• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.171-177
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• 2005

Fire in underground space may induce severe structural damage as well as heavy casualties. To protect underground structure and passengers from fire, it is very essential to characterize fire-induced damage on construction materials of underground structures. In this study, the high-temperature furnace was manufactured to evaluate fire-induced damage on underground structure materials. Especially, this study aimed at the evaluation of fire-induced damage on the shield TBM concrete segment. In the fire tests, furnace temperature was set to reach 1,200 degrees at five minutes after Ignition. The temperature of 1,200 degrees was kept during one hour, and the fire was extinguished after two hours elapsed. From the temperature measurement by thermocouples embedded in test specimens, the spatting was estimated to reach approximately 20 cm from the surface exposed to fire. After the fire tests, the alteration of physico-mechanical properties and microstructures of concrete segment was investigated from core specimens. The results showed that apart from spatting, the deterioration depth of the remaining concrete material amounted to approximately 10 cm from the spatting surface.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.71-74
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• 2007

With the changes of times the building materials tend to extend the demand for application under the special environment. Since high-ductile mortar is developed, the building materials show excellent performance like toughness, compression, tensile, and bending, etc. in the general concrete from the existing brittle point. And, recently they are widely used as repairing and reinforcing materials both at home and abroad because they are recognized as excellence like durability and fire-resistance. However, it is in a situation of creating problems in durability because it frequently happened deterioration of buildings that have already repaired and reinforced at a time when it requires reconstruction of recently deteriorated construction structure recently. Therefore, in this study improved with a more repair Material development and reinforcement of the second high-ductile mortar products for a variety of basic materials were presented want, research plans used include traditional repair materials and the newly developed PCM (polymer cement mortar) structural reinforcement type indicated that comparison. PCM analysis in order to present a rate depending on the types fiber 0, 1.2 and 2.0(%) at three levels and mixture water according to ratios of weight to Plain in the 2.0 and 1.85(kg) at two levels is set, the results were as follows. 1) This study has shown that PCM had excellent strain hardening behavior at the same time that the bending stress increased according to the fiber contents. 2) This study has shown that it had the durability performance due to the high substance transmission according to the fiber contents.

• Structural Engineering and Mechanics
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• v.66 no.1
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• pp.15-25
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• 2018

Post-construction subgrade settlement especially differential settlement, has become a key issue in construction and operation of non-ballasted track on high-speed railway soil subgrade, which may also affect the dynamic performance of passing trains. To estimate the effect of differential subgrade settlement on the mechanical behaviors of the vehicle-slab track system, a detailed model considering nonlinear subgrade support and initial track state due to track self-weight is developed. Accordingly, analysis aiming at a typical high-speed vehicle coupled with a deteriorated slab track owing to differential subgrade settlement is carried out, in terms of two aspects: (i) determination of an initial mapping relationship between subgrade settlement and track deflections as well as contact state between track and subgrade based on a semi-analytical method; (ii) simulation of dynamic performance of the coupled system by employing a time integration approach. The investigation indicates that subgrade settlement results in additional track irregularity, and locally, the contact between the concrete track and the soil subgrade is prone to failure. Moreover, wheel-rail interaction is significantly exacerbated by the track degradation and abnormal responses occur as a result of the unsupported areas. Distributions of interlaminar contact forces in track system vary dramatically due to the combined effect of track deterioration and dynamic load. These may not only intensify the dynamic responses of the coupled system, but also have impacts on the long-term behavior of the track components.

• The Journal of Information Systems
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• v.18 no.4
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• pp.131-153
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• 2009

Due to the deterioration of the business environment, many companies become more interested in IT adoption to strengthen their internal competence. The recent expansion of the ERP adoption in the small and medium-sized enterprises (SMEs) can be interpreted as an example for this. However there are still a number of questions over the outsourcing effectiveness and its performance of IT adoption by characteristics of SMEs. This study aims to investigate the relationship between the software process quality and the product quality, and additionally the moderating effect of IT adoption factors, from the case of SMEs' ERP adoption by the outsourcing. For this purpose, the empirical analysis through the structural equation model has been carried out, based on the software quality model defined in ISO/IEC 15504 and ISO/IEC 9126. The result of analysis shows that the acquisition process quality can affect the product quality characteristics, currently applied in the national software quality certification, and this supports the practical usefulness of the ISO standard of software engineering. But another result shows that there is little moderating effect by IT adoption factors, in contrast to the expectation, and this can be explained due to the inappropriate measurement and the data constraint such as short duration-time of IT adoption. These can be used as an informative reference for continuing studies of the quality model application and the effect of IT adoption factors in SMEs.

• Fire Science and Engineering
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• v.34 no.3
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• pp.8-17
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• 2020

In this study, the characteristics of HFIX insulated wire sheaths contaminated by pollutants were examined. KS C IEC 60811-1-3 standard was followed in performing the water-resistance wire tests. Pollutants were selected, and the specimens were exposed to the pollutants for a maximum duration of four weeks. The maximum tensile load and the elongation rate were measured each week. As the period of pollution exposure increased, the maximum tensile load of the specimens decreased by 6.22% and 6.52% at room temperature and high temperature, respectively, and 19.94% for specimens coated with a rust-proof lubricant. The elongation rate also decreased rapidly, such that the reductions in the properties of the sheath were significant. From the analysis of the surfaces using a scanning microscope, as the contamination period increased, structural changes such as perforation, split, and melting occurred, and the mechanical properties of the specimens decreased. Therefore, it is necessary to develop and follow an inspection cycle and periodically carry out repairs to prevent the deterioration of insulated wires.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.531-539
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• 2019

