• Steel and Composite Structures
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• 제19권1호
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• pp.173-190
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• 2015

This study presents an analytical investigation on the seismic response of a medium-rise buckling-restrained braced frame (BRBF) under the near-fault ground motions. A seven-story BRBF is designed as per the current code provisions for five different combinations of brace configurations and beam-column connections. Two types of brace configurations (i.e., Chevron and Double-X) are considered along with a combination of the moment-resisting and the non-moment-resisting beam-to-column connections for the study frame. Nonlinear dynamic analyses are carried out for all study frames for an ensemble of forty SAC near-fault ground motions. The main parameters evaluated are the interstory and residual drift response, brace displacement ductility, and plastic hinge mechanisms. Fragility curves are developed using log-normal probability density functions for all study frames considering the interstory drift ratio and residual drift ratio as the damage parameters. The average interstory drift response of BRBFs with Double-X brace configurations significantly exceeded the allowable drift limit of 2%. The maximum displacement ductility characteristics of BRBs is efficiently utilized under the seismic loading if these braces are arranged in the Double-X configurations instead of Chevron configurations in BRBFs located in the near-fault regions. However, BRBFs with the Double-X brace configurations exhibit the higher interstory drift and residual drift response under near-fault ground motions due to the formation of plastic hinges in the columns and beams at the intermediate story levels.

• Earthquakes and Structures
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• 제15권5호
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.

• Steel and Composite Structures
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• 제23권3호
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• pp.285-302
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• 2017

Buckling-restrained braced frames (BRBFs) are commonly used as the lateral force-resisting systems in building structures in the seismic regions. The nearly-symmetric hysteretic response and the delayed brace core fracture of buckling-restrained braces (BRBs) under the axial cyclic loading provide the adequate lateral force and deformation capacity to BRBFs under the earthquake excitation. However, the smaller axial stiffness of BRBs result in the undesirable higher residual drift response of BRBFs in the post-earthquake scenario. Two alternative approaches are investigated in this study to improve the elastic axial stiffness of BRBs, namely, (i) by shortening the yielding cores of BRBs; and (ii) by reducing the BRB assemblies and adding the elastic brace segments in series. In order to obtain the limiting yielding core lengths of BRBs, a modified approach based on Coffin-Manson relationship and the higher mode compression buckling criteria has been proposed in this study. Both non-linear static and dynamic analyses are carried out to analytically evaluate the seismic response of BRBFs fitted with short-core BRBs of two medium-rise building frames. Analysis results showed that the proposed brace systems are effective in reducing the inter-story and residual drift response of braced frames without any significant change in the story shear and the displacement ductility demands.

• Steel and Composite Structures
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• 제28권3호
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• pp.309-318
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• 2018

Buckling Restrained Braced (BRB) frames have been widely used as an efficient seismic load resisting system in recent years mostly due to their symmetric and stable hysteretic behavior and significant energy dissipation capacity. In this study, to provide a better understanding of the behavior of BRB frames with various beam-column connections, a numerical study using non-linear finite element (FE) analysis is conducted. All models are implemented in the Abaqus software package following an explicit formulation. Initially, the results of the FE model are verified with experimental data. Then, diverse beam-column connections are modeled for the sake of comparison from the shear capacity, energy dissipation and frame hysteresis behavior points of view until appropriate performance is assessed. The considered connections are divided into three different categories: (1) simple beam-column connections including connection by web angle and connection by seat angle; (2) semi-rigid connection including connection by web and seat angles; and (3) rigid beam-column connections by upper-lower beam plates and beam connections with web and flange splices. Results of the non-linear FE analyses show that these types of beam-column connections have little effect on the maximum story drift and shear capacity of BRB frames. However, the connection type has a significant effect on the amount of energy dissipation and hysteresis behavior of BRB frames. Also, changes in length and thickness of the angles in simple and semi-rigid connections and changes in length and thickness of plates in rigid connections have slight effects (less than 4%) on the overall frame behavior.

• 동아시아식생활학회지
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• 제8권4호
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• pp.399-411
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• 1998

Thinness has become a symbol for beauty, acceptance and competence for women in our society, and pressure to diet because of this unrealistic standard is one factor reponsible for the increasing incidence of eating disorder. Three hundred fifty college women in the Chonbuk area were surveyed from May to June 1998, to investigate the relationship among body image, eating disorder, dietary intakes, self esteem and sex role identity. This study identified a subgroup of women who were relatively satisfied with their body weight and who did not diet. This group was compared with subgroups of women who were dissatisfied with their bodies and either were or were not restrained eaters. The dissatisfied/dieting women had the highest BMI, binge eating disorder and night eating syndrom, had significantly lower calorie, protein, iron, vitamin B$_1$, and vitamin B$_2$ intake compared with the satisfied/non-dieting women. The dissatisfied /dieting women, who had lower self-esteem compared with the satisfied/non-dieting women, but the frequency of sex role identity was similga among the groups of women. BMI and binge eating disorder were positively correlated(r=0.157, p＜.01), but BMI and self esteem were negatively correlated(r=-0.202, p＜0.01). Especially, binge eating disorder and self esteem were negatively correlated (r=-0.126, p＜0.05).

