Betonarme binalar için perde duvar endekslerinin irdelenmesi.

An analytical study was carried out to evaluate shear wall indexes for low to mid-rise reinforced concrete structures. The aim of this study was to evaluate the effect of different shear wall ratios on performance of buildings to be utilized in the preliminary assessment and design stages of reinforced concrete buildings with shear walls. In order to achieve this aim, forty five 3D building models with two, five and eight storeys having different wall ratios were generated. Linearly elastic and nonlinear static pushover analyses of the models were performed by SAP2000. Variation of roof drift and interstorey drift with shear wall ratio was obtained and results were compared with the results of approximate procedures in the literature. Additionally, performance evaluation of building models was carried out according to the linearly elastic method of Turkish Earthquake Code 2007 with Probina Orion. According to the results of the analysis, it was concluded that drift is generally not the primary concern for low to mid-rise buildings with shear walls. A direct relationship could not be established between wall index and code performance criteria. However, approximate limits for wall indexes that can be used in the preliminary design and assessment stages of buildings were proposed for different performance levels.M.S. - Master of Scienc

Hu-Washizu fonksiyoneli temelli üç boyutlu karma formülasyon nonlineer çerçeve sonlu elemanı.

A three dimensional nonlinear frame finite element is presented in this analytical study by utilizing Hu-Washizu principle with three fields of displacement, strain and stress in the variational form. Timoshenko beam theory is extended to three dimensions in order to derive strains from the displacement field. The finite element approximation for the beam uses shape functions for section forces that satisfy equilibrium and discontinous section deformations along the beam. Nonlinear analyses are performed by considering aggregation of the stress-strain relations along certain control sections of the element. Fiber discretization of the sections accompanied by adequate material model ensures coupling of the stress resultants axial force, shear force, bending moment about both axes and torsion accurately. These attributes of the mixed element relax reliance on displacement approximations on the control sections of the beam element that are inevitable in displacement based elements. As a result, the element is free from shear-locking. Authentication and superiority of the proposed 3d element are displayed by comparing the ability of the mixed element to capture nonlinear coupling of axial, shear force, bending moments and torsion with the results of the similar 3d displacement based elements and exact solutions that are readily available in the literature. Moreover, linear elastic free vibration analyses of the proposed mixed element are carried out by using the flexibility based consistent mass matrix that is also derived in this study and it is pointed out that 3d mixed element has the ability of determining not only the fundamental vibration frequency but also higher order frequencies with a considerable accuracy by using only a couple of elements per member span.Ph.D. - Doctoral Progra

Deplasman Temelli ve Karma Formülasyon Kiriş Sonlu Elemanlarının Karşılaştırılması

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2011Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2011Bu çalışmada deplasman temelli ve karma formülasyon kiriş sonlu elemanlarının analitik olarak karşılaştırmasıyapılmıştır. Karma formülasyon kiriş elemanında, deplasman, gerilme ve birim uzama bağımsız alanlı değişimsel formülasyon kullanılmıştır. Deplasman temelli ve karma formülasyon kiriş sonlu elemanların bulunduğu yapı sistemlerin karşılaştırmasında Matlab© programında çalıştırılabilen açık kaynak kodlu FEDEASLab isimli yardımcı yazılım kullanılmıştır. Karşılaştırmanın yapıldığı sistemler sırasıyla dikdörtgen kesitli çelik ankastre kolon ve üç açıklıklı ve birkaç katlı betonarme çerçevedir. Karma formülasyon elemanların kullanıldığı sistem analizlerinde iterasyonlu ve iterasyonsuz çözüm algoritmaları olmak üzere iki yöntem kullanılarak bunların sonuçları deplasman temelli eleman sonuçlarıyla karşılaştırılmıştır. Sonuç olarak, bu çalışmada analizi yapılan sistemlerde, iterasyonlu çözüm yönteminin kullanıldığı karma formülasyon sonlu elemanların, iterasyonsuz karma formülasyon ve deplasman temelli sonlu elemanlara göre daha hızlı, doğru ve güvenilir sonuç verdiği ortaya konarak karma formülasyon elemanların modellemedeki avantajları gösterilmiştir

Capturing inelastic coupling of internal forces and exact vibration frequencies for 3 d Timoshenko beam finite elements

A three dimensional (3d) nonlinear frame finite element based on Timoshenko beam theory is presented in this analytical study by utilizing Hu-Washizu principle with displacement, strain and stress independent fields in the variational form. The finite element approximation for the beam uses shape functions for section forces that satisfy equilibrium and discontinuous section deformations along the beam. The element is free from shear-locking, and the superiority of the proposed model is displayed under nonlinear material behavior and modal analysis. Results for the inelastic coupling of 3d internal forces with proposed model are compared with results obtained from other element models and exact solutions. Vibration analyses are carried out by the use of force-based consistent mass matrix, and verification is undertaken with closed form solutions and 3d solid finite element analyses results