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Dışarıdan yapıştırılmış lifli polimerler ile güçlendirilmiş iki yönlü dçşeme-kolon bağlantılarının zımbalama kuvveti kapasitelerinin değerlendirilmesi: Veri tabanı çalışması
No full textReinforced concrete (RC) flat slab systems are widely utilised in construction practice mainly due to the shorter construction time, inexpensive formwork, a shorter structural depth, and architectural convenience. However, inadequate resistance to the high localised forces imposed to column support points yields a catastrophic and brittle punching shear failure, which is one of the greatest challenges of this context. Strengthening such connections using externally bonded fibre reinforced polymers (FRP) offers one of the most prevailing approach to overcome this problem. Despite the fact that there are numerous studies in the literature addressing FRP strengthening to improve the punching shear strength of such connections, the widely known standard ACI has not comprehensively comprised the effect of FRP strengthening in predicting the punching shear strength. However, some modifications introduced by individual authors have considered this effect to a certain degree. This study, therefore, aims to evaluate the punching shear strength prediction of flat slab-column connections strengthened with externally bonded FRP using ACI 318-19 code equation and modifications, including the FRP strengthening to the ACI code equation through a qualified database harvested from the recent literature. The study also conducts a sustainability analysis comprising carbon and glass FRP, the most commonly used FRP types in practice, in this thesis. More importantly, a new formula predicting the punching shear strength of flat slabs was derived using the comprehensive database through the non-linear regression analysis. The proposed model well-captured all the trends in influencing parameters compared to the ACI 318-19 code equation and its associated modifications and demonstrated a significant improvement in attaining enhanced preciseness of the punching shear strength of such connections.Betonarme kirişsiz döşeme sistemleri, daha kısa inşaat süresi, ucuz kalıp, daha kısa yapısal derinlik ve mimari kolaylık nedenleriyle inşaat uygulamalarında yaygın olarak kullanılmaktadır. Bununla birlikte, kolon destek noktalarında maruz kalınan yüksek kuvvetlere karşı katastrofik ve kırılgan bir zımbalama kuvveti arızasına yol açan yetersiz direnç, bu sistemlerde ki en büyük zorluklarından biridir. Dışarıdan yapıştırılmış lifli polimerler (FRP) kullanılarak bu tür bağlantıların güçlendirilmesi, bu sorunun üstesinden gelmek için en yaygın yaklaşımlardan birini sunmaktadır. Literatürde, bu tür bağlantıların zımbalama dayanımını iyileştirmek için FRP güçlendirmesini ele alan çok sayıda çalışma olmasına rağmen, ACI gibi yaygın olarak kullanılan bir standart, FRP güçlendirmesinin zımbalama dayanımı üzerindeki etkisini kapsamlı bir şekilde içermemektedir. Bununla birlikte, bireysel yazarlar tarafından tanımlanan bazı modifikasyonlar bu etkiyi bir dereceye kadar dikkate almaktadır. Bu çalışma, dıştan yapıştırılan FRP ile güçlendirilen döşeme-kolon bağlantılarının zımbalama dayanımını ACI 318-19 kod denklemi ve modifikasyonlar kullanılarak literatürden elde edilen nitelikli bir veritabanı aracılığıyla değerlendirmeyi amaçlamaktadır. Ayrıca, bu tezde pratikte yaygın olarak kullanılan karbon ve cam FRP'yi içeren bir sürdürülebilirlik analizi de yapılmıştır. Daha da önemlisi, lineer olmayan regresyon analizi ile kapsamlı veritabanı kullanılarak kirişsiz döşeme sistemlerinin zımbalama dayanımını tahmin eden yeni bir formül elde edilmiştir. Önerilen model, ACI 318-19 kod denklemi ve ilgili modifikasyonlara göre etkileyen parametrelerdeki tüm eğilimleri başarılı bir şekilde yakalamış ve bu tür bağlantıların zımbalama dayanımının daha yüksek hassasiyetle elde edilmesinde önemli bir gelişme göstermiştir.M.S. - Master of Scienc
Sürdürülebilirlik endekslerini etkileyen faktörler ve pirinç kabuğu külü içeren betonun yaşam döngüsü değerlendirmesi: bir veritabanı çalışması
