不同应变速率下混凝土吸能特性及尺寸效应的研究

为了解混凝土的尺寸效应,进行了混凝土动态抗压性能试验,分析了在不同试件尺寸(150,300,450 mm立方体)不同应变速率(10^-5/s,10^-4/s,10^-3/s,10^-2/s)下混凝土的应力-应变全曲线、吸能特性,并基于Bazant尺寸效应理论建立了含应变速率效应的混凝土强度的尺寸效应模型。结果表明,混凝土力学性能存在明显的尺寸效应和速率效应;混凝土单位体积的吸能能力随试件尺寸的增大而降低;在应变速率较小时,混凝土的吸能能力随应变速率的增大而增加;但应变速率超过一定值后,混凝土吸能能力增加不明显;混凝土应变软化程度随试件尺寸的增大而加深;在一定程度上,峰后应变软化程度取决于试件几何尺寸。

Energy Absorption Characteristics and Size Effect of Concrete under Different Strain Rates

Dynamic compressive test of concrete performance was conducted on specimens with different sizes (1 50, 300,450mm cubes)under different strain rates (1 0 -5 /s,1 0 -4 /s,1 0 -3 /s,1 0 -2 /s).The stress-strain curves and energy absorption characteristics were analysed.Moreover,size effect model of concrete strength in consideration of strain rate effect was established based on Bazant size effect theory.Results suggest that the mechanical properties of concrete display obvious size effect and rate effect;the energy absorption capacity per unit volume of concrete de-creases with the increase of specimen size,and when the strain rate is small,the energy absorption capacity increa-ses,but after strain rate exceeds a certain value,the increment of energy absorption capacity is not obvious;the strain softening of concrete intensifies along with the increase of specimen size,and the strain softening after peak depends on the specimen’s geometry size.