摘要
目的找出混凝土裂缝扩展对纤维增强材料FRP与混凝土界面粘结性能的影响规律.方法基于断裂力学理论,采用商业软件ANSYS中的界面单元模型(Cohesive Zone Model CZM),模拟素混凝土梁跨中I型裂缝扩展以及FRP与混凝土界面II型裂缝的扩展过程.结果随着混凝土裂缝的扩展,加固梁承载力出现两个峰值:第一个峰值出现在混凝土宏观裂缝扩展的起始点,此时FRP布的应力低于500 MPa,FRP与混凝土界面切应力在混凝土裂缝附近较大,其余部分切应力及界面滑移量基本为零,界面处于完全粘结状态.第二个峰值出现在FRP与混凝土界面发生剥离时刻,之后界面剥离从混凝土跨中裂缝位置向梁端部扩展,加固梁的承载力保持在第二个峰值上,FRP布应力达到1 480 MPa,界面粘结切应力及滑移量向FRP端部移动,跨中完全剥离的界面,切应力降为零,滑移量保持不变.结论计算得到的荷载随混凝土开裂的变化趋势及峰值荷载与试验值吻合较好,说明笔者提出的数值模拟方法能较准确地预测CFRP加固带缝混凝土梁的承载力.
The purpose of this research is to find the effect of propagation of concrete crack on the interfacial bond-slip relationship of FRP strengthened concrete beam. Based on the theory of fracture mechanics, the interface element known as the cohesive zone model （CZM）furnished by the commercial software ANSYS is adopted to simulate the propagations of both mode-Ⅰ crack in plain concrete and mode-Ⅱ crack on the FRP-concrete interface at different loading levels. With the progress of concrete crack, two peak points of load occur for the strengthened beam. The first peak point of load appears at the moment of progress of macro-crack of concrete, where FRP is entirely bonded with concrete. The stress in FRP is lower than 500 MPa, and the interfacial shear stress and slipping are close to zero except the region near concrete crack. The second peak point of load appears at the occurrence of interracial debonding between FRP and concrete. Then, the interfacial debonding extends from the middle to the end of the beam, during which the applied load remains at the second peak value. The stress in FRP reaches to 1 480 MPa in this case. The shear stress decreases to zero and the slipping remains the maximum value in the interface when debonding occurs. It is drawn that the variation trend of load with respect to the propagation of concrete crack and the peak points of loads are well identical to the experimental results. It demonstrates that the numerical model proposed in this paper can be used to precisely predict the loading capacities of the CFRP strengthened concrete beams of pre-cracks.
出处
《沈阳建筑大学学报（自然科学版）》
CAS
CSCD
北大核心
2017年第1期42-49,共8页
Journal of Shenyang Jianzhu University：Natural Science
基金
国家自然科学基金项目(51378089)
辽宁省自然科学基金项目(2014020008)
关键词
FRP
素混凝土梁
界面粘结滑移
CZM
FRP
plain concrete
interfacial bond-slip
cohesive zone model
