Uncertainty Models of Reinforced Concrete Beams in Bending: Code Comparison and Recycled Aggregate Incorporation

The bias factor of the Eurocode 2 [CEN (European Committee for Standardization) (2008). Eurocode 2: Design of Concrete Structures-Part 1-1: General Rules and Rules for Buildings] and ACI 318 [ACI (American Concrete Institute) (2014). Building Code Requirements for Structural Concrete and Commentary] flexural resistance models of reinforced concrete beams are compared with emphasis on the effect of the incorporation of coarse recycled aggregates sourced from concrete waste. The bias factor of the yielding moment calculations according to both codes is also investigated, and the bias in the cracking moment when Eurocode 2 material clauses are used. The database was composed of 174 beams, and the criteria that led to its development are discussed. The effect of recycled aggregate incorporation on the statistical descriptors of the bias factor is evaluated and probabilistic modeling using lognormal distributions is argued for. Preliminary partial safety factors for the bias factor of recycled aggregate concrete beams are proposed. No significant differences in the bias of the ultimate moment were found between the two comparison vectors: Eurocode 2 versus ACI 318 specifications and recycled versus natural coarse aggregate. The bias of the cracking moment increased when coarse recycled aggregates were incorporated, most probably due to the higher heterogeneity of recycled aggregates.