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https://hdl.handle.net/20.500.12452/6269

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Influence of Heat-Cool Cyclic Exposure on the Performance of Fiber-Reinforced High-Strength Concrete
(MDPI, 2023) Hakeem, Ibrahim; Hosen, Md. Akter; Alyami, Mana; Qaidi, Shaker; Özkılıç, Yasin
Sometimes civil engineering infrastructures have been constructed in hot and cold weathering regions such as desert areas. In such situations, the concrete is not only smashed by hot and cold processes but also spoiled by shrinkage cracking. Therefore, this study intends to examine the influence of heat-cool cycles on high-strength concrete comprising various fibers, such as natural date palm, polypropylene, and steel fibers, and their different volume percentages. The most popular technique for improving the structural behavior of concrete is fiber insertion. Fibers decrease cracking occurrences, enhance early strength under impact loads, and increase a structure's ability to absorb additional energy. The main goal is to examine the effects of three different types of fibers on regular concrete exposed to heat-cool cycles. For each type of fiber, three dosages of 0.2%, 0.6%, and 1% were used to create high-strength concrete. After 28 days of regular water curing and six months of exposure to heat-and-cold cycles, all specimens were tested. The heat-cool cycles entailed heating for two days at 60 degrees C in the oven and cooling for another two days at room temperature. The results of the experiment showed that fiber reinforcement in concrete improves its strength and durability. The flexural strength was substantially improved by increasing the date palm, polypropylene, and steel fibers into the high-strength concrete with and without heat-cool cycles. Adding increments of date palm, polypropylene, and steel fibers into high-strength concrete revealed a significant improvement in energy absorption capacity in both cases, i.e., with or without the implementation of heat-cool cycles. Therefore, the natural date palm fibers might be utilized to produce sustainable fibrous high-strength concrete and be applicable in severe weathering conditions.
The Influence of Input Motion Scaling Strategies on Nonlinear Ground Response Analyses of Soft Soil Deposits
(MDPI, 2023) Güzel, Yusuf; Elia, Gaetano; Rouainia, Mohamed; Falcone, Gaetano
A key issue for the estimation of ground shaking is the proper selection of input motions at the seismic bedrock. At the same time, the effect of the input motion scaling strategy on structural response is typically studied disregarding the presence of the soil deposit. In this work, different soft soil deposits are selected by varying the shear wave velocity profiles and the depth to the seismic bedrock, modelling the soil behaviour through a nonlinear constitutive model implemented into a fully coupled FE code. Seven input motions are retrieved for several selection strategies in conjunction with two seismic intensity levels. Hence, more than 300 one-dimensional ground response analyses are performed. The results of the analysed cases, which are presented in terms of spectral response at ground surface and amplification factors, indicate that: (i) the use of an advanced elasto-plastic soil constitutive model accounts for nonlinear ground response effects, including higher site amplification in the mid-period range and deamplification of the peak ground accelerations; (ii) the different scaling strategies lead to comparable mean values of the amplification factors, and (iii) the variability of the amplification factors is significantly reduced when the scaling strategy seeks the compatibility with the target spectrum over a specified period range. The research will aid the prediction of local seismic site response over large areas, particularly in the absence of the fundamental period of a structure and facilitate its use in general recommendation for quantifying and reducing uncertainty.
Experimental and Numerical Investigation of the Structural, Thermal and Acoustic Performance of Reinforced Concrete Slabs with Balls for a Cleaner Environment
(Springer, 2023) Arslan, Musa Hakan; Özkılıç, Yasin Onuralp; Arslan, Hatice Derya; Şahin, Ömer Sinan
This study conducted a comprehensive experimental and numerical assessment to investigate the effect of plastic circular balls placed in the middle of a section of a reinforced concrete slab on strength, ductility, thermal, and acoustic performance. The ball diameter/slab thickness (D/H), grades of concrete, and longitudinal tensile reinforcement ratio (q) in the slab were selected as the main variables. The variation in thermal and acoustic performance depending upon the ball’s diameter was investigated as well. The results showed that the slab’s load-carrying capacity, ductility, and energy dissipation capacity did not differ if the D/H ratio did not exceed 0.4; however, significant decreases in these values were observed when the D/H ratio exceeded 0.4. Moreover, the increase in the concrete and reinforcement’s strength had a negative effect on the slab with a D/H ratio of 0.8. The experimental results revealed that balled slabs are 3.15 times superior with respect to thermal conductivity and provide 1.38 times more insulation to absorb sound compared to nonballed slabs. In the numerical study of the slabs’ thermal performance, the mean surface temperature and heat flux on the slab where the heat transfer takes place decreased as the ball diameter increased. As seen in acoustic models, the level at which the slabs absorbed sound varied depending upon both the diameter of the balls and the sound frequency.
