• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.249-250
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• 2018

To control the floor noise generated in the apartment building, a method of reinforcing the floor at the floor is applied. However, since existing buildings are difficult to reinforce upper generations, the ceilings of lower generations should be reinforced. The purpose of this study is to analyze the reduction effect by measuring the impact noise after reinforcing the floor soundproofing material on the ceiling of the existing building. In order to ensure the economical efficiency and flame retardancy of the products used as building interior materials, the existing polyurethane foam was impregnated with mineral to prepare test specimens and attached to the concrete slab surface. As a result, it was shown that heavy impact sound can reduce 2dB~5dB and light impact sound can reduce 4~8dB.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.171-172
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• 2014

This is an experimental study on manufacturing of non-cement matrix. Materials like cement and blowing agent in foamed concrete is replaced by by-products from blast furnace slag and paper ash. Sample 43-PS-1 with density showed lowest. The compressive strength test result, showed a similar trend with density. And it showed that compressive strength of the 40-PS-1 was highest.

• Structural Engineering and Mechanics
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• v.64 no.5
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• pp.543-555
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• 2017

The non-linear behaviour of integral infilled frames (in which the infill and the frame are bonded together with help of various interface materials) is studied both experimentally and numerically. The experiments were carried out on one-sixth scale two-bay and three-storey reinforced concrete frames with and without infill against static cyclic loading. Three interface materials - cement mortar, cork and foam have been used in between the infill and the frame. The infill, interface and the frame are bonded together is called integral frame. The linear and non-linear behaviors of two dimensional bare frame and integral infilled frame have been studied numerically using the commercial finite element software SAP 2000. Linear finite element analysis has been carried out to quantify the effect of various interface materials on the infilled frames with various combinations of 21 cases and the results compared. The modified configuration that used all three interface materials offered better resistance above others. Therefore, the experiments were limited to this modified infilled frame case configuration, in addition to conventional (A1-integral infilled frame with cement mortar as interface) and bare frame (A0-No infill). The results have been compared with the numerical results done initially. It is found that stiffness of bare frame increased by infilling and the strength of modified frame increased by 20% compare to bare frame. The ductility ratio of modified infilled frame was 42% more than that of the conventional infilled frame. In general, the numerical result was found to be in good agreement with experimental results for initial crack load, ultimate load and deformed pattern of infill.

• Computers and Concrete
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• v.26 no.1
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• pp.75-94
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• 2020

The aim of this research is to investigate free vibration of a novel five layer Timoshenko microbeam which consists of a transversely flexible porous core made of Al-foam, two graphen platelets (GPL) nanocomposite reinforced layers to enhance the mechanical behavior of the structure as well as two piezo-magneto-electric face sheets layers. This microbeam is subjected to a thermal load and resting on Pasternak's foundation. To accomplish the analysis, constitutive equations of each layer are derived by means of nonlocal strain gradient theory (NSGT) to capture size dependent effects. Then, the Hamilton's principle is employed to obtain the equations of motion for five layer Timoshenko microbeam. They are subsequently solved analytically by applying Navier's method so that discretized governing equations are determined in form of dynamic matrix giving the possibility to gain the natural frequencies of the Timoshenko microbeam. Eventually, after a validation study, the numerical results are presented to study and discuss the influences of various parameters such as nonlocal parameter, strain gradient parameter, aspect ratio, porosity, various volume fraction and distributions of graphene platelets, temperature change and elastic foundation coefficients on natural frequencies of the sandwich microbeam.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.363-370
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• 2016

Lightweight geopolymers are more readily produced and give higher fire resistant performance than foam cement concrete. Lowering the density of solid geopolymers can be achieved by inducing chemical reactions that entrain gases to foam the geopolymer structure. This paper reports on the effects of adding different concentrations of aluminum powder on the properties of cellular structured geopolymers. The apparent density of lightweight geopolymers has a range from 0.7 to $1.2g/m^3$ with 0.025, 0.05 and 0.10 wt% of a foaming agent concentration, which corresponds to about 37~60 % of the apparent density, $1.96g/cm^3$, of solid geopolymers. The compressive strength of cellular structured geopolymers decreased to 6~18 % of the compressive strength, 45 MPa of solid geopolymers. The microstructure of geopolymers gel was equivalent for both solid and cellular structured geopolymers. The workability of geopolymers with polyprophylene fibers needs to be improved as in fiber-reinforced cement concrete. The lightweight geopolymers could be used as indoor wall tile or board due to fire resistance and incombustibility of geopolymers.

