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RISS 인기검색어
- 검색키워드
- 저자 : Kirac, Nevzat (검색결과 4 건)
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( Irem Kirac Utku ),( Yildiz Okuturlar ),( Esra Demir ),( Ozlem Harmankaya ),( Bulent Demir ),( Gonul Aciksari ),( Turgut Uygun ),( Alev Kural ),( Hanise Ozkan ),( Meral Mert ),( Abaki Kumbasar ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1
Background: Metabolic syndrome is a systemic disorder and manifests a group of conditions such as abdominal obesity, dyslipidaemia, hypertension, coronary artery diseases. The importance of epicardial adipose tissue recognized its contribution to inflammation by pro-inflammatory cytokines discharge has been proved. Several investigations were performed on vitamin D receptor in different tissues except bone. In this study the epicardial adipose tissue thickness (EATT) and the levels of vitamin D were measured and compared with healthy control group. Methods: A total of 148 patients (84 patients who had metabolic syndrome without diabetes and 64 healthy individuals) were enrolled into the study. In all patients, the EATT was calculated by ecocardiography and the level of serum 25(OH) vitamin D was monitored. Results: It has been observed that the EATT in patients with metabolic syndrome increases significiantly compared with healthy control group (p<0.001). No significant difference between patients and control group was found on the levels of 25 (OH) vitamin D (p=0.507). There was no correlation between 25 (OH) vitamin D and the EATT (p=0.622). Conclusion: We observed that the EATT increased in patients with metabolic syndrome. In contradiction to the literature; the levels of 25(OH) vitamin D has not been found high in patients with metabolic syndrome. The reason of this can be small number of patients in our study. A significant correlation was not found between the EATT and the levels of 25 (OH) vitamin D. Further studies with a larger patient population are required assess the relationship.
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Lateral buckling of reinforced concrete beams without lateral support
Aydin, Ruhi,Kirac, Nevzat Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.2
Reinforced concrete beams possess variable flexural and torsional stiffnesses due to formation of cracks in the tension area along the beam. In order to check the stability of the beam, it is thus more appropriate to divide the beam into a finite number of segments for which mean stiffnesses and also bending moments are calculated. The stability analysis is further simplified, by using these mean values for each segment. In this paper, an algorithm for calculating the critical lateral buckling slenderness ratio for a definite load level, in a reinforced concrete beam without lateral support at the flanges, is presented. By using this ratio, the lateral buckling safety level of a slender beam may be checked or estimated.
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Analytical and Parametric Investigations on Lateral Torsional Buckling of European IPE and IPN Beams
Tolga Yilmaz,Nevzat Kirac 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2
Lateral torsional buckling is one of the main failure modes controlling the strength of the slender thin-walled members. A transversely or transversely and axially combined loaded member that is bent with respect to its axis of greatest flexural rigidity may buckle laterally and twist as applied load reaches its critical value unless the beam is provided with a sufficient lateral support. This study intends to present a unique convenient equation that it can be used for calculating critical lateral-torsional buckling load of simply supported European IPE and IPN beams. First, an analytical model is introduced to describe lateraltorsional buckling behavior of beams with monosymmetric cross-section. The analytical model includes first order bending distribution, load height level and monosymmetry property of the section. Then, parametric study is carried out using the analytical solutions in order to establish a simplified equation with dimensionless coefficients. The effect of slenderness and loading positions on lateral-torsional buckling behavior of IPE and IPN beams are studied. The proposed solutions are compared to finite element simulations where thin-walled shell elements and beam elements including warping are used. Good agreement between the analytical, parametric and numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of European IPE and IPE beams can be determined by presented equation and can be safely used in design procedures.
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On the evaluation of critical lateral buckling loads of prismatic steel beams
R. Aydin,A. Gunaydin,N. Kirac 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.3
In this study, theoretical models and design procedures of the behavior of thin-walled simply supported steel beams with an open cross section under a large torsional effect are presented. I-sections were chosen as the cross section types. Firstly, the widely used differential equations for the lateral buckling for the pure bending moment effect in a beam element were adopted for the various moment distributions along the span of the beam. This solution was obtained for both mono-symmetric and bisymmetric sections. The buckling loads were then obtained by using the energy method. When using the energy method to solve the problem, it is possible to locate the load not only on the shear center but also at several points of the section depth. Buckling loads were obtained for six different load types. Results obtained for different load and cross section types were checked with ABAQUS software and compared with several standard rules.
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