Crack width prediction in RC members in bending: A fracture mechanics approach

Cracking is a very common occurrence in reinforced concrete (RC) structures. Cracks in RC structures are characterized by crack width and crack spacing. In the present study an expression is developed using a cohesive crack model having a bilinear strain softening relationship to predict crack widths in RC beams. One of the assumptions made in the development of the model is that there is complete loss of bond between the bar and the concrete. However, this crude assumption leads to too conservative values for crack width, since the frictional forces at the bar-concrete interface limit bar slip and consequently crack width. Therefore, it is necessary to introduce a restraining force to model bond and to find crack-closing displacement. The crack width values so obtained from the proposed model are compared with code predictions and with experimental results available in literature. The results show that the proposed approach is sound, consistent and realistic.