Bridge Strengthening Research

Source:

http://www.sciencedaily.com/releases/2007/09/070914163132.htm

Science Daily — These days, a drive across a bridge is not always a pleasure cruise. Mindful of the war on terrorism, it can often be a cautious experience.

In one scenario, someone sets off a series of bombs to weaken the cables and the key structural connections of a major city bridge, all during rush hour. Not easy to do, but now thinkable. This summer, the possibility of sabotage was quickly examined—then dismissed—when the I35W bridge in Minneapolis tragically collapsed into the Mississippi River.
As authorities monitor and stand guard over bridges, the Homeland Security Science & Technology Directorate is looking to scientists and engineers for the security technologies of tomorrow. What if, for instance, we could one day not only guard bridges but fortify them? Like Superman’s blue suit, what if the cables and connections on bridges could be shielded with protective sleeves or covers, making them nearly impossible for the villains to penetrate?
This is the goal of the Directorate's bridge-strengthening research. Through a partnership with the U.S. Army Corps of Engineers’ Engineer Research and Development Center, the Directorate’s Infrastructure and Geophysical Division is testing current bridge designs and investigating advances in steel and reinforced concrete to explore whether such shields could work.
The first step is to determine which bridges and materials are most vulnerable, says Stanley Woodson, who oversees the project at the Center’s Geotech and Structures Lab. A major focus, he says, are the cables and the support columns—or towers—that are used in the cable-stayed design of bridges. Unlike the cables of a suspension bridge, which are attached from tower to tower, the cables in a cable-stayed bridge are connected directly to accessible points along the horizontal bridge deck.
"In controlled experiments, Woodson’s team has been re-creating the forces holding up these bridges and blowing up samples of their cables using various kinds of explosives," say Dr. Mary Ellen Hynes, director of the research. "They then use sophisticated software to analyze the impact and results."
“We tension the cables just like a real bridge,” Woodson explains. “We want to see just how they’d react in an actual terrorist event.”
The next step will be more complicated, says Woodson: Determining what material would suffice for another layer of protection, and what form it should take. “We’re looking at the practical as well as the innovative,” he says, recognizing the potential for high costs.
By the end of 2008, Woodson and his team will be imitating concrete bridge towers and subjecting them to the same explosive testing.
Note: This story has been adapted from a news release issued by Department of Homeland Security.

Fausto Intilla

www.oloscience.com

Making Cars Smarter Than You

Source:

http://www.sciencedaily.com/releases/2007/08/070823180503.htm

Science Daily — Cars already automatically lock doors when they sense motion and turn on warning lights if they detect potential engine problems.

But they are about to get smarter.
The augmented cognition research team at Sandia National Laboratories is designing cars capable of analyzing human behavior.
The car of the future they are developing may, for example, deduce from your driving that you’re become tired, or during critical situations, tell your cell phone to hold an incoming call so you won’t be distracted.
The project started about five years ago with funding by the Defense Advanced Research Projects Agency (DARPA). Four years ago Sandia partnered with a major commercial automobile manufacturer, and three years ago did actual experiments on European roadways.
“We utilized data that already existed on the car’s computer to collect a wide range of physical data such as brake pedal force, acceleration, steering wheel angle, and turn signaling,” says Kevin Dixon, principal investigator. “And specialized sensors including a pressure sensitive chair and an ultrasonic six-degree-of freedom head tracking system measured driver posture.”
Five drivers were fitted with caps connected to electroencephalogram (EEG) (brainwave) electrodes to gauge electrical activity of the brain as they performed driving functions.
The researchers collected several hours of data in unstructured driving conditions that were imputed into Sandia software, referred to as “classifiers,” that categorized driving behavior. These classifiers could detect certain driving situations such as approaching a slow-moving vehicle or changing lanes in preparation to pass another vehicle.
The system detects the difficulty and stress of the task the driver is attempting. It then tries to modify the tasks and/or environment to lower the stress and improved specified performance parameters.
Similar experiments were conducted for off-road driving where conditions were much less structured than typical roadways.
“The beauty of this is that we aren’t doing anything new or different to the car,” Dixon says. “All the software that can make the determination of ‘dangerous’ or ‘safe’ driving situations would all be placed in the computer that already exists in the car. It’s almost like there is another human in the car.”
More recently, the researchers conducted experiments at Camp Pendleton with Marine Corps personnel driving a modified military vehicle. Once again the driver and a passenger sitting in the passenger’s seat were fitted with EEGs. The software classifier determined how difficult the driving situation was and who the best person of the two was to perform a task. For example, during a difficult driving maneuver, it might be best for the passenger to receive radio transmissions in order to not distract the driver
“Every year tens of thousands of people die in automobile crashes, many caused by driver distraction,” Dixon says. “If our algorithms can identify dangerous situations before they happen and alert drivers to them, we will help save lives.”
Sandia is a National Nuclear Security Administration (NNSA) laboratory.
Note: This story has been adapted from a news release issued by Sandia National Laboratories.

