• 대한기계학회논문집A
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• 제37권6호
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• pp.731-738
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• 2013

본 논문은 6 륜 독립구동/독립조향 차량의 독립 스티어-바이-와이어 장치의 고장 안전 주행 제어방법을 제시하였다. 조향부 고장 휠의 횡방향 타이어 힘이 차량 선회 운동에 저항력으로 작용할 수 있으므로, 이를 줄이기 위하여 본 고장 안전 주행 제어 알고리즘은 조향부 고장 휠에 높은 슬립률이 발생하도록 토크 입력을 가한다. 고슬립으로 인한 조향부 고장 휠의 종방향 타이어 힘 증가를 고려하기 위하여 종방향 타이어 힘을 추정하여 고장나지 않은 휠의 구동력 최적 분배에 구속 조건에 포함시킨다. 개루프 조향 및 폐루프 조향 시뮬레이션 결과 조향부 고장이 발생한 차량의 주행시 고장을 고려하지 않은 최적 구동력 분배 제어에 비하여 본 알고리즘 적용시 차량의 주행 성능이 보정됨을 확인하였다.

• 한국전산구조공학회논문집
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• 제23권3호
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• pp.267-274
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• 2010

합성구조는 전체가 동일한 재료 특성을 가지는 구조와는 달리 서로 다른 특성 즉 강재와 콘크리트의 구조로 결합되어 있다. 따라서 실제 모델링 시 이러한 재료 특성을 반영하지 않으면 실제 거동을 예측할 수 없으므로 콘크리트와 강재 사이에 인터페이스 요소를 연결하여 강재와 콘크리트의 슬립을 예측할 수 있게 한다. 인터페이스 요소는 일반적으로 사용되는 구성방정식은 적합하지 않고 실제 부착 및 슬립을 고려한 비선형 구성 방정식을 사용하여야만 적절히 사용할 수 있다. 이 계면요소를 이용하여 판형 강재 박스와 콘크리트의 접촉면을 묘사하였다. 그리고 강재 박스의 휨-좌굴 거동을 묘사하기 위해서는 일반적인 8절점 적합 요소의 사용은 부적절하므로 판형 강재 박스는 보강 변형도(Enhanced Assumed Strain) 고체요소를 사용하여 휨거동을 묘사할 수 있게 하였다.

• 한국자동차공학회논문집
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• 제24권5호
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• pp.581-587
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• 2016

Braking is a basic and an important safety feature for all vehicles, and the final braking performance of a vehicle is determined by the vehicle's ABS performance and tire performance. However, the combination of excellent ABS and tires will not always ensure good braking performance. This is due to the fact that tire performance has non-linearity and uncertainty in predicting the repeated increase and decrease of wheel slip when activating the ABS, thus increasing the uncertainty of tire performance prediction. Furthermore, existing studies predicted braking performance after using an ABS that used a wheel slip control as a controller, which was different from an actual vehicle's ABS that controlled angular acceleration, therefore causing a decrease in the prediction accuracy of the braking performance. This paper reverse-designed the ABS that controlled angular acceleration based on the information on brake pressure, etc., which were obtained from vehicle tests, and established a braking performance prediction analysis model by combining a multi-body dynamics(MBD) vehicle model and a magic formula(MF) tire model. The established analysis model was verified after comparing it with the results of the braking tests of an actual vehicle. Using this analysis model, this study analyzed the braking effect by vehicle factor, and finally designed a tire that had optimized braking performance. As a result of this study, it was possible to design the MF tire model whose braking performance improved by 9.2 %.