• Steel and Composite Structures
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• v.52 no.4
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• pp.391-403
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• 2024

The flexural behavior of composite sandwich wall panels with different thicknesses, numbers of holes, and hole forms, and arrangement form of longitudinal steel bar (uniform type and concealed-beam type) are investigated. A total of twelve composite sandwich wall panels are prepared, utilizing modified polystyrene particles mixed with foam concrete for the flexural performance test. The failure pattern of the composite sandwich wall panels is influenced by the extruded polystyrene panel (XPS) panel thickness and the reinforcement ratio in combination, resulting in both flexural and shear failure modes. Increasing the XPS panel thickness causes the specimens to transition from flexural failure to shear failure. An increase in the reinforcement ratio leads to the transition from flexural failure to shear failure. The hole form on the XPS panel and the steel bar arrangement form affect the loading behavior of the specimens. Plum-arrangement hole form specimens exhibit lower steel bar strain and deflection compared to linear-arrangement hole form specimens. Additionally, specimens with concealed beam-type steel bar display lower steel bar strain and deflection than uniform-type steel bar specimens. However, the hole form and steel bar arrangement form have a limited impact on the ultimate load. Theoretical formulas for cracking load are provided for both fully composite and non-composite states. When compared to the experimental values, it is observed that the cracking load of the specimens with XPS panels closely matches the calculations for the non-composite state. An accurate prediction model for the ultimate load of fully composite wall panels is developed. These findings offer valuable insights into the behavior of composite sandwich wall panels and provide a basis for predicting their performance under various design factors and conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.226-234
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• 2017

The physical properties of lightweight foamed concrete mixed with EPS waste and flame resistant EPS waste were investigated. For this purpose, the main variables considered were a cement content of 300 and $400kgf/m^3$ and an EPS replacement ratio of 0, 10, 20, 30, and 40% by the volume ratio of the foam. The water-cement ratio and the dilution concentration were fixed to 0.5 and 10% respectively. The test results showed that the apparent density meets degrees 0.5 and 0.6 of KS F4039, and they showed little difference between the two mixes of Type A and Type B, regardless of the unit cement content. The bending strength obtained through the compressive strength also met the degree of KS F 4039. The thermal conductivity was 1~3% higher for the mixes of EPS than the case of flame resistant EPS, but both mixes met the 0.4 degree of KS F4039. The absorption ratio showed the values above 20% with a 1~3% difference for the two mixes, which mean further studies will be needed to reduce the absorption ratio.

• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.5-14
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• 2016

The leakage of water under sewer pipelines is one of main sources of sinkholes in urban areas. We performed laboratory model tests to investigate the presence of cavities using impact-echo method, which is a nondestructive test method. To simulate a concrete sewer pipe, a thin concrete plate was built and placed over container filled with sand. The cavity was modeled as an extruded polystyrene foam box. Two sets of tests were performed, one over sand and the other on cavity. A new impact device was developed to apply a consistent high frequency impact load on the concrete plate, thereby increasing the reliability of the test procedure. The frequency and transient characteristics of the measured reflected waveforms were analyzed via fast Fourier transform and short time Fourier spectrum. It was shown that the shapes of Fourier spectra are very similar to one another, and therefore cannot be used to predict the presence of cavity. A new index, termed resonance duration, is defined to record the time of vibration exceeding a prescribed intensity. The results showed that the resonance duration is a more effective parameter for predicting the presence of a cavity. A value of the resonance period was proposed to estimate the presence of cavity. Further studies using various soil types and field tests are warranted to validate the proposed approach.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.557-563
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• 2009

This study is on the properties of inorganic porous calcium silicate material made from silica powder through the autoclaving curing, the results of this study should be utilized fundamental data for the development of noise reduction porous solid material using siliceous byproduct generated by various manufacture process. For the manufacture of autoclave curing specimen, various calcareous materials used and siliceous materials used silica powder. In this study, properties in density and compressive strength according to the change of W/B and C/S ratio, microscopy for the shape of pore, SEM and XRD for the examination of hydrate after autoclave curing are carried out respectively. The test results shown that the more slurry density decrease, the more W/B increase at the fresh state, this tendency shown similar to in hardened state. Among the specimens of C/S ratio, the compressive strength of C/S ratio of 0.85 gave the highest the compressive strength. In the results of XRD, tobermorite generated by autoclaving curing was created all of specimens regardless of C/S ratio. To ascertain pore structure, we compared with existing porous calcium silicate product(ALC, organic sound absorbing porous material). The results of microscope observation, pore structure of specimen of this study was similar to that of existing inorganic sound absorbing foam concrete. therefore, we could conformed a possibility of sound absorbing porous solid material on the basis of the results.

• Journal of Engineering Education Research
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• v.10 no.2
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• pp.44-61
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• 2007

The present investigation is concerned chiefly with new curriculum development at the Department of Mechanical System & Design Engineering at Hongik University with the aim of enhancing creativity, team working and communication capability which modern engineering education is emphasizing on. 'Mechanical System & Design Engineering' department equipped with new curriculum emphasizing engineering design is new name for mechanical engineering department in Hongik University. To meet radically changing environment and demands of industries toward engineering education, the department has shifted its focus from analog-based and machine-centered hard approach to digital-based and human-centered soft approach. Three new programs of Introduction to Mechanical System & Design Engineering, Creative Engineering Design and Product Design emphasize hands-on experiences through project-based team working. Sketch model and prototype making process is strongly emphasized and cardboard, poly styrene foam and foam core plate are provided as working material instead of traditional hard engineering material such as metals material because these three programs focus more on creative idea generation and dynamic communication among team members rather than the end results. With generative, visual and concrete experiences that can compensate existing engineering classes with traditional focus on analytic, mathematical and reasoning, hands-on experiences can play a significant role for engineering students to develop creative thinking and engineering sense needed to face ill-defined real-world design problems they are expected to encounter upon graduation.