Tensile Behavior of Ultra-High-Performance Concrete Reinforced with Reinforcing Bars and Fibers: Minimizing Fiber Content

When combining conventional reinforcement with fibers, differences in the structural behavior arise compared to reinforced and prestressed concrete. This fact is of special interest for ultra-high-performance concretes (UHPCs) because fibers are added to these concretes generally to improve ductility. With regard to durability, the positive influence of the fibers on the crack widths is significant. Especially for enhanced durability requirements, an essential improvement compared to reinforced concrete (RC) can be achieved by combined reinforcement. The mechanical relationships required for the analysis of the crack formation process of the two reinforcing elements-reinforcing bars and fibers-are presented in this paper They are linked with each other considering equilibrium and compatibility. The derived relationships are validated experimentally. Because of its universal formulation, the proposed model is not limited to UHPC but is generally applicable to all types of concrete.