PURPOSES : In this study, the basis for improving the maintenance method of road pavement in Jeju Island, where deterioration is accelerating, was presented through field construction and analysis of various combinations of maintenance methods. METHODS : Construction was performed on Jeju Island's Aejo Road, which has high traffic and frequent early damage, using various asphalt mixtures mainly applied in Jeju Island, with different maintenance cross-sections depending on the level of repair. The quality and performance of the asphalt mixture collected during construction were evaluated, and MEPDG was used to analyze the service life according to the type and maintenance level of the mixture. RESULTS : While the mixture for the surface layer satisfied the quality standards and had excellent rutting and moisture resistance performance, the asphalt mixture for the intermediate and base layer did not satisfy the quality standards such as air voids, so it was judged that quality control was necessary during production. The section repaired to the base layer was found to be advantageous for the integrated behavior of the pavement and had the best structural integrity. As a result of predicting the service life, the estimated life of the section where only the surface layer was repaired was analyzed to be approximately 7 years, the section where the intermediate layer was repaired was 14.5 years, and the section where the entire section up to the base layer was repaired was analyzed to be 18 years. CONCLUSIONS : In Jeju Island, where deterioration is accelerating, it was analyzed that when establishing a maintenance plan, it is necessary to consider repairing the middle and base floors in order to secure the designed life of 10 years.

PURPOSES : In this study, emissions from asphalt mixture production and construction processes are calculated and used to estimate the emission from each asphalt pavement layer. The calculated emissions for the processes are used as fundamental data to estimate the total emission from the entire life cycle of pavement engineering in South Korea. METHODS : A design proposal and the Korean standard, which provide quantitative information for activities, were used to estimate the amount of construction materials and energy consumption. Subsequently, the LCI DB from NAPA and the LCIA DB from EPA were utilized in conjunction with the estimated quantity to assess the effect of the emissions to determine their environmental impact categories. RESULTS : Calculation results show that 5.84 million ton of CO2eq is discharged from production and construction processes, whereas 3.24 million ton of CO2eq is discharged from operation processes in the pavement engineering sector. The total GHG emission, i.e., 9.08 million ton of CO2eq, is approximately 1.25% of the national GHG emission in 2018. The asphalt mixture production process results in the highest GHG emission in the life cycle of asphalt pavements. CONCLUSIONS : An LCI DB that accounts for the industrial characteristics of South Korea must be established to provide more reliable emission data to be used for national GHG reduction plans, including those for the pavement engineering sector.

PURPOSES : The evaluation of the road pavement thickness in an apartment complex through a methodology for estimating the number of construction vehicles is presented. We also show the usability of the new design criteria. METHODS : A field survey plan was established by conducting literature and preliminary surveys, and the structural performance of each section of the road pavement was compared through a structural analysis program. The load on construction vehicles is required for analyzing the ESAL factors of construction vehicles; it is calculated as a methodology for estimating construction vehicles because it is difficult to measure the traffic volume through visual inspection. Accordingly, the extent of damage predicted by road pavement sections in apartment complexes was analyzed to examine the possibility of applying the methodology for estimating the number of construction vehicles. RESULTS : If the road crack exceeds 20% as a result of the site survey of a previous study, structural damage to the road pavement occurs from construction vehicles. Compared to the actual traffic volume observation, an error of 5% took place; therefore, it is necessary to perform a design such that the damage caused by the load of the construction vehicle be 15% or less for proper road performance. Structural analysis through the KENPAVE program showed that the damage caused by the load of the construction vehicle exceeded 20% in all sections except section B (with a thickness of 46 cm). CONCLUSIONS : Owing to the limitations of the test construction section and environmental conditions, it is necessary to assess the effects of various variables by conducting an analysis. This is expected to be applied as a design basis considering more reliable construction vehicles.

