Abstract: Concrete is one of the most widely used materials in civil engineering,exhibiting significant cohesion-friction mechanical behavior.The cement gel contributes to the cohesive behavior,while the particle interlocking effect between coarse and fine aggregates manifests as the frictional behavior.By decomposing the mechanical response of concrete into cohesion behavior and friction behavior,the basic deformation and strength characteristics of concrete can be essentially grasped.This approach not only enhances understanding of concrete’s deformation mechanisms but also guides constitutive modeling.This study proposes an experimental methodology decoupling the cohesive and frictional characteristics of concrete,revealing their respective manifestation mechanisms and independent evolution laws under varying confining pressures.The results indicate that during the loading process,the softening behavior and stiffness degradation of concrete are primarily attributed to the deterioration of cohesive properties.Confining pressure mainly influences the frictional strength of concrete,with cohesive strength being less affected.Moreover,the differences in macroscopic shear strength among concretes of varying strength grades are mainly governed by variations in cohesive strength.Meanwhile,as confining pressure increases,the frictional strength and its increase amplitude of concretes with different strength grades exhibit similar trends.Furthermore,among the three strength grades of concrete (C30,C40,and C50),C30 concrete demonstrates the highest contribution of frictional strength to its macroscopic shear strength,making it the most significantly affected by confining pressure.Its strength increased by 51.43%,80.02% and 99.69% under confining pressures of 10MPa,20MPa and 30MPa,respectively.In contrast,C50 concrete exhibits the lowest contribution of frictional strength to its macroscopic shear strength,resulting in the least influence from confining pressure.Under the same confining pressure levels,its strength increased by 24.36%,51.35% and 65.93% respectively.