1,721,130 research outputs found
Stiffness requirements for wind girders in open-top cylindrical steel tanks
No full text© 2022 Elsevier LtdAboveground cylindrical storage tanks are very thin shell structures which are prone to buckling when subjected to wind pressure. Both external and internal pressures are developed due to wind action, and the magnitudes of the pressures generally vary around the circumference. A wind girder is generally used in open-top cylindrical tanks to increase their resistance against buckling. The wind girder must have adequate strength and stiffness in order to fulfill its function properly. Widely used design specifications provide recommendations for the design of the wind girder. Strength requirements are given in terms of stress resultants, while a minimum second moment of area is provided as a stiffness requirement. The recommendations for the stiffness requirement were developed by conducting Linear Elastic Bifurcation Analysis (LBA) of cylindrical shells subjected to uniform external pressure. This paper explores stiffness requirements for the wind girder in open-top cylindrical steel tanks. The relationship between the buckling strength and the second moment of area of the wind girder was explored through a finite element parametric study. Tank shells with different radius-to-thickness and height-to-diameter ratios and having different wind girder sizes were investigated by means of LBA. A buckling strength curve was developed based on the LBA results where the strengths can be predicted with 90% accuracy. In addition, a new second moment of area requirement was proposed. The parametric study was extended to investigate the behavior using Geometrically Nonlinear Analysis including Imperfections (GNIA). The same tank geometries were studied using GNIA and considering different imperfection amplitudes. A buckling strength curve, which takes into account imperfection amplitudes, was developed to be used in design
Behavior of Steel-Concrete Partially Composite Beams With Channel Type Shear Connectors
No full textTOPKAYA, CEM/0000-0003-0528-1756; Baran, Eray/0000-0002-0240-803XThis paper summarizes the findings of an experimental study investigating the flexural behavior of partially composite beams incorporating channel type shear connectors. Results from monotonic load testing of four full-scale steel-concrete composite beams and a steel beam are presented. The main effort focused on identifying the variation of strength and stiffness properties of beams with various degrees of partial composite action. Behavior of channel shear connectors in the composite beam specimens is related to those previously obtained from push-out tests of similar connectors. Finally, recommendations of the related AISC Specification on the strength and stiffness of composite beams are used for the assessment of the influence of the degree of partial composite action on flexural behavior. The experimental results revealed that even for beams with relatively low degree of partial composite action, major improvement on moment capacity and stiffness was obtained as compared to the steel specimen. The measured moment capacity of both the partially composite and fully composite beams agreed acceptably with the calculated capacities. The effective moment of inertia and the lower bound moment of inertia as specified by the AISC Specification were observed to overestimate the measured flexural stiffness of beams for all degrees of partial composite action investigated. (C) 2014 Elsevier Ltd. All rights reserved.Scientific and Technical Research Council of Turkey (TUBITAK) [212M038]This project was sponsored by the Scientific and Technical Research Council of Turkey (TUBITAK) under grant number 212M038. This financial support is gratefully acknowledged
An Experimental Study on Channel Type Shear Connectors
No full textTOPKAYA, CEM/0000-0003-0528-1756; Baran, Eray/0000-0002-0240-803XThis paper describes an experimental study on European channel shear connectors. While shear studs are widely used in steel-concrete composite elements, the channel connectors are also gaining popularity due to their certain advantages. The channel connectors do not require special equipment and standard welding procedures are adequate for attachment purposes. In addition, this type of connector offers higher amounts of shear resistance due to its high contact area with surrounding concrete. Although first studies date back to 1950s. little work has been done in the past to investigate their behavior. Majority of the work done to date was on channel connectors used in North America with a very limited parameter range. An experimental study consisting of 15 push-out tests was carried out to investigate the behavior of European type channel connectors with various heights and lengths. The ultimate resistance of the connectors obtained from experiments was compared against those predicted by North American steel design specifications. It was observed that the equations presented in American and Canadian specifications are too conservative. Based on a model that represents the typical failure mechanism in push-out tests, a new equation was developed for the ultimate resistance of channel shear connectors. It is shown that the developed equation is capable of predicting the ultimate resistance of channel connectors with reasonable accuracy. (C) 2012 Elsevier Ltd. All rights reserved.Atilim University [ATU BAP 2010-02]This project was funded by Atilim University under grant number ATU BAP 2010-02. This financial support is gratefully acknowledged
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Çelik çapraz elemanlarda yerel burkulma ve enerji sönümünün sonlu elemanlar metoduyla incelenmasi.
No full textSeismic provisions for steel buildings present limiting width-thickness and slenderness ratios for bracing members. Most of these limits were established based on experimental observations. The number of experimental studies is limited due to the costs associated with them. With the rapid increase in computing power; however, it is now possible to conduct finite element simulation of brace components using personal computers. A finite element study has been undertaken to evaluate the aforementioned limits for pin-ended pipe section steel braces. Fifty four tubular pipe brace models possessing different diameter-to-thickness ratios varying from 5 to 30 and slenderness ratios varying from 40 to 200 were analyzed. The effect of cyclic hardening modulus on the response of braces was explored. In all analysis, the models were subjected to reversed cyclic displacements up to ten times the yield displacement. Local buckling was traced during the loading history using a criterion based on local strains. Results are presented in terms of the ductility level attained by the member at the onset of local buckling. It is shown that local buckling of the section is influenced by the diameter-to-thickness and the slenderness ratios of the member. Moreover, the amount of hardening modulus was found to affect the local buckling response significantly. The need to include this material property into seismic provisions is demonstrated. Finally, the hysteretic energy dissipated by the member was quantified for each displacement excursion.M.S. - Master of Scienc
Bulkulması önlenmiş çaprazların deneysel ve nümerik olarak incelenmesi.
