• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.549-556
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• 2002

The natural frequency of a system is commonly used in evaluating the serviceability condition of a floor. However. the current equations recommended in many building codes do not consider the various material types of a slab system; thus. different results are observed. Likewise. the transformation of a slab section required to predict the natural frequency of a composite deck plate is complicated. due to the varying shapes of the deck plates. Therefore. a new and simplified method of transforming a composite slab into an equivalent concrete slab is proposed. he modified vibration prediction equation was proposed based on the current vibration prediction equation recommended by LRFD. Compared to other equations. it is the closest to those obtained from experiments. The modified equation provides about 14.3% more accurate results than that recommended by LRFD. Likewise. the applicability of the proposed equation to other types of composite deck plate floor system was validated.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.65-76
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• 2004

Walking loads are usually considered as nodal loads in the finite element vibration analysis of structures subjected to walking loads. Since most of the walking loads act on elements not nodes, the walking loads applied on the elements should be converted to the equivalent nodal walking loads. This paper begins with measuring walking loads by using a force plate equipped with load cells and investigates the characteristics of the walking loads with various walking rates. It is found that the walking loads are more affected by walking rates than other parameters such as pedestrian weight, type of footwear, surface condition of floor etc. The measured walking loads are used as input loads for a finite element model of walking induced vibration. Finally, this paper proposes the equivalent nodal walking loads that are converted from the walking loads acting on elements based on finite element shape functions. And the proposed equivalent walking loads are proved to be applicable for efficient analysis of floor vibration induced by walking loads.

• 한국해양학회지
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• v.19 no.1
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• pp.94-102
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• 1984

The origin of the East sea is discussed in the light of modern geophysical theories such as plate tectonics and sea-floor spreading. The origin of the East Sea was due to the tensional force of the back-arc spreading which was initiated as early as late Cretaceous time of Paleocene. The spreading was asymmetric with a fast movement of eastward or southeastward and a slow westward motions. The spreading, however, was confined to the East Sea due to the change of the Pacific Plate north-northwest to west-northwest during Eocene time. Further intensifying research based on more accurate seismic data as well as on geophysical and geological informations should be carried out continuously to understand if the spreading of the Japan Sea died out due to triple junction formed by mention of the Pacific, the Eurasian, and the Philippine plates since the Quaternary.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.575-586
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• 2004

This paper presents an experimental study on the flexural capacity of an encased(slim-floor) composite beam, which is a wider plate under bottom flange of H-beam with web openings. Five simple full-scale bending tests were conducted on the encased(slim-floor) composite beams at varying steel beam heights (250mm and 300mm), positions of web openings, and loading conditions. The test results revealed that the web-open encased composite beam had sufficient composite action, without any additional shear connection devices, because of the inherent shear-bond effects between the steel beam and the concrete, and a stable structural performance without web-opening reinforcements.

• Imaging Science in Dentistry
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• v.42 no.4
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• pp.219-224
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• 2012

Purpose: This study investigated the relationship between the roots of the maxillary molars and the maxillary sinus using cone beam computed tomography (CBCT), and measured the distances between the roots of the maxillary molars and the sinus floor as well as the thickness of the bone between the root and the alveolar cortical plate. Materials and Methods: The study sample consisted of 83 patients with normally erupted bilateral maxillary first and second molars. A total of 332 maxillary molars were examined using CBCT images. The vertical relationship of each root with the maxillary sinus was classified into four types on CBCT cross-sectional images. The distance between the sinus floor and root and the bone thickness between the root and alveolar cortical plate were measured. Results: In the buccal roots of the maxillary molars, a root protruding into the sinus occurred most frequently. A root projecting laterally along the sinus cavity was most common in the palatal roots of the maxillary first molars. The mesiobuccal roots of the maxillary second molar were closest to the sinus. The mesiobuccal roots of the first molars were closest to the cortical plate. Conclusion: The relationship between the roots of the maxillary molars and the sinus differed between the buccal and palatal roots. A root protruding into the sinus occurred more frequent in the buccal roots of the maxillary molars. The mesiobuccal root of the maxillary second molar was closest to the maxillary sinus floor and farthest from the alveolar cortical plate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.371-376
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• 1998

