• Geomechanics and Engineering
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• v.23 no.6
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• pp.503-512
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• 2020

Mining activities focus on the production of mineral resources for energy generation and raw material requirements worldwide and it is a known fact that shallow reserves become scarce. For this reason, exploration of new resources proceeds consistently to meet the increasing energy and raw material demand of industrial activities. Rock mechanics has a vital role in underground mining and surface mining. Devices and instruments used in laboratory testing to determine rock mechanics related parameters might have limited sensing capability of the failure behavior. However, methodologies such as, thermal cameras, digital speckle correlation method and acoustic emission might enable to investigate the initial crack formation in detail. Regarding this, in this study, thermographic analysis was performed to analyze the failure behaviors of different types of rock specimens during uniaxial compressive strength experiments. The energy dissipation profiles of different types of rocks were characterized by the temperature difference recorded with an infrared thermal camera during experiments. The temperature increase at the failure moment was detected as 4.45℃ and 9.58℃ for andesite and gneiss-schist specimens, respectively. Higher temperature increase was observed with respect to higher UCS value. Besides, a temperature decreases of about 0.5-0.6℃ was recorded during the experiments of the marble specimens. The temperature change on the specimen is related to release of radiation energy. As a result of the porosity tests, it was observed that increase in the porosity rate from 5.65% to 20.97% can be associated to higher radiation energy released, from 12.68 kJ to 297.18 kJ.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.717-720
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• 1999

Recently, the fiber composite materials such as carbon fiber, glass fiber, or aramid, have been frequently used in strengthening reinforced concrete structures. The fiber composite materials typically have orthotropic characteristic and the strength changes significantly acording to the direction of fibers and the method of the lamination. In this study, an algorithm to estimate the stress-strain relationship of the composite materials which have different fiber directions and symmetric or non-symmetric lamination has been developed by using Tsai-Hill and Tsai-Wu failure criteria and progressive laminate failure theory. This algorithm has been implemented to several stress-strain models for the laterally confined concrete compression members such as Mander, Hosotani, and Nakatsuka. The evaluated stress-strain behaviors by the different models are discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.921-926
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• 2001

In this paper the biaxial failure criteria and stress-strain response for plain concrete are studied under uniaxial and biaxial stress(compression-compression, compression-tension, and tension-tension combined stress). The concrete specimens of a square plate type are used for uniaxial and biaxial loading. The experimental data indicate that the strength of concrete under biaxial compression, f2/fl=-l/-1, is 17 percent larger than under uniaxial compression and the poisson's ratio of concrete is 0.1745. On the base of the results, a biaxial failure envelope for plain concrete that the uniaxial strength is 398kgf/$cm^{2}$ are developed. The biaxial failure behaviors for three biaxial loading areas are also plotted respectively. In addition, the characteristics of stress-strain response under biaxial compression are compared and verified with the experimental and analytical results.

• YAKHAK HOEJI
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• v.35 no.1
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• pp.38-44
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• 1991

It has been reported that the pharmacokinetic behaviors of drugs which are mostly metabolized in the liver are significantly different in patients with renal failure. Theophylline(TP) is mainly metabolized in the liver (approximately 90%) and renal clearance of the drug is negligible (less than 10%). Therefore, we have investigated the changes in pharmacokinetics of theophylline in normal, G-ARF and U-ARF rats after an intravenous administration. The total body clearance of TP decreased approximately 40% in U-ARF rats. The reduced CL$_{T}$, value in U-ARF rats could be due to reduced hepatic intrinsic clearance by up to 40% since it has been published that plasma protein binding of TP and liver blood flow does not change in U-ARF rats.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.76-83
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• 2014

This study was carried out an experimental and finite element analysis on the fracture behavior of straight pipes with local wall thinning under internal pressure. Local wall thinning was machined on the pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area has an eroded ratio of d/t=0.80~0.92 and an eroded length of l=25, 50 and 102 mm. Three-dimensional elastic-plastic analyses were also carried out using the finite element method, which is able to accurately simulate failure behaviors. In regards to the relation ship between pressure and eroded ratio, the criterion that can be used safely under operating pressure and design pressure were obtained from this calculation. The results of this calculation were in relatively good agreement with that of the experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.615-620
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• 1997

Further to static test on aged RC bridge slabs strengthened with TYFO glassfibers, fatigue tests have been done on aged RC bridge slabs with and without glassfibers. It can be seen from the test that fatigue behaviors of aged RC bridge slabs stiffened with TYFO glassfibers have been by and large improved comparing with those of aged RC bridge slabs without TYFO, but fatigue failure modes have not been changed become of bonding failure between tensile reinforcements and concrete. It is in particular noted from the test that bonding failure between concrete surface and TYFO have been observed. Further tests are strongly necessiated to develop appropriate anchoring method for improving fatigue life of aged RC bridge slabs strengthened with TYFO glassfibers.

• International Journal of Concrete Structures and Materials
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• v.5 no.1
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• pp.11-18
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• 2011

Carbonation in RC (reinforced concrete) structure is considered as one of the most critical deteriorations in urban cities. Although RC column has one mix condition, carbonation depth is measured spatially differently due to its various environmental and internal conditions such as sound, cracked, and joint concrete. In this paper, field investigation was performed for 27 RC columns subjected to carbonation for eighteen years. Through this investigation, carbonation distribution in sound, cracked, and joint concrete were derived with crack mappings. Considering each related area and calculated PDF (probability of durability failure) of sound, cracked, and joint concrete through Monte Carlo Simulation (MCS), repairing timings for RC columns are derived based on several IPDF (intended probability of durability failure) of 1, 3, and 5%. The technique of equivalent probability including carbonation behaviors which are obtained from different conditions can provide the reasonable repairing strategy and the priority order for repairing in a given traffic service area.

• Computers and Concrete
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• v.12 no.1
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• pp.65-77
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• 2013

This paper examines the dynamic response of an arch dam subjected to blast loading. A damage model is developed for three dimensional analysis of arch dams. The modified Drucker-Prager criterion is adopted as the failure criteria of the damage evolution in concrete. Then, Xiluodu arch dam serves as an example to simulate the failure behaviors of structures with the proposed model. The results obtained using the proposed model can reveal the reliability degree of the safe operation level of the high arch dam system as well as the degree of potential failure, providing a reliable basis for risk assessment and risk control.

• Steel and Composite Structures
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• v.20 no.6
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• pp.1221-1236
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• 2016

Modular structures consist of standardized modules and their connections. A modular bridge pier is proposed to accelerate bridge construction. Multiple concrete-filled steel tubes (CFTs) using commercial steel tubes were chosen as the main members. Buckling restrained bracings and enhanced connection details were designed to prevent premature low-cycle fatigue failure upon cyclic loading. The pier had a height of 7.95 m, widths of 2.5 m and 2.0 m along the strong and weak axis, respectively. Cyclic tests were performed on the modular pier to investigate structural performance. Test results showed that four CFT columns reached yielding without a premature failure of the bracing connections. The ultimate capacity of the modular pier was reasonably estimated based on the plastic-hinge-analysis concept. The modular CFT pier with enhanced bracing showed improved displacement ductility without premature failure at the welding joints.

• Journal of Korea Society of Industrial Information Systems
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• v.5 no.2
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• pp.62-69
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• 2000

In this paper, we propose two Buckley-James type nonparametric estimators for entropy of lifetimes under random censorship model. We investigate the small sample behaviors of the proposed estimators when the underlying distribution has decreasing failure rate, constant failure rate, and increasing failure rate. Also some examples are illustrated for analysing data.