• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.4
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• pp.35-42
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• 2018

This study evaluated the fire resisting capacity and post-fire serviceability of the concrete beams retrofitted by near surface mounted method(NSM) using GFRP plates. Main parameters in the test are grout materials and fire exposure. For the test, two types of grout materials between concrete substrate and GFRP plate were used; flame resisting epoxy and filling mortar. Four RC beam specimens were made and two of them were exposed to fire according to real scale fire curve proposed KS F 2257. After the fire exposure test, flexural test were performed to investigate the flexural performance of concrete beams including strength and deformation. From the test results, it was found that the beam retrofitted by NSM-GFRP presented higher flexural strength than that of the beam without retrofit, which indicates NSM-GFRP retrofit technologies is effective to maintain flexural strength even after fire exposure. In addition, the specimens grouted by epoxy showed good performance in strength but bad performance in ductility.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1066-1071
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• 2007

This case study refers to turbine-generator with retrofitted turbine rotor. Vibration problem occurring after the retrofit was mainly due to high vibration from exciter side. However, repeated test run and operation during scheduled maintenance caused high vibration from generator bearing, and post-overhaul test run before turbine vibration correction caused oil whip on the bearing. This case study shows how to analyze vibration condition of high turbine generator vibration detected during the post-overhaul test run and vibration condition of offline and online data to reflect it on establishing maintenance schedule and overhaul correction procedure. Vibration data could be acquired during steady load operation or even with varying speed and load. Each data is important for machinery condition evaluation. This case study shows that the vibration data during extreme condition is the key factor in analysis, which helps to find the machinery problem.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.238-246
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• 2008

This case study refers to turbine-generator with retrofitted turbine rotor. Vibration problem occurring after the retrofit was mainly due to high vibration from exciter side. However, repeated test run and operation during scheduled maintenance caused high vibration from generator bearing, and post-overhaul test run before turbine vibration correction caused oil whip on the bearing. This case study shows how to analyze vibration condition of high turbine generator vibration detected during the post-overhaul test run and vibration condition of offline and online data to reflect it on establishing maintenance schedule and overhaul correction procedure. Vibration data could be acquired during steady load operation or even with varying speed and load. Each data is important for machinery condition evaluation. This case study shows that the vibration data during extreme condition is the key factor in analysis, which helps to find the machinery problem.

• Transactions of the KSME C: Technology and Education
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• v.4 no.1
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• pp.11-18
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• 2016

Under the Renewable Heat Obligation (RHO) public buildings in the Republic of Korea larger than $10,000m^2$ must achieve an 11% overall reduction to thermal energy consumption. Well intended solutions have been proposed. However, not all option is evaluated on the same basis, potentially resulting in incomplete or sub-optimal solutions. What's more once projects are implemented, there are inconsistencies in the methods used to measure and evaluate operating performance of the post-retrofit case. The RETScreen decision tools and methodology can be used by decision makers, policy developers, architects, engineers and community leaders to evaluate and select the most effective solutions for Korea's RHO needs.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.1
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• pp.1-8
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• 2011

This article proposes a hybrid approach involved in determining the size of stormwater control facilities as part of a very large scale urban retrofit project. The objective of the proposed hybrid approach is to restore the pre-development hydrologic cycle. Firstly, an appropriate IETD is determined to isolate single storm events from the continuous rainfall record. Then, using the NRCS-CN method, direct runoff and infiltration volume are computed for every storm events. Long-term statistics of direct runoff and infiltration volume are analyzed in each case of pre-development, post development, post development with detention only, and post-development with the proposed hybrid approach. In order to preserve long-term statistics of direct runoff and infiltration volume in the case of pre-development, the size of detention and infiltration-based retention are estimated using the genetic algorithm. The result shows that the proposed hybrid approach is very useful for restoring statistics of natural direct runoff and infiltration volume.

• Earthquakes and Structures
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• v.8 no.1
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• pp.37-56
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• 2015

The Emilia, May-July 2012, earthquake has dramatically highlighted the only the hazards facing the people in insufficiently secured workplaces, but also the socio-economic consequences of interruption of production activities. After the event, in order to guarantee suitable safety levels, the Italian government asked for a generalized seismic retrofit of buildingsaffected by the earthquake under consideration. Considering that Emilia is one of the most industrialized Italian region, the number of the industrial buildings to be verified could however lead to not acceptable resumption of production time. So, with the aim to speed up the recovery, were leaved out from this request the buildings which had undergone a strong enoughshaking without any damage. In practice, the earthquakes were being used as a "test" to evaluate the seismic structural strength. Besides, the Italian government provision specifies also the zones, within which buildings that escaped evident damage are exempt from obligatory checks, and termed "exclusion zones", shall be individuated using the data provided by the Italian National Institute of Geophysics and Volcanology in the form of so-called "shakemaps". Obviously, the precision of such data greatly influences the determination of the exclusions zones and so all the economic issues related to them. Starting from these considerations, the present paper describes an evaluation of the reliability of the procedure of shakemap generation with specific regard to the seismic events that struck the Emilia region on May 20 and 29, 2012.

