In this study, the SBC system, a new mechanical joint method, was developed to improve the constructability of precast concrete (PC) beam-column connections. The reliability of the finite element analysis model was verified through the comparison of experimental results and FEM analysis results. Recently, the intermediate moment frame, a seismic force resistance system, has served as a ramen structure that resists seismic force through beams and columns and has few load-bearing walls, so it is increasingly being applied to PC warehouses and PC factories with high loads and long spans. However, looking at the existing PC beam-column anchorage details, the wire, strand, and lower main bar are overlapped with the anchorage rebar at the end, so they do not satisfy the joint and anchorage requirements for reinforcing bars (KDS 41 17 00 9.3). Therefore, a mechanical joint method (SBC) was developed to meet the relevant standards and improve constructability. Tensile and bending experiments were conducted to examine structural performance, and a finite element analysis model was created. The load-displacement curve and failure pattern confirmed that both the experimental and analysis results were similar, and it was verified that a reliable finite element analysis model was built. In addition, bending tests showed that the larger the thickness of the bolt joint surface of the SBC, the better its structural performance. It was also determined that the system could improve energy dissipation ability and ductility through buckling and yielding occurring in the SBC.

초고성능 콘크리트의 충전밀도 향상을 위해 잔골재보다 미세한 실리카플라워를 사용하여 물리적 특 성변화를 분석하였다. 평균입경 300㎛의 규사를 100㎛인 실리카플라워로 일부 치환하여 압축강도, 휨 강도 변화와 유동성 변화를 측정하였다. 실리카플라워 사용으로 인해 압축강도와 휨강도가 향상되었으 나 유동성 저하로 인해 동일한 유동성을 확보하기 위해 추가적인 고성능감수제의 투입이 필요하였다. 유동성 저하는 바인더 차이에는 큰 영향을 받지 않았으며, 추가적인 고성능감수제 투입은 유사하게 나 타났다.

본 연구에서는 폐타이어를 파쇄한 재생 SBR(Styrene-Butadience Rubber)을 사용하여 탄성 고무 층 의 파단 시의 인장 강도 및 연신도와 같은 인장특성 및 충격 흡수 및 수직 변형과 같은 동적특성을 평가하였고, 섬유 보강재를 혼입하여 탄성 고무 층의 취약점을 개선시키고자 하였다. 주요변수로 다짐 횟수, 바인더-고무분말 비율, 양생기간, 양생온도, 양생습도, 섬유 보강재의 종류를 고려하였다. 실험 결과, 재생 SBR을 사용한 탄성 고무 층의 인장 강도는 다짐 횟수, 바인더-고무분말 비율, 양생기간 및 온도가 증가함에 따라 증가하였으며, 파단 시 연신도는 양생온도와 기간에 영향을 받는 것으로 나 타났다. 충격 흡수와 수직 변형은 다짐횟수 및 바인더-고무분말 비율이 증가함에 따라 경도가 증가하 여 감소하는 경향을 나타내었다. 또한 양생온도가 탄성 고무 층의 인장 특성에 뚜렷한 영향을 미치며, 적절한 양생온도를 유지할 경우(약 50℃) 상대적으로 낮은 탄성 고무 층의 인장 특성을 개선할 수 있는 가능성을 제시하였다. 보강재로 폴리머 합성 섬유인 Polypropylene(PP), Polyester(PET), Nylon(NY)을 1%까지 혼입하는 경우 재생 SBR이 가진 충격 흡수 능력은 그대로 유지하면서, 인장강도를 향상시킬 수 있음을 확인하였다.

상변화 물질(PCM)은 상전이 동안 에너지를 흡수하거나 방출할 수 있는 잠열 저장 물질로 활용된다. 최근 수십 년 동 안, 연구자들은 다양한 온도 적용을 위한 건설 물질로의 다양한 PCM의 통합을 탐구해 왔다. 그러나, PCM을 통합하는 콘크리트 의 기계적 및 열적 반응은 통합 방법에 의해 영향을 받는다. PCM을 콘크리트에 추가하기 위한 여러 기술이 제안되었다. 그럼 에도 불구하고, 콘크리트에 마이크로 캡슐화 PCM(m-PCM)의 통합은 종종 기계적 강도의 상당한 감소를 초래한다. 기존 콘크리 트에 m-PCM의 추가와 관련된 한계를 극복하기 위해, 예외적인 강도 및 내구성 특성으로 인해 초고성능 시멘트 복합체(UHPCC) 가 선호된다. 따라서, 본 연구에서는 기존 기술의 단점을 해결하기 위해 PCM을 통합한 신규 나노 엔지니어링 UHPCC를 개발하 였다. 또한, 시멘트 복합체의 기계적 및 열적 성능을 향상시키기 위해 다중 벽 탄소 나노튜브(MWCNT)를 추가하였다. 결과는 MWCNT의 포함이 기계적 성능을 향상시켰을 뿐만 아니라 시멘트 복합체의 열적 성능을 향상시켰다는 것을 보여 주었다.

