The historic Victorian Smithfield Market is set to become part of a major cultural centre in London. As part of the redevelopment, buildings at the western end of the site, between the Poultry Market building and Farringdon Street, are undergoing significant changes. To support these works, temporary roofs were needed to cover the entire area, which were considered in two phases: Phase 2 and Phase 2a. At the outset of the project, the implications of load path limitations within the existing structure were not fully appreciated.
Initially, the potential limitations of the load paths within the existing structure weren’t fully understood. The original temporary works design relied on the floor slabs and perimeter walls to transfer the loads from the scaffolding and temporary roofs. However, after a review by the main contractor, it was determined that this approach was unfeasible, as the building’s fabric could not support the loads as initially planned. As a result, all restraint connections to the existing structure had to be severed, and a new load path had to be established. RDG was contracted to assess and modify the design to meet these new requirements.
The original design consisted of three temporary roofs positioned in a ‘C’ shape, supported by discrete scaffold towers, frames and gantry decking. To address the issues identified, a comprehensive 3D analysis model of the scaffolding and temporary roof structure was created that accounted for the incremental build. The model analysed the performance of the scaffold towers and ancillary scaffold structures to identify how the current load-paths could be amended to meet the specification.
The analysis revealed that several changes were necessary, including modification to the temporary roof bracing, installation of additional temporary roof support beams, and adaptions to the scaffold gantries to enable load transfers to the required locations. In addition, various sections of the scaffold and temporary roof required linking to create a pseudo isotropic temporary structure that shared and distributed the imposed loading to the prescribed locations.
The modifications to the design also ensured that each segment of the structure functioned independently during the staged erection process. As each segment was combined, the structure maintained the required load path and stability. Further assessments were conducted to ensure that the load path requirements would not be compromised during the staged dismantling of the temporary works. The revised design withstood extreme weather conditions over several years. With a design life of five years, it performed effectively, ensuring the safety and stability of the project throughout its duration.
