In this study, polyethylene terephthalate (PET) was substituted for 10%, 20%, and 30% of the sand volume in concrete. Compressive, splitting tensile, and flexural strength tests were applied to the concrete samples and stress–strain graphs were obtained. It was observed that PET substitution caused a decrease in the mechanical properties of the concrete. For this reason, the concrete with the best PET substitution rate (10%) was reinforced by wrapping it with carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP), and the same experiments were repeated. It was observed that a 10% PET substitution reduced the strength of the reference concrete by about 6%. However, wrapping the PET-substituted concrete with CFRP and GFRP increased the strength by about 1.9 and 1.5 times, respectively, surpassing that of the reference sample. In addition, this study provides a comprehensive database by bringing together experimental data from studies in which PET was used as a substitute by volume or weight instead of fine aggregate in concrete. The models proposed in this study, along with previous models, were tested for applicability. Similarly, the model suggestions in the literature for fiber-reinforced polymer (FRP)-confined concrete were tested with the experimental data in this study, and their suitability for PET-substituted concrete was discussed.

In this study, polyethylene terephthalate (PET) was substituted for concrete at 10%, 20%, and 30% of the sand volume. Compressive, splitting tensile and flexural strength tests were applied to concrete samples and stress-strain graphs were obtained. It was observed that PET substitution caused a decrease in the mechanical properties of the concrete. For this reason, the concrete with the best PET substitution rate was reinforced by wrapping it with carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP), and the same experiments were repeated. It was observed that the damage caused by PET substitution could be compensated by the wrapping. In addition, this study provides a comprehensive database by bringing together experimental data from studies in which PET was substituted by volume or weight instead of fine aggregate in concrete. Based on the experimental results and literature data, model suggestions for PET-substituted concrete were made. The models proposed in this study, along with previous models, were tested for applicability. Similarly, the model suggestions in the literature for fiber reinforced polymer (FRP)-confined concrete were tested with the experimental data in this study, and their suitability for PET-substituted concrete was discussed.

In this study, an effective strengthening method was investigated to improve the seismic performance of masonry brick walls. The strengthening method comprised the use of shotcrete, which was applied in both glass fiber-reinforced and unreinforced forms for steel plates and tie rods. Thirteen wall specimens constructed with vertical perforated masonry block bricks were tested under diagonal compression in accordance with ASTM E519 (2010). Reinforcement plates with different thicknesses (1.5 mm, 2 mm, and 3 mm) were anchored using 6 mm diameter tie rods. A specially designed steel frame and an experimental loading program with controlled deformation increments were employed to simulate the effects of reinforced concrete beam frame system on walls under the effect of diagonal loads caused by seismic loads. In addition, numerical simulations were conducted using three-dimensional finite element models in Abaqus Explicit software to validate the experimental results. The findings demonstrated that increasing the number of tie rods enhanced the shear strength and overall behavior of the walls. Steel plates effectively absorbed tensile stresses and limited crack propagation, while the fiber reinforcement in the shotcrete further improved wall strength and ductility. Overall, the proposed strengthening techniques provided significant improvements in the seismic resistance and energy absorption capacity of masonry walls, offering practical and reliable solutions to enhance the safety and durability of existing masonry structures.

In this study, High-Density Polyethylene (HDPE) granules were used as fine aggregate replacements in concrete to contribute to plastic waste recycling. Substitution rates were determined as 10%, 20%, and 30% by volume. Slump, density, and mechanical strength tests were applied to concrete samples. All strength values decreased as the HDPE substitution rate increased. Compressive strength decreased by 12–34%, tensile strength by 7–23%, flexural strength by 6–21%, and the modulus of elasticity by 15–34%. However, axial and lateral strain values increased between 4% and 44%. Density and slump values also decreased by 3–9% and 4–19%, respectively. Additionally, a database of previously published research on concrete and mortar was compiled and integrated with the experimental results obtained. This combined dataset was used to develop predictive models assessing the influence of HDPE substitution on the mechanical performance of cementitious composites. Exponential equations were formulated to estimate compressive strength, tensile strength, flexural strength, and modulus of elasticity. These formulations were compared with existing models reported in the literature. Statistical evaluation was conducted to measure predictive accuracy, and the results demonstrated that the models proposed in this study provided superior performance relative to earlier approaches.

Ülkemiz, önemli fay hatlarının üzerinde bulunmaktadır. Çeşitli parametreler açısından yapısal davranışın irdelenmesi yapıların deprem güvenliği için önemlidir. Sıkça tercih edilen taşıyıcı sistem türlerinden olan çelik yapıların davranışı üzerinde dolgu duvar etkisi bu çalışmada incelenmiştir. Uygulamada, dolgu duvarlar genellikle düşey yük olarak analizlere dahil edilirken, modele katılmadıkları için özellikle yatay yük altında yapısal davranış üzerindeki etkileri göz ardı edilmektedir. Bilindiği üzere; dolgu duvarların sayısal modele katılıp katılmamasının yapıların davranışı üzerinde olan etkisinin araştırılması yapı güvenliği açısından da önemli bir durum arz etmektedir. Çalışmada incelenen sayısal modeller SAP2000 programında üç boyutlu olarak analiz edilmiştir. Eşdeğer deprem yükü yöntemi ile deprem etkisi altında yapısal davranış incelenmiş ve artırımsal eşdeğer deprem yükü yöntemi ile yapı performansı araştırılmıştır. Analizlerden elde edilen sonuçlar ışığında sayısal modelinde dolgu duvarların basınç çubuğu olarak dikkate alındığı durumda, dolgu duvarların yalnızca düşey yük olarak dikkate alındığı duruma göre periyot değerlerinin arttığı, tepe noktası deplasmanlarının azaldığı görülmüştür. Diğer taraftan, aynı incelemede basınç çubuğu olarak dolgu duvarın modele katıldığı durumda taban kesme kuvvetinin arttığı ve daha az deplasman ile plastik mafsallaşma noktasına ulaşıldığı sonucuna varılmıştır.

The increasing use of low-density polyethylene (LDPE) has prompted growing interest in its application as a replacement for conventional aggregates in concrete. This study investigated the effects of replacing sand with 10%, 20%, and 30% LDPE granules in concrete. Compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, slump, and density tests were performed. The results showed a gradual decrease in compressive strength (from 26.91 MPa in the reference mix to 16.56 MPa with 30% LDPE), tensile strength (from 2.46 MPa to 1.84 MPa), and flexural strength (from 3.37 MPa to 2.59 MPa). Decreases were also observed in modulus of elasticity, slump, and density values. However, LDPE-substituted concretes increased their axial and lateral strain capacities, showing improvement in ductility and deformation ability. Experimental results demonstrated a delicate balance between mechanical strength and sustainability benefits. It was demonstrated that low rates of LDPE substitution could balance performance with environmental advantages. The experimental results presented in this study were combined with previous research to create a dataset. Based on this dataset, exponential models predicting the properties of LDPE-substituted concrete and mortar were proposed. The proposed exponential models outperformed existing linear models in prediction accuracy, yielding coefficient of determination (R²) values up to 0.981 and significantly reduced mean absolute percentage error (MAPE) values, ranging from 1% to 17% depending on the dataset.