紧凑四点剪切砼Ⅱ型断裂实验研究与数值分析

A COMBINED EXPERIMENTAL AND NUMERICAL INVESTIGATION OF MODE-ⅡFRACTURE OF COMPACT FOUR-POINT-SHEAR CONCRETE SPECIMENS

有关Iosipescu四点剪切实验的争论很多,国内外的研究者提出了各种各样的结果。本文对紧凑四点剪切加载下砼Ⅱ型断裂破坏机理进行了大量的实验研究和数值分析。通过对实验中试件裂纹的扩展过程及开裂角cq等的分析,结合有限元法对裂尖应力场进行了研究。分析了加载点与裂纹面的距离对Ⅱ型断裂性能的影响。可以看出,虽然随着加载点与裂纹面距离的缩短,CKⅡ在逐渐增大,但纯剪加载下裂纹扩展并不是沿剪应力所在方向,即破坏并不是剪切破坏。

The Iosipescu shear test has been investigated by a number of researchers and conflicting results have been reported. In this paper, a combined experimental and numerical approach is adopted to investigate the mode-Ⅱfailure mechanism of concrete subjected to four-point-shear loading. The process of the crack propagation and the anglecq of the crack initiating propagation are analyzed. The finite element method is used to study the stress distribution around the crack tip. The effect of the distance from the loading location to the crack surface on mode-Ⅱfailure mechanism of concrete specimen is studied. It is concluded that decreasing the distance from the loading location to the crack surface will lead to the increase of CKⅡ. Besides, the crack which initiate propagating from the notches, is not in the direction of the dominate shear stress. Thus, the failure is essentially not due to shear fracture.