Development, testing and installation of prestressing of the PCPV's at Hinkley Point B and Hunterston B

In order to keep the walls of the PCPVs at Hinkley Point B and Hunterston B as thin as possible it was desirable to have a prestressing system which permitted close spacing of the tendons and anchorages. A seven strand tendon system was adopted in which the strands are individually anchored by the well-established wedge and barrel system. The seven anchorages bear on to a square plate which transmits the anchorage load to the concrete via a cast steel trumpet. These seven strand anchorages are arranged in groups of four and precast into a steel box as an anchorage unit with an ultimate tendon load of about 1050 tonnes. The development leading up to the adoption of this prestressing system and anchorage arrangement is described. Full size proving tests were carried out on the four tendon anchorage box unit, together with an alternative arrangement using a square helix of bonded reinforcement. Information is given on the friction tests carried out on the completed vessel, prestressing of the PCPVs and the corrosion prevention methods adopted. (author)