The Majestic Centre, an A grade office tower in Wellington, is one of the largest and most complex seismic strengthening programmes ever undertaken in New Zealand.
The 32 storey Majestic Centre dominates the capital’s skyline, and is located on one of the city’s busiest traffic corridors. In the aftermath of the 2010 and 2011 Christchurch earthquakes, Kiwi Property Group undertook a detailed assessment of their national portfolio for earthquake resilience. The discovery that The Majestic Centre had a surprisingly low seismic capability of between 34% – 45% NBS was unexpected, especially in a ‘modern’ building constructed in the early 1990’s.
The Building Intelligence Group (TBIG) was engaged to help develop a strategy to achieve a low seismic risk category, targeting 100% NBS, while ensuring business continuity for multiple tenants. A number of options were considered including demolition / redevelopment, vacating the building to strengthen, or to take the challenging and unprecedented route of tackling a major structural intervention in a fully occupied building, on a scale that was uncharted territory in New Zealand.
“Tacking the seismic upgrade in a fully occupied building presented a highly challenging proposition for the project team” says Ian Macaskill, Managing Director for The Building Intelligence Group. “Impacting virtually every major structural element of the building, the work could be equated to a rebuild of the building from the inside out. Challenges sat on all fronts; developing bespoke engineering design and construction solutions that would prove to be world firsts; building strategic alliances with Council, including mapping out compliance pathways and; developing construction methodologies that enabled business as usual for the tenants.”
The five key structural weaknesses overcome included massive new shearcore foundation pads and piling, shear core confinement and strengthening (wrapping the lift core walls in a full metal jacket), strengthening the Level 5 Perimeter Transfer Beam supporting the main Tower structure, floor diaphragm strengthening, perimeter moment frame deformation, concrete floor supports and restraining exterior precast cladding.
By the numbers
- 664,000 man hours of labour
- 171 tonnes of reinforcing steel
- 1,300 cubic metres of concrete
- 1,325 tonnes of structural steel
- 54,000 bolts and anchors
- 2 km of post tensioning strand
The seismic rating of the building tower has been raised from 34 – 45%NBS to 100%NBS. Yet the intervention is hard to comprehend, and is virtually invisible to users of the building with appearance and functionality unchanged.
Greg Tolley, Development Manager for Kiwi Property Group comments “The Majestic Centre seismic strengthening project was challenging on all fronts, in particular structural design; buildability and the requirement to keep the building operational with an occupancy of approximately 80% throughout the entire project duration. TBIG skilfully weaved the complex requirements of the many different parties together and lead the project team to develop strategies and working methodologies that allowed the successful completion of the project.”
The project was a finalist in the 2017 NZ Property Council Awards.