A Proposal for Design Model for Determining the Flexural Bearing Capacity of RC Beams Reinforced by Steel with Reduced Modulus of Elasticity

Abstract

The design of concrete structures and elements in Europe and wider is conducted according to EN 1992-1-1. Among other design assumptions, the Eurocode 2 assumes the design value of the modulus of elasticity Es of reinforcing steel to be 200 GPa. However, what happens in the RC beam if the actual modulus of elasticity is significantly reduced. Does it affect the flexural bearing capacity of RC beam and to what extent? Another logical question is how to determine the actual flexural bearing capacity of the RC beam reinforced with reinforcing steel with a reduced modulus of elasticity and which design model to use for such determination. This study tries to answer such questions using an experimental approach and assumed calculation model with a comparison of experimental and calculation results. The experimental research from this showed that test RC beams reinforced by steel with reduced modulus of elasticity have significantly reduced flexural capacity in comparison with the designed flexural capacity of beams reinforced by steel with “normal” modulus of elasticity. In this regard, it is recommended to test the mechanical properties of the steel reinforcement prior to the installation at the site and not to rely on the producer’s factory production control certificate only. Additional issues considered in this research are observed effects of the reduced modulus of elasticity of reinforcing bars to Serviceability Limit States (stress limitation, crack width, and deflection control). Answers to such questions can inform decisions if retrofit is needed, is it feasible and if yes—which retrofit method to be used. This study does not discuss the reasons for the reduced modulus of elasticity in reinforcing steel.