• Steel and Composite Structures
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• 제22권6호
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• pp.1465-1486
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• 2016

Conventional plate I-girders are sensitive to local buckling of the web when they are subjected mainly to shear action because the slenderness of the web in out-of-plane direction is much bigger. The local buckling of the web can also cause the distorsion of the plate flange under compression as a thin-walled plate has very low torsional stiffness due to its open section. A new I-girder consisted of corrugated web, a concrete-filled rectangular tubular flange under compression and a plate flange under tension is presented to improve its resistance to local buckling of the web and distorsion of the flat plate flange under compression. Experimental tests on a conventional plate I-girder and a new presented I-girder are conducted to study the failure process and the failure mechanisms of the two specimens. Strain developments at some critical positions, load-lateral displacement curves, and load-deflection curves of the two specimens have all be measured and analyzed. Based on these results, the failure mechanisms of the two kinds of I-girders are discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.537-542
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• 1999

The design methodologies for carbon fiber sheet(CFS) strengthening of RC structures are not well established yet because the structural behavior of strengthened RC structures is more complex than that of unstrengthened ones. Even though the research for the methods using CFS has beed studied, the strengthening effects and structural behaviors of strengthened structures are not systematized yet. The purpose of this study is to carry out the experimental studies on three kinds of half scale RC slab bridges and to investigate the behavior of RC slab bridges from the experimental results. Typical flexural failure occurs in the non-strengthening slab like general RC slab bridges, and also the flexural failure occurs in the all area strengthened slab with sudden rip-off failure of strengthening material by punching shear. For the case of strip type strengthened slab, flexural failure occurs, with rip-off of second strip at the base of loading point. Strengthening effect on the slab using CFS is that the strength is increased upto 7~15 percent and the crack pattern is changed.

• Advances in concrete construction
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• 제4권4호
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• pp.319-332
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• 2016

In most cases strengthening reinforced concrete columns exposed to high strain rate is to be expected especially within weak designed structures. A special type of loading is instantaneous loading. Rapid loading can be observed in structural columns exposed to axial loads (e.g., caused by the weight of the upper floors during a vertical earthquake and loads caused by damage and collapse of upper floors and pillars of bridges).Subsequently, this study examines the behavior of reinforced concrete columns under rapid loading so as to understand patterns of failure mechanism, failure capacity and strain rate using finite element code. And examines the behavior of reinforced concrete columns at different support conditions and various loading rate, where the concrete columns were reinforced using various counts of FRP (Fiber Reinforcement Polymer) layers with different lengths. The results were compared against other experimental outcomes and the CEB-FIP formula code for considering the dynamic strength increasing factor for concrete materials. This study reveals that the finite element behavior and failure mode, where the results show that the bearing capacity increased with increasing the loading rate. CFRP layers increased the bearing capacity by 20% and also increased the strain capacity by 50% through confining the concrete.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.531-547
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• 2009

This paper presents the experimental results on the strength behavior and failure modes of box beam-to-circular column connections in steel piers. Previous research introduced parameters such as joint central angles, extension of horizontal stiffeners, and use of equivalent web depth, which ignored strength behavior and failure modes of box beam-to-circular column connections. The use of equivalent web depth $d_2$ is not reasonable when central angle ${\alpha}$ is closer to $90^{\circ}$; therefore, a monotonic loading test has been performed for eight connection specimens. From the test, it is identified that the connection with the circular column is stronger than the connection with the box-sectioned substitution column. Also, the strength of the beam-to-column connections with horizontal stiffeners is higher than the one of the no column stiffeners. The concrete-filled effect of box beam-to-circular column connection is also investigated, and the experimental yield strength of the connection is compared with the theoretical one. Also, more a reasonable equivalent web depth is suggested. The failure modes of connection are clearly defined.

• Computers and Concrete
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• 제22권3호
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• pp.291-303
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• 2018

As the concept of "sponge city" is proposed, the pervious concrete for permeable pavement has been widely used in pavement construction. This paper aims at investigating the dynamic behavior and energy evolution of pervious concrete under impact loading. The dynamic compression and split tests are performed on pervious concrete by using split Hopkinson pressure bar equipment. The failure criterion on the basis of incubation time concept is used to analyze the dynamic failure. It is demonstrated that the pervious concrete is of a strain rate sensitive material. Under high strain rate loading, the dynamic strength increases while the time to failure approximately decreases linearly as the strain rate increases. The predicted dynamic compressive and split tensile strengths based on the failure criterion are in accordance with the experimental results. The total damage energy is found to increase with the increasing of strain rate, which means that more energy is needed to produce irreversible damage as loading rate increases. The fractal dimensions are observed increases with the increasing of impact loading rate.

