Effectiveness of spirally shaped stirrups in reinforced concrete beams

• We study shear capacity of RC beams with traditional stirrups and continuous spirals.
• We study shear capacity of RC beams using CVC and SCC.
• Continuous spirals are a valid alternative for traditional stirrups.
• Continuous spirals can be safely designed with traditional methods.

Normally, shear reinforcement of concrete beams consists of traditional stirrups. Replacing the individual stirrups by a continuous spiral can reduce the labour cost for production of the reinforcement cage. In this paper the use of spiral shear reinforcement is investigated by testing of 24 reinforced concrete beams in a static four-point bending test. During the tests, crack evolution is monitored, and the fracture mechanisms of the beams are analysed and compared. The results indicate that, within the inclination range used, spirally shaped shear reinforcement is a valid alternative, that could be used in international codes. In addition, it confirms earlier findings that shear span-to-depth dependency is present, although it is not considered in some international codes, and that SCC (self compacting concrete) yields a more favourable critical crack evolution compared to CVC (conventional vibrated concrete).