• 한국해양공학회지
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• 제20권4호
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• pp.17-23
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• 2006

Monotonic four-point bending tests were conducted on straight pipe specimens, 102 mm in diameter with local wall thinning, in order to investigate the effects of the depth, shape, and location of wall thinning on the deformation and failure behavior of pipes. The local wall thinning simulated natural erosion/corrosion metal loss. The deformation and fracture behavior of the straight pipes with local wall thinning was compared with that of non wall-thinning pipes. The failure modes were classifiedas local buckling, ovalization, or crack initiation, depending on the depth, shape, and location of the local wall thinning. Three-dimensional elasto-plastic analyses were carried out using the finite element method. The deformation and failure behavior, simulated by finite element analyses, coincided with the experimental results.

• 한국해양공학회지
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• 제18권1호
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• pp.63-68
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• 2004

The purpose of this study is to estimate the contribution of concrete and shear reinforcement, in shear carrying capacity, on concrete beams, reinforced with steel and/or FRP rods. The experimental tests for 12 concrete beams, reinforced with steel and/or FRP rods, are carried out. Experimental parameters includes the mechanical properties of reinforcements in shear and bending, and the ratio of shear reinforcement. This study compares the experimental results of shear carrying capacity in concrete beams, reinforced with steel and/or FRP rods, with the proposed equations. According to the experimental results, the effect of the concrete in concrete beams reinforced with FRP rods is decreased with decreasing Young's modulus of longitudinal tensile reinforcement. This results from the large deflection of concrete beams reinforced with decreasing Young's modulus of longitudinal tensile reinforcement. Also, the contribution of shear reinforcement is smaller than the calculated value, using the truss analogy. This results from the fact that the stress redistribution is not exhibited after the break of shear reinforcement.

• 한국해양공학회지
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• 제16권2호
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• pp.67-71
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• 2002

Damage process of CFRP laminates was characterized by Acoustic Emission (AE). The main objective of this study is to determine if the sources of AE in CERP laminates could be identified from the characteristics of the waveform signals recorded during monotonic tensile test. The time history and power spectrum of each individual wave signal recorded during test were examined and classified according to their special characteristics. The wave from and frequency of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pull-out and fiber fracture as load is increased. Four distinct types of signals were observed regardless of specimen condition. The result showed that the AE method could be effectively used for analysis of fracture mechanism in CFRP laminates.

• Structural Engineering and Mechanics
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• 제15권4호
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• pp.437-449
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• 2003

The aim of this study is to develop an analytical model of a beam with open cracks and external strengthening which is able to predict its modal scheme components (natural frequencies and mode shapes). The model is valid as far as the excitation level is low enough not to activate non linear effects. The application field of the model are either the prediction of the efficiency of the reinforcement or the non destructive assessment of the structural properties. The degrees of freedom associated to the fault lips must be taken into account in order to introduce the effect of the external strengthening. In a first step, an analytical formulation of a beam with thin notches is proposed according to the references. The model is then extended to incorporate the strengthening consisting in a longitudinal stiffness applied in the vicinity of the cracks. In a second step, the analytical results are compared with these obtained from a finite element simulation.

• Structural Monitoring and Maintenance
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• 제6권4호
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• pp.269-289
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• 2019

This study investigated experimentally the response of thick reinforced concrete specimens having hollow cores with critical parameters. The investigation includes testing of twelve specimens that are solid and hollow-core slab models. Each specimen consists of two pieces, the piece dimensions are (1.2 m) length, (0.3 m) width and (20 cm) thickness tested under both monotonic and repeated loading. The test program is carried out to study the effects of load type, core diameters, core shape, number of cores, and steel fiber existence. Load versus deflection at mid span, failure modes, and crack patterns were obtained during the test. The test results showed that core shape and core number has remarkable influenced on cracking pattern, ultimate load, and failure mode. Also, when considering repeated loading protocol, the ultimate load capacity, load at yielding, and ductility is reduced.

• 한국추진공학회지
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• 제4권1호
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• pp.53-64
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• 2000

모드 I 응력확대계수를 결정하기 위한 스트레인게이지법이 연구되었다. CT 시험편과 3점 굽힘 시험편이 사용되었다. 시험편의 예리한 노치부는 와이어 방전 가공에 의하여 제작되었다. 균열 선단 영역으로부터 얻은 스트레인게이지 신호는 응력확대계수를 계산하는데 사용되었다. 시험 결과는 ASTM E399에 의하여 얻어진 결과 및 유한요소해석 결과와 비교하였다. 시험 결과들과 유한요소해석 결과는 잘 일치하였다. 이 방법을 적용할 때 스트레인게이지 부착 위치는 신중히 고려되어야 한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.31-34
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• 2006

이 논문에서는 선관통형 균열을 포함하는 정사각형 평판과 선관통형 균열이 연속체 손상이론을 이용에서 구한 유효 직교 이방성 탄성 물성치의 등가 연속체 모델로 대체된 평판의 모드형상과 고유진동수를 비교하여 SEEP에 기반하여 Lee 등이 [5] 제안한 연속체 손상이론을 검증하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.425-428
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• 2004

Nonlinear finite element analysis is conducted to predict the structural behavior of precast concrete column and steel beam connected by using bolted connections. The Nonlinear FEM program is based on the modified compression field theory which has good accuracy in the concrete structures. The link element is properly used to model the discontinuity between precast concrete column and steel beam. Predictions from the proposed model are compared with experimental results and it is concluded that structural behaviors of the composite structures, such as strength capacity, crack pattern and failure mode, can be predicted quite successfully.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.347-353
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• 2002

The compressive residual stress, which is induced by shot peening process, seems to be an important factor of increasing the fatigue strength. And then it was showed that residual stress was disappearenced at the high temperature. The fatigue characteristic study of a SUP9 spring steel processed shot peening is performed by considering the high temperature service conditions in the range of room temperature through $180^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. The fatigue resistance characteristics and fracture strength at high temperature is considerable lower than that of room temperature in the early stage and stable of fatigue crack growth region.

• 비파괴검사학회지
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• 제27권6호
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• pp.550-555
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• 2007

Stress intensity factor is one of the most important parameters in fracture mechanics. Both the stress field distribution and the crack propagation are closely related to these parameters. Due to the complexity of actual engineering problems, it is difficult to calculate the stress intensity factor by theoretical formulation, so photoelasticity method is a good choice. In this paper, modified two parameter method is employed to calculate stress intensity factor for opening mode by using data from more than one photoelastic fringe loop. For getting accurate experiment results, the initial fringes are doubled and sharpened by digital image programs from the fringe patterns obtained by a CCD camera. Photoelastic results are compared with those obtained by the use of empirical equation and FEM. Good agreement shows that the methods utilized in experiments are considerably reliable. The photoelastic experiment can be used for bench mark in theoretical study and other experiments.