Unified Approach for Minimum Reinforcement of Concrete Beams


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Title: Unified Approach for Minimum Reinforcement of Concrete Beams

Author(s): Alessandro P. Fantilli, Bernardino Chiaia, and Andrea Gorino

Publication: Structural Journal

Volume: 113

Issue: 5

Appears on pages(s): 1107-1116

Keywords: bending moment; ductility index; fiber-reinforced concrete beams; lightly reinforced concrete beams; minimum reinforcement

Date: 9/1/2016

The structural behavior of lightly reinforced concrete (LRC) and fiber-reinforced concrete (FRC) beams in bending is similar and depends on the amount of reinforcing bars and fibers, respectively. For this reason, a unified approach is introduced herein for the evaluation of the minimum reinforcement. Such approach is based on the definition of the ductility index (DI), which is a function of the difference between the ultimate bending moment and the effective cracking moment. DI is higher than zero when LRC and FRC beams show a ductile response, whereas it is negative in the case of a brittle behavior. In accordance with several experimental data, the linear dependence of DI on the amount of reinforcement can be demonstrated. Thus, a new design-by-testing procedure can be established to determine the minimum reinforcement (that is, reinforcing bars or fibers) of a concrete beam, which corresponds to DI equal to zero.