LIU Qinghui, LI Qian, GONG Huiling, CHANG Cheng
Considering both the meso-structure of concrete and the rough morphology of the new-to-old concrete interface, a mesoscale finite element model of new-old concrete beams is established to analyze their damage and failure process. A random aggregate model is employed to generate the meso-structure of concrete, in which aggregates are modeled as linearly elastic, while the mortar and the interfacial transition zone (ITZ) between mortar and aggregate are simulated using the concrete damaged plasticity (CDP) model, and the new-to-old concrete interface is modeled using a combined cohesive-friction model. Compared with experimental results of the flat interface, the relative error of flexural strength is 2.22%, validating the effectiveness of the model. The effects of the rough tooth depth (3 mm, 6 mm, 9 mm, and 12 mm) and number of rough teeth (2, 4, 6, and 8) on the new-to-old concrete interface are analyzed, along with the effect of interfacial friction coefficient. The results indicate that the geometric parameters of the rough teeth have a significant effect on the peak load, post-peak load, and damage evolution process. When the rough tooth depth R increases from zero to 12 mm, the peak load increases by 54.1%, and the post-peak load increases from zero to 3.91 kN. As the number of rough teeth N increases from 2 to 8, the peak load and post-peak load increase by 16.4% and 122.0%, respectively. The friction coefficient f notably impacts the post-peak load but has a limited effect on the peak load and crack propagation paths.
