Study on flexural mechanical properties and size effect of recycled coarse aggregate concrete beams based on <scp>3D</scp> mesoscopic simulation

Abstract The development of recycled concrete structures is an important way to utilize construction solid waste resources. This paper establishes 60 three‐dimensional mesoscopic numerical models that take into account the non‐homogeneity of recycled concrete materials. These models consider the cross‐section size, replacement rate, and high span ratio as design parameters. They also simulate and investigate the failure mechanism of recycled concrete beams under monotonous loading, revealing the impact of size on the nominal bending strength of these beams. In addition, this paper corrects the existing concrete bearing capacity calculation formula and compares it with the test data. The results show that: the maximum error between the fine finite element analysis results established based on ABAQUS software and the test results is 11%, which can be used for the study of the flexural performance of recycled concrete; the nominal bending strength of recycled concrete beams decreases with the increase of the size by 9.5%–26.5%, and there is a significant size effect; compared with ordinary concrete beams, the nominal bending strength decreases with the increase of replacement ratio. Compared with normal concrete beams, with the increase of replacement rate, the nominal bending strength decreased by 8.8%–26.5%, and the increase of replacement rate will obviously increase the size effect of recycled concrete beams; with the increase of span–depth ratio, the flexural load capacity of recycled concrete beams decreased by 17.33%–34.71%, and the nominal bending strength decreased by 24.9%–46.2%, and the size effect became more obvious; compared with the experimental results, the error of the modified formula proposed in this paper is between 2% and 11%, which can more accurately design the large‐scale concrete beams with a higher bending strength. Compared with the test results, the error of the correction formula proposed in this paper is between 2% and 11%, which enables more accurate design of large‐size recycled concrete members.