본 연구에서는 콘크리트 구조물의 내구성 고도화를 위하여 고속도로용 교각 기둥부에 대하여 내부 식성이 우수한 GFRP 보강근 적용하였으며, 설계적 분석, 축소모형 시험체 제작 및 성능 시험을 통하 여 실용화의 타당성를 검증하였다. 설계적으로 교각의 기둥부는 축방향 주철근을 GFRP 보강근으로 대체하였다. 일반적으로 GFRP는 압축부에 취약한 것으로 알려져 있으며, 국외 기준의 경우는 압축부 에 대하여 GFRP 보강근은 저항력이 없는 것으로 가정하고 있다. 본 연구에서는 탄성 교각에 대하여 기존 철근을 대체할 수 있는 GFRP 보강근의 설계적 방안 제시 및 실물 시험을 통한 성능 검증을 수 행하여 결과를 제시하였다. 본 연구 결과는 고속도로용 탄성 교각 기둥의 내구성 증진을 위한 설계 및 실용화에 있어 가능한 가이드라인을 제시할 것으로 기대된다. 다만, 본 연구에서 다룬 기둥부는 주철 근만을 GFRP 보강근으로 대체한 것으로, 향후 GFRP 나선형 보강근 등의 적용, GFRP의 축하중 분담 률 및 건조수축 크리프 특성, 기둥부의 최소 보강근비 산정 그리고 GFRP 보강근의 압축강도 측정법 등 상세 사항에 대한 추가적인 연구가 필요할 것이다.

Restraints of Branch Lines are used as earthquake-resistant support devices for fire-fighting pipes along with sway brace devices. The central types are aligned and fixed in a straight line with center of the pipe, but the eccentric types are fixed to on side of the pipe, so a bending moment occurs. In this study, three specimens each of central type and eccentric type were installed at an angle of 45° from the vertical and a monotonic compression load of 1340N was applied. All central type samples satisfied 17.8mm of the allowable displacement, but all eccentric type samples failed to meet the target load and buckled. Therefore, when considering the performance of eccentric type restraints, both compressive load and bending moment must be considered. Even through material mechanics calculations, the yield stress of eccentric type - 3/8 inch all threaded steel bolt - exceeds 320Mpa of the allowable stress. A experiment standards need to be established for eccentric type restraints.

대한민국의 도로의 증가로 인한 복잡화에 따라 터널의 수와 연장이 지속적으로 증가하고 있다. 본 연구는 시멘트콘크리트 포장의 성 능과 수명에 미치는 환경조건의 영향을 분석한다. 현재까지 시공된 고속도로의 많은 부분이 시멘트콘크리트 포장으로 되어 있으며, 이 에 대한 연구는 오랫동안 진행되어 왔다. 부등건조수축은 슬래브의 상하부 온습도 차이에 의해 발생하며, 일일 및 계절적 주기에 따라 발생한다. 일반적으로, 온습도 변화에 따라 컬링이나 와핑이 발생하는데, 컬링은 낮에는 높은 온도로 인한 하향 수축, 밤에는 낮은 온 도로 인한 상향 수축을 나타낸다. 그러나, 환경조건 변화에 따른 콘크리트 내부 습도 변화에 대한 이해는 아직 크게 연구가 진행되지 않아 포장 설계에 적절히 반영되지 못하고 있다. 이러한 연구는 터널 등 배수가 어려운 지역에서 콘크리트포장의 적절성을 판단하여 공용수명에 기여할 것으로 예상한다. 본 연구에서는 슬래브의 하부 조건이 콘크리트 내부 습도에 미치는 영향을 실험적으로 조사한다. 콘크리트 시편을 제작하여 특수한 환경조건에서의 습윤 차이를 모사하여 수분 이동 특성을 연구한다. 실험에서는 슬래브의 한쪽면을 고정하고 반대편이 부등건조수축으 로 인해 발생하는 변형률과 수직변위를 측정할 장비를 설치하여 시간에 따른 변화량을 확인한다.

