1,720,961 research outputs found
Çelik yapılarda yarı rijit bağlantıların doğrusal olmayan davranışının modellenmesi ve üç boyutlu yapısal çözümlemelere olan etkisinin araştırılması.
No full textIn steel frame structures, introducing the nonlinear force-deformation behavior of frame members with flexible joints will show closer results to the actual behavior. In this thesis, a mixed formulation frame finite element is developed from a nonlinear force-based method that can include localized semi-rigid connection response. The formulation of the element uses the three-fields Hu-Washizu-Barr principle, where displacement shape function approximation is omitted with the use of a force-based approach. The proposed element formulation can accurately capture the spread of plasticity along element length and section depth with a single element for each beam and column member. Introducing flexible connections to frame members does not necessitate additional nodes where the degrees of freedom do not increase. Also, nonlinear geometric effects and a correct shear area definition are applied to the elements with the use of the proposed element. Accuracy and robustness of the proposed element are presented at both member level and structural level for both the two-dimensional and three-dimensional rigid and semi-rigid steel frame structures. Verifications are conducted by considering studies presented in the literature, as well as the results obtained using advanced nonlinear finite element programs.Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Civil Engineering
ÖYBKDB'ler için 2 ve 3 boyutlu analiz yöntemlerinin karşılaştırılması.
No full textThe purpose is to compare the 2D and 3D analysis methodologies in investigating the performance of a Concrete Faced Rockfill Dam (CFRD) under static and dynamic loading conditions. Çokal Dam is the case study which is a CFRD located in northwest Turkey at the Thracian Peninsula. Rockfill interface and faceplate were simulated as nonlinear modulus of elasticity, detailed nonlinear tractive behavior and total strain rotating crack model, respectively. These behaviors were calibrated to define the exact behavior by detailed material tests. The analyses that cannot be done by 2D analyses, such as stress, crack width distribution along the face slab are conducted by 3D analyses to determine the necessity of these outcomes. Since effect of valley ends cannot be produced by 2D analyses, it is necessary to check 3D analyses to ensure liability of the results. Another comparison between detailed analysis of 2D models and linear elastic 2D models were covered to get practical and industrial solutions for the guiding methods of CFRDs for preliminary designs in this study.M.S. - Master of Scienc
A 2d Frame Element Taking Into Account Semi-Rigidity At Column Bases, Brace Ends Beam To Column Connections In Steel Structures
No full textIn this paper, a force-based 2D frame element formulation with spread of inelasticity through the element and localized semi-rigid connections at beam, brace and column base regions is presented. Inelasticity along member lengths is captured through fiber discretization of monitoring sections; furthermore, defining any type of semi-rigid connection along element length does not require introduction of additional nodes and degrees of freedom to the system. An accurate shear correction coefficient for wide flange sections is also taken into account in order to get closer match of shear effects with respect to exact solutions. The proposed element is designated for the performance based analysis of steel structures, since considering the presence of semi-rigid connections at beam column, column base and brace end regions through analyses will provide more realistic representation of the actual behavior of a structure. The proposed model is tested through available analysis program for validation purpose of gusset plate flexibility on brace ends in frames and the effect of the semi-rigidity on column bases with altering beam to column connection flexibility
An Accurate modeling approach for calculating the vibration characteristics of steel framed structures with semi rigid connections
No full textVibration characteristics of steel framed structures are affected by the presence of semi-rigid connections. In this study, a mixed formulation frame finite element is developed from force method, where the variational form of the element bases on the use of three-fields Hu-Washizu-Barr principle. Consistent mass matrix of the element is obtained such that determination of vibration frequencies of members with varying geometry and material distribution as well as the presence of semi-rigid connections at any section on the element is accurately captured without any need for specification of different displacement shape functions for each individual case. The element response does not necessitate further discretization due to the presence of semi-rigid connections. Benchmark numerical examples for a steel I-beam verifies the accuracy of proposed element with and without semi-rigid connection