The utilization of carbonaceous reinforcement-based polymer matrix composites in structural applications has become a hot topic in composite research. Although conventional carbon fiber-reinforced polymer composites (CFRPs) have revolutionized the composite industry by offering unparalleled features, they are often plagued with a weak interface and lack of toughness. However, the promising aspects of carbon fiber-based fiber hybrid composites and hierarchical composites can compensate for these setbacks. This review provides a meticulous landscape and recent progress of polymer matrixbased different carbonaceous (carbon fiber, carbon nanotube, graphene, and nanodiamond) fillers reinforced composites’ mechanical properties. First, the mechanical performance of neat CFRP was exhaustively analyzed, attributing parameters were listed down, and CFRPs’ mechanical performance barriers were clearly outlined. Here, short carbon fiber-reinforced thermoplastic composite was distinguished as a prospective material. Second, the strategic advantages of fiber hybrid composites over conventional CFRP were elucidated. Third, the mechanical performance of hierarchical composites based on carbon nanotube (1D), graphene (2D) and nanodiamond (0D) was expounded and evaluated against neat CFRP. Fourth, the review comprehensively discussed different fabrication methods, categorized them according to performance and suggested potential future directions. From here, the review sorted out three-dimensional printing (3DP) as the most futuristic fabrication method and thoroughly delivered its pros and cons in the context of the aforementioned carbonaceous materials. To conclude, the structural applications, current challenges and future prospects pertinent to these carbonaceous fillers reinforced composite materials were elaborated.

Discontinuum-based numerical methods can contain the multiple discontinuities in a model and reflect the thermal, hydraulic and mechanical characteristics of discontinuities. Therefore, discontinuum methods can be appropriate to simulate the model which require the detailed analysis of the coupled thermo-hydro-mechanical processes in fractured rock such as geothermal energy, CO2 geo-sequestration, and geological repository of the high-level radioactive waste. TOUGH-3DEC, the three-dimensional discontinuum simulators for the coupled thermo-hydro-mechanical analysis, was developed by linking the integral finite difference method TOUGH2 and the explicit distinct element method 3DEC to describe the coupled thermo-hydro-mechanical processes in both porous media and discontinuity. TOUGH2 handles thermo-hydraulic analysis by the internal simulation module, and 3DEC performs mechanical study based on the constitutive models of porous media and discontinuity with coupling the thermal and hydraulic response from TOUGH2. The thermal and hydraulic couplings are the key processes and should be carefully verified by sufficient cases, so this study performed the thermomechanical and hydro-mechanical simulations which are modelling the analytic solutions including the uniaxial consolidation, fracture static opening, and the heating of a hollow cylinder problems. Each thermo-mechanical and hydro-mechanical verification case is also validated by comparing with the results of the other continuum and discontinuum-based numerical methods. TOUGH-3DEC results follow the analytic solutions and show better accuracy than the continuum-based numerical methods in the static fracture opening problem. The developed TOUGH-3DEC simulator can be expanded to coupled thermo-hydro-mechanical-chemical analysis in fractured rock mass, and the simulator needs to be verified by more complicated coupled processes problems which require in the chemical coupling.

위험유해물질(HNS, Hazardous and Noxious Substances)은 해상운송 과정에서 다양한 사고에 노출되어 있어 많은 양이 바다에 유출 될 우려가 있다. HNS 유출에 따른 해양환경의 손상은 유류 유출에 의한 손상보다도 훨씬 큰 것으로 알려져 있다. 특히 해저로 침강하여 침적되는 HNS는 해저생태계에 돌이키기 어려운 피해를 주게 되므로, 반드시 회수되어야 한다. 해저로부터 HNS를 회수하기 위해서는 해저침적 HNS에 대한 정확한 탐지, 안정화 처리 및 회수를 위한 절차와 장비가 필요하다. 그 중에서도 기계적 회수장치를 개발하기 위해서는 성능지표를 이용하여 성능요건을 선정하고, 이를 토대로 기계적 회수장치에 대한 개념설계가 이루어져야 한다. 따라서 본 연구에서는 해저침적 HNS의 회수 절차에서 요구되는 기계적 회수장치에 대한 개념설계안을 제시하였다. 개념설계안으로 해저침적 HNS를 회수하기 위한 기본 시나리오를 제시하고, 자체적 밀폐 성능을 가지는 흡인 기초를 활용하는 방안을 채택하였다. 기계적 회수장치는 흡인 기초, 오 염 방지, 펌프 시스템, 제어 시스템, 모니터링 장비, 위치정보 장비, 이송 장비, 탱크로 구성된다. 이러한 개념설계안은 기계적 회수장치의 부품 및 형상을 결정하는 기본설계에 반영되어 활용될 것으로 기대된다.

