Located in the centre of the 13-acre glass ceiling of Waverley Station, Edinburgh since its construction in 1897, is the impressive Victorian glass dome. During a major refurbishment of the glass dome and surrounding ornate wrought iron work in 2013, it was decided that the dome required some form of external protection from damage.
A design for a steel frame, complete with a steel mesh covering, was issued to Millar Callaghan’s technical department. While detailing the fabrication drawings for the steel frame it was quickly realised that, even broken down to its smallest components, the steel frame was too heavy to allow it to be lifted into position with a crane. The reason for this was that the only access point for a crane was on the adjacent North Bridge which spans over the roof of Waverley Station. The acceptable point loadings for the bridge were well below point loads created by the outriggers of a cranes lifting a load at a 35- metre radius. After considering various options Millar Callaghan’s technical department calculated that the crane could lower the steel components onto the roof but only if it was within 9 meters of the crane.
PFC runners were laid onto the existing roof support steelwork. These runners ran down each side of the glass dome. The new steelwork was then lowered onto the runners in sections, where it was connected to a series of winches at the far side of the roof. The first section of the frame was winched out along the runners just far enough to allow the second frame to be lowered into position and connected to the first frame with crossbar sections. This process was repeated for the third and fourth sections. The frame was rolled out along the runners, one section at a time, until all four sections had been lowered down and attached to the frame. The completed frame was then winched to its final position directly over the glass dome. With the frame in position the base plates were anchored to the top flange of the existing roof support beam.
The installation of the main steelwork was carried out in one night, resulting in the contract being completed ahead of programme.
