Fatigue lives of asphalt beams in 2 and 4 point dynamic bending tests based on a 'new' fatigue life definition using the "Dissipated Energy Concept" : phase IV: DAB 0/8 Weibull stressed volume effect

The goal of this subproject was to investigate if a difference in the geometrical dimensions of the two and four point bending specimens could explain the obtained differences in fatigue lives from a statistical point of view (Weibull). It came clear that it is not possible to find this effect in a four point bending test by varying the length between the two inner clamps over a moderate interval (from 90 to 190 mm). The theoretical calculated effect is too small and will not be detected due to the larger variations in the fatigue lives. A calculation is carried out for this Weibull stressed volume and area effect taking a very simplified model for the trapezoidal specimen. In practice a factor of around 2 is noticed in the ratio of fatigue lives for four point and two point bending tests. This implicates that this statistical phenomenon can not explain the noticed differences in fatigue lives measured in both test equipments.