带初始损伤混凝土的动态抗压性能研究

对65个直径为68 mm的混凝土圆柱体试件进行试验分析,系统研究了不同初始损伤程度的混凝土试件在冲击荷载作用下的动态抗压特性。通过对混凝土试件预加不同的静态荷载,从而在试件内产生不同程度的初始损伤;利用SHPB设备进行不同速率下的冲击试验,研究初始损伤程度对混凝土动态抗压强度、应力应变关系以及破坏模式的影响。试验结果表明,初始损伤对混凝土动态抗压强度产生重要影响,其影响程度与混凝土试件的初始损伤程度密切相关,损伤程度在阈值以下时对混凝土的动态抗压强度影响较小,超过阈值时影响显著;随应变率增加,带损伤混凝土的动态抗压强度显著提高;含水率的增加降低了带初始损伤混凝土动态抗压性能。基于试验结果,提出了综合考虑初始损伤程度影响和应变速率效应的抗压强度预测模型。

A study on the dynamic compressive behavior of pre-damaged concrete

The dynamic compressive properties of concrete under impact load were systematically investigated through experiment on sixty-five concrete specimens (68 mm in diameter) with pre-damages by using a Split Hopkinson Pressure Bar (SHPB). The pre-damages were created by applying certain static load on the specimens and then unloading;the effect of pre-damages on the compressive strength,stress-strain relationship and failure mode of specimens were analyzed. Test data indicate that the degree of pre-damage has important influence on the dynamic compressive strength; however, there exists a threshold: when the pre-damage is below the threshold, there is little effect of pre-damages on the dynamic compressive strength;when the level of pre-damage is beyond the threshold,its effect becomes tremendous. The test data further confirm that the dynamic compressive strength of concrete increased with increasing strain rate. Furthermore, a higher water content of concrete led to a lower dynamic compressive strength. An empirical model has been proposed to predict the compression strength of concrete with different pre-damages at different strain rate.