Description of fatigue test method Four Point Bending (4PB) in use at the Dutch Road& Hydraulic Engineering Division (DWW) & Technical University Delft & Dutch Consultancy Agencies

The fatigue test used, is a four-point bending test. Prismatic specimens are fixed between four clamps. The two outer clamps do not allow vertical movement of the specimen. All four clamps shall allow free rotation and horizontal movement of the specimen. A vertical sinusoidal force is applied to the two inner clamps bringing the sample into flexion (bending). The test can be performed either in controlled deflection (strain) or controlled force (stress) mode. The test permits to determine at least the number of cycles to failure (breaking of specimen) for a given deflection or force level and follows the evolution in the (weighed) complex stiffness modulus of the sample during the test. This report gives a short overview of the test equipment, the allowable sizes of the specimens, the several parameters involved and the formulas for the backcalculation of the complex stiffness modulus (a weighed value for the beam).