21 Moorfields: designing against disproportionate collapse using a performance-based framework

21 Moorfields is an over-station commercial office development, located above Moorgate underground station in the heart of the City of London. The multistorey office building spans 55m between supports using an innovative combination of arches coupled with launching trusses and mega-trusses along the east and west facades. Due to the nature and location of the development, the project brief imposed tight robustness requirements, including designing for dynamic forces derived both from multiple permutations of member-removal and event-specific scenarios. This article discusses a performance-based approach to robustness assessment which was implemented on the project, in which the intent of the relevant building regulations was explicitly checked through realistic physics-based simulations.