansion agent through internal chemical prestressing. For this work, cement mortar samples with 10% replacement of cement binder with CSA (Calcium-Sulfo-Aluminate) expansion agent and 1% volume ratio of steel fiber are prepared. Including basic mechanical properties, initial cracking load and fracture energy are evaluated in cement mortar beam with notch. Initial cracking load and fracture energy in cement mortar with CSA and steel fiber increase by 1.75 and 1.41~1.53 times compared with those in cement mortar with steel fiber. With optimum mix design for steel fiber and CSA expansive agent, the composite with chemical prestressing can be applied to various members and effectively improve crack resistance to external loading.