Building the I-City
Beefing up the interconnections of a city’s utilities will go a long way toward making urban areas more resilient in the face of disaster. But what about strengthening the interconnections of the city itself? The same kind of redundancy and diversity found in the Internet, the water system and the power grid could be incorporated into city buildings and structures. Connecting those components electronically and then monitoring them could provide emergency-response crews with critical and timely information about any damage.
The system begins on the structural level with the buildings themselves. Additional support elements and secondary evacuation routes could help ensure that an event that compromises part of a structure doesn’t lead to a catastrophic loss of life. Oral Buyukozturk, a professor in the MIT Department of Civil and Environmental Engineering, calls this principle “the technology of redundancy.” Backup systems “should be incorporated into structures such that failure cannot be reached in one step,” he explains. “Rather, it should take several steps.”
While additional technologies such as stronger fireproofing might have delayed the accordion-like collapse of the World Trade Center towers, no one is suggesting that they could have prevented it. But the fact that few people escaped from offices above the stricken floors suggests that the airplane impacts did cut off most of the emergency stairwells in one step. And that, say Buyukozturk and others, brings the adequacy of tall-building evacuation systems into question. “We need better fire prevention methods and materials and better evacuation plans for tall buildings,” Buyukozturk says. “The stairway should only be the first level of evacuation. The second level should perhaps be a special vertical tunnel or elevator, maybe installed in a tube made of a material such as reinforced concrete that is less affected by heat.” Buyukozturk points to the pressurized service tunnel between the two railway tunnels under the English Channel as a working example. Thanks to the escape route the service tunnel provided, a November 1996 train-car fire that raged for nearly nine hours in one of the railway tunnels-causing considerable structural damage-killed no one.
When it comes to saving lives and stemming chaos in an emergency, it’s also crucial that infrastructure managers are able to act intelligently. To do that, they need information. A growing number of engineers and city planners say the kind of intelligence exemplified by power electronics and the information-sharing and analysis centers should be woven through a structure’s framework.
Researchers at Xerox’s Palo Alto Research Center, for example, are proposing that legions of tiny, wirelessly interconnected sensors literally be mixed into building materials to provide a continuous report on a structure’s physical state. “If you have sensors that are dirt-cheap and untethered-meaning they operate either on batteries or on passive energy that can be beamed to them-they could be blended into building materials such as concrete or brick,” explains Feng Zhao, principal scientist of Xerox’s Collaborative Sensemaking Project. “If each smart brick’ has embedded sensors wirelessly communicating with other bricks, then during an emergency they can detect the extent of the damage.”
Suppose a terrorist bomb blows a hole in a wall made from smart bricks or other networked materials. Some sensors would be knocked out of commission. But data collected from those that remained could allow structural engineers to quickly determine how big the hole is and how much stress has been placed on the remaining structure, explains Zhao. Even the demise of sensors could provide valuable information. “If these sensors are self-locating and part of the structure collapses, then as these bricks fall they are going to record and transmit their displacement,” Zhao adds. “Maybe you can reconstruct their trajectories to see exactly how the building collapsed and where people might be trapped, and you can actually send rescue workers to the right place. That could be really useful.”
Under more typical conditions, such sensor networks could be used to monitor the vibrations of passing vehicles or even footsteps, giving them obvious applications in the worlds of surveillance and military intelligence, which explains why Zhao’s group is partly funded by the U.S. Defense Advanced Research Projects Agency. But Xerox’s current prototype sensors range from a little larger than a quarter to the size of a shoebox, not quite small enough to incorporate into building materials. Zhao predicts it will take five to 10 years to make the hardware tiny enough and cheap enough-and suitably beef up the needed communications and data analysis software-to realize his vision. Nevertheless, he says his telephone has been “ringing off the hook” since September 11. “A lot of people think our sensor technology is right at the middle of making sure our cities are safer.”
Indeed, such technologies could readily be adapted to monitor entire cities and coordinate disaster response, says Franz-Josef Ulm, a colleague of Buyukozturk in MIT’s civil and environmental engineering department. “For about two years we’ve been discussing the concept of the I-City,’ where basically you use monitoring and simulation of the physical state of the infrastructure-tunnels, bridges, buildings and so forth-to solve questions of the operations of the city,” says Ulm.