• Steel and Composite Structures
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• 제46권4호
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• pp.451-469
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• 2023

The use of precast hollow-core slabs (PCHCS) in civil construction has been increasing due to the speed of execution and reduction in the weight of flooring systems. However, in the literature there are no studies that present a finite element model (FEM) to predict the load-slip relationship behavior of pushout tests, considering headed stud shear connector and PCHCS placed at the upper flange of the downstand steel profile. Thus, the present paper aims to develop a FEM, which is based on tests to fill this gap. For this task, geometrical non-linear analyses are carried out in the ABAQUS software. The FEM is calibrated by sensitivity analyses, considering different types of analysis, the friction coefficient at the steel-concrete interface, as well as the constitutive model of the headed stud shear connector. Subsequently, a parametric study is performed to assess the influence of the number of connector lines, type of filling and height of the PCHCS. The results are compared with analytical models that predict the headed stud resistance. In total, 158 finite element models are processed. It was concluded that the dynamic implicit analysis (quasi-static) showed better convergence of the equilibrium trajectory when compared to the static analysis, such as arc-length method. The friction coefficient value of 0.5 was indicated to predict the load-slip relationship behavior of all models investigated. The headed stud shear connector rupture was verified for the constitutive model capable of representing the fracture in the stress-strain relationship. Regarding the number of connector lines, there was an average increase of 108% in the resistance of the structure for models with two lines of connectors compared to the use of only one. The type of filling of the hollow core slab that presented the best results was the partial filling. Finally, the greater the height of the PCHCS, the greater the resistance of the headed stud.

• Steel and Composite Structures
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• 제50권3호
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• pp.319-336
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• 2024

Ultra-high-performance concrete (UHPC) has attracted increasing attention in prefabricated steel-concrete composite beams as achieving the onsite construction time savings and structural performance improvement. The inferior replacement and removal efficiency of conventional prefabricated steel-UHPC composite beams (PSUCBs) has thwarted its sustainable applications because of the widely used welded-connectors. Single embedded nut bolted shear connectors (SENBs) have recently introduced as an attempt to enhance demountability of PSUCBs. An in-depth exploration of the mechanical behavior of SENBs in UHPC is necessary to evidence feasibilities of corresponding PSUCBs. However, existing research has been limited to SENB arrangement impacts and lacked considerations on SENB geometric configuration counterparts. To this end, this paper performed twenty push-out tests and theoretical analyses on the shear performance and design recommendation of SENBs. Key test parameters comprised the diameter and grade of SENBs, degree and sequence of pretension, concrete casting method and connector type. Test results indicated that both diameters and grades of bolts exerted remarkable impacts on the SENB shear performance with respect to the shear and frictional responses. Also, there was limited influence of the bolt preload degrees on the shear capacity and ductility of SENBs, but non-negligible contributions to their corresponding frictional resistance and initial shear stiffness. Moreover, inverse pretension sequences or monolithic cast slabs presented slight improvements in the ultimate shear and slip capacity. Finally, design-oriented models with higher accuracy were introduced for predictions of the ultimate shear resistance and load-slip relationship of SENBs in PSUCBs.

• 한국구조물진단유지관리공학회 논문집
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• 제28권3호
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• pp.19-26
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• 2024

본 연구에서는 풍력타워 지지구조 연결부 1/12.5 축소모형 실험체의 압축거동을 실험적으로 분석하였다. 압축강도 140MPa의 고성능 시멘트계 그라우트를 연결부에 충전하였으며, 전단키 간격, 형상과 연결부 길이를 변수로 하여 실험을 수행하였다. 연결부 내의 전단키의 개수가 동일한 경우 연결부 길이보단 전단키의 간격이 작을수록 부착전단강도가 높게 나타났으며, 동일한 간격과 연결부 길이에서는 전단키의 높이가 높을수록 강도가 높게 나타났다. 또한 연결부 슬립량 1.0mm 내외까지 선형거동을 한 후 하중이 증가함에 따라 비선형 거동을 한후 7.0mm 내외의 슬립에서 최대 강도에 도달하는 것으로 나타났다. 전단키의 형상과 간격 등에 따라 강도가 증가함에 따라 파괴형태는 계면전단파괴에서 그라우트 파괴로 변화하는 것으로 나타났으며, 강섬유에 의해 취성적인 파괴는 발생하지 않는 것으로 나타났다.

