• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.1-8
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• 2014

The present study proposes a simple equation to straightforwardly determine the potential plastic hinge length in boundary element of reinforced concrete shear walls. From the idealized curvature distribution along the shear wall length, a basic formula was derived as a function of yielding moment, maximum moment, and additional moment owing to diagonal tensile crack. Yielding moment and maximum moment capacities of shear wall were calculated on the basis of compatability of strain and equilibrium equation of internal forces. The development of a diagonal tensile crack at web was examined from the shear transfer capacity of concrete specified in ACI 318-11 provision and then the additional moment was calculated using the truss mechanism along the crack proposed by Park and Paulay. The moment capacities were simplified from an extensive parametric study; as a result, the equivalent plastic hinge length of shear walls could be formulated using indices of longitudinal tensile reinforcement at the boundary element, vertical reinforcement at web, and applied axial load. The proposed equation predicted accurately the measured plastic hinge length, providing that the mean and standard deviation of ratios between predictions and experiments are 1.019 and 0.102, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.52-59
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• 2012

An analytical model is presented to predict the static behavior of the long-span prestressed concrete bridge deck(the long-span PSC deck). The finite element analysis is performed and the results are compared with that of the previous experimental test. The load-deflection relationship curves by FEM are in good agreement with the results reported in the previous study. The failure mode of all test specimens is predicted by the punching shear in this study. It is also observed in the previous experimental test. The main objective of this paper is presenting supportive method to predict static behavior of the long-span PSC deck slab. It is not simulating the punching shear behavior graphically.

• Composites Research
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• v.16 no.6
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• pp.41-47
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• 2003

Composites are widely used for aircraft, satellite and other structures due to its good mechanical and thermal characteristics such as low coefficient of thermal expansion(CTE), heat-resistance, high specific stiffness and specific strength. In order to use composites under condition of high temperature, however, material properties of composites at high temperatures must be measured and verified. In this paper, material properties of T700/Epoxy were measured through tension tests of composite specimens with an embedded FBG sensor in the thermal chamber at the temperatures of RT, $100^{\circ}$, $200^{\circ}$, $300^{\circ}$, $300^{\circ}$. Through the pre-test of an embedded optical fiber, we confirmed the embedding effects of an optical fiber on material properties of the composites. Two kinds of specimens of which stacking sequences are [0/｛0｝/0]$_{T}$. and [$90_2$/｛0｝/$90_2$]. were fabricated. From the experimental results, material property changes of composites were successfully shown according to temperatures and we confirmed that fiber Bragg grating sensor is very appropriate to strain measurement of composites under high temperature.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.85-91
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• 2010

In this study, the drying shrinkage strains were compared of 24~60 MPa concrete specimens subjected to various curing conditions and measurement methods were compared. And, the applicability of the test and prediction methods were investigated. According to the results, drying shrinkage was significantly reduced in 28 day curing condition. In the sealed curing case, drying shrinkage strain from demolding time was identical to the one of the standard curing case for low strength concrete, however, drying shrinkage strain was greatly increased than the standard case for high strength case because of the effect of autogenous shrinkage. The efficient measurement was possible using the embedded gage for concrete drying shrinkage, but, the measured value by contact gage was lower than the one by the embedded gage. The test results agreed with EC2 model better than the other.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.261-264
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• 2008

When the concrete is confined to width direction, stress-strain curve of concrete are different from the uniaxial behavior. In case of normal strength concrete, Mander model are used with concrete material model which considers confining effect. Sakino-Sun model showed experimental result of specimen-level and the highest accuracy. Therefore, Normal strength concrete used Mander model. and High strength concrete used Sakino-Sun model. But there are significant differences from actual data when medium strength concrete used Mander or Sakino-Sun model. and Limit scope of maximum or minimum compressive strength of concrete is not clear when applied to two models. Therefore, In this research, material nonlinear model of confined concrete is suggested when concrete which has 30-40MPa's strength is confined to width direction.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.297-303
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• 2016

Shrinkage Reducing Agent(SRA) was developed in order to control drying shrinkage cracks in concrete, and the use of SRA is increasing since it can control drying shrinkage cracks and improve the quality of concrete structures. Although there are many types of prediction equations of drying shrinkage strain, there is no prediction method which can consider the effect of SRA up to the present. Therefore, it is impossible to predict the tensile stress generated by drying shrinkage of SRA concrete, and to investigate the quantitative serviceability limit state of SRA concrete. In this study, the drying shrinkage of SRA concrete was investigated by experiment and analysis in order to suggest the predictability of drying shrinkage of SRA concrete. As a result, AIJ model, ACI model, GL2000 model showed there was a correlation between the predicted values and the experimental values within the error range of ${\pm}10%$. However, CEB-FIP model and B3 model underestimated the experimental values.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.3
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• pp.369-380
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• 2019

