初始损伤钢筋混凝土梁分形损伤本构及受弯承载力研究

Research on Fractal Damage Constitutive and Flexural Capacity of Reinfored Concrete Beams with Initial Damage

为明确初始孔隙在荷载作用下对混凝土结构的损伤及裂缝扩展路径的影响,设计并分别制作了初始孔隙为0%、2%、4%和6%的8根钢筋混凝土梁,开展单调静载受弯性能试验,分析其力学性能和表面裂缝分形维数变化情况。通过将裂缝分形维数引入混凝土本构关系中,提出了钢筋混凝土梁抗弯强度计算方法。研究结果表明:预制初始孔隙缺陷的钢筋混凝土梁仍满足平截面假定,预制孔隙一定程度削弱了混凝土的力学性能,同时跨中裂缝的产生、扩展和演化更迅速。裂缝扩展路径的分形维数可以反映钢筋混凝土梁的损伤程度及其破坏过程,本文建议的钢筋混凝土梁受弯承载力的理论值与试验值吻合较好。

In order to clarify the influence of initial voids on damage and crack propagation evolution of concrete structures under load,eight specimens of reinforced concrete beams with initial voids of 0%,2%,4%and 6% were designed and manufactured.The experiment bending behavior of reinforced concrete beams under monotonic static load was carried out,and the changes of mechanical properties and fractal dimension of surface cracks were analyzed. In the case of concrete,by introducing the fractal dimension of cracks into the constitutive relation of concrete,a method for calculating the flexural strength of reinforced concrete beams was proposed.The results show that the reinforced concrete beams with initial voids conform to the assumption of plane section. The initial voids reduce the mechanical properties of concrete,and make the flexural cracks appear earlier and develop faster.The fractal dimension of crack propagation path can be used to characterize the damage degree and damage evolution process of reinforced concrete beams.The theoretical and experimental values of the flexural capacity of concrete beams are in good agreement.