Numerical analysis of size effect in RC beams scaled along height or length using elasto-plastic-damage model enhanced by non-local softening

Numerical simulation results of laboratory tests on reinforced concrete beams subjected to four-point bending for a separate variation of the height and length were presented. Due to the lack of a geometrical similarity, two major failure mechanisms were observed: flexural failure mechanism with plastic yielding of reinforcement and shear failure mechanism with two different modes: brittle diagonal tension and brittle diagonal shear-compression. The shear strength increased with increasing effective height and decreased with increasing shear span-effective height ratio. In simulations, the finite element method was used, based on a coupled elasto-plastic-damage constitutive model for concrete under plane stress conditions. The constitutive model was enhanced by integral-type non-locality in the softening regime to yield mesh-independent results. The bond-slip law was assumed between concrete and reinforcement. Two-dimensional numerical calculations under plane stress conditions satisfactorily reproduced both experimental shear strengths and failure mechanisms with one set of input parameters. In addition, the effect of different material constants on strength and fracture was comprehensively studied. Advantages and shortcomings of the numerical approach were discussed. Contours of non-local equivalent strain measure with attached scale from FEM as compared with experimental cracks pattern for RC beams (Leff = 2700 mm): a) D = 180 mm, a = 1080 mm, ηl = 15, ηa = 6, b) D = 360 mm, a = 1080 mm, ηl = 7.5, ηa = 3 and c) D = 720 mm, a = 1080 mm, ηl = 3.75, ηa = 1.5 (experimental critical diagonal crack is marked by red arrow, numerical critical localization zone is marked by yellow arrow, note that beams are not proportionally scaled and steel bars are not shown). [Display omitted] •2D simulation results of size effect in RC beams were presented.•Coupled elasto-plastic-damage constitutive model for concrete was used.•The concrete model was enhanced by integral-type non-locality.•Satisfactory agreement between calculations and experiments was achieved.