Title: Fracture Mechanics and the Concrete Codes
Author(s): Arne Hillerborg
Publication: Symposium Paper
Appears on pages(s): 157-170
Keywords: beams (supports); building codes; concretes; flexural strength; fracture properties; reinforced concrete; reinforcing steels; shear properties; span-depth ratio; specifications; structural design; tensile strength; Structural Research
A fracture mechanics approach is presented. In this approach, the complete material behavior during tensile fracture is described in a way suitable for the analysis of failure of structures. Two examples are given of practical applications, in which the results can be compared with code specifications. The first is the cracking strength of a beam. It is demonstrated that the formal flexural stress that causes cracking decreases as the depth of the beam increases. The second example is the shear strength of a beam without shear reinforcement. The theoretical results show a good agreement with test results. There seem to be reasons to revise the rules in the ACI Building Code regarding the influence of beam depth, of span-to-depth ratio, and of the amount of longitudinal reinforcement on the shear strength. The tensile toughness of concrete, expressed as fracture energy, proves to be an important material property, which ought to be taken into account.