The Challenge
As part of the £850m redevelopment of the St. James Centre, Edinburgh, IKM carried out temporary works design for the demolition. The existing 1970’s
concrete buildings, consisted of a podium with large areas of retail space and car parks, with multi-storey offices above.
To allow a 50% reduction in programme whilst maintaining the adjoining John Lewis department store in full operation Ultra High Reach demolition was proposed with only limited areas of top-down deconstruct adjacent to boundaries. This presented temporary stability challenges, as stability elements were progressively removed as demolition progressed. In addition, structural investigations found that the concrete had significant localised strength degradation of up to 40%.
The Solution
IKM undertook detailed risk assessments, for structural hazards resulting from the methodology. The risk of progressive collapse due to under-strength concrete, the remote location of stability elements, and the presence of significant areas of flat slabs were identified as key to the temporary works design solution.
This was used to assess alternative solutions to demonstrate that high reach demolition could be used safely whilst achieving the ambitious programme.
Mitigation measures included:
- Detailed definition of the demolition zones, sequences and exclusion zones for each stage of the demolition
- Provision of temporary stability bracing in key areas, to ensure the risk of loss of stability or progressive collapse was As Low as Reasonably Practicable (ALARP)
Other design services included:
- Working platforms
- Propping to existing service tunnels and top-down deconstruct
- Independent checking of complex scaffold systems, vibration/acceleration monitoring
- Site supervision
