This is a great example of the power of technology to save lives and structures and prevent injuries. One every bridge is monitored in this fashion, we will have fewer structural disasters. It's all part of the Smart Society/IoT vision.
What would these MEMS sensors do in an earthquake? Obviously you wouldn't need them to detect the quake, but I'm curious if the MEMS would produce any interesting data. Probably the data they return post quake will be invaluable.
These would be useful on bridges that face the marine environment along with seismic issues, such as this high-profile, problem-prone construction project (with its own website!).
This is a great application! In India, the first customer that comes to my mind is "Indian Railways", which is Asia's largest railway network and world's second largest network. I was reading in some article that by 2016, Indian Railways could have the highest numbers of bridges in the world. If not the highest, but still the number is impressively large. Hence it could be a big opportunity for this kind of application at the same time making travel safer for so many people.
@Susan: Regarding "What would these MEMS sensors do in an earthquake?", they can provide VERY valuable data on transmissibility of the ground motions to the structure which is dependent on the structure's toplogy, mass and support conditions. That is the most valuable data input needed for prognostics.
@docdivakar, Interesting about MEMS sensors and earthquakes. USGS (United States Geological Survey) has been using MEMS for a while now. Here's a paper from 2005: "TREMOR: A wireless MEMS accelerograph for dense arrays" and additional info here. I don't have time to search for more right now, but if you find an interesting link, feel free to post it in this discussion forum.
With tens of thousands of structurally deficient bridges in the US alone (never mind the shaky freeway overpasses, weak tunnel walls, and dubious structures), I don't think we really need a lot of sensors to warn of a potential collapse. Periodic inspections should do the trick. Besides, would you really want the morning commute traffic report to include warnings from the bridges on various routes?
Tom, I don't know about you, but as someone who every work day rides twice over a major bridge in an earthquake zone -- and a bridge that is known to be not only unsafe in an earthquake but also prone to having things snap off it and land on cars -- I wouldn't mind knowing whether the bridge was feeling weak and under the weather on a certain day. (Sorry to anthropomorphize.) I'd simply avoid it and maybe work from home, just as I avoid it when there's a major accident. It could also help lighten the traffic load on the bridge. Sure maybe the bridge's data always show it is near collapse. But with the media attention this bridge gets, it would be good to give the public access to the data. I'd like to say the media attention would get the bridge fixed quickly, but it's taken over 20 years to get part of the bridge rebuilt. All I'm saying is many people who commute over bridges are watching to see what the traffic will be like every morning, so it's not a stretch that some of them might care to know how the bridge is doing structurally.
That's a great example of what I mean, Susan, and exactly why it doesn't make it worthwhile to build a comprehensive network of sensors in all infrastructure. The wester section of the Oakland Bay Bridge, to which you refer, was built in 1939 with supports resting on redwood columns driven into the mud beneath San Francisco Bay. In 1989, a relatively small section fell during the World Series earthquake -- a serious incident that I believe resulted in injuries, but given the size of the bridge and the magnitude of the quake, a relatively small occurrence.
It is arguable the Bay Bridge had been unsafe for many years because of those timbers and the way it was pieced together. And it has been increasingly unsafe each day since over the past 24 years. If there were sensors on that bridge, they would be in a constant state of alarm. Yet hundreds of thousands of commuters cross the bridge every day.
You suggest that a warning from sensors might prompt you to work at home? Then, knowing the bridge is in that condition, why do you come to work? What added value would sensors add to this equation? (All in all, I'd feel safer any day on the existing Bay Bridge than I would on, say, the Brooklyn Bridge. The Bay Bridge is not about to fall down. And there's no guarantee a strong quake wouldn't take out the new bridge either.)
Full disclosure: Yes, I'm among those skeptics who thought it would have made more sense to spend $6 billion on improving the schools or feeding the poor than on building a new bridge, which hasn't even opened and is already beset by nagging engineering issues that, no doubt, would be setting off the sensors left and right.
Speaking of working at home, why do we even need to build such expensive and impractical infrastructure when we're moving towards a world where most workers can do their jobs remotely?
I should think this (i.e., sensors embedded in all manner of infrastructure along with public access to the data) will become commonplace at some point. We are increasingly using them in vehicles, buildings and even our bodies to vastly improve monitoring of real-time "operating conditions." The benefits for doing so with infrastructure are equally clear - just on a larger scale.
The advantage of MEMS with wireless reporting capability is that engineering visits the bridge once to install....and can then monitor the bridge on a "dashboard."
This could save $$ on inspection visits as well as detecting changes in bridge integrity not readily spotted by the human eye that are indicators of needed repair or imminent failure.
True Peter, i think that it is a great example of how we can leverage today's techonology to save money and time. But i thought that sensors are used quite frequently to analyse the structural integrity. Isn't it very useful to use for example the piezo-material to know about the changes in the hotspots in a structure. Maybe the techniques used in the bridge are more sophisticated.
As long as cost of developing this technology for the bridges is a very small portion of the actual bridge, it is definitely an added value. In the reverse I would defnitely not suggest to use such a technology. But overall this sounds really cool application of the technology.
@Peter: I agree and I think that is what Susan, I and some of us are mentioning about. This is the direction to which the world is moving - Prognostics: proactive health checking and planning necessary maintenance schedule well in advance to safeguard the structures.. As you said, surely there will be companies providing this kind of services. This is certainly not aiming towards frightening the travelers with warning that something bad could occur.
We had a bridge collapse here in WA State a couple of months ago. Part of the issue was repeated strikes by 'oversized' trucks to the upper girders. A sensor array that could just measure some 'out of specification' vibrations would probably have helped identify an issue which could have been corrected prior to failure. Now, if the failure happens RIGHT AFTER a quick series of strikes, maybe it doesn't help much, but if the strikes happen over a period of time thats when sensors would help.
I think these sensor networks would be continuously monitoring many factors affecting the structural integrity of the bridge, including strain, tilt, deformation etc., as well as vibration, making sudden failure scenarios under any normal circumstances seem quite remote.
The variety of sensor measurements that could be made is quite extensive. Strain might be one of the more difficult measurements to make (and identifying the locations to make the measurement might be a problem). If we can find some smart materials where things like strain could be easily measured because the 'strain gage' is 'integrated' into the material that would be fantastic. Anyone know of any work going on it that area that might apply?
It seems like a sophisticated signal processing might be able to detect changes in resonance frequency of stuctural membors as a crack propogates. At least of the crack is not right at the end of the piece (where most cracks are likely to initiate!). I like the idea of something like this. I agree, strain is probably impossible to implement effectively.