• Journal of The Korea Institute of Healthcare Architecture
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• v.18 no.3
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• pp.51-59
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• 2012

Over a past century, the continuity in post-earthquake serviceability of medical facilities has been demonstrated to be essential for sustaining a society and/or a nation stable. However, not many countries including Korea have paid appropriate attention to such a lesson learned from the previous experiences of the countries located in high seismicity for various reasons, one of which may be the lack of social consensus in allocating a portion of the resources to the earthquake preparedness. As a result, an earthquake-related policy might have been pushed away out of the list of priority in the government agenda. Therefore, the present paper attempts to persuade the public general, experts and government officials together to seek a way to upgrade the seismic safety of the country a step forward by enhancing the seismic performance of medical facilities. For this the framework of seismic design codes and standards for medical facilities, and Californian experience in managing the seismic performance enhancement program and U.S.-Italian collaborative study to improve the seismic safety of Italian hospitals are reviewed. Finally, a list of further researches and practices to perform for seismic enhancement of medical facilities in Korea are suggested.

• Smart Structures and Systems
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• v.4 no.3
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• pp.367-389
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• 2008

Shape Memory Alloys (SMAs) are unique materials with a paramount potential for various applications in bridges. The novelty of this material lies in its ability to undergo large deformations and return to its undeformed shape through stress removal (superelasticity) or heating (shape memory effect). In particular, Ni-Ti alloys have distinct thermomechanical properties including superelasticity, shape memory effect, and hysteretic damping. SMA along with sensing devices can be effectively used to construct smart Reinforced Concrete (RC) bridges that can detect and repair damage, and adapt to changes in the loading conditions. SMA can also be used to retrofit existing deficient bridges. This includes the use of external post-tensioning, dampers, isolators and/or restrainers. This paper critically examines the fundamental characteristics of SMA and available sensing devices emphasizing the factors that control their properties. Existing SMA models are discussed and the application of one of the models to analyze a bridge pier is presented. SMA applications in the construction of smart bridge structures are discussed. Future trends and methods to achieve smart bridges are also proposed.

• Structural Engineering and Mechanics
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• v.63 no.4
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• pp.497-507
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• 2017

During recent earthquakes, a significant number of concrete structures suffered extensive damage. Conventional reinforced concrete structures are designed for life-time safety that may see permanent inelastic deformation after severe earthquakes. Hence, there is a need to utilize adequate materials that have the ability to tolerate large deformation and get back to their original shape. Super-elastic shape memory alloy (SMA) is a smart material with unique properties, such as the ability to regain undeformed shape by unloading or heating. In this research, four different stories (three, five, seven and nine) of reinforced concrete (RC) buildings have been studied and subjected to near-field ground motions. For each building, two different types of reinforcement detailing are considered, including (1) conventional steel reinforcement (RC frame) and (2) steel-SMA reinforcement (SMA RC frame), with SMA bars being used at plastic zones of beams and steel bars in other regions. Nonlinear time history analyses have been performed by "SeismoStruct" finite element software. The results indicate that the application of SMA materials in plastic hinge regions of the beams lead to reduction of the residual displacement and consequently post-earthquake repairs. In general, it can be said that shape memory alloy materials reduce structural damage and retrofit costs.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.5
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• pp.291-298
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• 2018

Existing reinforced concrete building structures have seismic vulnerabilities under successive earthquakes (or mainshock-aftershock sequences) due to their inadequate column detailing, which leads to shear failure in the columns. To improve the shear capacity and ductility of the shear-critical columns, a fiber-reinforced polymer jacketing system has been widely used for seismic retrofit and repair. This study proposed a numerical modeling technique for damaged reinforced concrete columns repaired using the fiber-reinforced polymer jacketing system and validated the numerical responses with past experimental results. The column model well captured the experimental results in terms of lateral forces, stiffness, energy dissipation and failure modes. The proposed column modeling method enables to predict post-repair effects on structures initially damaged by mainshock.