• Earthquakes and Structures
• /
• v.16 no.2
• /
• pp.235-251
• /
• 2019

Corrosion of reinforcement is the greatest threat to the safety of existing reinforced concrete (RC) structures. Most of the olden structures are gravity load designed (GLD) and are seismically deficient. In present study, investigations are carried out on corrosion damaged GLD beam-column sub-assemblages under reverse cyclic loading, in order to evaluate their seismic performance. Five GLD beam-column sub-assemblage specimens comprising of i) One uncorroded ii) Two corroded iii) One uncorroded strengthened with steel bracket and haunch iv) One corroded strengthened with steel bracket and haunch, are tested under reverse cyclic loading. The performances of these specimens are assessed in terms of hysteretic behaviour, energy dissipation and strength degradation. It is noted that the nature of corrosion i.e. uniform or pitting corrosion and its location have significant influence on the behaviour of corrosion damaged GLD beam-column sub-assemblages. The corroded specimens with localised corrosion pits showed in-cyclic strength degradation. The study also reveals that external strengthening which provides an alternate force path but depends on the strength of the existing reinforcement bars, is able to mitigate the seismic risk of corroded GLD beam-column sub-assemblages to the level of control uncorroded GLD specimen.

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.4
• /
• pp.93-104
• /
• 2021

In recent years, there has been a substantial theoretical and empirical study on the role that financial market development has significantly played in promoting economic growth and development in the world. The development of an economy requires the financial industry to be developed. In the context of rapid economic development, global warming has become a serious problem with issues such as rising average temperatures, climate change, rising sea level, and increasing carbon dioxide emissions. This study aims to examine the influence of economic growth, financial development, transportation capacity, and environmental degradation. Using time-series data from 1986 to 2019 and environmental degradation being measured by CO2 emissions, the study employs a quantity of ample unit root tests, the structural break unit root tests, Autoregressive Distributed Lag (ARDL), and cointegration bounds test. The results show that there is a significant long-term cointegration among study variables. Empirical findings also indicate that an increase in per capita GDP and financial development worsens environmental quality whereas transportation capacity and foreign investment can improve environmental quality.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1787-1791
• /
• 2007

For structural design and diagnosis, quantitative relationship between corrosive degradation and variation of mechanical properties such as tensile strength and fatigue strength is needed. But it is difficult to find data associated with corrosive degradation of structural structures. In this study, first of all we established the atmospheric corrosion test procedure. And using specimens of SM490A and SS400 on the atmospheric corrosion test bed, we carried out tensile and fatigue tests at regular intervals. And we studied the effect of post-weld heat treatment on the tensile and fatigue behaviour. It is found fatigue strength decreases as the atmospheric corrosion period increases.

• Structural Engineering and Mechanics
• /
• v.7 no.1
• /
• pp.69-80
• /
• 1999

The purpose of this study is to propose an analytical model for the simulation of the hysteretic behavior of RC (reinforced concrete) beam-column subassemblages under various loading histories. The discrete line element with inelastic rotational springs is adopted to model the different locations of the plastic hinging zone. The hysteresis model can be adopted for a dynamic two-dimensional inelastic analysis of RC frame structures. From the analysis of test results it is found that the stiffness deterioration caused by inelastic loading can be simulated with a function of basic pinching coefficients, ductility ratio and yield strength ratio of members. A new strength degradation coefficient is proposed to simulate the inelastic behavior of members as a function of the transverse steel spacing and section aspect ratio. The energy dissipation capacities calculated using the proposed model show a good agreement with test results within errors of 27%.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.421-426
• /
• 2005

In general, structural integrity of rolling stock structures should last more than 25 years. During the lifetime corrosive degradation occurs. For structural design and diagnosis, quantitative relationship between corrosive degradation and variation of mechanical properties such as tensile strength and fatigue strength is needed. In this study, first of all we established the atmospheric corrosion test procedure. At regular intervals using specimens of SM490A and SS400 on the atmospheric corrosion test bed, we carried out tensile and fatigue tests. The fatigue strength decreases as the atmospheric corrosion period increases. And we studied the effect of post-weld heat treatment on the tensile and fatigue behaviour.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.2
• /
• pp.149-157
• /
• 2003