No full textA typical buckling restrained brace (BRB) consists of a core segment and a buckling restraining mechanism. When compared to a conventional brace, BRBs provide nearly equal axial yield force in tension and compression. Buckling restraining mechanism can be grouped into two main categories. Buckling is inhibited either by using a concrete or mortar filled steel tube or by using steel sections only. While a large body of knowledge exists on buckling restrained braces the behavior of steel encased BRBs has not been studied in detail. Another area that needs further investigation is the detailing of the deboding material. For all types of BRBs a debonding material or a gap has to be utilized between the core brace and the restraining mechanism. The main function of the debonding material is to eliminate the transfer of shear force between the core brace and the restraining mechanism by preventing or reducing the friction. A two phase research study has been undertaken to address these research needs. In the first phase an experimental study was carried out to investigate the potential of using steel encased BRBs. In the second phase a numerical study was conducted to study the friction problem in BRBs. The experimental study revealed that steel encased braces provide stable hysteretic behavior and can be an alternative to mortar filled steel tubes. Material and geometric properties of the debonding layer for desired axial load behavior were identified and presented herein.M.S. - Master of Scienc
Çelik I-kesit kirişlerde dayanım ve rijitlik azalmasının sayısal olarak incelenmesi
No full textLocal buckling is detrimental to seismic performance of steel I-beams in moment
resisting frames (MRFs). Although limits of local buckling in these beams and the
beams’ rotation capacities were investigated in previous studies, none of them had
attempted to delay the degradation due to local buckling in steel MRFs. In this
study, AISC 360-16 and AISC 341-16 flange and web slenderness limits for steel Ibeams
were examined numerically and a method to delay the deterioration due to
local buckling was proposed. After validating the modelling approach adopted in
this study, beam sections with varying flange and web slenderness ratios were
generated and analyzed under both monotonic and cyclic loading. Moreover,
effectiveness of using a pair of vertical stiffeners in plastic hinge regions of MRF Ibeams
was demonstrated through cyclic analysis results. Results showed that AISC
341-16 highly-ductile flange slenderness ratio limit is adequate to attain 80% of
plastic moment capacity at 0.04 rad drift level, when the web slenderness ratio is
considerably less than the AISC 341-16 highly-ductile web limit. It was also shown
that the proposed stiffening method delayed degradation due to local bucking and
improved rotation capacity of steel MRF I-beams. Stiffener distances measured
from the beam end were given as a function of beam flange width.Yerel burkulma, moment aktaran çelik çerçeve (MAÇÇ) I-kirişlerinin deprem
performansında yıkıcı bir etkiye sahiptir. Önceki çalışmalarda MAÇÇ kirişlerinde
yerel burkulma sınırları ve bu kirişlerin dönme kapasiteleri araştırılmış olmasına
rağmen, MAÇÇ kirişlerinde yerel burkulmadan dolayı oluşan dayanım azalmasının
geciktirilmesi daha önce araştırılmamıştır. Bu çalışmada, AISC 360-16 ve AISC
341-16 başlık ve gövde narinlik sınırlarının yerel burkulma davranışıyla ilişkisi
sayısal olarak incelenmiş ve yerel burkulmadan dolayı oluşacak dayanım kaybının
geciktirilmesi için bir yöntem geliştirilmiştir. Bunun için, kullanılan sayısal
modelleme yöntemlerinin doğrulanmasının ardından, çeşitli başlık ve gövde
narinlik oranları kombinasyonlarına sahip çelik MAÇÇ kirişleri modellenerek hem
tek yönlü hem de tersinir tekrarlanır yükleme altında analiz edilmiştir. Ayrıca,
MAÇÇ kirişlerinin plastik mafsal bölgesine bir çift rijitlik levhası yerleştirilmesinin
etkinliği, tersinir tekrarlanır yükleme analiz sonuçlarıyla gösterilmiştir. Sonuç
olarak, kiriş gövdesinin narinlik oranı, AISC 341-16’da gövde için verilen yükseksünek
sınırının belirgin bir miktarda altında olmak kaydıyla, yine AISC 341-16’da
verilen yüksek-sünek başlık narinlik oranı sınırının, AISC 341-16’da özel moment
çerçeveleri için verilen dayanım ve dönme kapasitesi kriterini sağlamak için yeterli
olduğu gözlemlenmiştir. Ek olarak, bu çalışmada geliştirilen yöntemin MÖÇÇ
kirişlerinin yerel burkulma kaynaklı dayanım azalmasını önemli ölçüde geciktirdiği
ve bu kirişlerin dönme kapasitesini arttırdığı gösterilmiştir. Son olarak, kirişin
plastik mafsal bölgesine konulacak rijitlik levhasının kiriş mesnedinden uzaklığı,
kiriş başlık genişliğinin bir fonksiyonu olarak basit bir denklemle verilmiştir.M.S. - Master of Scienc
- …
