The March 2 incident has forced the closure of the chamber while the Health & Safety Excecutive investigates with help from engineer Ove Arup.
The closure is a further embarrassment for the Scottish Executive, following outrage over spiralling costs of the £431m Holyrood building project.
Arup’s latest report reveals that one bolt holding the 12ft strut in place was fractured and the other was missing. The company has discussed the findings with constractors Bovis Land Lease and Laing O’Rourke and temporary roof strengthening measures are being considered to allow the chamber to be reopened.
The strut, bolt and stainless steel socket have been taken to St Albans-based Stanger Materials Science for metallurgical tests. Determining the nature of the facture will help verify the integrity of other connections.
Peter Wilson, director of Napier University‘s Centre Manifesto Architecture Research Centre, said: “The roof structure is a great promotion of timber engineering which pushes the boundaries of what’s been done in recent years. We should not see a broken bolt as damaging the potential of timber use in interesting structures.”
The debating chamber roof spans 22m and consists of 60 laminated oak beams, made by Cowley Structural Timberwork, and 112 steel nodes which hold the timbers in place.
