• Steel and Composite Structures
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• v.25 no.4
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• pp.505-521
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• 2017

The steel plate shear wall with beam-only connected infill plate (SSW-BO) is an innovative lateral load resisting system consisting of infill plates connected to surrounding beams and separated from the main columns. In this research, the effects of perforation diameter as well as slenderness ratios of infill plates on the hysteresis behavior of SSW-BO systems were studied experimentally. Experimental testing is performed on eight one-sixth scaled one-story SSW-BO specimens with two plate thicknesses and four different circular opening ratios at the center of the panels under fully reversed cyclic quasi-static loading in compliance with the SAC test protocol. Strength, stiffness, ductility and energy absorption were evaluated based on the hysteresis loops. It is found that the systems exhibited stable hysteretic behavior during testing until significant damage in the connection of infill plates to surrounding beams at large drifts. It is also seen that pinching occurred in the hysteresis loops, since the hinge type connections were used as boundaries at four corners of surrounding frames. The strength and initial stiffness degradation of the perforated specimens containing opening ratio of 0.36 compared to the solid one is in the range of 20% to 30% and 40% to 50%, respectively.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.672-681
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• 2015

As a part of abating the formaldehyde emission of amino resin-bonded wood-based composite panels, this study was conducted to investigate hydrolytic stability of urea-melamine-formaldehyde (UMF) resin depending on various hydrolysis conditions and hardener types. Commercial UMF resin was cured and ground into a powdered form, and then hydrolyzed with hydrochloric acid. After the acid hydrolysis, the concentration of liberated formaldehyde in the hydrolyzed solution and mass loss of the cured UMF resins were determined to compare their hydrolytic stability. The hydrolysis of cured UMF resin increased with an increase in the acid concentration, time, and temperature and with a decrease in the smaller particle size. An optimum hydrolysis condition for the cured UMF resins was determined as $50^{\circ}C$, 90 minutes, 1.0 M hydrochloric acid and $250{\mu}m$ particle size. Hydrolysis of the UMF resin cured with different hardener types showed different degrees of the hydrolytic stability of cured UMF resins with a descending order of aluminum sulfate, ammonium chloride, and ammonium sulfate. The hydrolytic stability also decreased as the addition level of ammonium chloride increased. These results indicated that hardener types and level also had an impact on the hydrolytic stability of cured UMF resins.

• Journal of the Korean Wood Science and Technology
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• v.42 no.5
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• pp.605-614
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• 2014

This study investigated microstructural changes of cured urea-formaldehyde (UF) resins mixed with aqueous rubber latex emulsion after intentional acid etching. Transmission electron microscopy (TEM) was used in order to better understand a hydrolytic degradation process of cured UF resins responsible for the formaldehyde emission from wood-based composite panels. A liquid UF resin with a formaldehyde to urea (F/U) molar ratio 1.0 was mixed with a rubber latex emulsion at three different mixing mass ratios (UF resin to latex = 30:70, 50:50, and 70:30). The rate of curing of the liquid modified UF resins decreased with an increase of the rubber latex proportion as determined by differential scanning calorimetry (DSC) measurement. Ultrathin sections of modified and cured UF resin films were exposed to hydrochloric acid etching in order to mimic a certain hydrolytic degradation. TEM observation showed spherical particles and various cavities in the cured UF resins after the acid etching, indicating that the acid etching had hydrolytically degraded some part of the cured UF resin by acid hydrolysis, also showing spherical particles of cured UF resin dispersed in the latex matrix. These results suggested that spherical structures of cured UF resin might play an important role in hindering the hydrolysis degradation of cured UF resin.

• Advances in materials Research
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• v.6 no.2
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• pp.221-231
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• 2017

The concept design of the typha strawbale masonry came up as a result of the urgent demand for a means of constructing sustainable buildings, both in rural and urban settlement, not only suitable for dwellers but for keeping farm products by structures that will respond to the environmental eco-system, coupled with the fact that such structures are also affordable, durable and easy to maintain during their service period. The effects of contact between plaster and the stacked strawbale of a masonry needs to be established and design optimization for durability and stability of the masonry be obtained. The assessment will involve the application of plaster materials (cement and natural earth) to the wall specimen panels. Past works have shown that plastered strawbale walls have adequate resistance against the appropriate vertical loads, and further showed that the earth plaster can bear higher stress than the cement plastered straw bale. There is the implication that the collapse or response of the earth-strawbale wall is significantly higher compared to that of cement-strawbale from other straw-based masonries. Therefore the allowable stresses of plastered typha strawbale shall be predicted for their optimum values using SAP2000. The stress stability of each masonry is obtained by analytical model using the best fit variables for the wall height and thickness.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.388-394
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• 2005

A typical honeycomb sandwich panel consists of two thin, high-strength facings bonded to a thick, light-weight core. Each component by itself is relatively weak and flexible, but when it combind in a sandwich panel they produce a structure that is stiff, strong, and lightweight. In addition to use in honeycomb sandwich panels, honeycomb is used for energy absorption, radio frequency shielding, light diffusion, and to direct air flow.Accordingly, the usage of honeycomb sandwich structure is very widely applied to the aircraft, the automobile, and marine industry, etc., because of these advantages. Generally, this honeycomb sandwich structure is manufactured by autoclave process.In this study, the honeycomb sandwich structure was produced by prepreg. To prove the suitability the honeycomb sandwich structure with prepreg, The optimum design of the skin materials and honeycomb sandwich structure were evaluated with the theory of stress analysis.

