• Earthquakes and Structures
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• 제11권4호
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• pp.609-627
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• 2016

Results of an experimental program are presented in this paper for the influence of vertical load on the in-plane behavior of masonry infilled steel frames. Five half-scaled single-story, single-bay steel frame specimens were tested under cyclic lateral loading. The specimens included four infilled frames and one bare frame. Two similar specimens as well as the bare frame had moment-resisting steel frames, while the remaining two specimens had pinned steel frames. For each frame type, one specimen was tested under simultaneous vertical and lateral loading, whereas the other was subjected only to lateral loading. The experimental results show that the vertical load changes the cracking patterns and failure modes of the infill panels. It improves dissipated hysteresis energy and equivalent viscous damping. Global responses of specimens, including stiffness and maximum strength, do no change by vertical loading considerably. Regarding the ductility, the presence of vertical load is ignorable in the specimen with moment-resisting frame. However, it increases the ductility of the infilled pinned frame specimen, leading to an enhancement in the m-factor by at least 2.5 times. In summary, it is concluded that the influence of the vertical load on the lateral response of infilled frames can be conservatively ignored.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.37-42
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• 2000

The boiler tubes and steam Pipes operating both at high temperature and pressure for a long period of time in a power plant are degraded by creep because of internal pressure. So, the remaining life of a component is evaluated by the creep rupture strength. Although the conventional method to evaluate the creep damage is widely used, it has some disadvantages such as requires large size specimen and long employed to evaluate the correlation between fracture toughness and evaluation time. Recently, new method so called "small lunch test' is used to evaluate degradation of creep. In this study, a conventional creep test and a small punch test are conducted using 2.25Cr-1Mo steel which is mainly used for the boiler tubes and steam pipes in power plant. The creep life, approximately 1,500 hrs, is determined by conventional method under a severe condition then specimens for a small Punch test are obtained after certain time intervals such as 1/4, 1/2 and 3/4 of final rupture time, respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.453-458
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• 2001

Pipelines have the highest capacity and are the safest and the least environmentally disruptive way for gas or oil transmission. Recently, failures due to corrosion defects have become of major concern in maintaining pipeline integrity. A number of solutions have been developed for the assessment of remaining strength of corroded pipelines. However, these solutions are known to be dependent on material properties and pipeline geometries. In this paper, a Fitness-For-Purpose type limit load solution for corroded gas pipelines made of the X65 steel is proposed. For this purpose, a series of burst tests with various types of corrosion defects are performed. Finite element simulations are carried out to derive an appropriate failure criterion. And then, further, extensive finite element analyses are performed to obtain the FFP type limit load solution for corroded X65 gas pipelines as a function of defect depth, length and pipeline geometry. And also, a window based computer program far the assessment of corrosion defect, which is named as COPAP(COrroded Pipeline Assessment Program) has been developed on the basis of proposed limit load solution.

• 한국구조물진단유지관리공학회 논문집
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• 제7권2호
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• pp.247-261
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• 2003

The technique of posttensioning has been used successfully to improve the performance of existing concrete structures. However, very few applications of this technique can be found in steel structures. Posttensioning by means of high strength cable or bar can be used to effectively increase the working load capacity of Truss Bridges. The benefits of posttensioning trusses can be achieved in strengthening of existing structures as well as in the design of new structures. In this paper, the elastic behavior of posttensioned trusses with straight and draped tendon profiles is examined. For the analysis of posttensioned trusses in the elastic range of behavior, two methods are presented, namely, the flexibility method and the mixed-method, i.e., a combination of the stiffness and flexibility methods. Using the presented methods, the effects of design variables such as the tendon profile, truss type, prestress force, and tendon eccentricity on the working load and deflection of trusses are studied. The results show that the allowable load of truss increases proportionally with increase in prestress force and eccentricity. Posttesioning enlarges the elastic range, increases redundancy, and reduces deflection and member stresses. Thus, the remaining life of a truss bridge can be increased relatively inexpensively.

• 약학회지
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• 제46권3호
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• pp.168-173
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• 2002

The physicochemical properties of aloesin, which has been recently found to reduce renal toxicity induced by cis-platin, were studied including solubility, partition coefficient ( $P_{c}$ ), osmolality, and stability. The solubility of aloesin was about 500 mg/mι, and the $P_{c}$ value for n-octanol/water was 1.01 $\pm$ 0.03. The degradation of aloesin followed the pseudo-first-order kinetics and was dependent on temperature, pH and ionic strength. From the pH-rate profile, the optimal pH was found to be 2.0~3.0. Some metal ions increased the degradation rate in the rank order of M $n^{2+}$ ＞ F $e^{3+}$ ＞ C $u^{2+}$ ＞ F $e^{2+}$. On the other hand, other metal ions such as B $i^{3+}$, $Ba^{2+}$, Z $n^{2+}$, N $i^{2+}$, $Co^{2+}$ and $Mg^{2+}$ did not show the unfavorable effects. After autoclaving, aloesin contents remaining were 81.8~98.8% of initial concentrations depending on pH. The most stable pH was 3.98 in the autoclaving. Osmolality increased linearly as concentration increased.sed.creased.sed.

