用RILEM方法得到混凝土断裂韧度的尺度律

用两种不同配合比的混凝土制作了几何相似的直裂缝矩形截面三点弯曲梁,在MTS 815材料试验机上测试这两种混凝土的力学参数并记录了三点弯曲试件的荷载-加载点位移和荷载-裂缝端口张开位移的全过程曲线。用最大荷载和初始裂缝长度求得的断裂韧度KIC存在明显的尺寸效应,对此问题,用材料与结构研究实验所国际联合会(RILEM)推荐的方法分别得到两种混凝土材料的真实断裂韧度和有效断裂过程区长度,从而确定了混凝土断裂韧度的尺度律公式。从该公式能直接得到材料大尺寸试件的断裂韧度和断裂过程区长度,还能预测同材料的试验室尺寸下几何相似试件的断裂韧度测试值。

THE SIZE EFFECT LAW OF FRACTURE TOUGHNESS FOR CONCRETE OBTAINED FROM RILEM METHOD

Geometrically similar three-point bending beams with straight-through crack were prepared for concrete of two compositions.Through MTS 815 material test machine,mechanical parameters of two concretes were tested,and load vs.LPD(load point displacement) curves and load vs.CMOD(crack mouth opening displacement) curves of entire process were recorded for three-point bending specimens.There is a distinct size effect for fracture toughness K_(IC) calculated with maximum load and initial crack length.To cope with this problem,using the size-effect method recommended by RILEM(Réunion Internationale des Laboratoires et Experts des Matériaux),the material true fracture toughness and effective length of the fracture process zone were obtained.The size effect law of fracture toughness for the two concrete materials is thus determined respectively.Fracture toughness and fracture process zone length can be seen from this formula for large-sized specimens of the same material.It can also be used to predict the fracture toughness for geometrically similar specimens to be tested in laboratory.