9 April 2014

Trimble Navigation’s Christchurch Office was destroyed by a fire in May 2011 following the February earthquake. The redevelopment proposals presented to Trimble by Opus International Consultants incorporated the Architect’s vision of using the latest timber engineering while incorporating additional floor area to address both their current and future needs.

Officially opening in April 2014, it is the first (commercial) building in New Zealand to use both post-tensioned LVL frames and walls with energy dissipating devices for the lateral load resisting system. It is also the largest pre-stressed laminated timber (PRES-Lam) building ever constructed in terms of floor area (6000m2). Increased public awareness of safety and the benefits of timber as a structural material following the Christchurch earthquakes provided a platform for the use of this new technology at such a substantial scale.

Developed off the back of research at the Universities of Canterbury and Auckland, this damage limiting technology will reduce damage in future seismic events through the dissipation of energy and controlled rocking of the structure. Earthquake energy is absorbed with externally mounted “plug-and-play” energy dissipators, which are easily replaced following significant seismic events, providing economical repair alternatives. The timber is high grade laminated veneer lumber (LVL) fabricated in New Zealand from sustainable, locally grown timber. In the shear walls, this LVL is cross-banded to provide additional capacity.

Unique structural features

The use of high strength Spax screws and timber rivets in highly loaded seismic joints creates stiff, resilient connections with a low profile to minimise the impact of connections on the architecture. This is the first extensive use of riveted connections for seismic connections in New Zealand.

Multiple bay LVL timber frames are post-tensioned together with rocking points in the beam-column joints to allow the building to deflect under lateral load without damaging the structure or causing permanent deformation.

Damping in the frames and walls is provided by ductile energy-absorbing steel dissipators which are easily replaceable.

The coupled timber shear walls are post tensioned using high strength steel bars, and steel dissipators. Each bar is tensioned to 1.0 tonne. Shear pins connect the walls to the structure.

The floor has been detailed to allow for some movement of the frame joints without reducing the ability of the floor to transfer load to the frames and walls.

The floor is a timber-concrete composite construction using Hyspan LVL joists with a 7.6m span.

Ongoing monitoring

Extensive instrumentation has been installed by Trimble to monitor ongoing performance for both static and seismic loading. This monitoring will enable informed decisions on occupancy after a significant earthquake, and allow informed maintenance decisions when necessary.

Multi-disciplinary design

The multi-disciplinary Trimble design team from Opus provided architectural, structural, geotechnical, fire and building services design on this building. For this project we utilised our extensive skills in the performance based design to deliver a low-damage, resilient building that provides the owners and tenants with peace of mind in seismic events. Using sustainable materials and innovative design, this building is one of a number we have designed as part of the Canterbury rebuild.