• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.587-598
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• 2004

In this study, an experiment was conducted on the Slim Floor system, using a hollow core PC slab, which could reduce the over-all depth of a composite beam. The Slim Floor system is a method used in steel frame multi-story building construction, in which the structural depth of each floor is minimized after incorporating the steel floor beams within the depth of the concrete floor slab. This experimental study focused on the flexural behavior of the partially connected Slim Floor system with asymmetric steel beams encased in hollow core PC slabs. Ten full-scale specimens were constructed and tested in this study, with different steel beam heights, hollow core PC slabs, slab widths, and PC slab bearings. Observations made in line with the experiments indicated that the degree of shear connection without additional shear connection was 0.48-0.98 times more than that of the full shear connection, due to inherent mechanical and chemical bond stress.

• Imaging Science in Dentistry
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• v.39 no.2
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• pp.69-73
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• 2009

Purpose: This study compared panoramic radiography and cone beam computed tomography (CBCT) for evaluating the relationship between the maxillary sinus floor and the roots of maxillary molars. Materials and Methods: Paired panoramic radiographs and CBCT images from 97 subjects were analysed. This analysis classified 388 maxillary molars according to their relationship to the maxillary sinus floor on panoramic radiograph and CBCT. Correlations between these two radiographic techniques were examined. Results: Maxillary molar roots that were separate from the sinus floor showed the same classification in 100% of the cases when using these two imaging techniques. The corresponding percentage for such roots that were in contact with the sinus floor was 75%. When roots overlapped the maxillary sinus floor on panoramic radiographs, only 26.4% of maxillary first molars and 60.0% of second molars showed protrusion of roots into the sinus with CBCT. Conclusion : The results of the study suggest that roots projecting into the sinus on panoramic radiographs require a three-dimensional image in order to analyze the proximity of their apex to the sinus floor. (Korean J Oral Maxillofac Radiol2009; 39 : 69-73)

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.165-173
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• 2008

In order to promote the practicality of high-rise steel buildings, the development of structural system which have the better fire resistance, the changeable plan, and the quality control of construction with general composite beams is needed. In this research, new semi-slim floor which the defect of general slim floor was complemented was evaluated to investigate the concrete integration with slim-flor beam and the flexural performance. 5 simply supported semi-slim floor beam tests were performed with parameters; structural form of slab support beam, slab thickness, with or without web opening, and shear connection. Experimental results showed that all specimen s had good ductile behavior.

• Steel and Composite Structures
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• v.37 no.5
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• pp.589-603
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• 2020

This paper presents an investigation of the thermal performance of composite floor slabs with profiled steel decking exposed to fire effects from floor. A detailed finite-element model has been developed by representing the concrete slab with steel decking under of it and steel beam both steel parts protected by intumescent coating. Although this type of floor systems offers a better fire resistance, passive fire protection materials should be applied when a higher fire resistance is desired. Moreover, fire exposed side is so crucial for composite slab systems as the total fire behaviour of the floor system changes dramatically. When the fire attack from steel parts, the temperature rises rapidly resulting in a sudden decrease on the strength of the beam and decking. Herein this paper, the fire attack side is assumed from the face of the concrete floor (top of the concrete assembly). Therefore, the heat is transferred through concrete to the steel decking and reaching finally to the steel beam both protected by intumescent coating. In this work, the numerical model has been established to predict the heat transfer performance including material properties such as thermal conductivity, specific heat and dry film thickness of intumescent coating. The developed numerical model has been divided into different layers to understand the sensitivity of steel temperature to the number of layers of intumescent coating. Results show that the protected composite floors offer a higher fire resistance as the temperature of the steel section remains below 60℃ even after 60-minute Standard (ISO) fire and Fast fire exposure. Obtaining lower temperatures in steel due to the great fire performance of the concrete itself results in lesser reductions of strength and stiffness hence, lesser deflections.

• Imaging Science in Dentistry
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• v.38 no.2
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• pp.95-101
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• 2008

Purpose: To assess the positional relationship between the maxillary sinus floor and the apex of the maxillary first molar using cone beam computed tomograph (CBCT). Materials and Methods: CBCTs from 127 subjects were analysed. A total of 134 maxillary first molars were classified according to their vertical and horizontal positional relationship to the maxillary sinus floor and measured according to the distance between the maxillary sinus floor and the maxillary first molar. Results: Type III (The root projected laterally on the sinus cavity but its apex is outside the sinus boundaries) was dominated between 10 and 19 years and type I (The root apex was not in contact with the cortical borders of the sinus) was dominated (P<0.05) between 20 and 72 years on the vertical relationship between the maxillary sinus floor and the apex of the maxillary first molar. The maxillary sinus floor was located more at the apex (78.2%) than at the furcation (21.3%) for the palatal root. The distance from the root apex to the maxillary sinus floor confined to type I was increased according to the ages (P<0.05). Type M (The maxillary sinus floor was located between the buccal and the palatal root) was most common (72.4%) on the horizontal relationship between the maxillary sinus floor and the apex of the maxillary first molar. Conclusion: CBCT can provide highly qualified images for the maxillary sinus floor and the root apex of the maxillary first molar.