No full textThe rice husk ash (RHA), attained by burning the husk that is removed in the process of the production of rice, possesses high pozzolanic activity and therefore is a promising, supplementary cementitious material. The thesis comprises a large database comprising over 1000 data on the RHA incorporation in concrete to examine the principal sustainability components such as CO2 emissions, cost efficiency, and eco-strength efficiency, as well as to perform a comprehensive life cycle assessment attained during this practice. Independent determination of the boundary conditions played a vital role in both the sustainability and life cycle assessment. The results showed that the use of RHA along with the pozzolanic materials could lead to a 25% reduction in the CO2 emissions generated during the concrete production in conjunction with a 65% rise in the cost efficiency of such practices. Life cycle assessment has already shown that 30% RHA as cement replacement along with the 30% fly ash already resulted in a 59% reduction in a global warming potential along with the 46% reduction in ozone depletion. It was vital to perform the life cycle assessment to validate the preciseness of the sustainability analysis as well as to demonstrate that the results in both analyses are in a great correlation. The findings reported in this study do not only suggest significant sustainable consequences for the construction practice but also encourage greener waste management routes to be established for RHA.Pirinç üretimi sürecinde çıkarılan kabuğun yakılmasıyla elde edilen pirinç kabuğu külü (RHA), yüksek puzolanik aktiviteye sahiptir ve bu nedenle umut verici, destekleyici bir çimentolu malzemedir. Tez, CO2 emisyonları, maliyet verimliliği ve eko-güç verimliliği gibi temel sürdürülebilirlik bileşenlerini incelemek ve bu uygulama sırasında elde edilen kapsamlı bir yaşam döngüsü değerlendirmesini gerçekleştirmek için betonda RHA birleşimi hakkında 1000'den fazla veri içeren büyük bir veri tabanından oluşmaktadır. Sınır koşullarının bağımsız olarak belirlenmesi, hem sürdürülebilirlik hem de yaşam döngüsü değerlendirmesinde hayati bir rol oynadı. Sonuçlar, RHA'nın puzolanik malzemelerle birlikte kullanılmasının, beton üretimi sırasında ortaya çıkan CO2 emisyonlarında %25'lik bir azalmaya ve bu tür uygulamaların maliyet verimliliğinde %65'lik bir artışa yol açabileceğini göstermiştir. Yaşam döngüsü değerlendirmesi, %30 uçucu kül ile birlikte çimento ikamesi olarak %30 RHA'nın halihazırda küresel ısınma potansiyelinde %59'luk bir azalma ile birlikte ozon incelmesinde %46'lık bir azalma ile sonuçlandığını göstermiştir. Sürdürülebilirlik analizinin kesinliğini doğrulamak ve her iki analizdeki sonuçların büyük bir korelasyon içinde olduğunu göstermek için yaşam döngüsü değerlendirmesinin yapılması hayati önem taşıyordu. Bu çalışmada rapor edilen bulgular yalnızca inşaat uygulaması için önemli sürdürülebilir sonuçlar önermekle kalmaz, aynı zamanda RHA için daha yeşil atık yönetimi yollarının oluşturulmasını teşvik eder.M.S. - Master of Scienc
Factors Affecting Transfer Sorptivity of Lime and Cement Mortars in the Freshly-Mixed State
No full textThe sorptivity, S, is a measure of the ability of a porous material to absorb and transmit water by capillary action. Transfer sorptivity, A, is a measure of the ability of an absorbent substrate to withdraw water from a wet mortar mix. Desorptivity, R, on the other hand, is the parameter that quantifies water retaining ability of freshly-mixed natural hydraulic lime and cement mortars. The measurement of transfer sorptivity is essentially identical to that of sorptivity except that the brick is placed in contact with a wet mortar mix rather than with water. This paper concerns the combination of wet mortar and brick substrate and the interaction between them. The purpose of this paper is to investigate the influence of hydraulicity, mix water content and sand grain size on the transfer sorptivity of a range of freshly mixed hydraulic lime andPC mortars and to investigate the relationship between transfer sorptivity and desorptivity for the case a substrate material of constant sorptivity. The measurement of transfer sorptivity is not straight forward. Before such measurements could be carried out, it was necessary to confirm that the substrate material to be used was highly homogeneous. To this end, two types of bricks are first investigated to establish their suitability as substrate materials for these measurements. A methodology for the measurement of transfer sorptivity is developed. The results have been shown that the transfer sorptivity increases systematically with increasing hydraulicity; that the transfer sorptivity increases systematically as the water content of a mix is increased; and that the transfer sorptivity of a given mortar increases as the sand grain size is increased. These parameters have important practical consequences, not only in the initial adhesion of the mortar to the substrate but also in the strength of the set material. The ability to monitor the water retaining properties can also allow efficiency in masonry construction
