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30 December 2021 by Aurecon Hong Kong Ltd
When it comes to designing resilient buildings, certain countries are way ahead of the curve. Unfortunately, many in South East Asia are not among them. It is a peculiar shortcoming, when you consider China, Indonesia and The Philippines all make the list of the Top 15 ‘at risk’ countries for earthquakes in the world.
Consider also that we know that countries with advanced building codes and compliance systems to legislate for better design to protect against earthquakes have a strong track record in better preserving their cities and populations in the wake of earthquake events.
The first point to make is that increased seismic activity risk is very real in South East Asia (and worldwide) – and it may be getting worse. Several theories suggest that climate change may be fuelling this increase, creating changes and disturbances that nudge faults in the earth’s crust to rupture earlier.
Source: Maps of the World, What are Plate Tectonics, 15 October 2018
For instance, as glaciers melt due to global warming, this reduces the stress load on the earth’s crust below, which could trigger a seismic event. As water levels rise (a particular threat for South East Asia), this puts higher pressure on fault lines, which could, again, cause a tremor or worse.
A further knock-on effect of climate change is that the low-lying lands of South East Asia may become increasingly uninhabitable due to rising sea levels. Densely populated areas will experience heightened levels of immigration, amplifying the consequences should the unthinkable happen.
Although most new buildings in South East Asia are routinely designed to resist the cyclones that are a common occurrence here, because of the limited availability of seismic data they tend to be designed for a nominal seismic coefficient, exposing them to potentially devastating consequences.
Much of Asia is water-bound, with a high-water table, such that the effects of a tsunami following an earthquake could be considerable. Combined with the geotechnical considerations such as liquefaction, where the ground suffers a reduction in load-carrying potential, it becomes clear why this topic demands our attention.
In our region, the countries sitting above the boundary between the Indo-Australian and Eurasian plates (Myanmar, Philippines, Indonesia, Japan and China) are most vulnerable. There is no question that the devastating death toll earthquakes can inflict gives cause enough to design for them, but it is also worth considering the immediate and long-term economic consequences.
One study suggests that GDP per capita reduces by 1.6 per cent eight years after a severe earthquake in a heavily populated area. In Asian countries that have not reached the levels of development seen in the West, that impact is likely to be higher.
The good news is that there are already best-practice approaches to creating earthquake resilient designs that could be easily adapted for this region. Countries such as New Zealand, USA and Japan (among others) are leading the way, having experienced destructive seismic events. These countries understand the devastation, downtime and rebuild costs of earthquakes, and have developed strong practices to adapt to them and minimise their impact.
As South East Asia’s economies continue to evolve, they place an ever-increasing emphasis on the health and safety of their population. We believe this should include more stringent seismic requirements for the design of new structures and funding to strengthen (or demolish) non-compliant building stock. What is also interesting to observe is that this push for greater health and safety is not always driven by the government. In many cases, businesses have their own requirements.
For example, in New Zealand, the government’s guidelines around a structure’s ability to withstand earthquakes is laid out in formal legislation, (Earthquake-Prone Buildings) Amendment Act 2016. This stipulates that a minimum seismic rating of 34 per cent is required for all structures and provides timelines for compliance. Engineers’ professional bodies recommend that developers and building owners meet the level at 67 per cent.
Many corporate entities and government departments in New Zealand have developed policies stating they will not lease premises unless it has a minimum of 80 per cent of NBS, therefore forcing the hand of developers and building owners. When you add in the fact that it is difficult for owners to obtain insurance for buildings deemed to be earthquake prone and there is talk that insurance premium discounts may be introduced for owners and occupiers of seismic resilient structures, the business case begins to make even more sense.
In countries where there is a strong cultural and legislative set-up to protect against earthquakes, many government departments and clients fully understand the need to design seismically resilient buildings and carry out whole-of-life cost/benefit analysis. Clients appreciate that a low-damage design, with reduced cost of repairs and associated reduction in downtime, could more than offset the higher initial build cost. Methodologies for these assessments are reported in many engineering papers and advisories.
These countries will also have a support network to assist. This will include local universities offering courses in designing for seismic resilience and regularly undertaking research to produce structural engineers, architects and designers with the right skills. These universities can work alongside consultancies and research facilities to share their research, which will then influence future building codes and seismic assessment guidelines strengthening the industry further.
Aurecon was appointed as structural engineers for the significant refurbishment and structural strengthening of the Dunedin Law Courts in New Zealand.
Consider, for example, the 2011 Christchurch earthquake in New Zealand. During this seismic event, the ground motion was greater than what was expected in the then-applicable building code NZS1170.5:2004. This prompted a reassessment, and an increase in the code’s seismic coefficient from 0.22 to 0.3.
The lessons learnt from the 2011 Christchurch Earthquake along with the 2016 Kaikoura Earthquake, resulted in a significant update to New Zealand’s ’The Seismic Assessment of Existing Buildings’, to which Aurecon has contributed.
