混凝土断裂能尺寸效应的修正分形方法

A modified fractal approach for the size effect on fracture energy of concrete

提出了混凝土断裂能尺寸效应的修正分形方法。首先,根据混凝土的断裂特性,认为小尺寸混凝土构件的主宏观裂缝是一条分形曲线,而大尺寸混凝土构件的主宏观裂缝由分形曲线和直线两部分组成。然后,根据能量等价原理,导出了混凝土名义断裂能的计算公式。该公式反映了混凝土实验中所观测到的宏观物理现象,即混凝土名义断裂能随着构件尺寸的增大而增大,而且当构件尺寸趋向无穷大时,名义断裂能趋近于常数。最后,将理论预测与6组混凝土实验进行了比较,从而证实了本文方法的有效性。

A modified fractal approach for the size effect on fracture energy of concrete is pressented in this paper.Firstly,based on the fracture characteristics of concrete,it is considered that the main macroscopic crack of a small concrete specimen is a fractal curve,but that of a large concrete specimen consists of two parts:a fractal curve and a straight line.Secondly,according to the principle of energy equivalence,a calculation formula of fracture energy of concrete is derived.The formula reflects the macroscopic physical phenomena observed in concrete experiments that the nominal fracture energy of concrete increases with the increase of the specimen size and that the nominal fracture energy converges asymptotically to a constant when the specimen size tends to infinity.Finally,theoretical predictions are compared with six sets of concrete experiments and the effectiveness of the approach is then verified.