• Journal of the Korea Safety Management & Science
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• v.14 no.2
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• pp.83-89
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• 2012

In this study, FDS fire simulation experiments and measured wind speed by applying the exterior installation portion for blocking the spread of the fire was investigated. As a result, aluminum composite panels installed in the lower and the upper part of the panel to remove all the lower side, and then the maximum wind speed 0.24 m/s and the upper side 0.58 m/s were measured. In the FDS, the measured wind speed difference air currents are approximately 3.7 times in 12 seconds, the occurrence of 17 seconds early moment wind 2.2 m/s was measured from. Before and after the fire occurred in early of the air velocity about 39 seconds was 3.5 times difference. Such air currents caused by the temperature of the building but also by the building height was found. Turbulent flame of fire by expanding the vertical extent of damage become greatly important factor. Therefore, through the exterior installation portion of the block that can delay the spread of fire is expected that this should be taken.

• Earthquakes and Structures
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• v.13 no.5
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• pp.473-484
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• 2017

The objective of this paper is to report on a study of the use of unstiffened thin steel plate shear walls (SPSWs) for the seismic performance improvement of reinforced concrete frames with deficient lateral rigidity. The behaviour of reinforced concrete frames during seismic activities was rehabilitated with an alternative and occupant-friendly retrofitting scheme. The study involved tests of eight 1/3 scale, one bay, two storey test specimens under cyclic quasi-static lateral loadings. The first specimen, tested in previous test program, was a reference specimen, and in seven other specimens, steel infill plates were used to replace the conventional infill brick or the concrete panels. The identification of the load-deformation characteristics, the determination of the level of improvement in the overall strength, and the elastic post-buckling stiffness were the main issues investigated during the quasi-static test program. With the introduction of the SPSWs, it was observed that the strength, stiffness and energy absorption capacities were significantly improved. It was also observed that the experimental hysteresis curves were stable, and the composite systems showed excellent energy dissipation capacities due to the formation of a diagonal tension field action along with a diagonal compression buckling of the infill plates.

• Steel and Composite Structures
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• v.20 no.3
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• pp.545-569
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• 2016

Stiffeners have widely been used in lateral load resisting systems to improve the buckling stability of shear panels in steel frames. However, due to major differences between plate girders and steel plate shear walls (SPSWs), use of plate girder equations often leads to uneconomical and, in some cases, incorrect design of stiffeners. Hence, this paper uses finite element analysis (FEA) to describe the effect of the rigidity and arrangement of stiffeners on the buckling behavior of plates. The procedures consider transverse and/or longitudinal stiffeners in various practical configurations. Subsequently, curves and formulas for the design of stiffeners are presented. In addition, the influence of stiffeners on the inward forces subjected to the boundary elements and the tension field angle is investigated as well. The results indicate that the effective application of stiffeners in SPSW systems not only improves the structural behavior, such as stiffness, overall strength and energy absorption, but also leads to a reduction of the forces that are exerted on the boundary elements.

• Journal of the Korean Society of Food Culture
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• v.19 no.2
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• pp.193-199
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• 2004

The purpose of this study was to determine the organoleptic charateristics of cauliflower pickles made in various compounding ratio according to central conposite design for optimum organoleptic characteristics of the cauliflower pickles. The optimum mixing condition of cauliflower pickles were optimized, using central composite design with 3 variables and 3 levels, by response surface methodology. The various kinds of cauliflower pickle were made in various compounding ratio of vinegar, salt and sucrose - critical ingredients of pickle recipe - and were presented to reliable panels, who graded the subjects in 7 degrees for 4 items : color, flavor, hardness and overall quality. The optimum mixing conditions of cauliflower pickle were 603.50g of vinegar, 80.13g of salt and 251.07g of sucrose in the maximum point of overall quality.

• Steel and Composite Structures
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• v.14 no.6
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• pp.523-545
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• 2013

In this study, the effect of presence and distribution of masonry infill walls on the mid-rise steel frame structures having soft ground storey was evaluated by implementing finite element (FE) methods. Masonry infill walls were distributed randomly in the upper storey keeping the ground storey open without any infill walls, thus generating the worst case scenario for seismic events. It was observed from the analysis that there was an increase in the seismic design forces, moments and base shear in presence of randomly distributed masonry infill walls which underlines that these design values need to be amplified when designing a mid-rise soft ground storey steel frame with randomly distributed masonry infill. In addition, it was found that the overstrength related force modification factor increased and the ductility related force modification factor decreased with the increase in the amount of masonry infilled bays and panels. These must be accounted for in the design of mid-rise steel frames. Based on the FE analysis results on two mid-rise steel frames, design equations were proposed for determining the over strength and the ductility related force modification factors. However, it was recommended that these equations to be generalized for other steel frame structure systems based on an extensive analysis.