Multi-Scale Investigation of Concrete Structure Crack Propagation Based on Continuous and Non-Continuous Assumptions: A Review

Concrete structures play a crucial role in civil and military fields due to their outstanding compressive strength, durability, and ease of construction. However, further in-depth research on the crack propagation mechanism in concrete structures is key to future applications and development. While numerous studies have focused on individual simulation methods, integrated reviews that bridge multi-scale fracture behavior with multi-physics couplings and assess 3D model readiness remain limited. To fill this research gap, this paper systematically reviews and summarizes recent advances in crack propagation models for concrete structures, with emphasis on multi-scale coupling, multi-physics coupling, and 3D simulation capabilities. The paper discusses the necessity of model modification, and it also analyzes environmental conditions, as well as static and dynamic loads. It also examines the effects of coupled multi-physical fields on concrete crack propagation. Through comparative analysis, the limitations of existing models are revealed, and the urgency of developing more advanced models is emphasized. Moreover, this paper reviews the latest achievements of the three mainstream simulation methods. The aim is to help readers quickly grasp research trends, understand common issues, and recognize specific challenges. This theoretical foundation provides a valuable reference for optimizing subsequent models. Finally, this paper proposes illustrative examples of two damage models for fiber-reinforced polymer (FRP) strengthened concrete structures. The aim is to provide an empirical reference for improving and innovating future models and to promote in-depth exploration in the field of crack propagation research in concrete structures.