Bending performance of dapped-end beams having web opening: Experimental and numerical investigation
(Elsevier, 2023) Aksoylu, Ceyhun; Özkılıç, Yasin Onuralp; Çeledir, Emrullah; Arslan, Musa Hakan
Reinforced concrete dapped-end (purlin) beams are frequently used in prefabricated industrial structures. The main task of these beams is to safely carry the loads on the roof. Considering the number of these purlin beams in industrial buildings, it is extremely important for manufacturers to product these beams with less concrete without reducing the load carrying capacity. Since these purlin beams are under the effect of bending and shear forces, controlled creating openings in beam span can have significant economic benefits for the manufacturer. Therefore especially economic design perspective, it is so crucial to determine the amount of openings that will not cause a significant change in the bending behavior. In this study, the behavior of dapped-end purlins with openings was experimentally and numerically investigated. In the experimental step, seven purlin beams having different opening configurations were tested under four-point loading to investigate the openings effects on beam structural behavior. In this step opening length to total length varying between 0.075 and 0.325 was selected as a main parameter. After test, the numerical models were created and verified using experimental findings. After this step, in the parametric study part of the paper, the effects of shear span, depth of the opening and length of opening and different opening configurations (such as segmentation) which were not tested in experiments, were examined. The experimental outcomes revealed that increases in the opening did not provide a significant effect on the load capacity. This can be explained by the fact that the openings are in the bending region. The numerical findings showed that increasing shear span to depth ratio (av/d) ratio did not change rigidity but decreased the load capacity. However, no effect was observed on the opening height provided that it is at least as far away from the upper and lower longitudinal reinforcements bars as the concrete-cover margin. On the other hand, increasing opening/purlin length (especially higher than 0.375) reduces the capacity. However, segmented openings (multiple openings instead of single whole openings) did not reduce capacity even if total opening/ purlin length was 0.525.
Atıksuların sulamada kullanımı: toprak ve üründe kalıcı organik kirleticiler
(2015) Aydın, Mehmet Emin; Aydın, Senar; Bedük, Fatma; Tekinay, Arzu
Tarımsal sulamada kullanılan arıtılmış veya arıtılmamış atıksular pek çok kalıcı organik kirletici içerebilmektedir. Bu kirleticiler uzun süre sulama sonucunda toprak ortamında birikebilmekte, yetiştirilen ürüne bulaşabilmekte ve besin zinciriyle taşınarak insan sağlığını, toprak flora ve faunasındaki biyolojik faaliyetleri olumsuz şekilde etkileyebilmektedir. Konya kentsel atıksuları 2010 yılına kadar hiçbir arıtma işlemine tabi tutulmaksızın Ana Tahliye Kanalı ile Tuz Gölüne uzaklaştırılmıştır. Kurak dönemlerde Ana Tahliye Kanalı boyunca bu sular gıda ürünleri yetiştirilen tarımsal alanların sulanması amaçlı kullanılmıştır. Bu çalışmada kentsel atıksular ile sulanan tarım topraklarında ve bölgede yetiştirilen buğday ürünlerinde kalıcı organik kirleticilerden poliklorlu bifenil (PCB 28, 52, 101, 138, 153, 180) ve poliaromatik hidrokarbon (PAH) (naphthalene, acenaphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene) bileşiklerinin kalıntı miktarları belirlenmiştir. Konya topraklarının yüksek alkali özelliğe ve killi yapıya sahip olduğu tespit edilmiştir. Toprağın bu özellikleri kirleticilerin mobilitesini azaltarak zirai üretim yapılan üst katmanda birikmesine neden olmaktadır. Öte yandan, PCB ve PAH bileşiklerinin kuyu suyu ile sulanmış referans toprak örneklerinde tespit edilen miktarlarının atıksular ile sulanan zirai alanlardaki toprak örneklerinden daha yüksek veya yakın değerlerde olduğu tespit edilmiştir. Bu durum değerlendirilen sahada atıksu dışında PCB ve PAH kirletici kaynaklarının bulunduğunu ortaya koymuştur.
