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
Yazar: ÖMER FARUK ESKİCUMALI
Danışman: DOÇ. DR. MEDİNE İSPİR ARSLAN
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: İnşaat Mühendisliği = Civil Engineering

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.

Abstract:
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.