• 한국재난정보학회 논문집
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• 제19권2호
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• pp.262-269
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• 2023

연구목적: 터널에서 발생되는 화재로 인하여 구조물의 피해를 보호하기 위해 적용되는 PSC 슬래브에 부착된 내화패널의 성능을 평가할 목적으로 내화실험을 수행하였다. 연구방법: 내화실험은 RWS 화재 이력곡선 화재시간-온도곡선을 적용하였으며, 한국건설기술연구원(KICT)의 가열로를 이용하여 내화 성능을 평가하였다. 연구결과:국제터널학회(2004)에서 제시하는 기준으로 내화성능 실험을 실시한 결과, 내화패널과 콘크리트의 접촉면에서의 최대온도는 콘크리트에 손상을 주는 한계온도(380℃) 이하였으며, 접촉면과 25mm 이격된 지점에서의 최대온도는 철근에 손상을 주는 한계온도(250℃) 이하로 측정되었다. 실험결과로부터, 내화패널이 30mm두께로 부착된 PSC 슬래브 시험체는 내화성능을 가진 것으로 평가되었다. 결론: 터널이나 지하차도에서의 화재발생시 내화패널을 부착하는 보강방법은 화재로부터 구조물을 보호할 수 있으며 향후, 내화패널이 부착된 슬래브의 정적 성능시험을 수행하고, Pull-off test와 피로실험을 실시하여 내화패널의 부착성능을 확인하는 것이 필요하다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.69-73
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• 2001

Damage induced by low-velocity impact on the curved composite laminates was experimentally evaluated for CFRP cylindrical shells with the radius of curvatures of 50, 150, 300, and 500 mm. The result was then compared with that of flat laminates. The radius of curvatures and the effective shell stiffness appeared to considerably affect the dynamic impact response of curved shells. Under the same impact energy level, the maximum contact force increased with the decreasing radius of curvatures, with reaching 1.5 times that for plates at the radius of curvature of 50 mm. Since the maximum contact force is directly related to the impact damage, curved laminates can be more susceptible to delamination and less resistant to the low-velocity impact damage. The distribution of delamination along the thickness direction of curved laminates are also different from that of flat plates. Delamination was distributed rather even]y at each interface along the thickness direction of curved laminates. This implies that the effect of curvatures has to be considered for the design of a curved composite laminate.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.71-75
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• 2005

For the damage tolerance improvement of conventional laminated composites, stitching process have been utilized for providing through-thickness reinforcements. 2D preforms were stacked with S-2 glass plain weave and S-2 glass MWK (Multi-axial Warp Knit) L type. 3D preforms were fabricated using the stitching process. All composite samples were fabricated by RTM (Resin Transfer Molding) process. To examine the damage resistance performance the low speed drop weight impact test has been carried out. For the assessment of damage after the impact loading, specimens were examined by scanning image. CAI (Compressive After Impact) tests were also conducted to evaluate residual compressive strength. Compared with 2D composites, the damage area of 3D composites was reduced by 20-30% and the CAI strength showed 5-10% improvement.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.264-267
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• 2005

Impact damages are very important in the perspective of residual strength of composite structures such as aircrafts, ships, and trains because those damages are sometimes not visible on the surface of the point of impact and the impact resistance of laminated composites is usually not so high. Thus, the impact characteristics of laminated composites should he investigated for the safety of composite structures. This paper investigates the low-velocity impact and damage detection conducted on woven carbon/epoxy laminates. Experimental results show that the type of damage is dependent on the impact energy level and the delamination area becomes larger as the impact energy increases.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 봄 학술발표회 논문집
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• pp.37-43
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• 1990

This paper develops practical models and methods for the assessment of safety and rating of damaged and/or deteriorated bridges by incorporating a system identification technique for the explicit inclusion of the degree of deterioration or damage and of the actual bridge response. And, based on the proposed model, reliability-based rating methods are proposed as LRFR(Load and Resistance Factor Rating) and system reliability-index rating criteria. The proposed limit state model explicitly accounts for the degree of deterioration or damage in terms of the damage and response factors. The damage factor in the paper is proposed as the ratio of the current stiffness to the intact stiffness. Based on the observation and the results of applications to existing bridges, it may be concluded that the proposed rating models, which explicitly account for the uncertainties and the effects of degree of deterioration or damage based on the system identification technique, provide more realistic and consistent safety-assessment and capacity-rating.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.86-91
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• 2002