해상을 통하여 운송되는 화학물질은 6,000여종에 이르며, 이러한 화학물질에는 해양을 오염시키거나 해양생물에 해로운 HNS(Hazardous and Noxious Substances)가 포함되어 있다. 해상운송 과정에서 바다로 유출된 HNS는 해상 및 해중에서 물리적, 화학적 변화 를 거치게 되는데, 어떤 종류의 HNS는 해저로 침강하여 퇴적되기도 한다. 해저에 침적된 HNS는 해저생태계에 커다란 악영향을 주기 때문에 해저침적 HNS를 탐지․처리하여 회수하는 것이 바람직하다. 따라서 본 연구는 해저침적된 HNS를 회수하기 위한 기계장치를 개발할 때, 최우선으로 고려해야 하는 성능요건을 제시하였다. 해저의 오염물질을 회수하기 위하여 현재 사용되는 다양한 방식의 준설장비에 대하여 조사하고, 준설장비의 방식별 성능지표를 분석함으로써 기계장치에 대한 10가지의 성능지표를 선정하였다. 이러한 성능지표를 활용하여 해저침적 HNS 회수용 기계장치의 개발을 위한 성능요건을 제안하였다. 국내 항만의 수심을 고려하여, 해저침적 HNS 회수용 기계장치 의 성능요건을 생산율(50 ~ 300 m3/hr), 최대운용수심(50 m), 저질 종류(대부분의 저질 형태), 고형률(10 % 이상), 수평 작업 정확도(± 10 cm), 제한 유속(3 ~ 5 knot) 등으로 제안하였다. 이러한 성능요건은 해저침적 HNS 회수용 기계장치의 개념설계와 기본설계에 활용될 것으로 기 대된다.

PURPOSES: The purpose of this study is to evaluate the long-term physical and mechanical properties of domestic asphalt binders. METHODS: The physical properties are evaluated by penetration, softening point, penetration index, and binder viscosity. The mechanical properties were confirmed by the changes of G*, phase angle (δ), stiffness, and m-value. RESULTS: The physical properties of the asphalt binder were not clearly distinguished. In the case of G* flowing after using a pressure-aging vessel, the two types of PG 64-22 (a paving asphalt) showed similar results. However, the PG 76-22 binder was confirmed to have variations in value. The two types of PG 64-22 showed stiffness changes over time at the lowest temperatures, whereas the PG 76-22 binder maintained a constant range of change and exhibited stable behavior. CONCLUSIONS: The PG 76-22 binder showed stable behavior across physical and mechanical properties, but PG 64-22 binders showed viscosityy changes in some sections.

The main function of the general hospital building is to provide medical facilities and service. However, damage to the non-structural elements such as architectural, medical, mechanical and other components will interrupt those functions after the earthquake. Especially, it is considered that, damage to the non-structural elements is a serious event because it is directly associated with the lives of patients. Therefore, this study evaluated whether the certain non-structural elements of general hospital building has the seismic performance to provide hospital medical services after the earthquake. The evaluation is conducted by selecting the non-structural elements used in general hospital which are sensitive to acceleration, such as cooling towers, air handler, MRI and CT. As a result, the non-structural elements located on the upper floor without suitable support method did not meet the performance objective. Therefore, adequate anchorage against the seismic event is required for such non-structural elements that are acceleration-sensitives.

PURPOSES : The field application and performance of continuously reinforced concrete pavement (CRCP), constructed by using the mechanical tube-feeding method, are evaluated in this study. METHODS: The location of the rebar was evaluated by using the MIRA system. The early-age CRCP performance was evaluated via visual survey, in which the crack spacing and crack width were examined. RESULTS: The location of longitudinal reinforcing bars was evaluated via MIRA testing and the results showed that the longitudinal rebars all lie within a given tolerance limit (±2.5 cm) of the target elevation. In addition, owing to the low temperature when the concrete was pured, the crack spacing in the Dae-Gu direction is slightly wider than that of the Gwang-Ju direction. Almost all of the crack spacings lay within the range of 1.0 m~3.0 m. A crack width of <0.3 mm was measured at the pavement surface. However, as revealed by the field survey, the crack spacing was not correlated with the crack width. CONCLUSIONS : In CRCP constructed by using the mechanical tube-feeding method, almost all of the longitudinal reinforcing bars lay within the tolerance limit (2.5 cm) of the target elevation. The concrete-placing temperature affects the crack spacing, owing to variations in the zero-stress temperature. Crack survey results show that there is no correlation between the crack spacing and crack width in CRCP.

PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

Robots in various types carry and assemble parts through repeatedly and accurately moving to stored locations by combining linear motions. And, linear systems are used in orthogonal axes of robots and driven via ball screws, such as 2-axis cartesian coordinate robot in this paper. This paper presents the effect of the linear motion guide that is used in 2nd axis in 2-axis cartesian coordinate robot. Some simulation results show that the linear motion guide influence greatly in robot performance such as the nominal life of linear guide. When use LM guide that have capacity near in 2nd axis, this paper show that the nominal life on LM block of 1st axis increases 37.4% and that the specification of 2nd axis LM guide influences greatly the nominal life of 1st axis LM block.