• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.361-367
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• 2014

This paper investigates the punching shear strength of lightweight aggregate concrete (LWAC) slabs through a series of experimental study. Five full scale slabs were constructed using normal concrete and four different types of LWAC. Each lightweight aggregate (LWA) used in this study had different sources (clay, shale, or slate) and shapes (crushed or spherical shape). Based on the test results, the effect of the lightweight aggregates (LWA) on the punching shear behavior was investigated. From the test results, it was found that the punching shear failure surface of LWAC slab with spherical shape coarse aggregate was less inclined than that with crushed shape coarse aggregate, which resulted in an increase of the area of the shear failure surface. As a result, it leads to the increased punching shear strength of the slab. On the other hand, the failure surfaces of LWAC slab with crushed shape coarse aggregate and normal coarse aggregate were inclined similarly. Finally, the test results of this study were compared with the punching shear strength obtained from current design models, such as ACI and CEB-FIP, to examine the validation of current design model to predict the punching shear strength of the LWAC slab.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.341-350
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• 1997

The objective of this study is to investigate the structural behavior of the composite slabs with the new metal deckplate. The new deckplate can be used as structural member with topping concrete. So several experiments of this structural test and the fire resistance test were done. From this experiments. slabs with new metal deckpklate were verified as composite slabs. In this paper, this verifications were compared with the international design methods. For experiment. 49 specimens were made. the main parameters are deckplate thickness (1.2mm. 1.6mm) depth of topping concrete(85mm. 90mm). support condition(simple, 2-span), shear reinforcment(studs), span(2.7m, 3.0m, 3.3m. 3.6m. 3.9m) and shear span(L/3, L/4, L/7). We analyzed the structural behavior of composite slab throughout the moment-curvature relationship which is obtained with the program using the computer language. Turbo C. From this development for slab system, the reinforced concrete or steel structure building may be easy, economical for construction, And informations about the structural behavior of composite slabs will be utilized to established korea standard.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.651-659
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• 2015

Currently, social demands for long span building structures are increasing due to architectural planning purposes and economic efficiency. As a result, lighter board-type voiding materials were suggested. With the use of board-type voiding materials, a slab is able to become light weight and convenient. This process efficiently eliminates concrete where it is not required; considerably diminishing dead weight while maintaining the flexural strength of the slab. The reduction in concrete also allows for overall cost reductions and design flexibility. Also it can be ease with fixing the voided material that is composed of one body form. Although board-type voiding materials are ideal, the top and bottom concrete plates lack integrity. Because of this, test results show horizontal cracking towards the tops and bottoms of the concrete columns, or webs, connecting the slabs. The key to correcting this problem is to increase the shear strength. In order to increase the shear strength of the structure, horizontal shear area must increase. R70(100)-D-F has the largest horizontal shear area as it also shows stronger strength. As a result, shear strength ($V_{nh}$) is dependent on the horizontal shear area (N). $V_{nh}={\alpha}{\times}0.16{\sqrt{f_{ck}}}{\frac{{\pi}D^2}{4}}{\times}N({\alpha}=1.8125)$. The web columns have a shear span to depth ratio (a/d) that is less than 2; which classifies it as a deep beam. In this case, however, the shear strength of the deep beams may be as much as 2 to 3 times greater than that predicated conventional equations developed for members of normal proportions. As a result, ${\alpha}$ is suggested as an extra coefficient in the equation for shear strength ($V_{nh}$).

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.773-780
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• 2011

In this study, thermal stress analysis are carried out considering material properties, curing condition, ambient temperature, and casting date of the mass concrete placed in bottom slab and side wall of the in-ground type LNG tank as a super massive structure. Also, based on the numerical results, cracking possibility is predicted and counter measures to prevent the cracking are proposed. For the tasks, two optimum mix proportions were selected. From the results of the thermal stress analysis, the through crack index of 1.2 was satisfied for separately caste concrete lots except for the bottom slab caste in 2 separate sequences. For the double caste bottom slab, it is necessary introduce counter measures such as pre-cooling prior to the site construction. Also, another crack preventive measure is to lower the initial casting temperature by $25^{\circ}C$ or less to satisfy 1.2 through crack index criterion. In the $1^{st}$ and $2^{nd}$ caste bottom slab, the surface crack index was over 1.2. Therefore, the surface cracks can be controlled by implementing the curing conditions proposed in this study. Since the side wall's surface crack index was over 1.0, it is safe to assume that the counter preventive measures can control width and number of cracks.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.97-102
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• 2020