Modification of the surface of raw activated carbon using chemical solvents can significantly improve the adsorption performance of activated carbon. Triethylenetetramine is one of the most important chemical solvents used to modify raw activated carbon for formaldehyde removal indoor. We conducted the liquid impregnation experiments at different initial concentrations, temperatures, adsorbent dosage and time ranges to fully investigate the adsorption of triethylenetetramine on the surface of raw activated carbon for modification. We found that the Langmuir isotherm model and pseudo-first-order kinetic model fit quite well with the experimental data and the R2 are 0.9883 and 0.9954, respectively. The theoretical maximum adsorption capacity is 166.67 mg/g. The change in Gibbs free energy (ΔG0), enthalpy change (ΔH0) and entropy change (ΔS0) were also calculated to study the direction and driving force of the liquid adsorption process. In order to understand the adsorption process at the molecular level, a new activated carbon model based on the actual physical and chemical properties of activated carbon was carefully established in the Materials Studio to simulate the liquid-phase adsorption. The pore structure, elemental composition, functional group content, density, pore volume, and porosity of the activated carbon model converge close to the actual activated carbon and the adsorption isotherms obtained from the simulation agree well with the experimental results. The results show that the adsorption of triethylenetetramine on activated carbon is a spontaneous, endothermic and monolayer physical adsorption process.

Aluminum alloys, known for their high strength-to-weight ratios and impressive electrical and thermal conductivities, are extensively used in numerous engineering sectors, such as aerospace, automotive, and construction. Recently, significant efforts have been made to develop novel aluminum alloys specifically tailored for additive manufacturing. These new alloys aim to provide an optimal balance between mechanical properties and thermal/ electrical conductivities. In this study, nine combinatorial samples with various alloy compositions were fabricated using direct energy deposition (DED) additive manufacturing by adjusting the feeding speeds of Al6061 alloy and Al-12Si alloy powders. The effects of the alloying elements on the microstructure, electrical conductivity, and hardness were investigated. Generally, as the Si and Cu contents decreased, electrical conductivity increased and hardness decreased, exhibiting trade-off characteristics. However, electrical conductivity and hardness showed an optimal combination when the Si content was adjusted to below 4.5 wt%, which can sufficiently suppress the grain boundary segregation of the α- Si precipitates, and the Cu content was controlled to induce the formation of Al2Cu precipitates.

Asphalt concrete, which is used as a road base material, accounts for >90% of a road pavement. A huge amount of waste concrete and waste asphalt concrete aggregates are generated. Recently, carbon neutrality is promoted across all industries for sustainability. Therefore, to achieve carbon neutrality in the asphalt concrete industry, waste asphalt concrete aggregates should be recycled. Additionally, road base materials are prepared using additives to ensure structural stability, durability, and economic efficiency. In this study, recycled asphalt concrete aggregates were used to evaluate the physical properties of road base materials according to the type of polymer additive and mixing method, and the applicability of road base each material was evaluated. Results showed that when the acrylate-based polymer additive was mixed, the uniaxial compressive strength was 30% higher. Furthermore, the compressive strength of the split mix was improved by ~29% compared to the total mix.

The buffer is installed around the disposal canister, subjected to heating due to decay heat while simultaneously experiencing expansion influenced by groundwater inflow from the surrounding rock. The engineering barrier system for deep geological disposal require the evaluation of longterm evolution based on the verification of individual component performance and the interactions among components within the disposal environment. Thus, it is crucial to identify the thermalhydro- mechanical-chemical (THMC) processes of the buffer and assess its long- and short-term stability based on these interactions. Therefore, we conducted experimental evaluations of saturationswelling, dry heating, gas transport, and mineralogical alterations that the buffer may undergo in the heated-hydration environment. We simulated a 310 mm-thick buffer material in a cylindrical form, simulating the domestic disposal system concept of KRS+ (the improved KAERI reference disposal system for spent nuclear fuel), and subjected it to the disposal environment using heating cartridges and a hydration system. To monitor the thermal-hydro-mechanical behavior within the buffer material, load cells were installed in the hydration section, and both of thermal couples and relative humidity sensors were placed at regular intervals from the heat source. After 140 days of heating and hydration, we dismantled the experimental cell and conducted post-mortem analyses of the samples. In this post-mortem analysis, we performed functions of distance from the water contents, heat source, wet density, dry density, saturation, and X-Ray diffraction analysis (XRD). The results showed that after 140 days in the heated-hydration environment, the samples exhibited a significant decrease water contents and saturation near the heat source, along with very low wet and dry densities. XRD Quantitative Analysis did not indicate mineralogical changes. The findings from this study are expected to be useful for input parameters and THMC interaction assessments for the long-term stability evaluation of buffer in deep geological disposal.

This study aims to evaluate the structural safety of a structural thermal barrier, installed inside the structure of a building and performed the role of a load-bearing element and an insulation simultaneously, contributing to the realization of net-zero buildings. To ensure the reliability of the analysis model, the analysis results derived from LS-DYNA were compared with the experimental results. Based on the results shown through the flexural experiment, the reliability of the thermal cross-section insulation structure model for slabs was validated. In addition, the effect of the UHPC block on the load support performance and its contribution to vertical deflection was verified.

