不同尺寸混凝土的动态峰值应力-应变关系及峰后软化特性的研究

Dynamic Peak Stress-strain Relation and Post-peak Softening Properties of Concrete with Different Sizes

采用电液伺服大型多功能动静三轴仪对不同应变速率(10-5/s,10-4/s,10-3/s,10-2/s)下不同尺寸(150,300,450 mm)的立方体混凝土试件进行单轴动态压缩试验,对不同尺寸混凝土动态物理力学参数(峰值应力、峰值应变)、实验破坏机理及峰后应变软化进行分析,并对不同尺寸混凝土在不同的应变速率下的软化性能进行研究。研究结果表明:混凝土峰值应力、峰值应变都随试件尺寸增大而降低;混凝土强度随着应变速率的增加而增加;峰值应变后,随着试件尺寸增加,应力-应变曲线斜率绝对值增加,延性减小;试件尺寸为150 mm混凝土的软化现象随着应变速率的提高而愈加明显,且软化程度呈增加趋势,试件尺寸为300 mm和450 mm混凝土的软化现象随着应变速率的提高而变得越来越弱化,当应变速率增加到一定值时,软化现象又变得明显;在同一应变速率下,随试件尺寸的增加软化现象越来越明显。

The physical and mechanical parameters（ peak stress,peak strain）,failure mechanism and post-peak strain softening（ softening performance） of concrete with different sizes under different strain rates were researched through uniaxial dynamic compression test. The test was conducted on cubic concrete specimens of different sizes（ 150 mm,300mm,450mm） at different strain rates（ 10^- 5/ s,10^- 4/ s,10^- 3/ s,10^- 2/ s） by large multi-functional electro-hydraulic servo static triaxial machine. Results showed that concrete＇s peak stress and peak strain both reduced with the increase of specimen size; concrete strength increased with the increase of strain rate; after the peak strain occurred,the absolute value of the stress-strain curve slope increased whereas the ductility reduced as the specimen size increases. For the specimen size of 150 mm,concrete softening strengthened with increasing strain rate,and the softening degree increased; while for the specimen size of 300 mm and 450 mm,the softening weakened when strain rate increased,but when the strain rate increased to a certain value,the softening became apparent. At the same strain rate,the softening was increasingly apparent with the increase of specimen size.