Recently, various degradation mechanisms of lithium secondary battery cathode materials have been revealed. As a result, many studies on overcoming the limitation of cathode materials and realizing new electrochemical properties by controlling the degradation mechanism have been reported. Li-rich layered oxide is one of the most promising cathode materials due to its high reversible capacity. However, the utilization of Li-rich layered oxide has been restricted, because it undergoes a unique atomic structure change during the cycle, in turn resulting in unwanted electrochemical degradations. To understand an atomic structure deterioration mechanism and suggest a research direction of Li-rich layered oxide, we deeply evaluated the atomic structure of 0.4Li₂MnO₃_0.6LiNi_1/3Co_1/3Mn_1/3O₂ Li-rich layered oxide during electrochemical cycles, by using an atomic-resolution analysis tool. During a charge process, Li-rich materials undergo a cation migration of transition metal ions from transition metal slab to lithium slab due to the structural instability from lithium vacancies. As a result, the partial structural degradation leads to discharge voltage drop, which is the biggest drawback of Li-rich materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.229-232
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• 2008

In rapid cycle construction, RC structure which is not cured fully can be loaded with construction load and this construction load can influence on the safety of construction and cracks on slabs. Therefore, to reduce the term of construction, the safety of construction and prevention of cracks should be assured against construction load. In the previous study, temperature load can significantly influence on the behavior of structure under construction. However, existing construction sequential analysis or design code do not consider temperature load reasonably. In the present study, through construction sequential analysis method using FE analysis, the behavior of structure under construction was analyzed according to temperature changes. According to the results of analysis, as the temperature falls, shoring load drops and the temperature rises, shoring load rises. These variations of shoring load can affect the safety of construction. Moment of slab goes up by fall in temperature. This increase of moment can cause cracks on the slab. Therefore to assure the safety on construction and prevent cracks on slabs, temperature load has to be considered reasonably in construction sequential analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.7-12
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• 2016

In this study, a simplified collision model of pile protective structures against a navigation vessel was proposed and verified. The model of pile protective structure were composed by two plastic hinges at below of cap slab and the inside of ground. A nonlinear equation of motions was developed in consideration of the kinematic energy, potential energy and deformation energy in collision event. The developed simplified model were verified by the precise finite element collision analysis of the vessel and the protective structure.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.312-318
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• 2004

The wall in a subway structure is easily subject to crack occurrence since its expansion and shrinkage associated with hydration heat reaction is constrained by the slab. The greater problem is that the crack in the wall may be developed to pass through thickness and eventually deteriorate the structure due to rusting of reinforced steel. Thus, this study aims at controlling thermal cracks as much as possible and determining an optimized size of concrete placement through hydration heat analysis. For this study, effects of placement height, length, temperature and types of cement on the thermal cracks were evaluated by temperature rise, thermal stress and crack index. As results of parametric study, it was found that placement height and length do not have an effect on the temperature rise but have significant one on thermal stress which relates to direct possibility of thermal crack occurrence. This means that proper selection of size balancing internal constraint with external one is much more important than reducing the placement height and length simply. In order to prevent from thermal cracks most effectively, in addition, it was noted to reduce placement temperature and to use the cement blended with mineral admixture.

• Journal of the Society of Disaster Information
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• v.7 no.1
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• pp.75-85
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• 2011

In this study, the behavior were analyzed for the bow collision event. The model of protective Structure was consist of slab, RCP and non-linear soil spring. The ship was modeled by bow and midship. The bow model was composed by elastic-plastic shell elements, and the midship was composed by elastic solid element. According to the weight of the ship's change from DWT 10000 until DWT 25000 increments 5000. The head-on collision was assumed, its speed was 5knot. Analysis was carried out ABAQUS/Explicit. As the result, increasing the weight of the ship deformability in athletes and to increase the amount of energy dissipated by the plastic could be confirmed.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.7
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• pp.147-156
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• 2019

The purpose of this study is to consider structural issues and analyze construction sequences when constructing hanging floors supported by Mega truss. Since suspended structures were supported by the Mega truss, vertical load on suspended structures was needed to transfer from low to high. Deflection management of structures was the primary point under construction. The results of this study were as follows; The steel structures, which has relatively lighter self-weight, were constructed upwards after the base floor steel truss erection. Concrete Placing, which has relatively heavier self-weight, were performed in two phases to minimize structure's deflection. Slab was placed downwards from the top floor to lower floor whereas column was places upwards. Deflection measurements were carried out at every construction sequences.