Estimation of Steel Rebar Strength in Existing Concrete Bridges

To design a retrofit and/or maintenance protocol for existing reinforced concrete bridges, the assessment of rebar steel strength is generally required. The current methodology consists of uniaxial tensile tests performed on bar segments extracted from a structural element. Nevertheless, in several situations (e.g., the assessment of bridges in service), this traditional method cannot be used. Hence, a new simplified approach is introduced herein. It consists of the so-called “strength-for-age curves,” which relate the average strength of steel to the year of construction. Such curves are statistically computed from a database stored in the Department of Structural and Geotechnical Engineering of Politecnico di Torino (Italy). As a result, the yield and tensile strength values experimentally measured from rebar in two existing bridges in Northern Italy, built in 1930 and 1975, respectively, are correctly predicted by the proposed model.