European Technical Approvals for double-headed studs at shear reinforcement

Double-headed studs are used as punching shear reinforcement in reinforced or pre-stressed slabs and footings. Due to an improved anchoring behaviour, double-headed studs have a higher load capacity than stirrups. Double-headed studs are quick to install and are therefore more cost-effective than stirrups. Previously in Europe, national technical approvals specified the design of double-headed studs. Since the end of 2012, European technical approvals (ETAs) have been available. All approvals are based on the same design method, which is used in combination with EN 1992-1-1. It is necessary to distinguish between punching shear failure in slabs and foundations with and without shear reinforcement. In slabs and foundations with shear reinforcement, a failure can occur at maximum load level, in and outside the shear-reinforced zone. The ETAs provide design equations for all types of failure modes. To quantify the safety level of the design provisions for slabs, footings, and ground slabs with and without shear reinforcement, test evaluations based on a reliable data bank are shown. The paper also provides useful background information and additional design recommendations for applications which are not covered by the design provisions of the ETAs.