In this study, the change in the mold opening stroke of important functional parts according to the 20, 50, 80, and 100% increase in the injection speed of a hydraulic 150 ton hydraulic injection molding machine was studied to verify the accuracy of the injection speed and mold opening stroke and the reproducibility of the standard deviation. The null and alternative hypotheses were confirmed by conducting hypothesis verification according to the experimental condition change using the experimental design method.

Aluminum alloys are widely utilized in diverse industries, such as automobiles, aerospace, and architecture, owing to their high specific strength and resistance to oxidation. However, to meet the increasing demands of the industry, it is necessary to design new aluminum alloys with excellent properties. Thus, a new method is required to efficiently test additively manufactured aluminum alloys with various compositions within a short period during the alloy design process. In this study, a combinatory approach using a direct energy deposition system for metal 3D printing process with a dual feeder was employed. Two types of aluminum alloy powders, namely Al6061 and Al-12Cu, were utilized for the combinatory test conducted through 3D printing. Twelve types of Al-Si-Cu-Mg alloys were manufactured during this combinatory test, and the relationship between their microstructures and properties was investigated.

본 연구는 임해 매립지에 조성되는 골프장 부지의 자연적 장해요인을 분석하고 개선 요소를 검토하 여 향후 매립지에 조성되는 식재공사 등의 시행착오를 줄이고 경제성을 향상시키고자 한다. 선행 연 구자들의 임해 매립지 토양 환경의 이화학적 연구 결과를 토대로 영종도 국제공항 내 골프장의 토양 환경을 개선하는 방법을 배수 처리 체계와 함께 연구하였다. 그 결과로 사업 초기 단계에서부터 수목 또는 식물의 생장을 고려한 계획을 통해 경제적이며, 장기적으로 정상적인 식물 또는 수목의 생장에 도움을 꾀하고자 하였다. 연구결과로서 임해 매립지에서 식물 생육에 영향을 주는 요인 중 염분 상승 또는 식생 지반의 염분 과다는 식물 생육에 직접적인 영향이 있는 것으로 분석되었고 따라서 임해 매립지의 경우 탈염 과정을 거쳐 식물 생육에 적합한 토양으로 개선하여야 될 필요가 있으며, 이 과정 에서 염분 상승의 차단을 위한 차단층의 설치가 필요하다. 특히 모세관 상승의 차단은 입도가 큰 재료 일수록 차단 효과가 컸으며, 실험 결과를 미루어 볼 때 차단층의 두께가 클수록 확실한 모세관 상승 차단 효과가 있을 것이라 판단된다. 본 연구는 임해 매립지 조성 시 염분 상승에 의한 식물 생육 저해 요소를 감소시키기 위한 방법으로 식재기반 조성 시 매립 방법을 달리하여 지하수위를 저하 시킴으로써 모세관 상승에 의한 염분 상승을 근본적으로 차단하고자 실험적인 방법을 통해 차단층의 재료 선정 및 차단층의 두께를 결정하는데 연구의 의의를 두고 있다. 그러나 식재 단면층의 조성 두께 등 의 설정은 실내시험으로 인한 한계를 보이고 있다. 특히 서남해안의 경우 환경적 영향(밀물과 썰물의 조위 차, 일조량, 풍향, 풍량 등 염분 상승)이 되는 인자들의 변수 조건에 대한 미적용의 한계성과 염분 차단층 설치 시 염분 상승은 기대할 수 있으나 모관수 차단으로 인한 건조피해에 대한 대책은 연구과 정에서 부족했던 부분이다 추후 부족한 부분에 대한 연구는 향후 지속적으로 계속되어야 할 것이다.

