• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.928-937
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• 1989

Applicability of $T_{\delta}$ proposed by Shin et al as an instability parameter for ductile material is investigated, Both general fracture test and instability fracture test are performed using compact tension specimens of structural alloy steel(SCM4), The values of ( $T_{\delta}$)$_{app}$(applied tearing modules) estimated from the real load vs. crack growth curve measured from experiments are compared with those estimated from the limit load vs. crack growth curve. The results are:(1) the $T_{\delta}$ parameter may be used as a crack instability parameter:(2) the use of ( $T_{\delta}$)$_{app}$ estimated from the load-crack growth curve, proposed in this study is reasonably justified.ified.d.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.229-236
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• 2015

In this study, the resilient modulus test and Light Weight Deflectormeter (LWD) test were conducted to simulate the moving vehicle load for the evaluation of the internal failure of epoxy asphalt pavement. The Measured displacement in the resilient modulus test of epoxy asphalt concrete showed very little residual deformation under repeated loads unlike the conventional asphalt. Therefore, the test results were evaluated as a normal state due to its similarity with elastic deformation. The deflection results from the resilient modulus tests were converted to the surface deflection modulus and the normal range of surface deflection modulus was estimated applying LWD measurement of 1 SIGMA level. Internal failure of pavements were estimated using the suspicious failure range at $60^{\circ}C$ and hysteresis. Internal moisture penetration and a decrease in bonding were observed in partial areas at $140{\mu}m$ of surface deflection. However, the areas showed inflection points in the hysteresis. Field investigation by suggested criterion indicated a high degree of accuracy.

• Tunnel and Underground Space
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• v.13 no.6
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• pp.476-485
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• 2003

The purpose of this study is to present an analysis method for the prediction of the change of ground conditions. To this end, three-dimensional convergence displacements is analyzed in several ways to estimate the trend of displacement change. Three-dimensional arching effect is occurred around the unsupported excavation surface including tunnel face when a tunnel is excavated in a stable rock mass. If the ground condition ahead of tunnel face changes or a weak fracture zone exists a specific trend of displacement change is known to be occurred from the results of the existing researches. The existence of a discontinuity, whose change in front of the tunnel face, can be predicted from the ratio of L/C (longitudinal displacement at crown divided by settlement at crown) etc. Therefore, the change of ground condition and the existence of a fracture zone ahead of tunnel face can be predicted by monitoring three-dimensional absolute displacements during excavation, and applying the methodology presented in this study.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.551-558
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• 2015

Lateral displacement in the most complex-shaped tall buildings is caused by eccentric gravity loads which are induced by the difference in location between a center of mass and a center of stiffness. The lateral displacements obtained from analysis, using conventional procedures, are prone to overestimate the actual values because much of realignment efforts made during construction phase are ignored. In construction sequence analysis, the self-leveling of slab and the verticality of columns/walls could be considered at each construction stage. Moreover, the displacement compensation can be achieved by manual process such as re-centering - locating to global coordinates through surveying. Because the lateral displacement increases with the building height, it is necessary to set up adjustment plan through construction stage analysis in advance in order to result in displacements less than the allowable limits. Because analytical solution includes lots of assumptions, the pre-adjusting displacement should be reasonably controlled with considerations for the uncertainty due to these assumptions.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.324-329
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• 1998