The development of cost-effective electrocatalysts with high durability is one of the most important challenges for the commercialization of polymer electrolyte fuel cells (PEFCs). The durability of the electrocatalyst has been studied in terms of structural change in the active metal and the support. In particular, in fuel cell vehicles, degradation of the carbon-based support is known to have a significant effect on the electrocatalyst deterioration since the start-up/shut-down cycle is frequently repeated. The requirements for the support of the electrocatalyst include high surface area, electrical conductivity, chemical stability, and so on. In this study, we propose the evaluation methods for choosing better support materials and present the physicochemical properties that promising carbon supports should have. Three kinds of carbon materials with different crystallinity are compared. From in-depth study using X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and accelerated stress test, it is clearly confirmed that the durability of carbon-supported electrocatalysts is closely related to the physicochemical properties of the carbon supports.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.39-45
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• 2017

The LNG storage tank as core facility of LNG industry is mainly composed of the inner tank of nikel 9% steel and the outer tank of prestressed concrete. To respond proactively increased risk of structure performance deterioration due to fatigue of the inner tank and durability reduction of the outer tank, life evaluation program for LNG storage tank is needed. In this study, life evaluation program for LNG storage tank was developed to assess fatigue of the inner tank and durability(carbonation and chloride attack) of the outer tank. By defining the main three scenarios in the inner tank, the fatigue life analysis is conducted from structural analysis and Miner's damage rule. Carbonation progress of the outer tank is predicted according to thickness of cover concrete by using carbon dioxide contents and data of penetration depth. To consider a variety of input conditions and a reliability in results of chloride attack, the evaluation of choride attack for the outer tank is constructed through Life-365 program of open source.

• 보존과학연구
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• s.19
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• pp.3-22
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• 1998

The effect of pH on degradation of paper by some fungi, which able to degrade cellulose, was investigated. Trichoderma koningii, Aspergillus nigerand Penicillium nigulosum were cultured at $28^{\circ}C$ for 16 days in the selective medium (PH3, PH4, PH5, PH6, PH7, PH8, PH9, PH10, PHC) containing paper as substrate. Each paper was pretreated with each pH buffer (pH 3∼pH 10, D.W.)prior to addition to the selective medium. Enzyme activities in the each culture medium were measured spectroph to metrically using C.M.C., Avicel, PNPG as the substrates for endoglucanase, exoglucanase and $\beta$-glucosidase, respectively. In all experimental fungi, the enzyme activities of PH3 and PH9 medium were usually much higher than those of other experimental groups. However in the PH6medium, enzyme activity was lower than other groups. To analyze the concentration and pattern of protein in the each culture medium, the medium was concentrated by lyophilization. The protein concentration of PH3 and PH9 medium were relatively high (T.koningii; 6.31mg, 6,19mg, A.niger; 1.62mg, 1.96mg, P.nigulosum;2.50mg, 2.73mg, respectively), but that of PH6 was relatively low. The protein pattern of each medium was analyzed by using SDS-PAGE and VDS Image Master Analysis Program. The concentrations of bands in the each lane were usually high at lane2 (PH3) and lane8 (PH9) and low at lane5 (PH6). Therefore, the incresed cellulolytic activity of fungus against acidified paper could be result of structural change and deterioration of paper caused by being acidified.

• Earthquakes and Structures
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• v.17 no.5
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• pp.511-519
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• 2019

The concrete gravity dam is one of the most important parts of the nation's infrastructure. Besides the benefits, the dam also has some potentially catastrophic disasters related to the life of citizens directly. During the lifetime of service, some degradations in a dam may occur as consequences of operating conditions, environmental aspects and deterioration in materials from natural causes, especially from dynamic loads. Cumulative Absolute Velocity (CAV) plays a key role to assess the operational condition of a structure under seismic hazard. In previous researches, CAV is normally used in Nuclear Power Plant (NPP) fields, but there are no particular criteria or studies that have been made on dam structure. This paper presents a method to calculate the limitation of CAV for the Bohyeonsan Dam in Korea, where the critical Peak Ground Acceleration (PGA) is estimated from twelve sets of selected earthquakes based on High Confidence of Low Probability of Failure (HCLPF). HCLPF point denotes 5% damage probability with 95% confidence level in the fragility curve, and the corresponding PGA expresses the crucial acceleration of this dam. For determining the status of the dam, a 2D finite element model is simulated by ABAQUS. At first, the dam's parameters are optimized by the Minitab tool using the method of Central Composite Design (CCD) for increasing model reliability. Then the Response Surface Methodology (RSM) is used for updating the model and the optimization is implemented from the selected model parameters. Finally, the recorded response of the concrete gravity dam is compared against the results obtained from solving the numerical model for identifying the physical condition of the structure.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.97-105
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• 2019

In the current steel structures of high-rise buildings, high heat input welding techniques are used to improve productivity in the construction industry. Under the high heat input welding, however, the microstructures of the weld metal (WM) and heat-affected zone (HAZ) coarsen, resulting in the deterioration of impact toughness. This study focuses mainly on the effects of fine TiN precipitates dispersed in steel plates and B addition in welding materials on grain refinement of the HAZ microstructure under submerged arc welding (SAW) with a high heat input of 200 kJ/cm. The study reveals that, different from that in conventional steel, the ${\gamma}$ grain coarsening is notably retarded in the coarse grain HAZ (CGHAZ) of a newly developed steel with TiN precipitates below 70 nm in size even under the high heat input welding, and the refinement of HAZ microstructure is confirmed to have improved impact toughness. Furthermore, energy dispersive spectroscopy (EDS) and secondary-ion mass spectrometry (SIMS) analyses demonstrate that B is was identified at the interface of TiN in CGHAZ. It is likely that B atoms in the WM are diffused to CGHAZ and are segregated at the outer part of undissolved TiN, which contributes partly to a further grain refinement, and consequently, improved mechanical properties are achieved.