PURPOSES : In general, a high-performance concrete construction method is a method of loading mixed cement and other materials on a mobile mixer equipped with a concrete plant. However, the construction cost is high because the unit cost of the mixed cement is very high and the equipment usage fee of the mobile mixer is also high. To compensate for these drawbacks, a cellular spray concrete method was developed. This is a highly functional customized concrete construction method in which admixtures are added to high-flow concrete with cellular (air bubbles) added at the site and constructed through spraying. METHODS : Field workability evaluation using cellular concrete was carried out using a spray method in 2017 and an anti-foaming agent in 2018. The test construction section was set as a new road-pavement construction site. After construction, strength, durability characteristics, and void analysis were performed to compare the construction methods. The results of laboratory tests under optimal conditions were also compared to the on-field results. By comparing the indoor mixing and the on-field results, we analyzed whether there were any problems concerning the performance expression. The economic feasibility at the initial construction stage was analyzed by comparing the existing and the cellular concrete construction methods in terms of material cost and equipment usage fee. RESULTS : In the case of cellular spray concrete, construction through spraying is cumbersome, and the need to additionally use large equipment such as a pump car and compressor constitutes a disadvantage. However, the most relevant feature is that it can be constructed not only on the floor, but also on a slope. In the case of cellular concrete with an antifoaming agent, it was possible to quickly produce high-performance concrete using on-site remixing equipment. By supplying materials to the pouring surface using a conveyor, smooth construction and construction in narrow spaces were also possible. CONCLUSIONS : The cellular concrete method allows the immediate on-site production of high-performance concrete, and it is possible to selectively apply spray construction, antifoaming agent construction, etc.

PURPOSES : The purpose of this study is to measure and analyze the fugitive dust generated by each process through field tests to develop a technology to reduce fugitive dust generated during excavation-restoration work on road pavements. METHODS : The testbed was constructed based on a typical excavation-restoration construction section and comprised five sections for reproducibility and repeated measurements. The excavation-restoration work was divided into pavement cutting, pavement crushing, pavement removal, excavation, and restoration processes and fugitive dust generated by each process was measured. Fugitive dust (TSP, PM10, PM2.5, and PM1) was measured using a GRIMM particle spectrometer, which applies the principle of a light scattering spectrometer and can be measured in real-time. RESULTS : Analyses of the average mass concentration of PM10 generated by the excavation-restoration process are as follows: 1286.3 μg/m³ from pavement cutting, 246.8 μg/m³ from pavement crushing, 697.0 μg/m³ from pavement removal, 747.9 μg/m³ from excavation process, and 350.6 μg/m³ from the restoration process. In addition, the average particle size distribution of the excavationrestoration construction was in the order of PM10~PM2.5 (67 %), PM1 or less (24 %), and PM2.5~PM1 (9 %). The pavement cutting process is characterized by the emission of high concentrations of fugitive dust over a short time, compared to other processes. The pavement crushing process has the characteristic of steadily generating fugitive dust for a long period, although the emission concentration is small. CONCLUSIONS : In this study, it was found that the concentration and characteristics of fugitive dust generated during road pavement excavation-restoration works vary by process and the reduction technology for each process should be developed accordingly.

Of the daily noises, construction noises cause serious conflicts between a construction firm and residents due to their high sound pressure level and shocking, repetitive sound. While South Korea regulates construction noises on the basis of legal criteria to minimize the damage from the noises, the regulation only involves a weighted sound level (dB(A)), which is loudness, like other types of noises. However, since construction noises are characterized by very diverse spectra and waveforms, it has been indicated that they cannot be reflected only by physical loudness: SPLdB(A). In addition, the need to reflect acoustic psychological characteristics and meanings of human beings in evaluating construction noises has recently been indicated. This study aimed to use six Zwicker parameters to determine the sound quality and acoustic psychological characteristics of construction noises and analyze the correlation between physical indexes of construction noises, as found in literature review, and the Zwicker parameters. Loudness of construction noises were closely correlated with SPLdB(A); shocking noises were perceived as ‘loud, sharp, and annoying’ sound. The Zwicker parameters were most strongly correlated with loudness, followed by unbiased annoyance and sharpness, among the evaluation indexes; as for correlation with construction noises, ‘normal noises’ were closely correlated with loudness, ‘shocking noises’ were closely correlated with loudness, unbiased annoyance, and sharpness, and ‘fluctuating noises’ were closely correlated with loudness. Therefore, if loudness, unbiased annoyance, and sharpness were taken into account in terms of the sound quality in evaluating construction noises, it is expected to be useful to make and revise criteria for regulating the noises.

