Northwood Supa Centa

The centre experienced structural damage and liquefaction induced ground deformations following the 2010 and 2011 Canterbury earthquake sequence. Our client needed regular and prompt structural engineering and seismic assessments of their buildings to quickly and safely determine whether they were safe for occupation and continuing use.

As we had been involved in the civil design for the development, we had previous knowledge of the site and ground conditions. This put us in a knowledgeable position to provide detailed structural assessments on the seismic rating of each building. Following the seismic assessments, the client wanted to strengthen all the buildings in the complex so they could achieve a seismic rating of ‘A grade’.

It was very important to the client that the buildings remain safe, open, and operational following any earthquake activity and while they were being strengthened. This presented an interesting technical and logistical challenge.

We carried out damage inspections and seismic assessments immediately following each earthquake or significant aftershock. Working closely with the retail outlets, we assisted with the efficient re-opening of the businesses. We advised on any earthquake repairs required and whether continuing occupation was possible. This resulted in the businesses being safe to occupy and able to trade during the day and minimal disruption to rent income for our client.

The client asked us to design the strengthening work required for each building to be as close to 100% of New Building Standard as possible and achieve a seismic rating of ‘A grade’. We designed the strengthening so that it could be installed in parts. The construction (carried out by HRS Construction) was done overnight outside of normal business hours. The buildings were safe to occupy during normal trading hours and the businesses remained open during construction.

One significant technical complexity of this project involved strengthening and lifting the Countdown supermarket building which had suffered liquefaction-induced settlement in the earthquakes. We worked with Coffey Geotech engineers and Mainmark Ltd to design a solution that essentially pumped the building up by injecting expanding resins into the foundation . This work was carried out over a series of weeks which reduced the lifting stresses on the building and allowed the supermarket to remain open during the day.

Following our assessment and engineering work, we produced the building consent documentation and assisted our client through the consent process.

Throughout this project we were incredibly solution driven and did what was necessary for the buildings to remain safe and be open for trading during the day. The businesses remained open throughout the construction process with minimal interruption to trading. The teamwork and communication between all parties were key in developing and delivering a successful engineering project. We carried out construction monitoring, including liaising with contractors, and attending weekly site meetings. As most of the construction work was carried out overnight, this frequently involved site inspections at 2am.