Abstractpara-Benzylamine substituted oligophenol was synthesized via enzymatic oxidative polycondensation of 4-(benzylamino)phenol (BAP). Polymerization involved only the phenolic moiety without oxidizing the sec-amine (benzylamine) group. Chemoselective polycondensation of BAP monomer using HRP enzyme yielded oligophenol with sec-amine functionality on the side-chain. Effects of various factors including solvent system, reaction pH and temperature on the polycondensation were studied. Optimum polymerization process with the highest yield (63 %) and molecular weight (Mn = 5000, degree of polymerization ≈ 25) was achieved using the EtOH/ buffer (pH 5.0; 1 : 1 vol. ratio) at 25°C in 24 h under air. Characterization of the oligomer was accomplished by
Bu çalışmada, düşey işletme yükünün betonarme kirişlerin tersinir çevrimsel davranışına etkileri deneysel olarak incelenmiştir. İşletme yükü benzeşimi için kuvvet, deprem yükü benzeşimi için ise çevrimsel ve artan genlikli yer değiştirme kontrollü yükleme geçmişlerinin kullanıldığı deney programında, düşey yük etkisinin belirgin mertebede olmasının plastik mafsal çalışma biçimi üzerinde etkin olduğu gözlenmiştir. Çalışmada, işletme yükü etkisini içeren ve içermeyen tersinir-çevrimsel yüklemeler uygulanarak elde edilen deneysel sonuçlar birbirleriyle mukayese edilmiş ve ayrıca Türk Deprem Yönetmeliği Hasar Sınırı Yaklaşımı kabulleri yardımıyla elde edilen analitik sonuçlarla da karşılaştırılmıştır. Sınırlı sayıda deney numunesiyle yapılan bu karşılaştırmalarda, düşey yük etkisinin belirgin mertebede olduğu ve yön değiştirmeyen plastik mafsal davranışının meydana geldiği deney numunelerinde, Türk Deprem Yönetmeliği'nde tanımlanan analitik Göçme Hasar Sınırı yer değiştirme değerinin oldukça ihtiyatlı kalabildiği tespit edilmiştir.
Due to technological advancements, concrete can be currently
produced
with varying strengths and durability based on its intended use. However,
in many applications, concrete still needs to be improved in terms
of its mechanical and physical properties. The addition of fibers
to concrete is one of the most widely used methods for improving its
mechanical and physical properties. The study focuses on the effects
of the high aspect ratios and reinforcing indexes on the mechanical
properties of the hybrid and non-hybrid chopped glass fiber reinforced
concrete (CGFRC). In this study, the glass chopped fibers (GCFs) (fiber
diameter, ϕ = 0.015 mm) with four different volume fractions
(0, 0.5, 0.75, and 1%) and four different lengths (3, 6, 12, and 24
mm) were mixed into the concrete considering the aspect ratios between
200 and 2800 and the reinforcing indexes between 1 and 42. A total
of 51 samples were prepared for the study that included 3 control,
36 non-hybrid, and 12 hybrid samples. Then, the flexural strength
and compressive strength tests were conducted on the CGFRC samples.
To obtain detailed information about fiber pullout, fiber breakage,
debonding, or cracking in the matrix, digital microscopy and scanning
electron microscopy examinations were performed. The flexural strength
of the hybrid samples increased with the higher aspect ratios and
reinforcing index values, whereas the flexural strength of non-hybrid
samples decreased with the higher aspect ratios and reinforcing index
values in the CGFRCs. Moreover, all non-hybrid and hybrid CGFRC samples
had lower compressive strengths than the control samples in terms
of compressive strength. With an increase in the fiber volume fraction,
the mixing and workability of the samples considerably decrease, and
the increase of the fiber volume fraction caused brittle fractures
in concretes to be transformed into ductile fractures.
In this study, hysteretic behavior of RC beams with and without significant gravity load effects are investigated. To this purpose, an experimental program is carried out in which gravity loads are applied by force controlled test procedure whereas cyclic loads are applied by displacement controlled test procedure. The results of tests with gravity load effect are compared with the results of control specimens with increasing displacement loading profile. Experimentally observed damage states and deformation demands are compared with the respective values proposed by Turkish Seismic Design Code. It is found that, the loading procedure with significant gravity load effect leads to the formation of unidirectional plastic hinges. Besides, the deformation capacities of the specimens are found to be much higher than the code based deformation capacities.
Polymer materials are used in different engineering applications because of their excellent engineering properties. The use of these materials in different engineering fields has increased in recent years. It is predicted that polymer materials will be one of the most remarkable and popular engineering materials in the near future because of their unique properties. This paper focuses on Methyl Ethyl Ketone Peroxide (MEKP), which is one of the main catalysts and investigate its effect on the mechanical properties of Polymer Concrete (PC). The main aims of the study are to understand the mechanical properties of the polymer concrete including different amount of MEKP and to investigate the influence of MEKP on the mechanical characterizations of the PCs. For this purpose, five different samples containing 0.15% (Mixture-1), 0.25% (Mixture-2), 0.35% (Mixture-3), 0.45% (Mixture-4) and 0.55% (Mixture-5) MEKP of the total weight were prepared and some experimental studies were performed on the prepared mixtures. The obtained strength values were discussed and evaluated effect of MEKP on mechanical properties of PCs.
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