أداء الانثناء للأعتاب الخرسانية ثنائية الطبقة المسلحة بقضبان مختلفة الأنواع

Flexural Performance of Bilayer Concrete Beams Reinforced with Different Types of Rebars

Abstract

A bilayer concrete beam is a specialized structural element composed of two types of concrete layers. This configuration is designed to improve structural efficiency by providing enhanced flexural strength, durability, and ultimate load capacity throughout different operating situations. However, combining glass, carbon fiber reinforced polymer (GFRP, CFRP), steel, and hybrid reinforcement in bilayer concrete beams was a suitable substitute for standard steel reinforcing due to its impressive ratio of strength to weight and improved flexural performance and crack resistance. This study aims to experimentally and numerically evaluate the flexural performance (load capacity, crack propagation, and deflection) of bilayer concrete beams reinforced with different types of rebars (steel, CFRP, GFRP, or hybrid) under two-point loading. Fifteen models measuring (150, 200, and 1400) mm were fabricated on-site, six models consisted of a single layer of concrete, whereas nine models were constructed from bilayers of concrete. Normal-strength concrete (NSC) generally used in the tension zone, whereas high-strength concrete (HSC) applied in the compression zone to enhance material performance and structural behavior. The subjects were planned to be classified into four sections according to the reinforcement employed: steel, CFRP, GFRP, and different type of rebars. The nonlinear beam behavior was modeled using ABAQUS numerical analysis. An average difference in a maximum load of 2.1% and a maximum deflection of 4.93% showed that the numerical model matched experimental measurements. The findings indicated that the bilayer concrete system models exhibited an enhancement in ultimate load and the magnitude of the first crack load by 12.77% and 30.95%, respectively, compared to models built with a single layer of concrete. The hybrid reinforcement models exhibit a 7.3% greater ductility than those reinforced with a one type of rebar. The suggested hybrid designs improved structural performance, presenting a feasible method for sustainable and robust concrete structures.