Three dimensional frame element formulation for nonlinear analysis of semi rigid steel structures
No full textIn this paper, a force-based three-dimensional frame finite element formulation with spread of inelasticity through the element and localized nonlinear semi-rigid connections is developed. The proposed model utilizes Euler-Bernoulli beam theory assumptions, and adopts fiber discretization of monitored sections along element length and section depth for the spread of inelasticity in order to capture axial force and biaxial bending moment interaction. Defining any type of semi-rigid either linear or nonlinear connection behavior along element length does not necessitate any increase in number of degrees of freedom. The element is modelled with option of capturing nonlinear geometric effects. The proposed element is designated for the biased analysis of steel structures, since considering the presence of beam to column semi-rigid connections through analyses provides true behavior. The formulated element can also consider the presence of any type of connection that may be present in a steel structure; such as beam to column, column base, brace end connections. Specific to this study, moment-rotation response of beam to column connections is implemented for both the strong axis and weak axis bending directions. Numerical examples are considered to verify the results obtained from the developed finite element models with regards to other available structural analysis programs
Yarı rijit bağlantılı çelik çerçeve yapıların titreşim özelliklerinin modellenmesi
No full textYarı-rijitbağlantıların varlığı çelik çerçeve yapıların titreşim frekanslarını ve mod şekillerini önemli oranda etkileyebilmektedir. Bu tip yapılara etkiyen deprem yüklerinin doğru olarak tespit edilebilmesi içinse yarı-rijit çerçevelerin titreşim özelliklerinin doğru olarak modellenebilmesi gerekmektedir. Bu çalışmada bu amaca yönelik olarak karma formülasyon çerçeve elemanısunulacaktır. Bu elemanın türetimiüç alanlı Hu-Washizu-Barr ilkesine dayanmaktadır. Elemanın tutarlı kütle matrisi formülasyonla uyumlu olacakşekilde kuvvet bazlı yöntemle elde edilmiştir. Önerilen modelleme yöntemi değişken geometri ve malzeme dağılımına kolayca uygulanabilmekte ve yarı-rijit bağlantılar eleman üstünde istenilen yere serbestlik derecesinde artış olmadan yerleştirilerek rijitlik ve tutarlı kütle matrisleri elde edilebilmektedir. Kolon kiriş uç bağlantılarının incelenmesinde literatürde var olan ölçüt örnekler dikkate alınmıştır. Bu doğrulama çalışmasında, hem rijit ve hem de yarı-rijit bağlantı durumlarında titreşim frekansları ve mod şekilleri değerlendirilmiştir. Karşılaştırma çalışmalarında I-kesitli değişken flanj alanı gövde alanına sahip kiriş kesitleri incelenmiş, ayrıca çok katlı ve açıklıklı yarı-rijitçerçeve yapıların titreşim özellikleri karşılaştırılmıştır
Finite element model with semi rigid connections for vibration assessment of steel moment resisting framed structures
No full textIn this paper, a mixed formulation frame finite element with semi-rigid connections is developed. Consistent mass matrix of the element is obtained such that determination of vibration frequencies of members with varying geometry and material distribution as well as the presence of semi-rigid connections at any section on the element is accurately captured without the need to specify displacement shapes. An accurate shear correction coefficient for wide flange sections is taken into account in order to get closer match with exact solutions. Numerical examples on a portal frame and a multi-story steel moment resisting frame verify the accuracy of proposed element with and without semi-rigid connection
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Modeling of the nonlinear behavior of steel framed structures with semi rigid connections
No full textA mixed formulation frame finite element with internal semi-rigid connections is presented for the nonlinear analysis of steel structures. Proposed element provides accurate responses for spread of inelasticity along element length by monitoring the nonlinear responses of several crosssections, where spread of inelasticity over each section is captured with fiber discretization. Each material point on the section considers inelastic coupling between normal stress and shear stress. The formulation of the element also considers the presence of linear or nonlinear behavior of semi-rigid connection behavior without additional nodes and degrees of freedom, thus robustness of element response is maintained. Formulation of the element can include the presence of axial and shear deformations and rotation on localized connection region. For an accurate representation of cyclic behavior of connection regions, a multi-linear model is considered that accounts for strength and stiffness degradation as well as pinching of the hysteresis curves. Nonlinear response of the proposed element is assessed by considering steel framed structures with semi-rigid connections
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