The purpose of this paper is to quantitatively investigate aging state of epoxy coating on containment structure at nuclear power plant. In order to evaluate an physical bonding of the epoxy coating, adhesion test was performed on a degraded epoxy coating on concrete specimens fabricated by accelerated aging experiment. In addition, impedance data by ultrasonic test were measured to compare with adhesion data. From almost 50 % of the specimens, aging phenomena of epoxy coating such as pin hole, blistering was discovered. To improve reliability on quality degradation of epoxy, co-relation between two kinds of different data was analyzed. By tracing co-related these data, it was possible to figure out physical state of as-built epoxy coating. The possibility to develop new methodology of time - dependent aging state on epoxy coating was found and discussed.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.05a
• /
• pp.339-340
• /
• 2018

Contemporary concrete structures make use of underground spaces as parking lots and other comfort facilities for efficiency purposes. As underground environmental conditions are in constant exposure to degradation factors from the environment such as groundwater, hydraulic and soil pressure, structural movement and settlement, structural defects in the form of leakage occur. Current maintenance regulations and regimes are unable to respond to this field, as degradation mechanisms in underground environments are still unclear. In this regard, this study proposes the utilization of integrated information sharing system that can provide various technical information for construction designs to prevent leakages in underground concrete structures.

• Journal of Applied Reliability
• /
• v.16 no.1
• /
• pp.41-47
• /
• 2016

Purpose: The purpose of this study was to evaluate electrical and structural degradation of flexible CIGS sollar cell exposed to high temperature and humid atmosphere. Method: Accelerated degradation was performed for various time under $85^{\circ}C/85%RH$ and then electrical and structural properties were analyzed by 4-point probe method, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results: Sheet resistance of the top ITO layer increased with exposure time to the high temperature and humid atmosphere. Blunting of the protrusion morphology of ITO layer was observed for the degraded specimen, while no phase change was detected by XRD. Oxygen was detected at the edge area after 300 hours of exposure. Conclusion: Increase in electrical resistance of the degraded CIGS solar cell under high temperature and humid environment was attribute to the oxygen or water absorption.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.04a
• /
• pp.395-400
• /
• 2002

Epoxy coating and sealing used in nuclear plants for the protection of radiation degrades with aging and hazardous atmosphere. In order to evaluate the degradation of the epoxy, dependence of the acoustic impedance on the change of mechanical properties has been used. Unlike metals, the surface of the epoxy coating on a concrete liner is so wavy that the acoustic impedance is difficult to measure by using the reflectivity of the ultrasound on the interface surface because of the irregular reflection and propagation from the epoxy surface. SA(simulated annealing) algorithm is applied to calculate the acoustic impedance using a reflection wave from the rough epoxy surface. The surface waviness and acoustic impedance are taken into account and determined by SA method to evaluate the state of degradation quantitatively.

• Nuclear Engineering and Technology
• /
• v.56 no.10
• /
• pp.4254-4262
• /
• 2024

Reinforced concrete structures are subject to exposure to chloride ions in the air, leading to chloride penetration, and carbonation attacks resulting from exposure to carbon dioxide. This chemical degradation process induces corrosion of reinforcing bars within concrete, significantly impacting durability. Structures situated in coastal areas, such as nuclear power plants, are particularly susceptible to rapid chloride penetration due to the high chloride concentration in the air. This study utilizes existing experimental data to forecast the chloride diffusion coefficient employing artificial neural network (ANN technology). The total number of experimental data was 535 gathered from 18 papers. Through analysis of the chloride coefficient and predicted degradation depth, the effective cross-sectional area of concrete is examined, and the deterioration of wall performance is forecasted.