The government declared ‘2050 carbon neutrality’ as a national vision in October 2020 and subsequently pursued the establishment of a ‘2050 carbon neutrality scenario’ as a follow-up response. Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support structures for liquid hydrogen storage tanks, a thermal-structural coupled analysis technique was developed using Ansys Workbench. Analytical models were created based on the number and arrangement of supports to propose structurally safe support designs.

Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. However, the low density of hydrogen makes its storage an urgent technical problem for hydrogen energy development. Compared with the density of gas hydrogen, the density of liquid hydrogen is more than 1.5 times higher. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support for liquid hydrogen storage tank, technique of thermal-structural coupled analysis including geometry, mesh, and boundary condition were developed using Ansys workbench, and equivalent stress and deformation distributions were analyzed.

Decarbonization plays an important role in future energy systems for establishing a zero-carbon society. Hydrogen is believed to be a promising energy source that can be converted, stored, and utilized efficiently, leading to a broad range of possibilities for future applications. Hydrogen can be stored in various forms, including compressed gas, liquid hydrogen, hydrides, adsorbed hydrogen. Among these, liquid hydrogen has high gravimetric and volumetric hydrogen densities. There are a lot of previous studies on thermal behavior of MLI and VCS and optimization insulation system, but research on the insulation performance by varying the head shape of the tank has not been conducted. In this study, thermal-structural coupled analysis was conducted on the insulation system with VCS positioned between two layers of MLI for a liquid hydrogen storage tank. The analysis considered dome shapes (torispherical, circle, ellipses), and heat flux and temperature were derived from thermal analysis to predict insulation performance. Maximum equivalent stress and deformation were calculated from the structural analysis, and the optimal dome shape was proposed.

This study proposed a seismic reinforcement of RC columns with non-seismic details, a fiber reinforcement method of aramid sheets and MLCP (high elasticity aromatic polyester fiber material) with different characteristics, and 4 full-size column specimens and conducted experiments. The results show that a non-seismic specimen (RC-Orig) rapidly lost its load-bearing capacity after reaching the maximum load, and shear failure occurred. The RC column reinforced with three types of aramid did not show an apparent increase in strength compared to the unreinforced specimen but showed a ductile behavior supporting the load while receiving a lateral displacement at least 1.57 to 1.95 times higher than the unreinforced specimen. The fracture mode of the specimen, according to the application of lateral load, also changed from shear to ductile fracture through aramid-based reinforcement. In addition, when examining the energy dissipation ability of the reinforced specimens, a ductile behavior dissipating seismic energy performed 4 times greater and more stably than the existing specimens.

Middle size of membrane retractable roof is under 25m span which consists of various moving systems. Sliding carriage is the system that leads the membrane to parking place, transferring the load from the membrane to structural cable. When membrane moves roof, thus, structural behavior of sliding carriage, which may contain various shapes with friction coefficients, should be investigated by vertical load as well as horizontal load. Nummerical simulation of sliding carriage prototypes, in this research, were performed by incrementation of vertical load and horizontal load as well. Consequently, this paper evaluated proper shapes of inner holder of Sliding carriage and evaluated the effective contact area of inner hold.

최근 경주지진과 포항지진 피해사례에서 보이듯 조적벽체 구조물의 붕괴 위험이 사회적으로 큰 주목을 받고 있다. 본 연구는 수평하중에 대한 강성이 구조적으로 취약한 조적벽체 구조물에 대하여 개선된 보강재 설계 및 이를 통한 구조성능 평가를 수행하였다. 선행기술에서 제시한 FRP Plate 보강재의 경우 외부 부착 시 계면 부착파괴에 의한 보강성능 저감이 발생하는 것을 고려하여 본 연구에서는 사전제작 매립형 T-Joint BFRP 보강재를 개발하였으며, 이를 혼합 에폭시계 연성페인트와 혼합 하여 보강 구조물의 마감효과 및 에너지흡수성능을 개선하는 방법으로 제안하였다. 실험 결과, 보강 시험체의 강성은 약 1.37배, 에너지소산능력은 약 2.59배 개선됨을 확인하였다.

