The present study pertains to the load-deflection behavior and cracking moments of concrete beams with hybrid FRP-steel reinforcement. Under and over-reinforced hybrid beams were tested for failure along with reference beams with only steel or FRP reinforcement. The first-cracking moments of the beams were estimated analytically by using different uncracked moments of the inertia and modulus of rupture definitions. The uncracked moment of inertia definitions include the gross and uncracked transformed moments. The adopted modulus definitions are comprised of the experimental values from tests on prisms and the analytical values from the equations in different concrete codes. Furthermore, analytical methods were developed for estimating the deflections of concrete beams with hybrid FRP-steel or only FRP reinforcement. Two different types of elastic moduli, namely the secant modulus corresponding to the extreme compression fiber strain and the ACI 318M-19 modulus, were used in deflection calculations. Closer estimates were obtained by using the secant modulus, particularly in hybrid-reinforced beams. In the post-yielding region of the steel tension reinforcement, the deflection estimates were established to lay in closer proximity to the experimental curve when obtained by adding up the deflection increments instead of directly calculating the total deflections from the elastic curve equation. Accurate estimation of the cracking moment was found to be vital for the close prediction of deflections.

The present study pertains to the flexural behavior of RC beams with openings and non-metallic (GFRP) reinforcement. The main goal of preferring GFRP reinforcement over the conventional steel reinforcement was to safeguard the beams against the reinforcement corrosion. The presence of multiple regular transverse openings throughout the beam length increases the susceptibility of reinforcing bars to corrosion as the larger contact area in these beams with the outside environment increases the ingress of corrosive agents. Within the scope of the study, a total of 8 RC beams, including two reference beams without web openings, were tested under four-point bending. The test parameters were the flexural reinforcement ratio, the presence of short stirrups in the chords, and the presence of diagonal reinforcement spiraling around the openings. Since GFRP stirrups are difficult to bend, each stirrups was formed by connecting four individual FRP bars around the longitudinal bars. The opening circular geometry was adopted to avoid stress concentrations around the sharp corners of opening and to facilitate the placement and fixing of different schemes of reinforcement in the beams. The present tests depicted that the diagonal reinforcement around the openings have considerable contribution to the flexural behavior of RC beams with GFRP reinforcement and with multiple regular transverse openings. The RC beams with openings were able to approach their analytical flexural capacities in the presence of diagonal reinforcement for both moderately and heavily reinforced beam groups. The analytical deflection predictions of GFRP-RC beams with openings showed a good agreement with experimental data.

This study investigated the effect of the mechanical and durability properties of cementitious composite systems with supplementary cementitious materials (SCMs), including fly ash (FA), ground granulated blast furnace slag (GGBS), and bottom ash (BA), with similar specific surface areas (∼3,300 cm²/g). FA, GGBS, and BA were ground to a specific surface area of ∼3,300 cm²/g (about the cement-specific surface area) and then replaced with cement at 5 %, 10 %, 15 %, and 20 % replacement ratios. The compressive strength, flexural strength, length change, and rapid chloride ion permeability of the cementitious composites incorporating FA, GGBS, and BA with similar specific surface areas were recorded after 7-, 28-, and 90-day curing periods. As a result, cementitious composites containing GGBS improved the mechanical and durability properties at the maximum rate. It was shown that the properties of cementitious composites containing 20 % GGBS yielded better results than the control specimens without any SCMs.

The behavior of partially carbon fiber‐reinforced polymer (CFRP)‐wrapped square columns under axial compression load has been investigated in this study. In order to understand the partially wrapped specimen behavior thoroughly, non‐wrapped and fully CFRP‐wrapped reference specimens were added to the study. At this scope, axial compression tests of a total of 14 RC columns, 12 of which were partially wrapped, were carried out. The main parameters of the study were CFRP strip width, strip spacing, and partial wrapping location. The test results show that the confinement effect generally increases as the CFRP strip width increases, the strip spacing decreases, and the CFRP strips are located between two stirrups. The key parameter for stress–strain responses of partially CFRP confined square columns is the actual confinement ratio ( f _l / f _co ). In addition, the peak stress of confined concrete and the ultimate compressive strain were predicted by different models. The predictions show good agreement with the test results.

Korozyona uğramama özellikleri sayesinde cam takviyeli polimer (CTP) donatıların kullanım alanı genişlemekte her geçen gün daha fazla ilgi görmektedir. CTP’den üretilmiş boyuna ve enine donatıların kullanıldığı çalışmalar gün geçtikçe artmaktadır. CTP donatıların bükülememesi nedeniyle CTP etriyeler 90° kanca açısına sahip olacak şekilde fabrikada üretilmektedir. Biri referans olmak üzere toplam beş adet CTP donatılı betonarme kirişin dört nokta eğilme testleri gerçekleştirilmiştir. Referans kiriş CTP boyuna donatılara ve çelik etriyelere (135° kanca açısı) sahiptir. Çalışmada parametreler olarak, iki farklı a/d oranı ve iki farklı etriye aralığı tercih edilmiş ve bu parametrelerin kiriş kesme ve eğilme davranışı üzerindeki etkileri incelenmiştir. Bu kapsamda ilgili parametrelerin kirişlerin kırılma modu, enerji sönümleme kapasitesi, yük deformasyon ilişkisi üzerindeki etkileri belirlenmiştir. Ayrıca farklı yönetmelik ve modellerce önerilen kesme ve eğilme kapasitesi ifadeleri kullanılarak tahminler yapılmış ve deneysel verilerle karşılaştırılmıştır. Deneysel verilerle oldukça uyumlu sonuçlar elde edilmiştir.

Yüksek korozyon dayanımına sahip olan FRP donatıların (enine ve boyuna donatı) kullanımı gün geçtikçe yaygınlaşmaktadır. Ancak çelik donatılara kıyasla düşük elastisite modülü değerine sahip olan FRP donatılar betonarme kirişlerin çatlama dayanımını azaltmaktadır. Bu çalışmada temel amaç a/d>2.5 olan ve kesme donatısı bulunmayan FRP boyuna donatılı kirişlerin kesme davranışlarını ve dayanımlarını incelemektir. Bu kapsamda literatürde bulunan 149 deney verisi kullanılarak bir veri tabanı oluşturulmuştur. Literatürde sıklıkla kullanılan yönetmelikler ve modeller ile kesme dayanımları tahmin edilmiştir. Kesme dayanımını etkileyen değişkenler araştırılmıştır. Ayrıca, kesme donatısı bulunmayan FRP donatılı betonarme kirişlerin kesme tasarımı için yeni bir model önerilmiştir. Mevcut yönetmelik ve modellere göre önerilen model ile, deneysel sonuçlara daha yakın tahminler elde edilmiştir.