Glass/phenolic composite laminates have been used in the field of non-flammable light rail transit and their applications have expanded more widely. Low velocity impact tests have been used to evalute the effect of temperature and acceleration aging on low velocity impact response of phenolic matrix composites reinforced with woven E-glass fabric. The damage of matrix cracking and delamination are suddenly reduced the compressive strength after impact. The damage area increases with increasing temperature and impact energy. UT C-scan is used to determine damage areas by impact loading. Therefore, all this observations indicate reduced impact damage resistance and damage tolerance of the laminates at elevated temperature.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.295-300
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• 2002

To establish an optimum condition in the surface treatment and curing process will be an important parameters for the fabrication of multilayered hybrid composite materials, A17075/CFRP (CARALL : carbon fiber reinforce aluminum laminates). Effects of carbon fiber direction and thickness variation in tensile strength were investigated. And impact damage behavior of carbon fiber reinforce plastic (CFRP) and CARALL were investigated also, it was found that a partial stress increase in order of epoxy adhesive, A17075, CFRP. And the partial stress of CFRP carried out a great portion of applied stress. The impact damage resistance of CARALL was higher than that of CFRP. This is because both side Al sheet of CARALL absorb a great of impact damage.

• 한국도로학회논문집
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• 제16권1호
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• pp.31-39
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• 2014

PURPOSES : Surface treatment material for pavement preventive maintenance should be inspected field applicability. This study(Part II) aimed to checkup coating characteristics and performance analysis using lab and field tests. The hydrophobic - low viscosity filling material for pavement preventive maintenance is presented in Part I, which is a series of companion study. METHODS : Relative comparison between general asphalt mixtures and surface treatment asphalt mixtures are analyzed and measured for the field application such as indirect tensile strength ratio(TSR), abrasion resistance, crack propagation resistance, temperature resistance, coating thickness, permeability resistance and skid resistance in terms of british pendulum number(BPN). RESULTS : It is found that TSR, crack propagation resistance and permeability resistance is increased as against uncoated asphalt specimen. Abrasion resistance and temperature resistance is secured from the initial coating thickness point of view, which is about 0.2~0.3mm. Skid resistance on the surface treatment pavement is satisfied with the BPN criteria of national highway because of exposed aggregate and crack sill induced pavement deterioration and damage cracks. CONCLUSIONS : The hydrophobic - low viscosity surface treatment material for pavement preventive maintenance is validated on field applicability evaluation based on quantitative analysis of coating thickness and performance analysis using lab and field tests.

• 대한기계학회논문집A
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• 제30권4호
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• pp.393-401
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• 2006

The influences of stress triaxiality on ductile fracture have been investigated for various specimens and structures. With respect to a transferability issue, recently, the interests on local approaches reflecting micromechanical specifics are increased again due to rapid progress of computational environments. In this paper, the applicability of the local approaches has been examined through a series of finite element analyses incorporating modified GTN and Rousselier models as well as fracture toughness tests. The ductile crack growth of nuclear carbon steels is assessed to verify the transferability among compact tension (CT) specimens with different in-plane size. At first, the basic material constants were calibrated for standard CT specimens and used to predict fracture resistance (J-R) curves of larger CT specimens. Then, the in-plane size effects were examined by comparing the numerically estimated J-R curves with the experimentally determined ones. The assessment results showed that the in-plane size effect should be considered for realistic engineering application and the damage models might be used as useful tool for ductile fracture evaluation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.485-488
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• 2008

터널 화재시 화재강도는 매우 높으며 터널 내부에서 화재 발생은 높은 화재강도에 의해 구조요소인 숏크리트 및 콘크리트 라이닝의 화재 노출표면에서 폭열 발생을 유발시키는 동시에 터널 안정에 있어 중요한 역할을 수행하는 앵커 등의 터널에 매입된 강재 또한 고온의 노출로 인한 열전달로 급격한 응력감소가 발생하게 된다. 따라서 본 실험에서는 화재강도(Modified Hydrocarbon Curve)와 매입된 강재의 내화 유무를 변수로 정하여 콘크리트 라이닝의 내부에 매입된 강재의 열전도를 알아보기 위한 화재시험을 수행하였다. 또한 최근 ITA(International Tunneling Association)에서 연구한 도로 터널내화구조 기준에 따라 강재의 열손상 임계 온도범위를 산정하여 열적 손상 정도를 평가하였다.