Asma Köprülerin Analiz Yöntemleri

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Bu çalışmada, asma köprülerin deterministik ve stokastik dinamik analizleri; geometrik olarak lineer olmayan davranış dikkate alınarak incelenmektedir. Uygulama olarak Boğaziçi Asma Köprüsü seçilmiştir. Yer hareketi olarak 1971 San Fernando depremi Pacoima Barajı S16E bileşeni ile 1992 Erzincan depremi doğu-batı bileşeni ivme kayıtları kullanılmaktadır. Stokastik analizlerde yer hareketini temsil etmek üzere Clough ve Penzien tarafından düzeltilerek elde edilen filtre edilmiş beyaz gürültü modeli dikkate alınmaktadır. Yer hareketi modeli, mesnetlere etkiyen yer hareketlerinin yansıma ve kırılmalarla değişebilir olmasından kaynaklanan korelasyon etkisini, dalga yayılma etkisini ve zemin özelliklerinin yer hareketine etkisini içermektedir. Analizler sonucunda köprü kuleleri ve tabliyesine ait yerdeğiştirme ve kesit tesirleri elde edilmiştir. Yer tabakasının karmaşık yapısından dolayı, yer hareketlerinin farklı noktalardaki değişiminden doğan etkilerin asma köprüler gibi uzun açıklıklı sistemlerin deterministik ve stokastik analizlerinde dikkate alınması gerektiği vurgulanmaktadır.In this study, deterministic and stochastic dynamic responses of suspension bridges are investigated by considering geometrically nonlinear behavior. Bosporus Suspension Bridge is chosen as an example. S16E component of Pacoima Dam record of 1971 San Fernando earthquake and east-west component of 1992 Erzincan earthquake are used as ground motions. Filtered white noise model modified by Clough and Penzien is considered as a ground motion in the stochastic analyses. The ground motion model includes the effects of incoherence, wave passage, and site response. The bridge towers and deck displacement and internal forces are obtained in the end of the analyses. Because of the complex nature of earth crust, it is emphasized that the multiple support seismic excitations should be taken into account in the deterministic and stochastic analyses of long span structures like suspension bridges

Ekmeklik Buğdayda Organik Ve Konvansiyonel Yetiştiriciliğin Karşılaştırması Üzerine Bir Araştırma

Bu araştırma, 2008-2009 vejetasyon döneminde Gerek – 79 Ekmeklik Buğday çeşidinin konvansiyonel, organik ve atık mantar kompostu (0-2400-4800-7200 kg/da) uygulama koşullarındaki verim, verim unsurları ve kalite üzerine etkilerinin belirlenmesi amacıyla Konya-Sarayönü koşullarında tesadüf blokları deneme desenine göre 3 tekerrür olarak yürütülmüştür. Araştırmada her üç yetiştirme ortamında da tane verimi, başak boyu, başak ağırlığı, başakta tane sayısı, başakta tane ağırlığı, bitki boyu, başakçık sayısı, bindane ağırlığı, protein, gluten, hektolitre özellikleri incelenmiştir. Araştırma sonucunda, en yüksek tane verimi 371,63 kg/da ile atık mantar kompostu uygulamasının 7200 kg/da dozunda elde edilmiştir. Konvansiyonel uygulamada elde edilen tane verimi 276,94 kg/da, organik tarım uygulamasında 195,36 kg/da olarak belirlenmiştir. Sonuç olarak, ekmeklik buğday yetiştiriciliğinde atık mantar kompostu uygulamasının konvansiyonel uygulamaya alternatif olacağı ve atık mantar kompostunun organik materyallerle hazırlanması durumunda, organik tarım üreticileri için elverişli bir gübre materyali olabileceği tespit edilmiştir

Center of rigidity and center of shear in wall-frame systems

Binalarda burulma olması durumunda yapıya ilave deprem kuvvetleri etkimekte ve iç kuvvetler ve yer değiştirmeler artmaktadır. Bu nedenle düşey taşıyıcı sistemlerin planda mümkün olduğunca burulma etkisini azaltıcı şekilde yerleştirilmesi önemlidir. Burulma etkilerini en aza indirmek için rijitlik merkezi ile ağırlık merkezinin mümkün olduğunca yakın olması gerekmektedir. Her ne kadar mevcut deprem yönetmeliklerinin birçoğunda analiz aşamasında rijitlik merkezinin belirlenmesine ihtiyaç duyulmasa da özellikle burulma etkilerinin azaltılması açısından rijitlik merkezinin yerinin bilinmesi önemlidir. Uygulamada rijitlik merkezi ve kayma merkezi kavramları zaman zaman karıştırılmakta ve yanlış olarak bulunabilmektedir. Perde-çerçeve sistemlerde perde ve çerçevede hâkim davranışın farklı olması nedeniyle, perde ve çerçevelerin boyutlarının yapı yüksekliği boyunca sabit olması durumunda bile rijitlik merkezi kattan kata değişmektedir. Rijitlik merkezi bu tür yapılarda bazı katlarda plan dışına bile çıkabilmektedir. Bu çalışmada öncelikle rijitlik merkezi ve kayma merkezi kavramları kısaca açıklanmıştır. Daha sonra rijitlik merkezi ve kayma merkezinin bulunması için bir yaklaşım önerilmiştir. Sunulan yaklaşım literatürden alınan iki örnek üzerinde uygulanarak elde edilen sonuçlar literatür ve ETABS yazılımı ile karşılaştırılmış ve sunulan yöntemin uygunluğu gösterilmiştirIn case of torsion in buildings, additional earthquake forces affect the structure and internal forces and displacements increases. For this reason, it is important to place the bearing systems in the plan as much as possible to reduce the torsion effect. To minimize torsion effects, the center of mass and center of rigidity should be as close as possible. Although most of the existing earthquake seismic codes do not require the determination of the center of rigidity in the analysis phase of the structures, it is important to determine the center of rigidity in terms of reducing the torsional effects. In practice, the concepts of center of rigidity and shear center are sometimes confused and found to be incorrect. Particularly in the structural system of wall-frame, due to the different behavior of wall and frame, the center of rigidity varies from the story to story even if the dimensions of the walls and frames are constant throughout the height of the structure. In such buildings, the center of rigidity may even go out of plan on some storey. In this study, firstly the concepts of center of rigidity and shear center in multi-storey buildings are briefly explained. An approach was then proposed to find the center of rigidity and the shear center. The presented approach was applied on two examples taken from the literature and the results were compared with the literature and ETABS software and the suitability of the presented method was demonstrated