• Steel and Composite Structures
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• 제4권3호
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• pp.211-226
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• 2004

This paper presents a study on the structural behaviour of modular steel scaffolds through both experimental and numerical investigations. Three one-storey and three two-storey modular steel scaffolds were built and tested to failure in order to examine the structural behaviour of typical modular steel scaffolds. Details of the tests and their test results were presented in this paper. Moreover, an advanced non-linear analysis method was employed to evaluate the load carrying capacities of these scaffolds under different support conditions. Comparisons between the experimental and the numerical results on the structural behaviour of these modular steel scaffolds were also presented. Moreover, the restraining effects of external supports in practical situations were also studied through finite element methods. The predicted load carrying capacities and deformations at failure of these models under partially restrained conditions were found to be close to the experimental results. A codified design method for column buckling with modified slenderness ratios was adopted for practical design of modular steel scaffolds.

• Steel and Composite Structures
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• 제8권1호
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• pp.35-52
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• 2008

The paper investigates the seismic performance of a Partially-Restrained (PR) steel-concrete composite frame using the probabilistic approach. The analysed frame was tested at the ELSA laboratory of the Joint Research Centre of Ispra (Italy), while the representative beam-to-column composite connections were tested at the Universities of Pisa, Milan and Trento (Italy). The component modelling of both interior and exterior composite joints is described first, including the experimental-numerical validation. The Latin Hypercube method has been used to draw the probabilistic distribution curves of joints, and then the whole PR composite frame has been analysed. Pushover and incremental dynamic analyses have been carried out using the non-linear FE code SAP2000 version 9.1. The fragility and performance curves of the PR composite frame have been determined for four damage limit states.

• 한국도로학회논문집
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• 제15권5호
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• pp.101-110
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• 2013

PURPOSES : The purpose of this study is to evaluate the durability of ternary blended concrete mixtures adding ultra fine admixture. METHODS : From the literature review, crack was considered as the main distress failure criterion on concrete bridge deck pavement. To reduce the initial crack development due to drying shrinkage, CSA expansion agent and shrink reduction agent were used to ternary blended concrete mixtures as a admixture. Laboratory tests including chloride ion penetration test, surface scaling test, rapid freeze & thaw resistance test, non restrained drying shrinkage and restrained drying shrinkage test were conducted to verify the durability of ternary blended concrete mixtures. RESULTS : Based on the test results, proposed mixtures were verified as high qualified durable materials. Expecially initial drying shrinkage crack was not occurred in ternary blended concrete mixtures with CSA expansion agent. CONCLUSIONS : It is concluded that the durability of proposed ternary blend concrete mixture was acceptable to apply for the concrete bridge deck pavement.

• 한국식생활문화학회지
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• 제28권6호
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• pp.576-584
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• 2013

Increasing numbers of Korean adults, especially women, are adopting vegetarian diets for various reasons. In this study, the characteristics of vegetarianism among females residing in Seoul were examined. In addition, the dietary habits and eating behaviors between vegetarians and non-vegetarians were investigated. A total of 148 females (73 vegetarians, 75 non-vegetarians) were recruited and questionnaires regarding their demographic characteristics and eating habits were completed. The eating behavior and daily intake of food groups was assessed using the three factor eating questionnaire-R18 (TFEQ-R18) and food frequency questionnaire, respectively. The ages, BMI, education, and religious affiliation were not significantly different between the two groups. More than 30% of vegetarians had followed a vegetarian diet for longer than 24 months. The most common motivations for vegetarianism in study participants were 'health or weight control' (46.6%) followed by 'environmental concerns or animal welfare' (24.7%). Vegetarians had a lower intake of cereals, Kimchi, and soda, but a higher intake of potatoes and sweet potatoes, vegetables, mushrooms, seaweed, and fruits compared to non-vegetarians. Significant differences in eating behavior scores were also found between the two groups; in particular, vegetarians reported higher levels of restrained eating and emotional eating than non-vegetarians. Scores of uncontrolled eating, however, were not significantly different between the two groups. In conclusion, these results suggest that while vegetarianism is associated with healthy dietary habits, it is associated with restrained eating behaviors which may increase the risk of eating disorders in women.

• 디지털융복합연구
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• 제16권4호
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• pp.221-229
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• 2018

본 연구의 목적은 신체억제대를 적용한 치매노인 환자의 구체적인 특성과 부작용 발생 관련성을 파악하기 위함이었다. 2016년 5개 요양병원에서 치매노인에게 신체억제대를 적용한 간호사, 간호조무사, 요양보호사를 대상으로 구조화된 설문지를 이용하여 자료를 수집하였다. 190개의 자료를 SPSS 21.0의 신뢰도 분석, 기술통계, 카이제곱검정으로 분석하였다. 연구결과 '75- 84세' 연령의 환자가 58.3%, 1일 총 적용시간 중 '17-24시간'인 환자가 22.6%, 밤에 적용한 환자가 57.4%, 낙상과거력이 없는 환자가 54.2%를 차지하였다. 연령은 국소부종, 관절구축과 관련성이 있으며 특히 85세 이상의 환자에서 관절구축의 발생빈도가 25%로 나타났다(p<.05). 보행능력은 욕창과 관련이 있었으나 걸을 수 없는 환자보다 걸을 수 있는 환자의 욕창 발생빈도가 오히려 더 많았다. 총 적용시간은 피부발적, 국소부종, 관절구축의 3가지 부작용과 관련성이 있음을 알 수 있었다(p<.05). 본 연구를 기초로 신체억제대를 적용한 환자 돌봄 시 연령과 총 적용시간을 고려한 접근이 필요함을 제언하는 바이다.