中文摘要：

本文通过混凝土三点弯曲梁的外贴碳纤维布（CFRP）加固试验,研究外贴CFRP对混凝土梁断裂特性的影响。试验通过在混凝土表面粘贴应变片法监测混凝土的起裂,由夹式引伸仪测得荷载-裂缝口张开位移曲线,发现该曲线除混凝土起裂点外,还存在另外两个临界点。在此基础上,基于虚拟裂缝模型计算了三个临界点的应力强度因子。试验结果表明,外贴CFRP加固混凝土梁能明显提高梁的极限承载力和延性;减小梁的挠度,同时可延缓混凝土裂缝的扩展。另外,计算分析得到的三个临界点的应力强度因子无明显尺寸效应,可以用来表征CFRP加固混凝土梁的断裂特性。

英文摘要：

This paper examines the effect of bonded CFRP on the fracture properties of three-point bending concrete beams post-strengthened with CFRP sheets. Strain variations in the concrete are experimentally measured for concrete crack initiation and extension by attaching strain gauges on the surface of concrete. Load versus crack mouth opening displacements （CMOD） curves are obtained by the fracture mechanics gauges. Results show that there exist two other critical points on the curve besides concrete crack initial point. Stress intensity factors at these three critical points were computed by a fictitious crack model. Experimental results reveal that externally bonded CFRP can enhance strength and ductility of cracked concrete beams, decrease the deflections of beams, and arrest concrete crack extension. The computed results show that the size of specimens has little effect on these stress intensity factors, and thus they are suitable parameters to describe the fracture properties of concrete beams poststrengthened with CFRP sheets.