본 연구는 주증기배관으로 사용되고 있는 SA106. Gr.C의 모재와 용접계에 대해서 파괴인성에 미치는 온도와 하중속도의 영향을 살펴보기 위해서 다양한 온도와 하중속도에서 J-R 시험 및 인장시험을 수행하였다. 두 재료 모두 동적변형시효의 영향을 받고 있는 온도영역에서 약 40% 정도의 파괴인성 감소가 관찰되었으며, 하중속도에 따른 파괴인성 감소영역은 serration과 인장강도 증가 영역의 하중속도 의존성과 일치하였다. 원자력발전소 운전온도에서 모재와 용접재 모두 하중선변위속도가 4.0mm/min 일 때 파괴인성치의 최저를 보였으며, 하중속도가 증가함에 따라 증가하여 동적하중속도(800, 40mm/min)일 때 최대를 보였다. 모재와 용접재를 비교하면 용접재에서 serration이 뚜렸했고, 보다 넓은 온도영역에서 관찰되었다. 또한 인장강도의 증가가 보다 고온에서 형성되었다. 이러한 특성은 용접재가 모재에 비해 냉각률이 크고 미세한 결정입으로 이루어져있으며, 망간의 함량이 높기 때문으로 판단된다.

• Composites Research
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• v.12 no.3
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• pp.45-54
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• 1999

In this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded SMA wire actuators is performed. For the purpose of enhancing the critical buckling load, buckling control is investigated through the use of reactive moment associated with the shape recovery force of SMA wire actuators. To improve the control authority for the buckling and postbuckling control of the SMA-composite beam, closed-loop control is used. The buckling and postbuckling control behaviours are presented and discussed qualitatively and quantitatively on loaddeflection plots considering the stacking sequence of the laminate, slenderness ratio of the beam and activation conditions of the SMA wire actuators. By maintaining the desired deflection shape with the proper reactive moment, buckling control can be extended to the postbuckling of the SMA-composite beam subjected to an external load.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.19-26
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• 2012

In the present study, anchor type nail with PC-strand which can add up the pre-stress at the nailing to increase the resistance and shear stress in the whole ground has been investigated. Load-displacement and wall displacement have been analyzed by experimental model and numerical analysis of anchor type nail, nailing, and non-nailing to examine the behavior of anchor type nail. From the experimental results, it was found that horizontal displacement is considerably decreased according to increasing the load in case of anchor type nail added pre-tension. Especially, it was observed that resistance of displacement at the upper wall is increased. The results of numerical analysis show the same results of experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.77-86
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• 1989

A modified $C^{*}$ integral as load parameter in creep fracture is proposed considering the effect of crack growth. It is shown that the parameter does not depend on crack velocity. By performing experiment using STS 304 stainless steel at 600.deg.C the validity of the parameter is investigated. The results show that the parameter is a good measure as a load parameter in creep fracture and the rate of crack tip opening displacement can also be a creep load parameter for STS 304 at 600.deg. C.C.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.187-196
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• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of pile should be known accurately. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanism of drilled shaft socketed into weathered rock was investigated. For the investigation, five cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the Held test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The f-w (side shear resistance-displacement) curve of the pile in moderately weathered rock reached to yielding point at a for millimeter displacements, and after yielding point, the rate of resistance increment dramatically decreased. However, the f-w curve in the highly/completely weathered rock did not show the obvious yielding point, and the resistance gradually increased showing the hyperbolic pattern until relatively high displacement (>15 mm). The q-w (end bearing resistance-displacement) curves showed linear response at least until the base displacement of approximately 10 mm, regardless of rock mass conditions.

• Journal of the Korean Geotechnical Society
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• v.31 no.2
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• pp.47-63
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• 2015

A fundamental study of drilled shafts subjected to lateral cyclic loading in weathered soil was carried out based on field tests and numerical analysis. The emphasis was given on quantifying the cyclic p-y curve function from lateral cyclic loading tests and three-dimensional finite element analysis. Lateral cyclic loading tests and three-dimensional finite element analysis were carried out to investigate the behavior of drilled shafts according to the direction of cyclic loading. Based on the field tests and numerical analysis, a modified lateral load transfer relationship and design chart with degradation factors were proposed by considering the characteristics of cyclic loading. It was found that the prediction by the proposed p-y curve function is in good agreement with the general trends observed by in-situ measurements, and it represents a practical improvement in the prediction of lateral displacement and bending moment distribution of drilled shafts subjected to cyclic loading.