Geri kazandırılmış pet lifli polimer ile güçlendirilmiş düşük dayanımlı beton silindirlerin monotonik ve tekrarlı yüklemeler altında basınç testleri
Compressive strength tests of low strength concrete cylinders confined with recycled pet fiber polymer under monotonic and cyclic loading
- Tez No: 876254
- Danışmanlar: DOÇ. DR. MEDİNE İSPİR ARSLAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2024
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Yapı Mühendisliği Bilim Dalı
- Sayfa Sayısı: 117
Özet
Deprem öngörülemez ve kaçınılmaz bir gerçektir. Türkiye ise aktif deprem kuşağı üzerinde olduğu için yapılarımızın depreme karşı dayanıklı olması hayati önem taşımaktadır. Ancak maalesef mevcut yapı stoğumuzda depreme karşı dayanıksız oldukça fazla yapı mevcuttur. Bu yapıların acilen yıkılıp tekrar inşa edilmesi veya güçlendirilmesi gerekmektedir. Yapıların yıkılıp tekrar inşası oldukça zor ve maliyetli olacağı için sismik açıdan güçlendirilmesi akılcı bir çözüm olacaktır. Taşıyıcı elemanların lifli polimer sargılar ile güçlendirilmesi yapının mukavemet artışı ile birlikte deformasyon kapasitesini önemli ölçüde arttırmaktadır. Türkiye'deki yapıların depremde yıkılmasının temel sebeplerinin düşük beton dayanımı ve enine donatı detayının yetersiz oluşu da göz önüne alındığında lifli polimer sargı ile güçlendirme en hızlı ve ekonomik çözüm olarak karşımıza çıkan alternatiflerden biri olabilmektedir. Bu çalışma kapsamında Türkiye'deki riskli binalardaki beton dayanımını temsilen basınç dayanım ortalaması 8.4 MPa olan düşük dayanımlı betonlar, atıl durumdaki malzemelerin geri dönüştürülmesinden elde edilmiş, yüksek kopma uzama kapasitesine sahip PET lifli polimer kumaş ile sargılanarak eksenel yük altında test edilmiştir. PET lifli polimer sargı tabaka sayısı, PET lifli polimer sargı kumaş yoğunuğu ve yükleme tipi test parametreleri olarak seçilmiş olup, sargılı ve sargısız toplam 16 adet numune İstanbul Teknik Üniversitesi Yapı Malzemesi Laboratuvarı'nda test edilmiştir. Yapıların güçlendirilmesinin efektif çözüm olup olmadığının belirlenebilmesi için mühendislik çözümleri, ekonomik faktörler ve yapısal ihtiyaçların iyi belirlenmesi gerekmektedir. Bu sebeple deneysel çalışmaların üreteceği veri ve bu veri esas alınarak önerilecek ampirik bağıntılar oldukça önem taşımaktadır. Çalışma kapsamında deney sonuçları mevcut modellerin dayanım ve şekil değiştirme kapasitesi tahminleri ile karşılaştırılarak sunulmuştur. Yapılan çalışma sonucunda PET lifli polimer sargı ile güçlendirmenin beton numunelerin basınç dayanımını ve şekil değiştirme kapasitesini önemli ölçüde arttırdığı ortaya konmuştur. PET lifli polimer kumaşın geri dönüştürülmüş malzemeden elde edilmiş olması, ekonomik ve sürdürülebilir olması ile birlikte uygulama kolaylığı da göz önüne alındığında yapıların sismik açıdan güçlendirilmesi açısından potansiyelinin araştırılması gerektiği sonucuna varılmıştır.