Fausto Intilla

www.oloscience.com

Drive-by-wire And Human Behavior Systems Key To New Urban Challenge Vehicle

Source:

http://www.sciencedaily.com/releases/2007/08/070810194840.htm

Science Daily — Virginia Tech's entry in DARPA's Urban Challenge is moving forward to the qualifying rounds, thanks in part to a custom-designed drive-by-wire control system and unique navigation software that makes the vehicle's driving decisions almost human."VictorTango," a team of Virginia Tech engineering and geography students, is among 36 semi-finalists selected by DARPA (Defense Advanced Research Projects Agency) to vie for the $2 million Urban Challenge prize. Qualifying rounds begin Oct. 26 at the former George Air Force Base in Victorville, Calif., and the final event will take place Nov. 3.

Urban Challenge teams are attempting to develop vehicles that can maneuver a 60-mile course of simulated military supply missions in less than six hours -- with no human intervention allowed past the starting line. The vehicles will have to obey California traffic laws, merge into moving traffic, navigate traffic circles, negotiate intersections, and avoid a variety of obstacles.VictorTango has converted two Escape hybrids donated by Ford Motor Co. into autonomous vehicles by outfitting them with a "drive-by-wire" system, a powerful computer system, laser scanners, cameras, and a GPS (global positioning system), said Patrick Currier, a mechanical engineering (ME) graduate student. The students dubbed the vehicles "Odin" after the chief god in Norse mythology."The drive-by-wire system allows the computers to control the throttle, brake, steering, and shifting and to drive the vehicle," Currier said. "This system was custom developed by the team and is unique in that it is completely hidden from view, enabling Odin to retain full passenger capabilities." TORC Technologies LLC, a company in Virginia Tech's Corporate Research Center founded by alumni of the university's robotics program, has worked with VictorTango to develop the software for the vehicle's computer system. VictorTango and TORC developed Odin's sophisticated navigational software, which is modeled on human behavior. "To successfully navigate in an urban environment, Odin processes all of the sensor information, classifies the situation, and then chooses a behavior, such as passing another vehicle, staying in the lane, or parking," Currier explained. This "human-like" system makes Odin capable of choosing the best course out of millions of possible courses, he said.The team has outfitted Odin with four computers that perform specialized sensor processing and hardware interface tasks and two powerful servers that provide the primary computing power. Three laser scanners mounted on the vehicle's bumpers can scan a combined 360-degree field of view 12.5 times per second to detect obstacles. "These scanners are capable of detecting and tracking cars at a distance of up to 100 meters and are Odin's primary method of detecting other vehicles," Currier said.Four more laser scanners are mounted on Odin's roof rack -- two to detect small obstacles such as curbs and potholes and two to check the vehicle's blind spots when it changes lanes or merges into traffic.Two cameras mounted on the roof rack serve two purposes -- they enable Odin to sense its location and identify its proper position in the traffic lane, and can also positively determine if an obstacle detected by the scanners is another vehicle.Odin's GPS has been coupled with an inertial measurement unit and wheel speed sensors to measure movement in all directions. "This system provides Odin with accurate position, even if the GPS signal is temporarily lost," Currier said."Odin is now capable of driving on a marked road, following moving traffic, passing stopped vehicles, handling four-way intersections, and performing three-point turns," Currier said. The vehicle is being fine-tuned so that it can merge with moving traffic, pass moving vehicles, and park. Currier is one of 10 graduate students on the Virginia Tech team, which also has included as many as 50 undergraduates. The students are guided by four faculty advisers, three of them from Virginia Tech -- professor Alfred Wicks and assistant professor Dennis Hong of the College of Engineering's ME department, and geography department chair Bill Carstensen of the College of Natural Resources. The team's founding adviser, Charles Reinholtz, a former Virginia Tech Alumni Distinguished Professor of ME and engineering education and now the chair of ME at Embry-Riddle Aeronautical University in Florida, continues to work with VictorTango. In October 2006 VictorTango was one of only 11 "track A" teams chosen to receive $1 million contracts to develop autonomous vehicles capable of conducting simulated military supply missions in an urban setting. In all, 89 teams from universities and industry entered the competition in 2006. In addition to the $1 million from DARPA and the two Escapes from Ford, the Virginia Tech team received a $100,000 grant from Caterpillar and additional sponsorship from National Instruments and several other corporations. VictorTango qualified for the semi-finals during a site visit DARPA judges made to Virginia Tech earlier this year. The team's vehicle successfully demonstrated its fully autonomous capabilities, driving a road course and interacting with human-driven vehicles.DARPA is sponsoring the Urban Challenge as a more sophisticated follow-up to the two Grand Challenge competitions, which were held in 2004 and 2005 in the Mojave Desert. Virginia Tech competed in both of those contests, and the university's two entries placed eighth and ninth in 2005. "The Urban Challenge will be far more difficult to navigate than the open desert in the Grand Challenge," Currier said. "In the Grand Challenge, the vehicles followed a GPS 'bread crumb' trail and the obstacles they maneuvered around were static. In the Urban Challenge, vehicles must obey the rules of the road and avoid moving traffic."

