Shear behaviour of prestressed double tees in self-compacting polypropylene fibre reinforced concrete

Self-compacting fibre reinforced concrete (SCFRC) is a useful material in precast industry, leading to a significant reduction in construction time and costs, and possibly even labour shortages. The addition of fibres enhances the behaviour of structures at both serviceability limit state (durability, cracking, deformation) and ultimate limit state (bearing capacity and ductility), allowing in many cases to replace, totally or partially, the web reinforcement. In this context, the present paper focuses on the use of macro-synthetic fibres as shear reinforcement in self-compacting concrete prestressed double tees. Experimental results of full-scale tests on six prestressed double tees made in self-compacting concrete and self-compacting polypropylene fibre reinforced concrete are presented. Firstly, shear tests were conducted in areas where the prestressing is uniformly distributed, in order to evaluate the possibility of replacing the minimum amount of shear reinforcement by macro-synthetic fibres only. Secondly, several tests were also carried out at the end zones, which are more critical in shear since the beneficial effects of prestressing is not totally active. Experimental results show that macro-synthetic fibres can be used as shear reinforcement both in the zone with uniform prestressing (minimum shear reinforcement) and in the end zones (shear reinforcement required by equilibrium). Finally, the experimental results obtained were compared against the predictions of three international codes: Eurocode 2, ACI318-11 and Model Code 2010.