Özet (Çeviri)
Earthquake is an unpredictable and inevitable reality that can cause great destruction and loss of life. Since Turkey is located on a geopolitically active earthquake zone, it is vital that our buildings are resistant to earthquakes. However, unfortunately, there are many buildings in our current building stock that are not resistant to earthquakes. These structures need to be urgently demolished and rebuilt or strengthened. Since the demolition and reconstruction of buildings will be very difficult and costly, especially in cities with high population such as Istanbul, seismic strengthening would be a rational solution. Reinforcement is an important practice to improve the structural performance of existing structures. Nowadays, structures can be strengthened with very different methods. One of the seismic strengthening applications is to strengthen the carrier elements by wrapping them with fibrous polymer wraps. It is known that this application significantly increases the deformation capacity of the structure along with the increase in strength. Considering the two main reasons why buildings in Turkey collapse in earthquakes: low concrete strength and insufficient transverse reinforcement detail, reinforcement with fibrous polymer wrap appears as the fastest and most economical solution. Additionally, reinforcement with fibrous polymer wrapping has economic and environmental benefits as well as structural benefits. This study consists of introduction, preparation of samples, material properties and tests, experimental setup, test results, comparison of test results with existing models, and conclusion and recommendations, and these parts are explained in detail. The elements to be taken into consideration during laboratory experiments are specifically stated. Within the scope of this study, PET fiber polymer wraps with large rupture strain, obtained from the recycling of waste materials, and low strength concretes with an average compressive strength of 8.4 MPa, produced to represent the concrete strength in risky structures in Turkey, were wrapped with PET fiber polymer fabric and tested under axial load. . Following the preliminary experiments, a total of 16 cylindrical samples were tested within the scope of this study, and 12 of these samples were reinforced by wrapping with two different PET fiber polymers with low and high density. PET FRP jacket was wrapped on the previously prepared concrete surface using the wet lay-up technique by hand and reinforcement was provided. The strengthened samples were additionally reinforced with Carbon FRP near the cap to prevent premature failure near the cap. The samples were designed and tested as a minimum of 2 identical pieces in order to minimize experimental errors. All of the samples had dimensions of 150 × 300 mm and were tested under monotonic and cyclic loads with displacement control. Displacements on the sample were measured with 4 straingages and 8 LVDTs. The number of wrapping layers, PET fiber polymer wrapping fabric density and loading type were chosen as test parameters and the experiments were carried out at Istanbul Technical University Construction Materials Laboratory. During the experiment, data were collected on each sample using straingages, linear variable differential transformers, loadcell, switch box and data logger and transferred to the computer. Before the axial pressure tests, a total of 12 PET fiber polymer fabrics, 6 low density and 6 high density, were subjected to coupon tensile tests at Istanbul Technical University Faculty of Aeronautics and Astronautics, Composite and Structure Laboratory. In the coupon tensile tests, the samples exhibited bilinear behavior as expected. According to the results of the fibrous polymer coupon tensile test; While high density fibrous polymer samples have an average tensile strength of 309.48 MPa and a deformation capacity of 8.49%; low density fibrous polymers have a tensile strength of 476.64 MPa and a deformation capacity of 7.53%. As can be seen from here; Although low-density PET fiber polymer fabric has greater tensile strength than high-density PET fiber polymer fabric, it has a lower deformation capacity. At the same time, the elastic modulus of low-density fibrous polymer samples is higher than that of high-density fibrous polymer samples. According to the results of axial compression tests, while unwrapped reference samples have a compressive strength of 8.38 MPa, samples reinforced with 1 layer of PET fiber polymer wrapping have an average compressive strength of 27.92 MPa, and samples reinforced with 2 layers of PET fiber polymer wrapping have an average compressive strength of 42.1 MPa. When the samples are examined in terms of deformation capacity; While unwrapped reference samples had an average deformation of 0.4%, samples reinforced with 1 layer of low-density PET fiber polymer wrapping had an average deformation of 7.21%, and samples reinforced with 2 layers of low-density PET fiber polymer wrapping had an average deformation of 8.72%. Based on these results, it is clearly seen that increasing the number of PET fiber polymer wrapping layers increases the compressive strength and deformation capacity of the sample. Increasing the fibrous polymer wrap fabric density significantly increased the compressive strength of the sample. While samples reinforced with 1 layer of low- density PET fiber polymer wrapping reached an average compressive strength of 27.92 MPa, samples reinforced with high-density PET fiber polymer wrapping reached an average compressive strength of 33.78 MPa. The deformations of samples reinforced with low-density fibrous polymer wrapping are less than the entire deformation of samples reinforced with high-density wrapping. However, despite these test results, considering the small number of samples; It is not correct to establish a direct correlation between the density of PET fiber polymer fabric and its deformation capacity. When the test results are compared according to the loading type, there is no correlation between the loading type and sample behavior. In order to determine whether strengthening structures is an effective solution, engineering solutions, economic factors and structural needs must be well determined. For this reason, existing empirical relationships revealed as a result of experimental studies are very important. Within the scope of the study, the experimental results were obtained from İlki et al. (2004), Jiang and Teng (2007), Teng et al. (2009), Wei and Wu (2012), Pimanmas and Saleem (2019) and Yuan et al. (2022) by comparing them with the strength and deformation capacity estimates obtained from the empirical relations presented in their studies. Among the studies examined, the compressive strength estimate closest to the experimental results was given by Teng et al. (2009) model. The strain capacity prediction estimate closest to the experimental results was given by Wei and Wu (2012) model. Although the predictions presented with empirical correlations can give close results when compared to the experimental results, it would not be appropriate to use the correlations for the current experimental results since no correlation presented can predict both the estimated compressive strength and deformation capacity very closely at the same time. More studies need to be done in the future and new predictions need to be presented for PET FRP with large rupture strain, which has started to be used instead of traditional FRPs. As a result of the study, it was revealed that reinforcement with PET fiber polymer wrapping significantly increased the compressive strength and deformation capacity of LCS cylinders. It has been concluded that PET fiber polymer fabric is a promising material for seismic strengthening of structures, considering that it is obtained from recycled material, is economical and sustainable, and is easy to apply.
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