Crack Propagation Law of Reinforced Concrete Beams

During the process of the shear and bending failure of reinforced concrete beams, the cracks generated on the side of the beam are mostly type I–II composite cracks. Considering the material nonlinearity and geometric irregularity of reinforced concrete, it is of great significance to study the dynamic evolution law of crack propagation in reinforced concrete members. Crack propagation consists of the elongation of the crack length at the surface of the concrete material, as well as the widening of the crack width. In this paper, a finite element model of simply supported reinforced concrete beams is established by considering material nonlinearity and geometric nonlinearity and considering the damage of the concrete. Comparing the experimental results, the finite element model can accurately reflect the strain changes of longitudinal reinforcement and stirrups with a maximum error within 10%. The crack development of concrete is basically consistent with the experimental results. It shows the accuracy of the finite element analysis. On this basis, a beam–column joint is analyzed and its crack propagation under reciprocating load is investigated. An important contribution is made to the preliminary analysis of the actual crack control project. The nonlinear finite element results show that the compressive damage to the concrete of the joint is insignificant at 0.1. but the tensile damage is significant at 0.96. The cracks in the connection between the frame and the floor slab mainly show bending cracks and the concrete damage in the floor slab is higher than that in the beam.