Saturday, April 12, 2008

Popular Mechnics Special Report on Rebuilding Aamerica


Popular Mechanics published a series of interesting articles on rebuilding America's Infrastructure.
Stories include:
5 Engineering Lessons From the New, Reopened Minnesota Bridge
Bridge's Sensors Scan Tragedy Before It Strikes
Green Tech Plans Hide Obama-McCain Disparity on Infrastructure
How to Fix American Infrastructure
4 Big Reasons the D.C. Area's New Super Bridge Took One of America's Top Engineering Honors
For Hard-Charging Innovators, Rebuilding America Means Making Deals With the Government 
10 Expert Solutions for a Smarter, Cleaner U.S. Electric Grid
10 Expert Solutions for a Better American Water Supply
New Minnesota Bridge’s Super Sensors Scan Tragedy Before It Strikes: First Look New Minnesota Bridge Is America's Smartest Yet
6 Questions for Intelligent Bridge Geek Jerome Lynch
Engineers Go Gonzo to Bombproof U.S. Bridges
Building the Earthquake-Proof Bay Bridge
10 Expert Solutions for Harder, Better, Faster and Stronger Buildings and Bridges
5 Questions for Geologist Jeff Mount on California’s Crumbling Delta Levees
Sacramento Delta Tops Experts List of 5 to Fix
The Lessons of Hurricane Katrina
6 Questions for Port of Los Angeles Chief Geraldine Knatz
5 Questions for Lillian C. Borrone on Boosting Efficiency in America's Ports
The 10 Pieces of U.S. Infrastructure We Must Fix Now
5 Disasters Coming Soon If We Don't Rebuild U.S. Infrastructure
Report Sees Dire Future for Warming's Impact on U.S. Transport
First Look: New Minnesota Bridge Plans Arise as Bad Plates Fingered in Collapse
Minn. Bridge Collapse Reveals Brittle America
Will Longest U.S. Underground Expressway See the Light?
SPECIAL REPORT: Highway of the Future
Mega Engineering: Building the World's Toughest, Strongest, Biggest Projects
Special Report: The Lessons of Hurricane Katrina
3 Ways to Re-Engineer the Gulf and Stop Katrina 2.0

Thursday, April 10, 2008

An SHM system for the new Minnesota Bridge


The St. Anthony Falls Bridge is already under the microscope as construction continues at breakneck speed to replace the collapsed I-35W bridge—and it’s already pushing new boundaries in intelligent design. But by turning the lens on itself, America’s smartest bridge could have an even bigger impact. 
A new high-tech structural health monitoring system equipped with 240 sensors should inform how we monitor other bridges and, eventually, determine how we build them. For all the details and an exclusive animation of the accelerometer-laden fiber-optic rig, we sat down with Figg Engineer Group CEO Linda Figg, who’s heading up St. Anthony Falls' design, before she appeared at the PM-NSF Bridge to the Future summit today. 
Some details of the sensing system have been ironed out, but most are being determined as the bridge goes up—much like its entire design and construction, which occurred almost simultaneously. The importance of the sensors, Figg insisted, is that all the information they collect will funnel into a database, eventually helping other engineers determine how best to design and build a bridge. 
To round up that data, the system—a collaboration between the University of Minnesota and the Minnesota Department of Transportation—will employ at least four different kinds of sensors: accelerometers (red), chloride penetration sensors (magenta), linear potentiometers (blue) and wire strain gauges (green). "The accelerometers will measure vertical deflections [or deformation] with traffic loads," Figg said. The chloride penetrating sensors will evaluate the condition of surface wear and tear by measuring whether or not salt is penetrating the pavement on the bridge deck. Repair and replacement are pricey, so early monitoring should make up for the initial cost of the sensors. 
Meanwhile, linear potentiometers will measure pressure to keep track of St. Anthony Falls’ expansion joints and bearings; Figg said UMinn and Mn/DOT would correlate that data with design codes to analyze how the bridge performs over its lifespan. Finally, the wire strain gauges will measure temperature as well as the amount of force per sq. in. placed on the concrete—all important in assessing a bridge's condition. 
The four sensors will be hardwired using fiber optics through the bridge, then wirelessly transmitted for analysis. They will account for about 100 of the sensors on the bridge; the University of Minnesota will outfit 140 more for research purposes. 
[Erin McCarthy via Popular Mechanics.com]

German Institute to Develop SHM

Several Fraunhofer institutes and various industrial partners are currently working on an SHM system that will use ultrasound to detect any damage to the technical structures of aircraft, pipelines or wind turbines. The core of the sensors used is made up of ceramic piezo fibers that convert mechanical energy into electrical impulses and vice-versa. Any piezo element can be used as either a transmitter or a receiver. It can excite the structure to produce vibrations, and it can record vibrations in the structure.
The ultrasound waves spread out in certain patterns depending on the type of structure. Cracks and other flaws alter this wave pattern in the same way as a rock changes the pattern of waves in a lake. Even a group of four piezo elements is sufficient to locate flaws accurately to the nearest centimeter – flaws that are often no more than a few millimeters in size.
“Our system is intended to supplement the checks used up to now,” says Bernhard Brunner of the Fraunhofer Institute for Silicate Research ISC, Würzburg. But that is only the first step. If the SHM systems prove successful, the researchers can envisage a status-dependent maintenance and repair system: “to save inspections and therefore time,” adds Brunner’s project partner Bernd Frankenstein of the Fraunhofer Institute for Non-Destructive Testing IZFP in Dresden. He is in no doubt that SHM systems will eventually replace conventional test methods, at least in part. The task of the Fraunhofer Institute for Structural Durability and System Reliability LBF is to create deliberate flaws in structures, which can then be detected during tests.
There are even more reasons for teaching structures to ‘feel’. It helps to make better use of valuable resources, both materials and energy. This is particularly noticeable in the aviation industry, where each gram less in the weight of the aircraft increases its potential payload as well as reducing exhaust fumes.
Continuous monitoring by SHM systems is also expected to yield greater safety, particularly for equipment such as offshore wind farms that are not readily accessible. The artificial nervous system fulfills a dual task in such cases: It monitors the structure and at the same time delivers data about occurrences in the structure during day-to-day operation. Data of this kind, which hardly existed until now, will help to optimize the next generations of components.
[Fraunhofer-Gesellschaft via physorg.com]

Monday, April 7, 2008

Scientists use an old bridge for new tests


Scientists at Britain's National Physical Laboratory say they have saved a 46-year-old foot bridge from demolition and will use it to develop new technology.
Scientists at the facility -- the national measurement standards laboratory for the United Kingdom -- said the 14-ton, 66-foot-long and 16-foot-high bridge had been used to allow access from one side of the NPL site to the other.
With redevelopment of the NPL site the bridge had become redundant. But rather than demolish the bridge, researchers will use it as a demonstrator to try different techniques for maximizing a structure's lifetime while minimizing maintenance costs.
During the three-year project the bridge will be loaded until it cracks, repaired using new composite repair methods and then retested.
NPL officials said the opportunity to have a large scale structure that can be abused while being monitored is a once-in-a-lifetime event and will provide evidence for the cost saving benefits of structural health monitoring.