Dairesel kesitli düşülü bacalarda hava-su karışımının deneysel çalışma ve CFD modelleme ile analizi
(2017) Kumcu, Şerife Yurdagül; Uçar, Muhammed
Düşülü bacalar, kanalizasyon ya da yağmur suyu gibi basınçsız akan borulu sistemlerde, hattın yönünü değiştirmek, düşü sağlamak ve enerji kırmak amacı ile kullanılan, genellikle dairesel kesitli imal edilen su yapılarıdır. Çalışma prensiplerinde akımın içinde oluşan hava miktarı önemlidir. Bu çalışma kapsamında, dairesel kesitli düşülü bacaların, farklı akım şartlarında havalanma özelliklerini araştırmak amacı ile fiziksel modelleme ve sayısal modelleme yapılarak, sonuçlar birbiri ile karşılaştırılmıştır. Fiziksel modellemeler, yapıların projelendirme zorluklarını aşmak, inşaat aşaması tamamlandıktan sonra geri dönüşü olmayan hataları önceden görerek hesap hatalarını gidermek için çok önemlidir. Ancak, fiziksel modellemelerde ihtiyaç duyulan; zaman, mekan, işçilik ve maliyet gibi parametrelerden herhangi biri eksik olursa fiziksel model yapmak mümkün olmayabilir. Bu durumda, yüksek performanslı bilgisayarların kullanılması ile hızlı sonuçlar veren, CFD (hesaplamalı akışkanlar dinamiği) kodlarının yazılması ile de hidrolik yapıların davranışlarını gerçeğe yakın modelleyen matematiksel modellemelere başvurulabilir. Bu çalışma kapsamında, deneysel çalışma ile test edilen akım şartları, matematiksel modellemeyle de incelenmiştir. Sayısal modelleme için, VOF (Akım Hacmi) metodu ve RANS (Reynolds ortalamalı Navier-Stokes) denklemleri ile çözüm yapan FLOW-3D programı kullanılmıştır. Laboratuvar ortamında oluşturulan fiziksel modelde akım şekilleri ve akımın havalanma miktarı incelenmiş, bunun için d0,12 m çapında gelen - giden akım boruları ve D0,358 m çapında düşülü baca kullanılmıştır. Fiziksel deney gözlemleri, gelen akım derinliğine bağlı olarak düşüm havuzunda, giden akım borusunda ve akımın çarptığı baca duvarında farklı akım rejimlerinin oluştuğunu göstermiştir. Deneysel çalışma aşamasında, çift uçlu fiber optik ölçüm cihazı kullanılarak, gelen-giden akımın arasına yerleştirilen dairesel düşü bacası içerisinde hava-su karışım oranları ölçülmüştür. Farklı akım şartları için, boşluk oranı yüzdesi, kabarcık sıklığı ve kabarcık boyutlarının ölçümü gerçekleştirilmiştir. Düşüm havuzunda yapılan ölçümlerden alınan sonuçlar, akımın havalanma mekanizmasının çok karmaşık bir yapıda olduğunu, akım rejimlerinin tespitinin oldukça zor olduğunu göstermiştir. Sayısal modellemede bütün test sonuçları Flow3D programında tekrar edilmiş olup CFD (hesaplamalı akışkanlar dinamiği) modelinin tutarlılığı incelenmiştir.
Mechanical characterization of recycled tires in concrete
(2016) Köroğlu, Mehmet Alpaslan
Waste tires have been an increasing problem every year due to the increase of vehicle sales. The disposal of waste tires has presented very serious problems to the human community in the world. Currently, some research has been studied on not only waste tire chips (WTC) but also recycled steel tire fibres (RSF) in concrete. Present study is focusing on the usage of WTC and RSF in concrete mixture. The different weight of WTC and RSF is mixed in concrete in order to investigate the effect on mechanical properties. By adding WTC and RSF obtained a satisfactory improvement on cracking control, compressive strength, flexural strength and also tensile strength, Moreover, compressive, flexural and tensile strength was positively affected by the addition of WTC and RSF for some mixtures. More percentage of weight fractions added gives high result in tensile strength. However, the workability of the concrete reinforced with both WTC and RSF was negatively affected.

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