The effect of bosentan on plasma ischemia-modified albumin levels in acute mesenteric ischemia

Objective: Our aim in this study was to examine the effects of bosentan, an orally active antagonist of endothelin A and B receptors, on plasma ischemia-modified albumin (IMA) levels in mesenteric ischemia induced rats. Material and Method: In this randomized, controlled trial 36 mature female wistor rats were divided into three groups. Group 1 (n=12) was the control group which only laparotomy was performed. Group 2 (n=12) was the ischemia group and group 3 (n=12) was the bosentan pretreated (100 mg/kg-1 day, 1 gavage/day for two days before surgery) ischemia group. In the ischemia groups (GR 2 and GR 3) following laparotomy the superior mesenteric artery was clamped using a bulldog clamp during laparotomy. Blood samples were taken at 30 minutes from all groups and IMA levels were studied. Results: Plasma IMA levels in the ischemia group (GR 2) was significantly higher compared to those of the control (p<0.001) and bosentan pretreated group (GR 3) (p=0.002). Serum IMA levels were higher in GR 3 than control group but there were no statistical significance (p=0.659). Conclusion: These preliminary results suggest that bosentan might have a protective effect in mesenteric ischemic conditions

Are neutrophil to lymphocyte ratio and platelet to lymphocyte ratio clinically useful for the prediction of early pregnancy loss?

Objectives: Red cell distribution width (RDW), mean platelet volume (MPV), plateletcrit (PCT), platelet distribution width (PDW), neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) have all been identified as systemic inflammatory markers. The aim of this study to investigate whether the use of systemic inflammatory markers can predict early pregnancy loss.Material and methods: A total of 137 patients with early pregnancy loss was compared with 148 participants in the control group who had given birth at term. In the study group, CBC values were included in the study at the time of referral to the hospital for routine follow-up, while patients did not experience early pregnancy loss. In the control group, CBC values of the patient before the seventh week of pregnancy were included in the study. Results: There was no significant difference between the two groups in terms of RDW, MPV, PCT and PDW values. The NLR and PLR values were significantly higher in the early pregnancy loss group than the control group (p &lt; 0.05).Conclusion: Our findings suggest that high NLR and PLR values are potent markers for the prediction of early pregnancy loss

A rare complication of recurrent cerebrovascular infarct: Bilateral vocal cord paralysis

Bilateral vocal cord paralysis (BVCP) is usually the result of an iatrogenic injury especially secondary to thyroid and parathyroid surgery. However, BVCP that cause airway obstruction due to serebral cortical stroke very rarely has been reported. We, herein report a case of BVCP that resulted in respiratory arrest as a late and life threatening complication of recurrent cerebral infract. A 67 years old male patient admitted the emergency room with complaint of respiratory insufficiency. His complaint was progressed during last 3-4 months. He had two cerebral infractions attacks in a month approximately one year ago. On admission, physical examination revealed that, he had bilateral wheezing and stridor. He had right sided hemiplegia and had no history of heart failure or chronic obstructive lung disease. Endoscopic laryngoscopy was performed to evaluate upper airway obstruction. Laryngoscopy revealed that bilateral vocal cords were fixed and immobile at midline. Due to recurrent respiratory arrest, insufficient and fixed BVCP, open tracheostomy was perormed. After operation, he had no respiratory insufficiency or any complications. So he discharged from hospital with normal respiratory function

Value of Caffeic Acid Phenethyl Ester Pretreatment in Experimental Sepsis Model in Rats

Background and Aim. The aim of this study was to determine the actions of caffeic acid phenethyl ester (CAPE) on the changes of endothelin-1 (ET-1) level, tumor necrosis factor- (TNF-) alpha, and oxidative stress parameters such as superoxide dismutase (SOD) activities and malondialdehyde (MDA) levels in experimental sepsis model in rats. Materials and Methods. Twenty-four rats were randomly divided into three experimental groups: sham (group 1), sepsis (group 2), and sepsis + CAPE (group 3), n = 8 each. CAPE was administered (10 mu mol/kg) intraperitoneally to group 3 before sepsis induction. Serum ET-1, serum TNF-alpha, tissue SOD activity, and tissue MDA levels were measured in all groups. Results. Pretreatment with CAPE decreased ET-1, TNFalpha, and MDA levels in sepsis induced rats. Additionally SOD activities were higher in rats pretreated with CAPE after sepsis induction. Conclusion. Our results demonstrate that CAPE may have a beneficial effect on ET and TNF-alpha levels and oxidative stress parameters induced by sepsis in experimental rat models. Therefore treatment with CAPE can be used to avoid devastating effects of sepsis