• 한국실내디자인학회논문집
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• 제24권3호
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• pp.38-47
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• 2015

This study evaluated non-liturgical space of catholic churches based on the four principles of universal design; accessible design, supportive design, safety-oriented design, and adaptable design. To design those spaces in terms of supportive design principle, diaper exchanging station needs to be placed in the restroom. Findings of this study are as follows: In terms of accessible design, valid width of entrance door to each room(more than 800mm), installation of elevator, height of riser in the stair, and width of step board were appropriate, but there were many spaces where door sils were not removed. In terms of supportive design, notice board at teacher's room and installation of storage closet, and width of passage to office(more than 1,200mm) were also appropriate, but storage closet at a meeting and prayer room, and space for storing flowers appeared inappropriate. To design those spaces in terms of supportive design principle, diaper exchanging station needs to be placed in the restroom. In terms of safety-oriented design, installation of round-edged furniture, use of non-slip flooring material, installation of safety emergency bell at a restroom, and installation of wall handle were required. In terms of adaptable design, space for wheelchair users at each room, installation of the furniture that can adjust the height, installation of desk with different height at an office, installation of toilet and basin considering children were considered to be necessary.

• 한국치위생학회지
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• 제12권1호
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• pp.1-15
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• 2012

Objectives : The purpose of this study was to examine the effect between job stress in jobholders and xerostomia. Methods : 250 jobholders living in Jecheon city were the subjects of this questionnaire. The questionnaire was made up of three contents and 37 items: general characteristic(13), job stress(14), degree & behavior of xerostomia(10). The data were analyzed by two-sample t-test, one-way ANOVA to examine the subjects general characteristics, job stress and degree of xerostomia and were analyzed by Chi-square test to examine the subjects general characteristics, job stress and behavior of xerostomia. Results : Only 215 jobholders were evaluated due to inadequate responses. The results were as follow. 1. As general characteristic of jobholder, male(83.7%) were more than women(16.3%), 30~39 year-old(47%) in age variable, university graduation(63.7%) in the last educational background variable, 2~3 million won(31.2%) in the month average income variable, 1~5 year(33.5%) in tour of duty variable, non-smoker(47.9%) in smoking variable were most. Married(58.6%) were more than unmarried(39.5%). Alcoholic(69.8%) were more than non-alcoholic(30.2%). 2. As classification of job stress, high strain group was 28.4%, active group was 26%, low strain group was 24.2%, passive group was 21.4%. 3. Analysis of effect between general characteristic and degree & behavior of xerostomia showed smoker were statistical significantly higher than non-smoker on 'dry eat', 'Am-sal', 'Night awake', 'Slip-liq'and 'Gumcandy'(p<0.05) and showed alcoholic were statistical significantly higher than non-alcoholic on 'Dry PM', 'Night awake, $H_2O$-bed'(p<0.05). 4. Analysis of effect between job stress and degree & behavior of xerostomia showed hight strain group were statistical significantly higher than low strain group on 'Dry PM', 'Dry-day', 'Am-sal', 'Eff-life'and 'Night awake'(p<0.05). Conclusions : As high strain group were higher than other groups on degree & behavior of xerostomia, stress would be factor that have an effect on xerostomia. Thus consider and management of stress is necessary for diagnosis and treatment of xerostomia.

• Steel and Composite Structures
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• 제3권2호
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• pp.75-95
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• 2003

A numerical model is presented to simulate the mechanical behaviour of composite steel and concrete columns taking into account the interaction between the hollow steel section and the concrete core. The model, based on displacement finite element methods with an Updated Lagrangian formulation, allows for geometrical and material non linearities combined with heating over all or a part of the section and column length. Comparisons of numerical calculations made using the model with 33 fire resistance tests show that the model is able to predict the fire resistance, expressed in minutes of fire exposure, of composite columns with a good accuracy.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.134-137
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• 2001

In this paper on-line model is derived from investigating via series of finite element process simulation. Some variables that little affect on non-dimensional parameters. ie. forward slip and torque factor. is extracted from composing on-line model Especially, this research focused on deriving on-line model which exactly predict roll force and roll power in the roughing mill process under small shape factor and small reduction ratio. The prediction accuracy of the proposed model is examined through comparison with predictions from a finite element process model