ABSTRACT
Modern designers are increasingly designing very slender structural components for wall and flooring systems. This requires more accurate estimation of the tensile properties of concrete. In particular, the modulus of rupture of concrete and therefore the characteristic flexural strength of unreinforced beams, depend on the beam depth. This size effect is investigated experimentally by bending tests of a set of unreinforced concrete beams (with a range of depths) and by finite element analysis.
The experimental results are shown to agree with the CEB-FIP Model Code equation for the size effect. A distributed crack model is shown to adequately describe the size effect in terms of both the tensile strength of the concrete and the boundary layer thickness. Finite element software is used to further investigate the size effect. Predictions using the software are shown to be normalised to fit the same curve, indicating that the software is unable to model a size effect. However, the finite element analysis is shown to satisfactorily predict the fracture positions observed in the experimental tests.
