Size Effect on Flexural Compressive Strength of Concrete Specimens

In estimation of the ultimate strength of a concrete flexural member, the effect of member size is usually not considered. For various types of loading, however, the strength always decreases with an increase of member size. In this study, the size effect of a flexural compression member was investigated by experiments. For this purpose, a series of C-shaped specimens subjected to axial compressive load and bending moment was tested using three different sizes of concrete specimens with a compressive strength of 52 MPa. The three different size specimens were varied in height and width of their cross sections, which had a 1:2:4 ratio. The thickness of the specimens were constant where the size effect in outplan direction is not considered. The test results are curve fitted using least square method (LSM) to obtain the new parameters for the modified size effect law (MSEL). The MSEL curve, graphed with new parameters, is compared with the uniaxial compressive strength of concrete cylinder test results; the results show a much stronger size effect in C-shaped member compared to the cylinder members.