Recently various composite beams in which concrete is filled in the U-shaped steel plate have been developed for saving story height and reducing construction period. Due to the high flexural stiffness and strength, they are widely being used for the building with large loads and long spans. The semi-slim AU composite beam has proven to take highly improved stability compared to the existing composite beams, because it consists of the closed steel section by attaching cap-type shear connectors to the upper side of U-shaped steel plate. In this study the finite element analyses were performed to evaluate the safety of the AU composite beam with unconsolidated concrete which were sustained through the closed steel section during the construction phase. The analyses were performed on the two types of cross section applied to the fabrication of AU composite beams, and the results were compared to the those of 2-point bending tests. In addition, the flexural performance according to the space of intermittent cap-type shear connectors and the location of reinforcing steel bars for compression was comparatively investigated. Through the results of analytical studies, it is preferable to adopt the yield moment of AU composite beam for evaluating the safety in the construction phase, and to limit the space of intermittent shear connectors to 400 mm or less for the construction load.

기존의 교면 포장이나 측구 시공에 적용한 건설재료들의 성능저하로 인해 유지보수비가 증가하고 있는 추세이다. 이에 본 연구에서는 현장 실험을 통해 개질유황 콘크리트의 내구성을 평가하는데 있어 기존의 고정형 팬믹서와 건 비빔 시 자전속도 변환이 가능한 가변형 팬믹서를 이용하여 내구성 평가 시험으로 콘크리트의 압축강도 시험을 수 행하였다.

As the 3D laser scanning technology capable of databaseing large sewage box culverts becomes possible, it is necessary to develop a standardization manual that can clearly distinguish the structural and operational defect types of box culver and analyze the defect data. In this study, we collected and analyzed defects in sewage box culverts of 14,827m in total by selecting three districts in Korea. The major defects were surface damages, and their defect densities were 2.17 m2/m, 0.27 m2/m and 0.10 m2/m for aggregate exposure, Steel reinforcement exposure, and Steel reinforcement projecting. In order to support the decision of the box culverment management, it was divided into five grades and each defect code and defect score were allocated. The results of this study are useful for the diagnosis of the sewage box culverts in Korea and it is expected to support a decision making for management.

우주의 자원과 영토에 대한 개별 국가의 소유권을 인정하지 않는 「UN 외기권 우주조약(1967)」과는 달리, 달에 매장된 광물 채굴에 대한 이권을 보장한 「US 상업적 우주 발사 경쟁력 법」이 2015년 채택됨에 따라 미국 및 일본의 민간 기업은 접근 가능한 행성에 존재하는 고부가가치의 자원 채취를 위한 기술 개발을 선제적으로 진행하고 있다. 더욱이 미국, 유럽과 중국을 포함한 우주 기술 선진국은 행성 자원의 확보에 한정되지 않고, 달 또는 화성에서의 실제 거주 환경 조성을 위한 현지 자원 활용(In-situ Resource Utilization, ISRU) 개념을 활용한 유인 탐사 및 거주 환경 건설 로드맵을 구체화하는 추세이다. 유럽 우주국(European Space Agency, ESA) 경우 2030년 완공을 목표로 실제 우주인이 거주하는 문 빌리지(Moon Village)와 같은 대규모 거주지 건설계획을 2016년 발표하고 이를 실현하기 위한 컨소시엄을 구성하고 있으며, 중국에서도 최근 유사한 컨소시엄 구성하거나 유럽 우주국의 컨소시엄에 공조하는 등 행성 개발 주도권을 확보하기 위한 노력을 경주하고 있다. 컨소시엄 구성을 통한 행성 개발 전략은 주도국의 입장에서는 비용과 실패의 위험성을 분산시키는 장점이 있으며, 우리나라와 같은 참여국의 입장에서는 기여도에 따라 이권을 확보할 수 있는 기회가 된다는 점에서 매우 중요한 의미를 갖는다. 특히 투자 자원의 한계가 있는 우리나라의 경우에는 기술적인 기여를 통한 참여가 바람직한 것으로 판단되는데. 이는 행성 개발에 필요한 기반시설에 대한 설계법이나 통합 규정 등의 개발과 함께, 시공 장비 및 운송 기반시설 등에 포괄적으로 적용될 수 있는 전략 응용 기술을 포함하는 원천기술 개발에 집중하는 것이 효율적인 대안으로 예상된다. 그러나 행성 개발을 위하여 기초적으로 필요한 예상 인프라와 거주지의 종류 및 규모를 추산하기 위해서는 현지 가용 자원의 종류 및 양과 거주 인원 등에 대한 정보가 필요한 반면, 필요 자원의 종류 및 양과 거주 인원 역시 인프라와 거주지의 종류 및 규모에 대한 결정이 선행되어야 추산될 수 있는 순환 논리의 어려움이 대두된다. 따라서 본 연구에서는 행성 탐사 및 거주지 개발을 위하여 ESA와 미국 항공 우주국(National Aeronautics and Space Administration, NASA)에서 제안한 ISRU 개념을 활용한 행성 운송 인프라 건설의 필요성을 검토하기 위한 기초연구를 수행하였다. 이를 위하여 운송 인프라의 설계에 고려해야하는 행성의 환경 인자들에 대하여 세부적으로 고찰하고 선정하였으며, 이를 실현하기 위하여 요구되는 기술들을 구분하였다. 다음 Fig. 1과 Fig. 2는 본 연구에서 고찰한 목표 기술의 정의 방법과 PISCES(Pacific International Space Center for Exploration Systems)에서 제작한 이착륙 패드 건설 장비를 각각 나타내고 있다