In this analysis, the analytical model was verified through the normal mode analysis of the piston for the 2.9 liter IDI (indirect injection) engine. Heat transfer analysis was carried out by selecting two cases of applied temperature using the validated model. The first case was a condition of 350℃ on the piston upper surface and 100℃ on the piston body and inner wall. In the second case, the conditions were set to give a temperature of 400℃ on the upper surface of the piston and 100℃ on the piston body and the inner wall. In addition, the temperature distribution due to heat transfer was obtained for the pistons with boundary conditions of two cases, and then the thermal stress distribution due to thermal expansion was obtained using the input. Using this analysis result, the thermal stress caused by thermal expansion due to the thermal conduction of the piston is examined and used as the basic data for design.

최근 국내 구조물들의 노후화가 진행됨에 따라 구조물 보강과 관련된 연구에 대한 관심이 높아지고 있다. FRP보강은 노후화가 진행되어 성능이 저하된 구조물을 보강하는데 사용되며 주로 유리섬유를 사용한다. 그러나 이 유리섬유는 환경적 재 활용의 문제점이 대두되고 있다. 따라서 본 연구에서는 친환경적이고 내열성이 우수한 현무암 섬유를 활용한 휨 보강 플레이트 적용방법과 기존 FRP 외부부착의 문제점을 해소하기 위하여 연성 코팅용 보강페인트를 활용한 휨 보강 페인팅 적용방법을 통하여 각각의 경우에 대한 3점 휨 시험을 통하여 보강성능을 평가, 비교하였다. 그 결과 BFRP 보강의 경우 무보강 시험체에 비하여 약 1.2배 높은 강성 값을 나타내었고 콘크리트-BFRP 계면 부착력에 의한 연성효과도 나타났다. 반면 연성 코팅 보강페인팅 적용을 통한 휨 보강의 경우, 무보강 시험체에 비하여 약간의 개선효과는 나타났으나 실험체 제작의 오차 등을 고려할 때 실질적인 보강효과는 크게 나타나지 않았다. 따라서 연성 코팅페인팅을 활용한 보강방법의 경우, 향후 다양한 시공조건에 따른 추가연구가 필요할 것으로 판단된다.

유한요소법(finite element method)은 다양한 분야에서 재료의 역학적 거동을 더욱더 현실적으로 해석하고 예측하는 방법으로 다양한 분야의 제품 개발에 적용되고 있다. 하지만 섬유배향과 변형률 속도가 역학적 특성에 영향을 미치는 유리섬유 강화 플라스틱 복합재료에 관한 수치해석을 이용한 접근 방법은 현재까지 다소 어려움이 있다. 본 연구의 목적은 고분자, 고무, 금속 등과 같은 다양한 복합재료를 위한 선형, 비선형 다중스케일 재료 모델링 프로그램인 Digimat의 수치해석 재료 모델을 활용하여 유리섬유 강화 플라스틱 복합재료의 역학적 특성을 정의하고 검증하는 것에 있다. 또한 이를 통해 좀더 현실 적으로 고분자 복합재료의 거동을 예측하고자 한다. 이를 위해 다양한 고분자 중 30wt%의 단섬유 질량 비율을 갖는 폴리부 틸렌 텔레프탈레이트(polybutylene terephthalate, PBT)의 섬유배향과 변형률 속도에 따른 인장 특성을 참고문헌을 통해 조사하였다. 또한 Moldflow 프로그램을 사용한 사출해석을 통해 유리섬유 배향 정보를 계산하였으며 이를 매핑(mapping) 과 정을 통해 유한요소 인장 시편 모델에 전달하였다. 대표적인 유한요소 상용 프로그램 중 하나인 LS-DYNA는 유리섬유 배향과 변형률 속도에 따른 복합재료의 인장 특성을 연구하기 위해 Digimat과의 연성해석(coupled analysis)에 활용되었다. 그리고 유리섬유 강화 플라스틱 복합재료를 해석하기 위한 LS-DYNA의 다양한 비등방성(anisotropic) 재료 모델들의 장단점을 서로 비교하고 평가하였다.

The purpose of this study is focused on evaluating the flexural behavior of concrete beam, which are arranged by mechanically spliced reinforcing bar. To compare the existent lapping method with newly registered splicing method, four cases of concrete beam are tested to be failed flexurally by monotonic loading. Based on test results, ductility of specimen mechanically all spliced by parallel threaded coupler is approximately 4 times greater than those of other specimens.