• 한국해양공학회지
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• 제29권2호
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• pp.199-206
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• 2015

Regular high-strength carbon steel is currently the most commonly used pipe material for onshore and offshore pipelines. The corrosion of offshore pipelines is a major problem as they age. The collapse of these structures as a result of corrosion may have a heavy cost is lives and assets. Therefore, their monitoring and screening is a high priority for maintenance, which may ensure the integrity and safety of a structure. Monitoring risers and subsea pipelines effectively can be accomplished using eddy current inspection to detect the average remaining wall thickness of corroded low-alloy carbon steel pipelines through corrosion scaling, paint, coating, and concrete. A test specimen for simulating the offshore pipeline is prepared as a standard specimen for an analysis and experiment with differential bobbin eddy current sensors. Using encircling coils, the signals for the defect in the simulated specimen are analyzed and evaluated in experiments. Differential bobbin eddy current sensors can diagnose the defects in a specimen, and experiments have been carried out using the developed bobbin eddy current sensor. As a result, the most optimum coil parameters were selected for designing differential bobbin eddy current sensors.

• Wind and Structures
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• 제21권3호
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• pp.331-352
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• 2015

A series of wind tunnel tests were conducted on tapered super high-rise buildings with a square cross section by applying synchronous pressure measurement technology. The effects of global strategy of chamfered modification on aerodynamic loads and wind-induced responses were investigated. Moreover, local aerodynamic strategies of opening a ventilation slot in the corner of equipment and refuge floors were carried out. Results show that the global strategy of tapered elevation increased the vortex shedding frequency, but reduced vortex shedding energy, leading to reduction of across-wind aerodynamic loads and responses. Chamfered modification suppressed the across-wind vortex shedding effect on tapered buildings. Opening the ventilation slot further suppressed the strength of vortex shedding and reduced the residual energy related to vortex shedding in aerodynamic loads of chamfered buildings. Finally, the optimized locations of local aerodynamic strategies were suggested.

• 한국가스학회지
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• 제7권2호
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• pp.1-6
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• 2003

본 연구에서는 이미 개발되어 있는 부식결함의 잔존강도를 평가식을 이용하여 파단, 대누출, 소누출의 손상모드 예측하는 절차를 제시하였다. 또한 이 손상모드에 따라 손상확률을 예측할 수 있는 방법을 제시하고 여기에 부식속도 정보를 결합하면 일정기간 경과 후 손상확률도 예측할 수 있음을 보였다. 이 결과는 노후배관의 수명 또는 교체주기의 예측에 매우 유용하게 활용될 수 있을 것이라 판단된다.

• 한국가스학회지
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• 제7권2호
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• pp.14-21
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• 2003

도시가스 배관에서 위험을 유발할 수 있는 사건의 발생빈도를 구하기 위하여 주요 사고원인인 굴착공사, 외부부식, 지반침하 및 장치손상 등에 의한 사고발생빈도를 구하는 방법을 제시하였다. 굴착공사로 인한 손상은 FTA에 의해 기본사상(Basic event)을 도출하고, 부식에 의한 손상확률은 시간변화에 따른 부식결함의 잔존강도를 평가하는 평가식을 제시하였다. 지반침하로 인한 손상은 기준손상율을 구하고 여기에 손상모드인자 및 보정인자를 고려한 모델을 이용하여 구하였다. 장치원인에 의한 손상확률은 고유고장율과 특정고장율 자료를 모두 반영할 수 있는 방법을 제시하였으며 그 계산 예도 제시하였다.

• 천문학회지
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• 제35권3호
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• pp.151-157
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• 2002

From the data of solar wind observation by ACE spacecraft orbiting the Earth-Sun Lagrangian point, we selected 48 forward interplanetary shocks(IPSs) occurred in 2000, maximum solar activity period. Examining the profiles of solar wind parameters, the IPSs are classified by their shock drivers. The significant shock drivers are the interplanetary coronal mass ejection(ICME) and the high speed stream(HSS). The IPSs driven by the ICMEs are classified into shocks driven by magnetic clouds and by ejectas based on the existence of magnetic flux rope structure and magnetic field strength. Some IPSs could be formed as the blast wave by the smaller energy and shorter duration of shock drivers such as type II radio burst. Out of selected 48 forward IPSs, $56.2\%$ of the IPSs are driven by ICME, $16.7\%$ by HSS, and $16.7\%$ of the shocks are classified into blast-wave type shocks. However, the shock drivers of remaining $10\%$ of the IPSs are unidentified. The classification of the IPSs by their driver is a first step toward investigating the critical magnitudes of the IPS drivers commencing the magnetic storms in each class.