Phase 1 of the Post & Mail redevelopment is now complete. This phase of the project comprised the demolition of the existing building followed by the construction of a six-storey basement car park with a further three levels of the new structure above ground level.
The original Post & Mail Building was completed in 1964 to provide a new headquarters for the Birmingham Post & Mail; the functional areas of the original building included printing presses, foundries, ink stores, newspaper distribution areas and offices.
Located in Birmingham city centre, the development occupies the full site area of the former building, 75m x 50m, and is directly surrounded by two highways, a live multi-storey car park and an office building.
The design and construction of the Phase 1 structure included provision for Phase 2 of the redevelopment. Phase 2 will involve the construction of a twenty-storey mixed-use building on top of the completed Phase 1 development.
For Phase 1, the client’s brief was clear from the start – create the best car park in Birmingham whilst maximising the opportunities for future development on the site without the need for constructing new foundations.
Realising client objectives
Ramboll’s innovative structural engineering strategies, attention to detail and pioneering analysis techniques allowed the client to fully realise their objectives. Ramboll demonstrated that the completed development, planned to be up to 23-storeys above ground level, could be constructed on the existing foundations without any strengthening works, despite significant increases in loading compared to the original design.
To maximise the value of the client's asset and minimise the extent of new works needed, Ramboll applied a range of innovative structural engineering and construction techniques, including;
- A detailed analysis of the existing basement slab, including 3D Finite Element and settlement analyses, demonstrating that the existing foundations could support significantly increased loading from the Phase 1 and future Phase 2 developments, without modification of the existing structures.
- Thin post-tensioned concrete slabs supported on steel columns at all new floor levels were used to maximise the number of parking levels, with the car park slabs utilising the Vertical Circulation Module system to increase the number of car park spaces and to reduce ramp requirements.
- The use of composite steel/concrete columns in the basement to support high loading from the Phase 2 development and to avoid the requirement for applied fire protection to the columns.
- Highly developed collaborative 3D model incorporating existing structures, new structures, steelwork, temporary works and precast concrete cladding.
Overcoming challenges to deliver design and construction excellence
The project and site requirements led to many challenges. Minimal record information for the original building was available but the redevelopment required a comprehensive understanding of the existing structures. Ramboll developed this insight via the archive information, photographic records, visual surveys, intrusive surveys and material testing.
To allow the existing 17m deep basement structure to be retained and reused in the permanent works, Ramboll developed detailed phasing sequence information to inform specific requirements. Used through the early stages of the project to communicate the sequence critical design aspects of the project; the use of the sequence information ensured that the works to remove and replace the structural elements that propped and stabilised the perimeter retaining walls were completed in a safe manner.
Significant temporary works systems were required for the basement levels and other parts of the building, such as a section of the retained façade. Ramboll developed design principles and strategies for all major temporary works installation including coordination with the existing, new and temporary works structures. It was particularly important to define these design principles due to the complexity of the geometrical arrangement of the existing structures, the temporary works and the new structures. Ramboll maximised the benefits of using BIM to resolve the challenges of coordinating multiple phased works, resulting in the façade retention being successfully restrained by the new structure.
Design and construction excellence is apparent throughout the new six storey basement car park, from the ground-breaking car parking technologies to the extremely high quality finishes found throughout the car park, many of which can be considered to rival those found in education and commercial buildings.