考虑应变率效应的混凝土材料单轴压缩特性尺寸效应研究

为了研究尺寸效应和应变速率对混凝土力学性能和变形能力的影响,对3种尺寸(70、100、150 mm)228个混凝土立方体试块分别在4种应变速率下(10^-5、10^-4、10^-3、10^-2/s),进行了试验研究。试验结果表明:同一应变率下,混凝土峰值应力随着尺寸的增大而减小,混凝土峰值应变随着尺寸增大而逐渐增大,并分析得出应变速率较大时,峰值应变由骨料弹性变形决定;应变速率较小时,峰值应变由水泥凝胶体黏性流动和混凝土裂缝扩展决定。同一尺寸下,混凝土峰值应力随着应变速率的增大而增大;混凝土弹性模量随应变速率的增大也呈现逐渐增大的趋势。指出动态加载下,混凝土弹性模量变化幅值不是一个确定的值,用静态下的弹性模量简单乘以一个放大或折减系数,不能满足计算动态加载下弹性模量的要求。通过线性回归分析,发现混凝土动态弹性模量和应变速率的对数成线性增长关系,对两者关系进行拟合,发现混凝土弹性模量与应变速率的关系曲线与试验结果吻合较好。

Experimental study on dynamic rate relevance of concrete size effect

In order to study the influence of size effect and strain rate on mechanical properties and deformation capacity of concrete,228 pieces of three different sizes of concrete cube specimens(70,100,150 mm),in four different strain rates(10^-5,10^-4,10^-3,10^-2/s)were studied.The results showed that at the same strain rate,the peak stress of concrete decreases with the increase of size,and the peak strain of concrete increases with the increase of size.It is concluded that the peak strain is determined by the elastic deformation of aggregate when the strain rate is large,and the peak strain is determined by the viscous flow of cement gel and the crack propagation of concrete when the strain rate is small.At the same size,the peak stress of concrete increases with the increase of strain rate,and the elastic modulus of concrete increases with the increase of strain rate.It is pointed out that the change amplitude of elastic modulus of concrete under dynamic loading is not a definite value.The elastic modulus under static loading is simply multiplied by an amplification or reduction factor,which can not satisfy the requirement of calculating elastic modulus under dynamic loading.Using linear regression analysis,it is found that the logarithm of dynamic elastic modulus and strain rate of concrete increases linearly.It is found that the relationship curve between elastic modulus and strain rate of concrete is in good agreement with the experimental results.