疲劳载荷与环境因素耦合作用下结构混凝土的耐久性研究

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

以能量和残余应变作为损伤变量,将损伤过程划分为三个阶段。针对损伤发展的第二阶段,研究疲劳载荷与环境因素协同作用下混凝土耐久性的劣化情况。随着残余应变的增加,结构混凝土中氯离子扩散系数和空气渗透系数均变大,而且当残余应变超过60×10-6时,增加幅度变得明显。尤其当残余应变增加到120×10-6时,相应的系数提高了一个数量级。结论同样适合疲劳载荷与冻融循环的耦合作用。因此,可以把残余应变分别为30×10-6～60×10-6和120×10-6视为影响混凝土耐久性的起劣区间和陡劣点。

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.