Background: The multiple hop test is an active performance test that has been commonly used to assess individuals with functional ankle instability. Previous studies have suggested that insufficiency of dynamic postural stability and passive stability during dynamic activities can have an influence on performance in the multiple hop test. However, no study has investigated the effects of dynamic postural stability training and ankle bracing on multiple hop test performance in individuals with functional ankle instability. Objects: The purpose of this study was to compare the immediate effects of dynamic postural stability training versus ankle bracing in the performance of the multiple hop test for participants with functional ankle instability. Methods: Twenty-nine participants with functional ankle instability who scored below 24 in the Cumberland Ankle Instability Tool were selected. The participants were randomly divided into two groups: a dynamic postural stability training group (n1=14) and an ankle bracing control group (n2=15). The multiple hop tests were performed before and after applying each intervention. Dynamic postural stability training was performed using visual-feedback-based balance-training equipment; participants in this group were asked to perform a heel raise in a standing position while watching the centering of their forefoot pressure to prevent excessive ankle inversion. Ankle bracing was applied in the control group. Results: When comparing the pre- and post-intervention period for both groups, both methods significantly improved the results of the multiple hop test (p<.05). However, no significant differences were shown between the dynamic postural stability training and ankle bracing groups (p>.05). Conclusion: Both dynamic postural stability training and ankle bracing showed significant improvement (2.85 seconds and 2.05 seconds, respectively) in test performance. Further study is needed to determine the long-term effects of dynamic postural stability training and to determine whether insufficient dynamic postural stability is a causative factor for functional ankle instability.

Lifting plan in the large spacial structure is an important factor influencing the efficiency and economy of the construction process. The purpose of this study was deriving the requirements for lifting techniques as the basic research in the double spoke wheel roof structure construction. In the lift up erection method, management plan of the interference error in the column and outer-ring was needed that occur during lifting roof structure. In the bent erection method, material usage reduction plan was required by the structural design of the temporary bent. In the hybrid erection method, lifting plan was needed that minimizes weather condition and crane usage. All lifting techniques were required Value Engineering model for reduction of cost and construction period.

Middle size of membrane retractable roof is under 25m span which consists of various moving systems. Trolley is the system that leads the membrane to parking place, transferring the load from the membrane to structural cable. When membrane closes roof completely, thus, structural behavior of trolley, which may contain various material with different friction coefficients, should be investigated by vertical load. Nummerical simulation of trolley prototypes, in this research, was performed by incrementation of vertical load. Consequently, this paper studied proper friction characteristics and provided the effective inner materials of trolley.

The objective of this research is to development of a parametric design system for membrane structures. The parametric design platform for the spatial structures has been designed and implemented. Rhino3D is used as a 3D graphic kernel and Grasshopper is introduced as a parametric modeling engine. Modeling components such as structural members, loading conditions, and support conditions are developed for structural modeling of the spatial structures. The interface module with commercial structural analysis programs is implemented. An iterative generation algorithm for design alternatives is a part of the design platform. This paper also proposes a design approach for the parametric design of Spoke Wheel membrane structures. A parametric modeling component is designed and implemented. SOFiSTik is examined to interact with the design platform as the structural analysis module. The application of the developed interface is to design optimally Spoke Wheel Shaped Ductile Membrane Structure using parametric design. It is possible to obtain objective shape by controlling the parameter using a parametric modeling designed for shape finding of spoke wheel shaped ductile membrane structure. Recently, looking at the present Construction Trends, It has increased the demand of the large spatial structure. But, It requires a lot of time for Modeling design and the Structural analysis. Finally an optimization process for membrane structures is proposed.

In this paper, time and frequency domain characteristics of Gyeong-ju earthquakes were investigated, and nonlinear time history analyses were conducted for bi-linear hysteretic structures excited by short-duration ground accelerations. Previous studies showed that larger inelastic displacements than the peak displacement of the corresponding elastic system were observed especially for the structures with structural period shorter than 0.3s, and the similar results could be obtained when long-duration ground accelerations were used as excitation loads. For the short-duration earthquakes, however, the inelastic displacements were not so large and almost identical to the peak elastic displacements.