The Need for Smart Sensor Systems

January 23, 2011 | By More

Singapore’s modern Mass Rapid Transit (MRT) system has 79 stations and over 130km of track around the island, with more built annually.

Nicholl Highway collapse

On 20 April 2004 at approximately 3.30pm, the retaining wall holding the underground tunnel being constructed for the new Circle Line near Nicoll Highway MRT station collapsed, resulting in a 30m deep cave-in that spread across six lanes of the Nichol Highway. The collapse killed four people and injured three.

The subsequent official inquiry found that instrument readings had shown that the retaining walls were under stress but the warnings had not been acted on.

Halfway across the world on the evening rush hour of 1 August 2007, Minnesota’s fifth busiest bridge on I35W suddenly collapsed, killing 13 people and injuring 145. It had been carrying 140,000 vehicles daily.

Investigations later concluded that although a steel plate was the cause of the collapse, the integrity of the bridge had already been compromised through years of modifications to the bridge.  Two inches of concrete had been added to the road surface over the years, increasing the deadload by 20%. In

I35W Collapse in Minnesota, USA

addition, over half a million pounds of equipment and construction material had been resting on the bridge above its weakest point at the time of collapse.

The 10 lane, 504 ft replacement bridge was opened on 18 September 2008 with much fanfare and innovation deployed. It employs 323 sensors embedded in different sections mesuring stress, strain, movement continuously. In addition, temperature sensors were installed that will trigger anti-icing chemicals when the temperature drops to below freezing.

It is estimated by the US Corps of Engineers that in the US there are over 70,000 structurally deficient bridges, 150 of the country’s levee pose a high risk of failing during major flooding and that 3,500 of their dams are deficient.

More smart sensors and systems are now being deployed in projects around the world to monitor important infrastructure. The new field of Structural Health Monitoring is fast emerging as a key to public safety where conventional monitoring is inadequate. The list is increasing. In China alone, the landmark list includes:

  • 2008 Olympic Stadium and Aquatics Center, Beijing
  • 104-story World Trade Center, Shanghai
  • 66-story Park Hyatt Hotel complex, Beijing
  • 240m concrete arch dam, Ertan, Sichuan
  • 8266m cable-stayed bridge, Shantou, Guangdong
  • base-isolated China’s Earthquake Administration data center, Beijing

Elsewhere dams, bridges, tunnels, buildings, oil & gas pipelines, rail lines are being incorporated with smart sensors.  The list goes on.

In Singapore they are used in all MRT excavation projects as a requirement by BCA (Building & Construction Authority), the Tuas Second Link, HDB blocks at Punggol, the Fort Canning tunnel, Changi Terminal 3, and many others.

Structural Health Monitoring is here to stay.

Disclosure:  We are have an interest in helping this technology succeed.
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Category: Sensor Systems, Viewpoints

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About the Author ()

EngTong, pioneer and innovator. Graduated from Imperial College London with an MBA from Cranfield School of Management. Lived in Scotland, England, California, Beijing and led teams in Italy, France, Japan, Taiwan and Malaysia to do the impossible. Now based in Singapore and believes the future is to blend the sophistication of western management practices with the strength of Asian Values. Trained as a Chartered Engineer. Member of IET, Associate of City and Guilds and a certified SixSigma Champion.

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