• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.609-613
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• 2004

An economic analysis is one of the most dominant factors to determine the project feasibility of super tall building. In economic considerations, it is very important toadopt optimum structural floor systems because these are dependent on both the cost and the duration of construction. The economics affected by structural floor systems are more distinct athigher story. As the story increases, the construction cost of floor system. is accumulated linearly, while the cost of lateral resisting system is increased geometrically. The purpose of this study is to investigate the economical effects of super tall buildings through application of optimum structural floor systems. Three types of structural systems(RC beam-column frame, RC flat plate frame, and Steel frame) of super tall buildings having 50-stories are considered in this study and compared to RC flat plate slab with other systems. Analytical result shows that RC flat plate slab using lightweight concrete ismost effective in both the cost and the duration of construction.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.1
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• pp.41-51
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• 2004

FRP re-bar in concrete structures could be used as a substitute of steel re-bars for that cases in which aggressive environment produce high steel corrosion, or lightweight is an important design factor, or transportation cost increase significantly with the weight of the materials. But FRP fibers have only linearly elastic stress-strain behavior; whereas, steel re-bar has linear elastic behavior up to the yield point followed by large plastic deformation and strain hardening. Thus, the current FRP re-bars are not suitable concrete reinforcement where a large amount of plastic deformation prior to collapse is required. The main objectives of this study in to evaluate the tensile behavior and the fracture mode of hybrid FRP re-bar. Fracture mode of hybrid FRP re-bar is unique. The only feature common to the failure of the hybrid FRP re-bars and the composite is the random fiber fracture and multilevel fracture of sleeve fibers, and the resin laceration behavior in both the sleeve and the core areas. Also, the result of the tensile and interlaminar shear stress test results of hybrid FRP re-bar can provide its excellent tensile strength-strain and interlaminar stress-strain behavior.

• Steel and Composite Structures
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• v.29 no.5
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• pp.635-645
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• 2018

Beam-column joints play a significant role in static and dynamic performances of reinforced concrete frame structures. This study contributes a numerical approach of topologically optimal design of carbon fiber reinforced plastics (CFRP) to retrofit existing beam-column connections with crack patterns. In recent, CFRP is used commonly in the rehabilitation and strengthening of concrete members due to the remarkable properties, such as lightweight, anti-corrosion and simplicity to execute construction. With the target to provide an optimal CFRP configuration to effectively retrofit the beam-column connection under semi-failure situation such as given cracks, extended finite element method (X-FEM) is used by combining with multi-material topology optimization (MTO) as a mechanical description approach for strong discontinuity state to mechanically model cracked structures. The well founded mathematical formulation of topology optimization problem for cracked structures by using multiple materials is described in detail in this study. In addition, moved and regularized Heaviside functions (MRHF), that have the role of a filter in multiple materials case, is also considered. The numerical example results illustrated in two cases of beam-column joints with stationary cracks verify the validity, benefit and supremacy of the proposed method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.146-147
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• 2021

An increase in carbon emissions leads to the problem of global warming and is an issue to be solved in other countries. The problem of carbon dioxide has many effects not only on global warming but also on people. According to the World Health Organization (WHO), 4.3 million people have died because harmful substances generated indoors cannot be discharged to the outside and accumulate in the human body through the respiratory tract. In response to this situation, in order to reduce the generation of pollutants in the building itself, soak into lightweight bubble concrete to adsorb and purify indoor pollutants, mix charcoal, investigate the appropriate amount and physical characteristics, and check carbon dioxide This is an experiment for grasping the adsorption capacity, and the results are as follows. As the replacement rate of rice husk charcoal increased, the compressive strength tended to decrease, and the carbon dioxide reduction rate tended to increase. It is judged that the charcoal of rice husks shows a low density and the physical adsorption is smooth due to the porous structure. Since it is excellent in the basic physical properties and carbon dioxide adsorption surface of this experiment, it is judged that it has sufficient potential for use as an indoor finishing material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.22-29
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• 2015

In this study, we tested to develop and apply structural insulation performance improvement concrete to field, which had compressive strength in 24 MPa and thermal conductivity twice as much as normal concrete. After experiment about slump and air contents, combination product of Plain and calcined diatomite powder showed reduction of slump and air contents and combination product with micro foam cell admixture, we cannot find result of slump and air contents reduction. Unit weight of combination product with insulation performance improvement materials decreased more than that of Plain. In the test of compressive strength, compressive strength of insulation performance improvement concrete decreased more than that of Plain but was content with 24 MPa. thermal conductivity of insulation performance improvement concrete tended to decrease. Freezing and thawing resistance of insulation performance improvement concrete was similar to that of Plain. In carbonation resistance test, combination product with calcined diatomite powder showed the result which was similar to that of Plain. In carbonation resistance test, combination product with micro foam cell admixture showed a increase compared to that of Plain and length variation of combination product generally increased.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.4
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• pp.17-24
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• 2010

The hollow RC(Reinforced concrete) pier has the merit of lightweight pier compared with solid RC pier. However, the hollow RC pier shows a low ductile behavior due to brittle failure of inside concrete. To overcome this problem, the internally confined hollow reinforced concrete column has been developed. In this study, the behavior of internally confined hollow RC piers were evaluated with safety ratio, ductility, total material cost, the total weight of the pier, etc. The chosen parameters for the study are hollow ratio, thickness of internal steel tube, intervals between vertical re-bars, numbers of horizontal re-bars, and strength of concrete. As a result of parameters study, the usage of a minimum necessary thickness of the internal steel tube is the most effective.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.191-198
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• 1999

