• Imaging Science in Dentistry
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• 제54권2호
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• pp.147-157
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• 2024

Purpose: The aim of this study was to explore the correlations of cone-beam computed tomographic findings with the apnea-hypopnea index in patients with obstructive sleep apnea. Materials and Methods: Forty patients with obstructive sleep apnea were selected from the ear-nose-throat (ENT) outpatient clinic, Faculty of Medicine, Mansoura University. Cone-beam computed tomography was performed for each patient at the end of both inspiration and expiration. Polysomnography was carried out, and the apnea-hypopnea index was obtained. Linear measurements, including cross-sectional area and the SNA and SNB angles, were obtained. Four oral and maxillofacial radiologists categorized pharyngeal and retropalatal airway morphology and calculated the airway length and volume. Continuous data were tested for normality using the Kolmogorov-Smirnov test and reported as the mean and standard deviation or as the median and range. Categorical data were presented as numbers and percentages, and the significance level was set at P<0.05. Results: The minimal value of the cross-sectional area, SNB angle, and airway morphology at the end of inspiration demonstrated a statistically significant association (P<0.05) with the apnea-hypopnea index, with excellent agreement. No statistically significant difference was found in the airway volume, other linear measurements, or retropalatal airway morphology. Conclusion: Cone-beam computed tomographic measurements in obstructive sleep apnea patients may be used as a supplement to a novel radiographic classification corresponding to the established clinical apnea-hypopnea index classification.

• 한국강구조학회 논문집
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• 제17권4호통권77호
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• pp.459-467
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• 2005

본 연구는 외측 다이아프램을 사용하여 현장용접에 의한 각형강관 기둥과 H형강 보를 접합법의 개발에 목적을 둔다. 본 연구에서 제안하고 있는 것은 현장용접을 이용한 외측 보강재에 의한 특정 타입의 기둥-보 접합부이다. 이 접합부의 구조적 거동은 실험적으로 검토되었다. 두 가지 하중 유형 실험은 세부적으로 주어진 실험 변수 하에 수행되었다. 먼저 제안된 접합부의 기본적인 특성을 연구하기 위하여 양단부에서 보를 핀 지지한 후 중앙점에서 기둥을 가력한 대칭 하중재하 실험을 기술하였다. 두 번째는 이 접합부의 구조적 성능을 연구하기 위하여 기둥의 양단은 단순지지로 하고 H형강 보 양단에서 하중을 제어하는 역대칭 하중재하 실험을 기술하였다. 실험 결과, 본 논문에서 제안한 외측 보강재 타입의 접합부는 정량적 평가 방법이라는 것을 알 수 있었다.

• Steel and Composite Structures
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• 제27권5호
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• pp.545-554
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• 2018

This study presents a novel method of improving the strength and stiffness of cold-formed steel (CFS) beams. Flexural members are primary members in most of the structures. Hence, there is an urgent need in the CFS industry to look beyond the conventional CFS beam sections and develop novel techniques to address the severe local buckling problems that exist in CFS flexural members. The primary objective of this study was to develop new CFS composite beam sections with improved structural performance and economy. This paper presents an experimental study conducted on different CFS composite beams with simply supported end conditions under four point loading. Material properties and geometric imperfections of the models were measured. The test strengths of the models are compared with the design strengths predicted by using Australian/New Zealand Standard for cold-formed steel structures. Furthermore, to ensure high precision testing, a special testing rig was also developed for testing of long span beams. The description of test models, testing rig features and test results are presented here. For better interpretation of results, a comparison of the test results with a hot rolled section is also presented. The test results have shown that the proposed CFS composite beams are promising both in terms of better structural performance as well as economy.

• 한국해양공학회지
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• 제9권1호
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• pp.22-35
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• 1995

A simplified numerical procedure have proposed to trace the dynamic behaviour of offshore tubulars subjected to lateral collision impacts. The local denting and overall bending deformation of the struck tubular are represented by a non-linear spring and an elastic visco-plastic beam respectively. In this method a temporal finite difference method and a spacial finite element method are employed. Using this method various boundary conditions are able to considered and their effects on the extent of damage can be quantified. The extent of damage due to collision can be obtained as results of the dynamic analysis. The predictions using the proposed method have been correlated with existing test results and then the reliability of the procedure has been substantiated. The characteristics of the dynamic response of tubulars under lateral impacts are compared for simply supported roller and fixed end conditions and their effects on the extent of damage are specfied.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.354-361
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• 2002

This paper propose section properties factor to generate stress history for fatigue analysis and safety inspection of steel bridge. A methodology is described for the computation of numerical stress histories in the steel truss bridge, caused by the vehicles using section properties factor. The global 3-D beam model of bridge is combined with the local shell model of selected details. Joint geometry is introduced by the local shell model. The global beam model takes the effects of joint rigidity and interaction of structural elements into account. Connection nodes in the global beam model correspond to the end cross-section centroids of the local shell model. Their displacements are interpreted as imposed deformations on the local shell model. The load cases fur the global model simulate the vertical unit force along the stringers. The load cases fer the local model are imposed unit deformations. Combining these, and applying vehicle loads, numerical stress histories are obtained. The method is illustrated by test load results of an existing bridge.

