Pre-deflecting a steel platform to support a new organ at Manchester Cathedral, UK

Abstract

The cathedral in Manchester, UK, is one of the most impressive examples of a late mediaeval collegiate church in England. The cathedral has been without a permanent organ since the 1940s, and since then, there has been an aspiration to reinstate one. In 2010, the cathedral commissioned a new grander organ, almost twice the size of its predecessor and weighing approximately 15 t. It was to be positioned beneath the chancel arch, in a prominent central setting between the nave and the choir. The organ would be supported 3.5 m above ground level on a suspended steel platform concealed within the pulpitum. The challenge was to provide a platform within the constraints of not loading the mediaeval rood screen, no visible structure, no discernible deflection during the construction of the organ and with full reversibility. The steel platform was preloaded with a series of lead weights to induce the permanent deflections before the building of the organ itself was started. The lead weights were sequentially removed during the organ building to control the deflection and the load transfer to the existing Victorian cast-iron structure.