DURABILITY OF STRUCTURAL CONCRETE UNDER THE EFFECT OF MULTI-FACTORS OF FATIGUE LOADING AND ENVIRONMENTAL FACTORS

From the entire process of deteriorated performance of bending fatigue damage,combined with residual strain and accumulated energy release,the second linear and steadily developing phase was described,which almost occupies 80% of the whole fatigue life.Aimed at the second phase of fatigue damage,the durability of structural concrete under the effect of multi-factors of fatigue loading and environmental factors was investigated mainly in the paper.As the residual strain exceeds 60 10-6,both the diffusion coefficient of chloride ion and the air permeability coefficient increased with the increment of residual strain.Especially,when the residual strain is 120 10-6,the corresponding coefficient raised 10 times.In the case of freeze-thaw cycles,there is also the same tendency.Therefore,the values of residual strain from 30 10-6-60 10-6 and its 120 10-6 are considered as the starting range and the accelerating point of affecting the durability of structural concrete,respectively.