Cs-137, a radioactive isotope of caesium, is a commonly occurring fission product that is generated during the nuclear fission of U-235 and other fissionable isotopes in both nuclear reactors and weapons. Due to its long half-life of about 30 years and propensity to accumulate in sediments and marine organisms, Cs-137 is considered a major radionuclide for environmental radioactivity monitoring. In April 2021, as the Japanese government decided to discharge Fukushima contaminated water into the sea, the monitoring of marine radioactivity in South Korea has become increasingly significant. In this study, as an initial step towards establishing a standardized procedure for analyzing radioactive caesium in seawater, the radioactivity of Cs-137 was analyzed on a 2 L of seawater spiked with 10 Bq of Cs-137 standard solution supplied by KRISS. The seawater was collected from Im-nang Beach, situated at a distance of approximately 2 kilometers from DIRAMS. The radioactivity of Cs-137 in seawater was determined according to the improved AMP procedure presented by M.Aoyama in 2000. The seawater was pretreated using Ammonium Phosphomolybdate (AMP) coprecipitation, which has a high selectivity for caesium (Kd = ~5500), and the activity of Cs-137 was determined by gammaspectroscopy and subsequently corrected via the weight yield. The weight yield of the dried AMP/Cs compound was more than 93%. For the gamma-spectroscopy analysis, the AMP/Cs compound was dissolved in a cylindrical U8 beaker with NaOH to ensure that its shape and volume were consistent with the CRM (KRISS, 221U890-1) used to calibrate the detector. The dissolved compound was then positioned directly onto the detector housing and subjected to a measurement duration of 80,000 seconds utilizing a p-type HPGe (Ortec, GEM60) with a relative efficiency of 54%. The activity of Cs-137 was determined to be 10.81 Bq, confirming the reproducibility of the AMP coprecipitation and weight yield methods. The present experiment was carried out using a 2 L sample, but a large volume of seawater would be required to achieve a sufficient minimum detectable activity (MDA) for Cs-137 in natural seawater. Thus, a standardized procedure for analysis of radioactive caesium in natural seawater will be established through the analysis of a large volume of seawater in future studies.

Airborne surveys are an essential analysis method for rapid response and contamination identification in the early event of a radiation emergency. On the other hand, airborne surveys are far from the ground, so it is necessary to convert the dose rate at a height of 1 m above the ground. In order to improve the accuracy of the analysis value, a lot of analysis of the measurement data is required. In our previous research, we developed MARK-A1, an instrument for rapid radiation aerial survey in high radiation environment, and MARK-M1, a multipurpose instrument for radiation detection. In this study, a large unmanned aerial vehicle (UAV) was used to conduct airborne surveys using three types of detectors in the Jeju Island environment. The NaI(Tl) detector uses one 3-inch scintillator (38 mm φ × 38 mm H), and the LaBr3 detector uses two 2-inch scintillators (25 mm φ × 25 mm H). The CZT detector uses a detector with dimensions of (15 mm × 15 mm × 7.5 mm). The UAV has a payload of 15 kg (J10, JCH systems Inc. Seoul, Korea). Three different detectors were operated at a constant height of 20 m, 30 m, and 50 m. The flight experiments were performed in the west near Jeju City. Dose rate conversion factors were used to convert the dose rate from the measured spectra, and hovering flights were conducted between 1 and 50 meters to derive altitude correction factors. In this paper, the data measured with each detector in the same area were compared and the differences were derived.

Geologic disposal at deep depth is an acceptable way to dispose of high-level radioactive waste and isolate it from the biosphere. The geological repository system comprises an engineered barrier system (EBS) and the host rock. The system aims to delay radionuclide migration through groundwater flow, and also, the flow affects the saturation of the bentonite in the EBS. The thermal conductivity of bentonite is a function of saturation, so the temperature in the EBS is directly related to the flow system. High-temperature results in the two-phase flow, and the two-phase flow system also affects the flow system. Therefore, comprehending the influencing parameters on the flow system is critical to ensure the safety of the disposal system. Various studies have been performed to figure out the complex two-phase flow characteristics, and numerical simulation is considered an effective way to predict the coupled behavior. DECOVALEX (DEvelopment of COupled models and their VALidation against EXperiments) is one of the most famous international cooperating projects to develop numerical methods for thermo-hydro-mechanicalchemical interaction, and Task C in the DECOVALEX-2023 has the purpose of simulating the Fullscale Emplacement (FE) experiment at the Mont-Terri underground research laboratory. We used OGS-FLAC, a self-developed numerical simulator combining OpenGeoSys and FLAC3D, for the simulation and targeted to analyze the effecting parameters on the two-phase flow system. We focused on the parameters of bentonite, a key component of the disposal system, and analyzed the effect of compressibility and air entry pressure on the flow system. Compressibility is a parameter included in the storage term, defining the fluid storage capacity of the medium. While air entry pressure is a crucial value of the water retention curve, defining the relation between saturation and capillary pressure. From a series of sensitivity analyses, low compressibility resulted in faster flow due to low storage term, while low air entry pressure slowed flow inflow into the bentonite. Low air entry pressure means the air easily enters the medium; hence the flow rate becomes lower based on the relativity permeability definition. Based on the sensitivity analysis, we further investigate the effect of shotcrete around the tunnel and excavation damaged zone. Also, long-term analysis considering heat decay of the radioactive waste will be considered in future studies.