On shaky ground

Earthquakes have a profound impact on communities. Not only is there something unsettling about the earth moving beneath you, they also kill thousands of people every year, destroy billions of dollars of infrastructure and often render whole areas of cities uninhabitable.

The recent earthquake that smashed the medieval Italian city of Amatrice viscerally shows the power of nature – 300 people were killed and entire towns and villages were flattened in the August event.

Closer to home, the 2011 earthquake in Christchurch caused widespread damage  to buildings already weakened by the 2010 Canterbury  earthquake, and killed 185 people – it was New Zealand’s third deadliest disaster.

Not only was it a deadly quake, it also put financial pressure on New Zealand’s second-most populous city.

The total estimated repair and rebuild cost [from the 2010 and 2011 earthquakes] amounted to $NZD40 billion.  Considering that the population of the Greater Christchurch region is around 400,000, this is equivalent to a rebuild cost of $NZD100,000 per person.

AECOM National Practice Leader for Sustainability and Resilience Will Symons, says that because of the human and financial effects it is essential for leaders to implement resilience- based strategies.

“A solution based on resilience provides city leaders with access to funding which has the capacity to improve the daily life of residents. This funding can also help reduce the risks of other shock events the city may face, while also reducing the consequences of future earthquakes,” he says.

“Fundamentally, resilience strategies should help cities and their communities to think in more interconnected ways, about problems. Strategies developed with, and by communities should identify actions that will improve people’s lives each and every day, whilst also enabling them to move forward post-shock into the ‘new normal’ that these events often create. “

Despite this, Symons says that it can be expensive for cities to do the work they need to do to prepare.

“Earthquakes are very difficult to predict, in likelihood or intensity. This uncertainty can make investing in preparedness difficult for fiscally constrained cities,” Symons says.

Resilience strategies should help cities and their communities to think in more interconnected ways about problems

For this reason the AECOM structural team sought to find a low-cost solution that would increase the resilience of structures, in both medium-rise and low-rise buildings.

“For decades the industry was focused on the life safety objective, with little to no consideration given to functionality, or even reparability of the damage to a building following an earthquake event,” AECOM structural engineer Jae Park says.

“In designing new buildings in Christchurch, AECOM has actively employed low-damage design that allows buildings to function and be reparable following an earthquake event.  This permits the business activities and operations to be carried out as well as ensuring safety of its tenants, when other businesses might be suffering from business interruptions due to building closure.”

‘’The objective of low-damage technology is to design the lateral resisting system so that damage is limited to readily replaceable elements.  This gives greater building resilience by minimising damage in the primary structural system, while also potentially reducing damage to non-structural elements.’’

Such design concepts and technologies are not just applicable to new buildings, but can be applied in existing buildings.

AECOM’s application of this design concept to a seismic strengthening of an existing building was recognised and received a high commendation award by the New Zealand Society for Earthquake Engineering (NZSEE) in 2016.

Symons says that innovative designs such as these are part of a resilience arsenal which puts community needs at the centre.

“Although we cannot accurately predict an earthquake’s occurrence or reduce their likelihood, there are many things we can do to minimise their consequence to communities, whilst also making people’s lives better each and every day.”