NUMERICAL SIMULATION OF FAILURE PROCESS OF THREE-POINT BENDING CONCRETE BEAM CONSIDERING HETEROGENEITY OF TENSILE STRENGTH AND POST-PEAK SOFTENING CURVE

Considering the heterogeneity of the tensile strength and post-peak softening curve, failure processes of two three-point bending concrete beams are numerically modeled using FLAC. The load-CMOD curve, the distributions of the horizontal stress and plastic tensile strain in the middle span of the beam, the length of the strain localization zone and real crack, and the distributions of failed elements in tension and real crack are presented. Quantitatively, the numerical load-CMOD curves are consistent with the experimental results of C40 concrete. After the heterogeneity of the tensile strength and post-peak softening curve are considered, real cracks are initiated at several spots. Then real cracks initiated coalesce and simultaneously new real cracks are initiated. After the peak load, the increasing tendency of the length of the strain-softening region becomes slower at higher CMODs. After real cracks are initiated, the length of the strain-softening region approximately remains constant. As CMOD increases, initially, the beam does not rotate around the cross section in the middle span and then the rotational angle approximately remains constant that is followed by the rotational angle becoming larger and larger. The thickness of the tensile strain localization region is about 3 to 4 times of the element size.