A novel coupled multiphysics mesoscopic model for concrete damage evolution under dry–wet cycles

Concrete structures exposed to prolonged dry–wet cycles in aqueous environments undergo progressive damage, threatening their structural integrity. This study investigates the underlying damage mechanisms by analyzing the coupled evolution of multiple physical fields under dry–wet cycling. A coupled mesoscopic damage model (SSM-damage) was developed by integrating damage mechanics, seepage theory, moisture-induced swelling behavior, and mass transport theory. A multiphase mesoscopic modeling method is proposed to capture and accurately represent moisture-driven swelling effects. The synergistic evolution of porosity, permeability, and damage, along with its influence on the mechanical response under cyclic wetting and drying, is examined. The model and its numerical implementation are validated against experimental results, revealing reductions in load-bearing capacity by 7.9%, 17.8%, and 23.6% after 10, 30, and 50 cycles, respectively, with damage primarily concentrated during high-moisture phases. This study introduces a novel theoretical and numerical framework for modeling dry–wet cycling processes.