• Steel and Composite Structures
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• v.20 no.1
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• pp.107-125
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• 2016

Steel shear wall system has been used in recent years in tall buildings due to its appropriate behavior advantages such as stiffness, high strength, economic feasibility and high energy absorption capability. Coupled steel plate shear walls consist of two steel shear walls that are connected to each other by steel link beam at each floor level. In this article the frames of 3, 10, and 15 of (C-SPSW) floor with rigid connection were considered in three different lengths of 1.25, 2.5 and 3.75 meters and link beams with plastic section modulus of 100% to the panel beam at each floor level and analyzed using three pairs of accelerograms based on nonlinear dynamic analysis through ABAQUS software and then the performance of walls and link beams at base shear, drift, the period of structure, degree of coupling (DC) and dissipated energy evaluated. The results show that the (C-SPSW) system base shear increases with a decrease in the link beam length, and the drift, main period and dissipated energy of structure decreases. Also the link beam length has different effects on parameters of coupling degrees.

• Steel and Composite Structures
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• v.9 no.3
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• pp.255-274
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• 2009

This paper presents an experimental study of a newly developed composite floor system, built up from thin-walled C-profiles and upper concrete deck. Trapezoidal sheeting provides the formwork and the fastening of the sheet transmits the shear forces between the C-profiles and the deck. The modified formation of the standard self-drilling screw in the beam-to-sheet connection is applied as shear connector. Push-out tests are completed to study the composite behaviour of the different connection arrangements. On the basis of the test results the behaviour is characterized by the observed failure modes. The design values of the connection stiffness and strength are calculated by the recommendation of Eurocode 4. In the next phase of the experimental study six full-scale composite beams are tested. The global geometry is based on the proposed geometry of the developed floor system. The applied shear connections are selected as the most efficient arrangements obtained from the push-out tests. The experimental behaviour of the composite beams are discussed and evaluated. As a conclusion of the experimental study the Eurocode 4 plastic design method is validated for the developed composite floor.

• Journal of Korean Society of Steel Construction
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• v.13 no.1
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• pp.29-40
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• 2001

Steel frames are increasingly used in commercial buildings. and most steel frames are designed to achieve composite action with the concrete floor slab. The advantages of 'composite construction' are now well understood in terms of structural economy. good performance in service. and ease of construction. But. these conventional composite construction system are difficult to apply steel framed apartment due to their large depth. So. in this study we developed Semi Slim Floor system which could reduce the overall depth of composite beam. Semi Slim Floor system is a method of steel frame multi-story building construction in which the structural depth of each floor is minimised by incorporating the steel floor beams within the depth of the concrete floor slab. Twelve composite slab specimens with different deck-type. slab width. with or without stud bault and concrete topping thickness were tested to evaluate the flexural capacity.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.109-113
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• 2009

Purpose : The purpose of this study was to examine the inferior expansion of the maxillary sinus floor following maxillary molar extraction. Materials and Methods : Cone beam computed tomographic images of 59 subjects were used to evaluate the height difference of the maxillary sinus floor between extraction sites and contralateral dentate sites. The height of the maxillary sinus floor was defined as the vertical distance to the Frankfort plane from the level of the anterior nasal spine to the most inferior point of the sinus floor. We examined the difference in sinus pneumatization according to the number of missing teeth and the vertical relationship of the molar roots to the sinus floor. Results : The inferior expansion of the maxillary sinus floor was $1.20{\pm}1.86\;mm$ on the maxillary first molar and $1.90{\pm}2.42\;mm$ on the maxillary second molar. Increased expansion was observed in cases where two proximate molars were extracted. There was no significant difference in sinus pneumatization following extraction according to the vertical relationship of the molar roots to the sinus floor. Conclusion : The results of this study confirm that sinus pneumatization occurs following maxillary molar extraction. In situations where pneumatization can affect treatment after molar extraction, three-dimensional radiography should be considered.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.53-58
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• 2016

SLIM AU(A plus U-shaped) composite beam was developed for reducing the story height in the residential buildings, and saving the cosrtuction cost of floor structures. Structural performance and economic feasibility of the composite beam have been sufficiently approved through the structural experiments and the analytical studies. However, the verification for fire safety is necessary for the practical application of the composite beam. The fire resistance tests with and without loading were performed for the fire safety verification, and the test results were summarized in this paper.