When a extreme loading such as blast is applied to prestressed concrete (PSC) structures and infrastructures for an instantaneous time, serious property damages and human casualties occur. However, a existing design procedure for PSC structures such as prestressed containment vessel (PCCV) and gas storage tank do not consider a protective design for extreme internal blast scenario. Particularly, an internal blast is much more dangerous than that of external blast. Therefore, verification of the internal blast loading is required. In this paper, the internal blast resistance capacity of PSC member is evaluated by performing internal blast tests on RC and bi-directional PSC scaled down specimens. The applied internal blast loads were 22.68, 27.22, and 31.75 kg (50, 60, and 70 lbs) ANFO explosive charge at 1,000 mm standoff distance. The data acquisitions include blast pressure, deflection, strain, crack patterns, and prestressing force. The test results showed that it is possible to predict the damage area to the structure when internal blast loading occurs in PCCV structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.775-786
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• 2022

In the plant structures including nuclear power plants, penetrations are frequently installed in walls and slabs to reinforce facilities during operation, and reinforcing bars are sometimes cut off during concrete coring. Since these penetrations are not considered at the design or construction stage, cutting of reinforcing bar during opening installation is actually damage to the structure, structural integrity evaluation considering the stress transition range or effective width around the new penetration is necessary. In this study, various nonlinear analyses and static loading experiments are performed to evaluate the effect of reinforcing bar cutting that occurs when a penetration is newly installed in the shear wall of wall-type building of operating nuclear power plant. In addition, the decrease in wall stiffness due to the installed new penetration and cutting of reinforcing bars is evaluated and the stress and strain distributions of rebars around penetration are also measured.

• Journal of Yeungnam Medical Science
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• v.14 no.2
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• pp.274-284
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• 1997

조기 유방암에 대한 바람직한 치료는 유방의 형태를 최대한 보존하면서 악성 종양을 치료하는 것이다. 이러한 목적을 충분히 달성하기 위하여 최대한 조기에 유방암을 진단하고 미용상 종양 절제술에 적합한 환자를 선택하여 절제 범위를 최소화한 유방 보존술을 시행하며 수술 후 유방 전체에 대한 근치적인 방사선 치료를 적절히 시행하면 된다. 여러 연구에서 전통적인 치료법인 근치적 또는 변형 근치적 유방 절제술의 성적과 비교하여 차이가 없으므로 조기 유방암의 치료에는 이상적인 치료법으로 인정된다. 이와 병행하여 액와부 림프절 및 전신적인 재발에 대한 진단 및 예방을 위하여 액와 림프절에 대한 충분한 외과적인 처치와 병리학적인 검사를 시행하여 불필요한 방사선 치료로 인한 부작용을 최소화하여야 한다. 만약 전신적인 치료가 요구되는 경우에는 항암제 및 내분비 요법을 병행하여 재발을 억제해야 유방 보존술의 장점을 살릴 수 있다. 결론적으로 이 치료법이 조기 유방암 환자의 삶의 질을 개선시키면서 최상의 치료 효과를 얻기 위해서는 유관 진료 각과의 의료진이 유기적으로 협조하여 조기 진단률을 높히고, 유방 보존술 및 방사선 치료 과정에서 환자들에게 치료 결과에 대한 확신을 심어주도록 열심히 노력해야 된다. 또한 치료와 연관된 부작용이나 합병증을 최대한 줄여나가는 방향으로 치료 방법을 계속 보완 발전시키는 것이 매우 중요하며 아직도 발전의 여지가 많은 이 치료법이 조기 유방암의 이상적인 치료법으로 정착하기 위해서는 향후 다양한 임상적인 경험을 통한 더 많은 연구가 필요하리라 생각한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3424-3432
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• 1996

For mechanical system operating at high temperature, damage due to the interaction effect of creep and fatigue plays an important role. The objective of this paper is to develop a modified creep-fatigue damage model which separately analyzes the pure creep damage for hold time and the creep-fatigue interaction damage during startup and shutdown period. The creep damage was calculated by the general creep damage equation and the creep-fatigue interaction damage was calculated by the modified equation which is based on the frequency modified strain range method with strain rate term. In order to verify the proposed model, a service of high temperature low cycle fatigue tests were performed. The test specimens were made from inconel-718 superalloy and the test parameters were wave shape and hold time. A good agreement between the predicted lives based on the proposed model and experimentally obtained ones was observed.