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Resonate S k y t e c

FREE | December 2018

n e w s l e t t e r

NHM Challenges: Anywhere, anytime The beginning of December marked two months since the Sulawesi disaster in Indonesia. For an extremely seismically active region, what was unique about Sulawesi?

Bernard Toh | Director Skytec

Season’s Greetings! Skytec would like to wish all our clients and friends a Safe and Merry Christmas and a Happy New Year! We are closed from the 15th of December 2018 and will reopen on the 14th of January 2019. Our mag ‘Resonate’ is designed to create awareness amongst our valued clients and the community about natural hazard management (NHM), engineering issues and the part we play in finding solutions to them - with you! Also check out what we have been up to work-wise. Skytec

Improving resilience together www.skytec.co.nz admin@skytec.co.nz +64 3 260 1950 | +64 21 0396 901

Sadly Sulawesi wears the mantle of the most devastating global seismic event of 2018. At time of writing the clean-up continues; with Relief Web noting Aid efforts are focusing on providing WASH support (water, sanitation and hygiene) to 152,000 people. 133,360 are still displaced as a result of the earthquake.

detectors were unfortunately damaged by the violent shaking. The city of Palu is also located at the end of a long natural bay which funnelled tsunami waves towards the city. As well as houses, critical lifeline infrastructures like hospitals, government buildings and bridges weren’t spared either.

Sulawesi is home to very different plate tectonics found in Aotearoa. Its ‘strike-slip’ faults typically displace land horizontally, not vertically. Dana Hunter explains a good way to understand this is to put your hands underwater and slide them together: the surface ripples, but there’s no large displacement of water.

Other complications became apparent: The majority of Sulawesi’s buildings are made of bricks with inadequately reinforced concrete beams and columns (if any), which affected their stability. Almost fully booked hotels for the Palu Nomoni festival collapsed. Some are built on land susceptible to liquefaction risk and the surrounding hill slopes of the city/towns are often deforested and exposed to weather - which can lead to devastating landslide from ground accelerations in an earthquake (Photo credit: Lip Kee Yap - Mount Tangkoko, North Sulawesti, CC BY-SA 2.0).

Despite this, the earthquake caused major soil liquefaction in areas in and around Palu. In two locations this led to mudflows which submerged buildings causing hundreds of deaths with many more missing. It is thought that landslides contributed to the tsunami’s massive waves with its height reaching four to seven metres, striking the Palu, Donggala and Mamuju settlements. The earthquake happened during the Palu Nomoni Festival, which is held on the beach every September and included an international paragliding event. Countless festival-goers were directly in the tsunami’s path and were unaware it was coming. Tsunami

Sulawesi is the 11th largest island in the world - only slightly smaller than Great Britain. Yet Sulawesi’s combination of factors resulted in an epic challenge in terms of what we currently know about island plate movements, how to better prepare communities for such events (through awareness and emergency infrastructure) and, understanding that the aftermath for survival and rebuilding is an ongoing one.


Innovate: What’s new at Skytec What are non-invasive investigations and why do we do them? Skytec provides non-destructive/non-invasive testing (NDT) services to develop condition assessments for concrete, masonry, timber structures and foundations.

On the Road This section illustrates Skytec’s work, including challenges and the solutions provided to assist our clients’ needs. Through an insurance claim Skytec undertook invasive/non-invasive and ground investigations of a single level residential house in Blenheim. Our role was to assess the damage to the house on behalf of the insurer as a consequence of the Kaikoura earthquakes and land subsidence (landslides) in 2016. So we undertook a detailed non-destructive floor scan for reinforcing to find out if there was any …and we couldn’t find any! There was little or no reinforcement in the original concrete floor of the house built in 2005. Reinforcing allows/provides better performance in the event of an earthquake and where the ground subsides. Skytec’s position was that any repair strategy needed enough detail to be accurate in pricing. The end result was that with the investigations, we provided better certainty for the landowner and insurer: but not as expected. We recommended that the house be built new, as it would be more affordable than undertaking an expensive repair on the damaged one(which had unreliable performance).

Feedback A community member asked: “Earthquake prone commercial building owners often have to face high costs for seismic strengthening of their buildings. Are there more affordable ways to strengthen?” They can include things like: - Dimensional structural survey - Concrete cutting and sample coring up to 400 mm diameter - Floor level and verticality surveys - Condition assessment of existing structure - Structural sampling for use in further testing - Non-invasive steel reinforcement testing - Foundation investigations NDT is used when we want to minimise the damage to structures when testing, particularly when a building is sensitive to any intrusive work and this is a priority. Skytec produces strengthening proposals for this type of building using NDT. As an example we were involved with a heritage building (over 100 years old) and had to ascertain the quality of the materials used in constructing it. We carried out investigations to find out the quality and form of construction. With the consideration of the investigations’ findings, we formulated a cost effective and appropriate repair methodology.

Skytec: The answer is a resounding Yes! Costs associated with seismic strengthening are often high because of many factors. One of the factors that has a huge impact on costs is uncertainty of quality and form of construction. Engineers will visually inspect earthquake prone buildings... but with a visual inspection, there is not sufficient structural information to then provide a clear assessment of seismic strength (this includes any inherent structural strength of an existing building). Skytec often goes a step further than visuals, by performing structural survey and a combination of invasive and non-invasive investigations. From our experience working on residential/commercial/government buildings, these investigations can lead to solutions that are more cost effective (up to 67% reduction in building costs) as compared to only doing visual inspections. Skytec have appropriate high tech gear to carry them which means we can ensure their quality and quick turnaround of projects.

Do you have questions or enquiries? Please email us at admin@skytec.co.nz or contact us through the website.

Skytec Resonate Improving resilience together

www.skytec.co.nz admin@skytec.co.nz | +64 3 260 1950 | +64 210 396 901

© 2018 Skytec Engineering Consultants Limited

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Skytec Resonate - December 2018  

Hi! Welcome to Skytec’s newsletter, Resonate. Resonate’s purpose is to create awareness amongst our valued clients and the community about n...

Skytec Resonate - December 2018  

Hi! Welcome to Skytec’s newsletter, Resonate. Resonate’s purpose is to create awareness amongst our valued clients and the community about n...

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