The purpose of this study is investigating characteristics of the concrete containing Fly-ash according to different 4 mix design, that is, the first mix design is partial replace Fly-ash of cement, second is partial replace Fly-ash of cement and fine aggregate, third is partial replace Fly-ash of fine aggregate, fourth partial replacement of fine and coarse aggregate. For this purpose, selected test variables were water-binder ratio with two levels of 45%, 50%, and Fly-ash contents with four levels 0%, 10%, 20%, 30%, As the result of this study are as follow. 1) The result of mix design of a partial replacement of cement, the slump-flow value was appeared a promotive effect of viscosity. But in case of the over with Fly-ash 10% and the other mix design was not changed slump value. 2) The unit weight of the mixing rate with Fly-ash 0% was $1.875{\sim}1.884t/m^3$, the other mix design 10% over with Fly-ash was $1.846{\sim}1.615t/m^3$, the difference was appeared less about 15% than that. 3) In design, partial replace Fly-ash of fine aggregate, this compressive strength was appeared that the concrete age after 7 days was higher than in partial replacement of cement, therefore, the default of a concrete with Fly-ash, that is the earlier compressive strength was to lessen, was improved. 4) The thermal conductivity of the all mix design was $0.447{\sim}1.144kcal/mh^{\circ}C$, this value was as good as a lightweight aggregate concrete.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.2
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• pp.82-86
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• 2011

Lightweight aggregate which is composed of sintered polycrystalline materials usually has a certain portion of pores inside of it. Because of such a structural characteristics, it tends to that movement of water in aggregate shows an abnormal behavior against the change of outside environment. In general, water movement behavior is controlled by porosity, distribution of pore size; however, dense surface layer will also affect water movement behavior in case of artificially sintered aggregates. Factors affecting water movement behavior in the aggregate are pore distribution, pore shape, pre-wetting method, etc. In this study, absorption characteristics of aggregate under the pressure and absorption rate according to water dipping time are analyzed for the basis of pressure pumping of lightweight concrete. Two kinds of aggregates were used for the test: one is made by 'L' company in Germany and the other is of our own made at the pilot plant in Kyonggi University. Absorption rate of aggregate is measured according to water dipping time, vacuum pressure, and quenching condition. Absorption rate of aggregate with $300^{\circ}C$ quenching is higher than that of aggregate with 24 hr water dipping. Generally the more vacuum the higher water absorption rate. Water absorption rate of 'L' aggregate under -300 mmHg is 54 % higher than that of aggregate with 24 hr water dipping; however, only 2 % increase in water absorption was measured for the K622 and K73 which were of our own.

• Korean Journal of Agricultural Science
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• v.24 no.2
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• pp.182-193
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• 1997

The normal cement concrete is widely used material to build the construction recently, but it has a fault to increase the dead load on account of its unit weight is large compared with strength. Therefore, many engineers are continuously searching for new materials of construction to provide greater performance at lower density. The main purpose of the work described in this paper were to establish the physical and mechanical properties of synthetic lightweight aggregate concrete using perlite on fine aggregate and expanded clay, pumice stone on coarse aggregate. The test results of this study are summarized that the water-cement ratio was shown 47% using expanded clay, 56% using pumice stone on coarse aggregate, unit weight was shown $l,622kgf/m^3$ using expanded clay, $l,596kgf/m^3$ using pumice stone on coarse aggregate, and the absorption ratio was shown same as 17%. The compressive strength was shown more than $228kgf/cm^2$, tensile and bending strength was more than $27kgf/cm^2$, $58kgf/cm^2$ at all types, and rebound number with schmidt hammer was increased with increase of compressive strength. The static modulus was $1.12{\times}10^5kgf/cm^2$ using expanded clay, $1.09{\times}10^5kgf/cm^2$ using pumice stone on coarse aggregate, and stress-strain curves were shown that increased with increase of stress, and the strain on the maximum stress was shown identical with $2.0{\times}10^{-3}$, approximately.

• Steel and Composite Structures
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• v.23 no.2
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• pp.187-194
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• 2017

To reuse a broken plain concrete (PC) arch, a retrofitting method was proposed to ensure excellent structural performances, in which carbon fiber reinforced polymers (CFRPs) were applied to repair and strengthen the damaged PC arch through bonding and wrapping techniques. Experiments were carried out to reveal the deformation and the load carrying capacity of the retrofitted composite arch. Based on the experiments, repairing and strengthening effects of the CFRP retrofitted broken arch were revealed. Simplified analysing model was suggested to predict the peak load of the CFRP retrofitted broken arch. According to the research, it is confirmed that absolutely broken PC arch can be completely repaired and reinforced, and even behaves more excellent than the intact PC arch when bonded together and strengthened with CFRP sheets. Using CFRP bonding/wrapping technique a novel efficient composite PC arch structure can be constructed, the comparison between rebar reinforced concrete (RC) arch and composite PC arch reveals that CFRP reinforcements can replace the function of steel bars in concrete arch.