Note: This story has been adapted from a news release issued by Virginia Tech.

Fausto Intilla

www.oloscience.com

Full-time Sensors Can Detect Bridge Defects

Source:

http://www.sciencedaily.com/releases/2007/08/070811213550.htm

Science Daily — Networks of small, permanently mounted sensors could soon check continuously for the formation of structural defects in I-beams and other critical structural supports of bridges and highway overpasses, giving structural engineers a better chance of heading off catastrophic failures.A Sandia National Laboratories team is developing and evaluating a family of such sensors for use on a variety of safety-critical structures.

Full-time monitoring sensors already have been tested and proven by Sandia for use on aircraft structures.Over time, the stresses on a bridge caused by traffic, weather, and construction can result in the formation of tiny cracks in the steel and concrete structures of bridges. Exposure to wind, rain, and other elements can cause corrosion that can become a structural concern as well. Like nerve endings in a human body, permanently mounted, or in-situ sensors offer levels of vigilance and sensitivity to problems that periodic checkups cannot, says Dennis Roach, who leads the Sandia team.Structural health monitoring (SHM) techniques, as they are called, are gaining acceptance in the commercial aviation sector as a reliable and inexpensive way to alert safety engineers to the first stages of defect formation and give them the earliest possible warning that maintenance is needed. With sensors continually checking for the first signs of wear and tear, engineers can detect cracks sooner, do the right maintenance at the right time, and possibly prevent massive failures, he says.Where flaws formSandia’s SHM work is an extension of its decades of research in non-destructive inspection (NDI) technologies currently used in manual inspections of commercial aircraft — to scan for small cracks in the airframe, for example. The SHM sensors being developed or evaluated at Sandia can find fatigue damage, hidden cracks, erosion, impact damage, and corrosion, among other defects commonly encountered in bridges.The Sandia team already has developed or evaluated several types of inexpensive, reliable sensors that could potentially be mounted on important infrastructure, typically where flaws are expected to form. “If I usually get fatigue damage in a particular area, that’s where I am going to install a sensor,” Roach says.One promising SHM sensor, a Comparative Vacuum Monitoring (CVM) sensor, is a thin, self-adhesive rubber patch, ranging from dime- to credit-card-sized, that detects cracks in the underlying material. The rubber is laser-etched with rows of tiny, interconnected channels or galleries, to which an air pressure is applied. Any propagating crack under the sensor breaches the galleries and the resulting change in pressure is monitored.The CVM sensors — manufactured by Structural Monitoring Systems, Inc. (SMS) — are inexpensive, reliable, durable, and easy to apply, says Roach. More important, they provide equal or better sensitivity than is achievable with conventional inspection methods and can be placed in difficult to access locations, he says.Some other sensors being considered include flexible eddy current arrays, piezoelectric transducers that can interrogate materials over long distances, embedded fiber optics, and conducting paint whose resistance changes when cracks form underneath.Smart structures possible“When we set out to do NDI, in the back of our minds we knew that eventually we wanted to create smart structures that ‘phone home’ when repairs are needed or when the remaining fatigue life drops below acceptable levels,” Roach says. “This is a huge step in the evolution of NDI.”“These sensors have been tested and shown to detect defects and fatigue in metal structures where safety is of utmost concern,” says Roger Hartman, manager of Sandia’s Infrastructure Assurance and NDI Department. By combining networks of sensors of various types with other advanced materials work Sandia has done, such as using composite materials to repair damage to a highway bridge or watching for the first signs of fatigue using computerized prognostics and health management algorithms, “you begin to evolve a system approach to making important infrastructure elements safer and more reliable,” Hartman says. Ultimately, a structural engineer might plug a laptop or diagnostic station into a central port on a bridge to download structural health data. Eventually “smart structures” fitted with many sensors and augmented with PHM algorithms could self-diagnose and signal engineers that repairs are needed or that they will be needed in a defined time downstream.Sandia already is investigating applying SHM to a variety of structures. In addition to bridges and aircraft, SHM techniques could be used to monitor the structural well-being of spacecraft, weapons, rail cars, oil recovery equipment, pipelines, buildings, armored vehicles, ships, wind turbines, nuclear power plants, and fuel tanks in hydrogen vehicles, Roach says. “There is widespread recognition that SHM’s time has come, an opinion you would not have heard from many people a few years ago,” he says.Sandia is a National Nuclear Security Administration laboratory.

Note: This story has been adapted from a news release issued by Sandia National Laboratories.

Fausto Intilla

www.oloscience.com