• International Journal of Reliability and Applications
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• 제13권1호
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• pp.1-17
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• 2012

This Paper deals with the stochastic behavior and failure analysis of a Viscose Staple Fibre Plant which produces fibre for making clothes. The fibre making plant is a complex system with various subsystems as: Vendor (supplies Charcoal and Sulphur, raw materials for the process), Carbon di sulphide Plant, Acid Plant, Pulp Plant and Processing Plant. The considered system can completely fail due to failure of any of the subsystems. The Carbon di Sulphide Plant can fail in two different ways, due to lack of Sulphur or Charcoal. Processing Plant has the configuration 5-out-of-10: d and 6-out-of-10: f. It is also assumed that the system can fail due to workers strike and catastrophic failure. All failures follow exponential time distribution whereas all repairs follow general time distribution. Preventive Maintenance policy has been applied to reduce the failure in the system. Various reliability characteristics such as transition state probabilities, steady state behavior, reliability, availability, M.T.T.F and the cost analysis have been obtained using supplementary variable technique and Gumbel-Hougaard copula methodology.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.527-532
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• 2000

The armor composite material targets such as aramid FRMLs with different type and ply number of face material and different type of back-up material, were studied to determine ballistic impact resistance and dynamic failure behavior during ballistic impact. Ballistic impact resistance is determined by $\textrm{V}_{50}$ ballistic limit, a statical velocity with 50% probability for complete penetration, test method. Also dynamic failure behaviors are respectfully observed that result from $\textrm{V}_{50}$ tests. $\textrm{V}_{50}$ tests with $0^{\circ}$ obliquity at room temperature were conducted with projectiles that were able to achieve near or complete penetration during high velocity impact tests. As a result, ballistic impact resistance of anodized Al 5052-H34 alloy(2 ply) is better than that of anodized Al 5052-H34 alloy(1 ply), but Titanium alloy showed the similar ballistic impact resistance. In the face material, ballistic impact resistance of titanium alloy is better than that of anodized Al 5052-H34 alloy. In the back-up material, ballistic impact resistance of T750 type aramid fiber is better than that of CT709 type aramid fiber.

• 한국세라믹학회지
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• 제26권5호
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• pp.645-654
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• 1989

Specimens of WC-Co were indented to measure the resulting crack size and unindented samples were fractured in 3-point flexure to obtain the strength and to measure characteristic features on the fracture surface. Fracture toughness was determined using fractography and compared to those determined using identation techniques. We show that principles of fracture mechanics can be applied WC-Co composites and can be used to analyze the fracture process. The fracture surfaces were examined by scanning electron microscopy and optical microscopy. Characteristic feature observed in glasses, single crystals and polycrystalline materials known as mirror, mist, hackle, and crack branching were identified for these composites. We discuss the importance of fracture surface analysis in determining the failure-initiating sources and the failure behaviorof WC-Co composites.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.102-105
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• 2000

Recently, applications of integrated large composite structures have been attempted to many structures of vehicles. To improve the cost performance and reliability of the integrated composite structures, it is necessary to judge structural integrity of the composite structures. For the judgement, we need fracture simulation techniques for composite structures. Many researches oil the fracture simulation method using FEM have been reported by now. Most of the researches carried out simulations considering only matrix cracking and fiber breaking as fracture modes, and did not consider delamination. Several papers have reported the delamination simulation, but all these reports require three-dimensional elements or quasi three- dimensional elements for FEM analysis. Among fracture mechanisms of composite laminates, delamination is the most important factor because it causes stiffness degradation in composite structures. It is known that onset and propagation of delamination are dominated by the strain energy release rate and interfacial moment. In this study, laminated composite has been described by using 3 dimensional finite elements. Then impact behavior of the laminated composite is simulated using FEM(ABAQUS/Explicit) with progressive failure mechanism. These results are compared with experimental results.

• 비파괴검사학회지
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• 제30권2호
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• pp.116-120
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• 2010

차축과 차륜으로 구성되는 철도차량 윤축은 차량의 운행과 관련하여 안전과 직결되는 중요한 철도 부품의 하나이다. 본 연구에서는 철도차량의 차축 재료의 인장파괴거동에 대한 특성을 분석하였다. 20년 이상 운행된 전기기관차 및 디젤전기기관차의 차축 시편에 대하여 연장시험을 수행하였다. 인장시험 동안 시편의 파괴특성을 모니터링하기 위해 고속 적외선카메라가 사용되었는데, 인장시험 동안의 시편 표변의 온도 변화를 모니터링하여 온도 분포로부터 인장파괴거동을 설명하고 파괴모드를 규명하고자 하였다.