ON FATIGUE OF PLAIN AND FIBRE-REINFORCED CONCRETE GROUND SLABS

摘要

The fibre role in the fatigue behaviour of slabs, when subjected to prevailing bending is investigated. Six circular slabs (radius = 220 mm, thickness 50 mm) resting on a natural sand support were centrally loaded. A single type of medium-length hooked fibre was used (ZP30/0.5), as a reasonable compromise among fibre length, slab thickness and maximum aggregate size. Three different volume contents were investigated (0.00, 0.40, 0.80%). The natural sand support was designed in order to keep the soil stiffness k equal to 0.1 N/mm~3. Previous static loading tests on similar slabs were carried out with the same soil stiffness, comparable to a dense sand or mix of crushed stone and sand. The fatigue life for plain and fibre reinforced concrete was estimated by using some empirical relations conceived for plain concrete. The comparison is really surprising. In fact, even though the equations were calibrated on simple test specimens, they also seem to predict very well the fatigue life of slabs resting on a sand support, where crack propagation is controlled by a statically undetermined system corresponding to the 3D structure. This experience suggests the introduction of a new method to verify ground slabs at the Serviceability Limit States.