基于数字图像相关技术的混凝土剪切破坏实验研究

剪切破坏是工程实际中混凝土破坏的主要形式之一,而对其进行全场非接触的观测和研究却仍面临着一些困难,因而结合数字图像相关技术(digital image correlation,DIC)对混凝土的直接剪切破坏问题开展实验研究。分别对旧混凝土、未凿毛新旧结合混凝土及凿毛新旧结合混凝土三种不同类型的试样进行剪切破坏时的对照实验,具体对破坏时的应力应变分布,破坏断面情况,破坏时强度大小等进行比较。实验中将混凝土边缘外表层切除,以展现出的内部纹理作为数字图像相关技术所需要的自然散斑场;采用高分辨率的数字相机对发生剪切变形的混凝土表面进行图像采集,再通过DIC技术进行后处理以获得剪切破坏过程中变形场的分布。实验结果表明在承受剪切载荷时,经过凿毛处理的新旧结合混凝土粘合面的应变范围、应变分布复杂程度、应变数值均大于未凿毛处理试件,因而确定凿毛新旧结合混凝土试件的抗剪强度大于未凿毛新旧结合混凝土试件;研究结果同时验证了DIC技术在混凝土剪切破坏测试中的有效性和可靠性,即DIC技术可以更直观和全面地获得混凝土剪切应变分布情况,适用于混凝土结构剪切破坏的监测。

Experimental Research of Concrete Shearing Failure based on Digital image correlation

Shearing failure is one of the main concrete failure mode, while it is difficult to directly measure sheared concrete surface, so the digital image correlation (DIC) technique is employed to research the problem. Three type concrete, including old concrete specimen, old-new combined concrete specimen, and roughened combined concrete specimen, are used to perform shearing test, and the strain distribution, failure strength, failure mode are compared. Before the experiments are conducted the cover on the concrete surface is removed, thus the context of concrete is exposed to serve as the natural pattern in the digital image correlation technique. High resolution digital camera are used to capture images of specimen surface, and then the deformation field are obtained from the images. Experimental results show that the roughened concrete behaves better than common concrete according to several aspects such as strain distribution, shearing strength. Also, the experiments validate effectiveness and reliability of the digital image correlation technique, meaning that this technique could extract the deformation of sheared concrete directly, and could be used to monitor the shearing failure of structures.