현장에서 양생 또는 고형화 과정을 거치는 일반 시멘트 콘크리트, 자가다짐 시멘트 콘크리트, 아스팔트 콘크리트, 고분자 개질 혼합물과 같은 도로포장 재료의 유동 특성은 시공시점에서의 환경조건과 함께 도로포장 구조물의 초기 성능을 결정하는 중요한 요소이다. 따라서 재료의 양생이 완료되는 시점까지 포설 및 다짐에 영향을 미치는 재료의 유동 특성을 검토하는 것은 기존 혼합 및 포설 장비의 개선뿐만 아니라 새로운 장비의 개발을 통한 시공과정 개선 및 최적화를 위해서도 매우 중요한 과정이라 할 수 있다. 또한 건축 또는 토목 구조물의 시공 및 유지관리에 활용되는 건설정보 모델링이 향후 부재의 역학적 거동과 연계된 시공 및 유지관리를 포함하는 통합적인 수준으로 발전될 것임을 고려할 때, 경험에서 벗어나 실험적으로 검증된 역학적 기반의 설계 및 시공 방법을 제시하는 것은 매우 중요한 의미를 갖는다. 건설재료의 유동은 그 최종 형태에 따라 순수전단 유동, 신장유동, 이들의 중간 정도에 해당하는 유동의 3가지로 구분하여 분석적 해를 유도할 수 있다. 그러나 분석적 해를 활용하는 방법은 비교적 단순한 경계조건에 대한 재료의 유동적 특성을 예측하는데 유용하게 활용될 수는 있으나, 경계조건이 복잡해질수록 해를 계산하는 것이 거의 불가능하여 컴퓨터를 활용한 수치해석 기법을 적용하는 것이 합리적이다. 한편 유동성 재료의 동적 거동을 해석하는 방법으로는 이산요소법이나 전산유체역학(computational fluid dynamics, CFD)을 활용할 수 있는데, 입자형 재료 사이에 존재하는 유체의 양이 상대적으로 적어 입자와 입자 사이 또는 입자와 경계조건과의 상호작용이 중요하게 고려되어야 할 경우에는 이산요소법이 바람직한 반면, 시멘트 페이스트와 같이 균질의 재료로서 연속체의 특성을 나타내는 경우에는 CFD를 활용하는 것이 바람직한 것으로 알려져 있다. 본 연구에서는 연속체로 가정할 수 있는 유동성 재료의 시간에 따른 거동을 예측하기 위한 CFD의 활용성을 평가하고자 하였다. 이를 위하여 미니콘 실험에 대하여 분석적 해와 CFD를 활용한 결과를 비교하여 수치해석에 활용된 가정과 모형의 타당성을 검증하였으며, 검증된 모형을 활용하여 주요 입력변수에 대한 민감도 분석을 수행하여 시간에 따른 재료의 슬럼프와 퍼진 정도의 변화를 확인하였다.

In Korea, the occurrence frequency of earthquakes has recently increased, compared with the past. So, the various damages for cultural properties due to earthquake can be expected, and especially fortress structure is vulnerable to earthquake. Therefore, the resonable seismic characteristics evaluation is required to secure the safety for fortress structure with the various construction and configuration types. Also, we should consider the various applied load conditions as design variables. To this end, this study classifies fortress structures according to the construction and configuration types, and then applies the discrete element method to model and analyze fortress structures. Finally, the seismic characteristics is evaluated through slip condition due to the analysis results considering the various design variables.