砼断裂韧度尺寸效应的试验研究

为研究混凝土断裂韧度的尺寸效应，将基于Weibull统计破坏的尺度律与基于Bazant能量释放的统一尺度律进行对比，进行了三种混凝土断裂韧度，即起裂韧度 、失稳韧度 及临界裂缝尖端张开位移CTODc的试验研究。采用在建桥梁所用高强混凝土材料制作了6组几何相似，最大尺寸为S×H×B=1280 mm×320 mm×160 mm，总共18根带预制缺口的素混凝土平面应变三点弯曲试件，应用MTS材料试验机、动态应变仪等测试手段获得了试件的载荷-加载点位移、载荷-裂缝口张开位移全过程曲线以及裂缝前沿应变等。计算结果发现考虑了裂缝前沿过程区影响后的混凝土断裂韧度仍然表现出一定程度的尺寸效应，而Bazant统一尺寸效应律较Weibull尺寸效应律更适合预测大尺寸混凝土材料的断裂韧度。

Experimental study on size effect of fracture toughness of concrete

In order to study size effect on the fracture toughness of concrete, comparing the size effect law deduced from the Weibull’s statistical theory with that from Bazant’s scale sffect law, three fracture parameters of Initiation toughness,unstable toughness and critical crack tip opening displacement were tested. The three-point bending beams were carried out from actual bridge superstructure construction site with series of 6 groups of notched beams in geometric similarity, in which the maximum dimensions were S×H×B=1280 mm×320 mm×160 mm. By Material Test System, dynamic stain tester, author obtained the curves of load(P)-crack mouth opening displacement, P-displacement on loading points and the strain in front of cracks, etc.. Results indicate that double-K toughness considering the influence of process zone on the crack tip also have uptrend to a certain extent, as well as the critical crack tip opening displacement. The size effect law suggested by Bazant is more suitable to predict the fracture toughness of concrete in big sizes.