• Steel and Composite Structures
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• 제52권4호
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• pp.405-418
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• 2024

To study the influence of different reduced beam section (RBS) on the mechanical performance of modular boltedwelded hybrid connection joints (MHCJs), this article uses ABAQUS to establish and verify the finite element model (FEM) of the test specimens on the basis of quasi-static test research. Based on, 14 joint models featuring different RBS are devised to evaluate their influence on seismic behavior, such as joint failure mode, bending moment (M)-rotation angle (θ) curve, ductility, and energy consumption. The results indicate that when the flange and web are individually weakened, they alleviate to some extent the concentrated stress of the core module (CM) and column end steel skeleton in the joint core area, but both increase the stress on the flange connecting plate (FCP). At the same time, the impact of both on seismic performance such as bearing capacity, stiffness, and energy consumption is relatively small. When simultaneously weakening the flange and web of the steel beam, forming plastic hinges at the weakened position of the beam end, significantly alleviated the stress concentration of the CM and the damage at the FCP, improving the overall deformation and energy consumption capacity of joints. But as the weakening size of the web increases, the overall bearing capacity of the joint shows a decreasing trend.

• Steel and Composite Structures
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• 제7권2호
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• pp.87-103
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• 2007

This paper presents some of the results from an experimental research project on the behavior of extended end-plate connections subjected to moment conducted at the Structural Laboratory of Jordan University of Science and Technology. Since the connection behavior affects the structural frame response, it must be included in the global analysis and design. In this study, the behavior of six full-scale stiffened and unstiffened cantilever connections of HEA- and IPE-sections has been investigated. Eight high strength bolts were used to connect the extended end-plate to the column flange in each case. Strain gauges were installed inside each of the top six bolts in order to obtain experimentally the actual tension force induced within each bolt. Then the connection behavior is characterized by the tension force in the bolt, extended end-plate behavior, moment-rotation relation, and beam and column strains. Some or all of these characteristics are used by many Standards; therefore, it is essential to predict the global behavior of column-beam connections by their geometrical and mechanical properties. The experimental test results are compared with two theoretical (equal distribution and linear distribution) approaches in order to assess the capabilities and accuracy of the theoretical models. A simple model of the joint is established and the essential parameters to predict its strength and deformational behavior are determined. The equal distribution method reasonably determined the tension forces in the upper two bolts while the linear distribution method underestimated them. The deformation behavior of the tested connections was characterized by separation of the column-flange from the extended end-plate almost down to the level of the upper two bolts of the lower group and below this level the two parts remained in full contact. The neutral axis of the deformed joint is reasonably assumed to pass very close to the line joining the upper two bolts of the lower group. Smooth monotonic moment-rotation relations for the all tested frames were observed.

• 한국강구조학회 논문집
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• 제12권4호통권47호
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• pp.351-362
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• 2000

이 논문은 반복하중을 받는 관통형 고력볼트를 사용한 엔드플레이트형식 콘크리트 충전 각형강관 기둥-H형강 보 접합부의 거동에 관한 연구이다. 주요변수는 엔드플레이트의 두께(16mm, 22mm, 25mm)와 기둥의 두께(9mm, 12mm)이다. 각 변수에 대해 실험결과와 비교 분석한다. 보-기둥 접합부의 에너지 흡수능력을 구하고, 접합부 패널의 전단내력을 분석한다. 접합부 패널의 전단 내력은 von Mises 항복조건에 의한 강재의 내력과 콘크리트 충전효과를 고려한 Strut 모델을 사용한 콘크리트의 내력을 단순누가해서 구한다.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.190-194
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• 2006

This research investigates vehicle structure acceleration and vehicle deformation with RCAR crash test. To investigate vehicle damage characteristics in an individual case, it is possible to RCAR low speed crash test. In this study, two tests were conducted to evaluate difference between RCAR new condition and RCAR old condition. A two large vehicles were subjected to a frontal crash test at a speed of 15km/h with an offset of 40% $10^{\circ}$ angle barrier and flat barrier. The results of the 15km/h with an offset of 40% $10^{\circ}$ angle barrier revealed high acceleration value on the vehicle structure and high repair cost compared to the RCAR 15km/h with an offset of 40% flat barrier. So in order to improve damage characteristics in low speed crash of vehicle structure and body component of the monocoque type passenger vehicles, the end of front side member and front back beam should be designed with optimum level and to supply the end of front side member as a partial condition approx 300mm.

• 한국건축시공학회지
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• 제20권5호
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• pp.449-457
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• 2020

생활수준의 향상과 3D 업종 기피 현상으로 국내 건설현장에는 젊고 유능한 국내 노동자를 찾아보기 힘들고, 대부분 외국인 노동자가 그 대체인력으로 기여하고 있으나 여전히 기능공 부족 및 고령화로 인해 품질이 저하되고 있는 실정이다. PC화 공법은 공장에서 제작되고 현장에서 조립하는 공법으로 노동력 및 품질향상을 기대할 수 있다. 본 연구는 PC 공법에 적용할 수 있는 걸이형 PC보의 개발 및 개발된 PC보의 현장적용성 여부를 판단하기 위한 기초자료를 제공하는 위한 것이다. 걸이형 PC보 양 단부에는 U형 연결재가 설치되어 있으며, U형 연결재를 통해 간단히 시공되는 공법이기 때문에 U형 연결재의 역할은 매우 중요하다. 또한, U형 연결재는 걸이형 PC보에서 최종파괴가 발생되는 부분이므로 U형 연결재의 성능이 곧 걸이형 PC 보의 성능을 좌우하게 된다. 구조실험을 통해 U형 연결재의 재료물성을 파악하였으며, 파악된 재료시험 결과를 토대로 부분실험에 해당되는 단부실험 및 구조실험을 실시하여 현장 적용성 여부를 확인하였다.