October 6, 2011

Column | Korky Koroluk

Damage assessment improvements needed

The photos were arresting: Several workers in bosun’s chairs working their way down the outside of the Washington Monument, checking for damage from the earthquake that hit the area in August.

That there was damage was already known. A large crack had been spotted near the top of the obelisk soon after the quake, and, as a result, the monument has been closed to the public since then.

Now, four workers dangling against the monument’s faces were doing a detailed inspection, expected to take several days. Each carried a digital camera, an iPad computer loaded with data from a 1999 restoration, a two-way radio, and masonry tools for removing loose pieces of stone or mortar. Each also had a soft mallet to tap the stones, listening for sounds that might indicate problems not visible from the outside.

It’s been a bad year for man-made structures. Earthquakes, floods and tornadoes have caused widespread damage in many parts of the world, including the United States, Japan, New Zealand, India and Pakistan. And it’s provided a reminder that most structures — even in such tech-savvy nations as the U.S. and Japan—are still inspected by a very low-tech way: by looking at them.

We need better ways to spot and assess damage. We need better ways to follow slow deterioration so we can act before the damage becomes crippling. We need something more than looking with the human eye and tapping and listening with the human ear.

Help is on the way, but it’s mostly still under development. Small, agile, flying robots can carry cameras and peer into nooks and crannies that are hard for a person to get to. They perform wonderfully in the laboratory, but working in the field usually isn’t as easy as working in the lab.

Wall-climbing robots have been used for interior painting for a while now, but climbing an exterior wall, especially one with a rough surface, is a different problem.

But now there is at least one research team that has built a robot that can climb over uneven surfaces — at least in the lab. So we likely need something else while we wait for robot technology to develop a bit further.

A researcher at the Massachusetts Institute of Technology has devised what he calls a “sensing skin.” These are flexible patches that can be glued to areas where cracking is likely to occur.

The patches are made of stretchable plastic mixed with titanium oxide. Each has an electrical charge stored in it, which will vary with any movement in the part of the structural member under each patch.

A part of the structure’s daily maintenance routine would be to have a computer check each patch to measure its charge. A change would be the signal to take a closer look at that particular area.

Another researcher has installed sensors in some sections of the suspension cables of New York City’s Manhattan Bridge. The sensors track humidity, temperature, and the rate of corrosion of the steel cables.

Both the flexible patches, and the sensors in bridge cables, are in the fairly near future, which is a good thing. Insurance industry figures tell us that losses from natural disasters are at record levels this year. And as bigger storms occur in a warming world, those losses are likely to continue to grow. We’ll need all the tools we can get to measure damage.

That’s why we should be at installing methods to assess the condition of existing infrastructure of all kinds, and ensuring that those assessment tools are built into any new infrastructure we want to protect.

They could extend the life of many structures, and the cost, when spread over the structure’s life, would be miniscule.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com

Print | Comment