FIBRE RC DECK SLABS WITH DIMINISHED STEEL REINFORCEMENT

This brief article describes the results of research undertaken to investigate the feasibility of constructing a bridge deck slab using polypropylene fibre reinforced concrete with limited or no steel reinforcement. The half scale model used was a two girder bridge having a 200 mm thick slab on girders spaced at about 2.2m and with a span of about 7.3m. The first model had no diaphragms at the supports and three intermediate diaphragms, one at mid span and one at each end of the quarter span locations. The second model had fairly substantial diaphragms added at the supports. No superplasticizers were used in the mix design. The first model failed under a concentrated load of about 177 kN. The mode of failure was not that of pure flexure, nor did it resemble the punching shear type of failure observed in deck slabs incorporating steel reinforcement. The second model failed at about 222 kN in practically the same mode as that of the first model. A 25% increase in the failure load establishes the significance of the diaphragm at the supports. The failure load for the second model corresponds to about 890 kN, which is about 18 times the maximum permissible weight of one half of the axle of a vehicle. However, unless the failure zone can be restricted to within a close proximity of the zone of load application, the presence of other concentrated loads on the deck cannot be neglected. The model was analysed using the finite element program ADINA. A plot of load-deflection relationships under the load for different degrees of restraint provided by the transverse diaphragm is presented. This too showed the significant affect upon failure load of the diaphragms. The French title of this article is: Dalles en beton renforce de fibres et avec une armatures metallique reduite. The German title of this article is: Fahrbahnplatten aus Faserbeton mit reduzierter Stahlbewehrung. For the covering abstract of the conference see IRRD 851274.