As the requirement of high-rise buildings in big cities increases, steel structural system becomes more popular in spite of the relatively higher material cost compared to that of the concrete structural system. Most of the steel structure adopts metal deck floor system because of the easiness in construction. However, the metal deck floor system has a weakness on vibration which became very important factor in office buildings, hotels and residential buildings as the more sensitive machines being used. Therefore, most, of the building codes in many countries restrict the natural frequency of the each floor should be higher than or equal to 15 Hz. Floor vibration of the KEM deck composite floor system which has been , developed recently from the engineers and scientists in Korea was measured. Also, the simplified analytical derivation of natural frequency for each floor was studied according to the measured natural frequency for each different boundary condition of the floor. As the length of the slab gets bigger, the natural frequency of the slab becomes lower even though the structural designer still considers it as a one-way slab.

• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.18-23
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• 2013

The purpose of this study were to develop and validate a prototype slipmeter used on-site floor. The developed slipmeter was dreg sled type. It measured static coefficient of friction(SCOF). The developed slipmeter was evaluated with ASTM 2508-11 which use four different standard surfaces(polished granite, glazed porcelain, vinyl composite tile, and ceramic tile). The SCOF was then measured with developed slipmeter under the three different contaminants and seven different floors. The test results of slipmeter were also compared with those of BOT-3000, floor surface roughness, and human perception. The test results revealed that developed slipmeter successfully ranked all four standard surfaces and differentiated among standard surfaces with varying degrees of slipperiness. The developed slipmeter couldn't properly measure slipperiness under the two kind of floors(polished tile, ground steel plate) and one kind of contaminant(glycerol). The test results of developed slipmeter had stronger correlation with those of BOT-3000 and floor roughness under the water and detergent solution than under the glycerol. The test results of developed slipmeter also showed stronger correlation with those of BOT-3000 and surface roughness than those of human perception. The newly developed slipmeter had been found to give consistent results under the test conditions except for two kind of floors(polished tile, ground steel plate) and one kind of contaminant(glycerol).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.159-160
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• 2014

The floor impact noise arising between upper and lower households in residential houses has been known as one of major causes worsening residential environment and still led to serious social troubles in a residential community. It is known that the heavy weight floor impact noise is induced by flexural vibration modes in the relatively lower frequency ranges. In this study, a procedure is examined to evaluate the relations between the vibration modes and the corresponding noise of the slab. In the process, for simplicity of the numerical analysis, it is assumed that the slab is simply supported plate-like structure and the acoustic mode formed in the lower room by acoustic boundary conditions is ignored.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1417-1420
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• 2006

In this paper, floor impact is studied by using 1-D wave model and predicted insertion loss is compared to the measurements done in the mock-up. A mock-up is built by using 6t steel plate, and two identical cabins are made where 25t or 50t panel is used to construct wall and ceiling inside the steel structure. Various floating floor structures are studied, in which mineral wool thickness, height, and stiffness changes are investigated. It is shown that the wave model and measurements are in good agreements in general, although there occur significant discrepancies in the low frequency range below 200 Hz.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.199-202
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• 2005

KCI 2003 provides minimum thickness of slab that satisfies serviceability to static displacement. Previous study (Han, et al. 2003) showed the several slabs that designed according to minimum thickness criteria had floor vibration problem. In this study, evaluate the floor vibration serviceability of KCI 2003 minimum thickness requirements for 2-way flat plate and propose the minimum thicknesses of 2-way slabs that satisfy floor vibration criteria according to several boundary condition. For this purpose, one degree of freedom model is used and Monte Carlo simulation is performed.