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
Factors Affecting Transfer Sorptivity of Lime and Cement Mortars in the Freshly-Mixed State
No full textThe sorptivity, S, is a measure of the ability of a porous material to absorb and transmit water by capillary action. Transfer sorptivity, A, is a measure of the ability of an absorbent substrate to withdraw water from a wet mortar mix. Desorptivity, R, on the other hand, is the parameter that quantifies water retaining ability of freshly-mixed natural hydraulic lime and cement mortars. The measurement of transfer sorptivity is essentially identical to that of sorptivity except that the brick is placed in contact with a wet mortar mix rather than with water. This paper concerns the combination of wet mortar and brick substrate and the interaction between them. The purpose of this paper is to investigate the influence of hydraulicity, mix water content and sand grain size on the transfer sorptivity of a range of freshly mixed hydraulic lime andPC mortars and to investigate the relationship between transfer sorptivity and desorptivity for the case a substrate material of constant sorptivity. The measurement of transfer sorptivity is not straight forward. Before such measurements could be carried out, it was necessary to confirm that the substrate material to be used was highly homogeneous. To this end, two types of bricks are first investigated to establish their suitability as substrate materials for these measurements. A methodology for the measurement of transfer sorptivity is developed. The results have been shown that the transfer sorptivity increases systematically with increasing hydraulicity; that the transfer sorptivity increases systematically as the water content of a mix is increased; and that the transfer sorptivity of a given mortar increases as the sand grain size is increased. These parameters have important practical consequences, not only in the initial adhesion of the mortar to the substrate but also in the strength of the set material. The ability to monitor the water retaining properties can also allow efficiency in masonry construction
Investigation of the Punching Shear Provisions for Reinforced Concrete Plates Under Lateral Loading
No full textFlat Plate structures are categorized as an economical structural systems for medium height and office buildings. However, punching shear failure causes brittle and sudden damage to flat slab-column connections and hence it’s significant should not be underestimated in the design of such connections. Punching shear can occur due to the transfer of shear forces combined with unbalanced moments between slabs and columns. Punching shear is an undesirable mode of failure that occurs without warning and can lead to progressive collapse of large areas of slab or even complete structure. Partial collapse of department store - 1994 Northridge earthquake is a sever example of the failure. The aim of this work is to assess the provisions provided by ACI 318-08 (ACI Committee 318, 2008) and ACI 421.2R-10 (Joint ACI-ASCE Committee 421, 2010) for interior slab-column connections. For this purpose a database for slabs without shear reinforcement and with shear reinforcement was developed. The existing drift capacity model of the slab-column connections was also re-examined based on the developed data base and available shear strength degrading models. A revised model based on slab span-to-thickness ratios was suggested to assess the requirement of shear reinforcement
Influence of Zeolite and Powdered Bayburt Stones on the Mechanical Properties of Cement Mortars
No full textMass Gain in Fired Clay Ceramics
No full textThe paper aims to investigate the mass gain in fired clay ceramics following reheating in order to gain a better understanding of the underlying kinetics of the rehydroxylation reaction using advanced gravimetric analysis. The effects of temperature on the kinetics of mass gain in fired clay ceramic following reheating to 500 ºC are investigated. Arrhenius plots are constructed at different temperatures and the activation energy of the chemical recombination reaction calculated. Following reheating at 500 ºC, fired clay ceramics gain mass due to the chemical recombination of atmospheric moisture and hence mass gain occurs in two distinct steps that both are linear with (time)1/4. Separating Step II data from Step I provides insight to the nature of the Step II reaction
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
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