Looking to countries with established programs for designing seismic-resilient buildings highlights the opportunities available in South East Asia. At present, few governments provide funding for research into seismic resilient technologies, meaning there is a shortage of universities offering relevant courses and a skills gap further down the line. For many clients, investing up-front in seismic resilience is rarely considered because there is little historical practice of it in this region.
However, as Asia continues to attract growing numbers of foreign investors, such considerations will play an increasingly important part in where capital flows. Just as many companies have policies that forbid staff from traveling with airlines with inadequate safety ratings, their purchasing or leasing decisions for facilities will increasingly favour buildings with a higher level of seismic resilience.
Rather than wait for this shift to trickle into the engineering practice in South East Asia, we see an opportunity to make voluntary strides now. As a bonus, this would also negate the need for any future changes to be fast-tracked into retroactive measures following an unexpectedly disastrous event. This needs to start with governments – and clients – being alert to the advantages of seismic resilient design (and its whole-of-life cost benefit) and, in response, introducing amended building codes to achieve increased levels of seismic resilience.
The good news is, in the first instance there is no need to reinvent the wheel. Using the U.S. code (for example) as a foundation for a country to develop its own code would be a great start for many countries in South East Asia. In fact, it has already happened in some countries such as Indonesia and the Philippines– but we need the remaining countries to follow suit.
If this happened, it would also create a need for the region’s construction industry to be better educated in seismic resilient design, prompting the upskilling of university lecturers. With the introduction of appropriate courses and facilities (with equipment such as shake tables), a new generation of engineers, architects, designers, fabricators and contractors will emerge in this region.
Inevitably, to deliver better seismic-resilient performance in buildings means an increase in capital cost at the outset. Yet while the perceived expense of seismic resilient techniques often limits its use to prestigious, high-budget buildings, in most cases it adds only a small percentage to total building costs (approximately 5-7 per cent and can be even less). This relatively minor increase in cost needs to be considered in the context of significantly improved business continuity following a seismic event.
It is not only new buildings that should consider increased seismic resilience either. Upgrading existing buildings to meet a good level of new code levels is also going to bring resilience benefits but inevitably incur costs. However, when one considers the role that many buildings play in communities (temples, historical centres and more) it’s easy to see that the process of preserving and protecting them extends far beyond the functional. For many populations, local buildings define their heritage, identity and sense of belonging.
Other key structures that would benefit from retrospective seismic-resilience design include those that are critical for continuity in the wake of an earthquake. These include key institutions such as power stations, hospitals, utilities, ambulance and fire stations. Needless to say, it is vital these facilities maintain their post-disaster functionality even if much of the other infrastructure has been destroyed.
As the process of building seismic resilience is not new (just relatively new to most of South East Asia), there are a number of smart engineering techniques we can harness. These include opportunities to embrace the ever-emerging possibilities that digital engineering offers.
As a start, using digital tools will make it easier to show clients and other stakeholders the impact of earthquakes and how seismic resilient design can mitigate the effects. Further down the line, digital engineering should also lead to the development of tools and software to help those less familiar with seismic resilient design.
When it comes to the design stage, there are a number of techniques that can be harnessed. These include base isolation which Aurecon successfully used in the Christchurch Art Gallery.
Based on observations carried out following the 2011 Christchurch Earthquake, the buildings equipped with base isolators performed extremely well. Base isolators separate a building’s superstructure from the ground through a mechanism that helps the building ‘hover’. This reduces the effect of ground motions on the superstructure, which in turn reduces the seismic forces the superstructure is designed for.
Base isolator used in the Christchurch Art Gallery.
Aside from base isolators, another option is the use of an eccentrically braced frame with replaceable active link within the structural steel design of a building. Aurecon has also employed this design technique for a hospital in Auckland and it involves adding suitably well detailed active links to allow the structure to undergo inelastic deformation and dissipate energy.
The remaining members are designed for the over-strength of the active link. What this means is that the inelastic deformation is concentrated and controlled in the active link (like a fuse in an electric circuit). While these active links absorb the damage caused by an earthquake, they are easily removed and replaced in preparation for any future incidents post-event.
Other seismic resilient design techniques include ‘PRESSS’ or rocking technology, ringfeder springs, sliding hinge joints and damping mechanisms. Aurecon was the first consultant to incorporate sliding hinge joints into New Zealand Building Designs.
For governments in particular, the advantages of keeping crucial infrastructure operational may well be the only incentive needed to implement some form of seismic resilient legislation. More generally, safer building stock will help to minimise the impact of an event, requiring less disruption, and reducing the long-term effects on the economy.
Even before an earthquake strikes, building owners will be far better placed to attract foreign investors who place greater store in higher seismic resilience, and can even use this to demonstrate greater design resilience and long-term operational benefits. Should the unthinkable happen, the lower damage levels will enable the building to return to operational normality far quicker.
While our age of disruption has taught us to ‘expect the unexpected’, the events of the past years have shown us just how severe the impact can be if we are not prepared. Seismic threats to South East Asia are real, and so are the consequences of not mitigating against them. We can take steps to make a change. We can learn from others. Ultimately, we can create a future built environment that is smarter, safer and engineered for life.
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