SHM on Government Technology

An article on SHM of bridges appeared in "Government Technology "

http://www.govtech.com/gt/261440?topic=117693

Entitled "Wireless Sensors May Help Governments Monitor Health of Aging Infrastructure" it describes the consequences of the 35W bridge collapse and some of the technologies that might prevent similar accidents in the future.
In particular, the article introduces a wireless technology perfected at Clarkson University by the team of prof. Kerop Janoyan:

New York is one of many states re-evaluating bridge inspection methods after the Minneapolis bridge collapse by turning to SHM technologies. The state department of transportation's pilot program uses wireless sensors placed on bridges to transmit data on stress and vibration, and should warn if a bridge is weak or needs repairs. The system, designed by Clarkson University associate professor Kerop Janoyan, is expected to help engineers monitor the state's 17,000 bridges.
"Providing more information is the first step to a feedback system," Janoyan said. "Without information, you can't have any feedback when ultimately you're trying to control potential damage."
A New York bridge between Canton and Potsdam is serving as a test site - 40 wireless channel sensors affixed to the bridge log in real-time data to a base station. Each sensor is about the size of a few decks of playing cards, and cost about $200. The battery-powered sensors are connected to a computer that aggregates sensor data and determines whether to alert inspectors.

The article than describes the work of prof. Farhad Ansari at the University of Chicago on optical fiber sensors:
The Department of Civil and Materials Engineering at the University of Illinois at Chicago is developing a similar bridge monitoring approach, using fiber-optic wires instead of wireless sensors. A research program at the university called - Smart Sensors and NDT Laboratory - develops fiber-optic sensors for monitoring structures during construction and throughout their service lives.
The Illinois Department of Transportation awarded a $55,000 contract in September 2007 to the laboratory - to devise a system that can detect bridge scour - when sediment is washed from the bottom of the river and weakens a bridge's support. The project involves embedding a fiber-optic sensor in a rod and driving the rod into a river base near the piers.
Fiber-optic sensors assess a bridge's overall health by measuring microfractures and vibration frequency. Fiber optics promise many innovations for bridge monitoring since they are smaller and more flexible than electrical wires, are immune to interference from wireless devices, and aren't prone to fires or explosions, said Farhad Ansari, professor and head of the Civil Engineering and Materials Department at the University of Illinois at Chicago.

The article also describes projects at the University of Michigan on "sensing paint" at at Sandia National labs on remote sensing.

35W bridge collapse pictures

In this interesting document, it is possible to observe a large number of pictures of the 35W bridge that collapsed into the Mississippi river.

http://www.ntsb.gov/dockets/Highway/HWY07MH024/387406.pdf

In particular it is interesting to notice that some of the gusset plates appear to be buckled as early as 2003 and the fractured plate show signs of corrosion.

Other related documets and reports can be found here:

http://www.ntsb.gov/dockets/Highway/HWY07MH024/default.htm

SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring

I am currently at the
SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring conference in San Diego.

Several interesting trends emerged in this edition:

• The seems to be a growing interest in aerospace applications, SHM and smart structures for active control.


• The civil engineering and structural monitoring parts are attracting less presentations and little new work. Probably more specific conferences such as SHMII and IABMAS are becoming more relevant in this field.


• A lot of papers as usual on Fiber Optic sensing and a growing number on wireless sensing. This technology is maturing and appears now adapted for field use, but mostly limited to short- and medium-term applications.


• Besides the usual bridges, other structures were also monitored, including aircraft, oil platforms and buildings.

Norhwestern University pubblications

Here is a list of interesting papers and presentations on "Improved Condition Monitoring for Bridge Management / Non-Destructive Evaluation" published by the insfrastructure Technology Institute at northwestern University.

2nd Asia-Pacific Workshop on Structural Health Monitoring

Conference Announcement:

Organiser: Materials Australia
Location: Melbourne, Australia
Date: December 02-04, 2008

This is the second in a series of biennial Asia-Pacific workshops that focuses on the field of Structural Health Monitoring (SHM). This is a particularly promising area that has attracted significant attention in recent years for its wide potential of applications, particularly for civil infrastructures, and maritime and aircraft structures. The purpose of the workshop is to allow a forum where key and emerging technical issues that are critical and unique in structural health monitoring can be discussed and identified, as well as allow current state-of-the-art technologies and R&D activities in the field to be presented. The workshop is also intended to promote exchanges and cross-fertilisation among many disciplines.

The workshop shall focus on, but is not limited to, the following topics:

- Sensor and Actuator Development
- Reliability of Structural Health Monitoring Methodologies
- Bio-inspired sensors
- Damage Identification and Properties/ Integrity Characterisation and Assessment: Intelligent Processing of Materials and Structures
- System Integration
- Applications (particularly in the field of aircraft, automotive, rail and maritime structures, civil and petroleum infrastructure, textiles etc)
- Homeland Security

Website: http://www.materialsaustralia.com.au/SHM2008/

SHM for aeropase structures

In this article you will find an interesting overview about the future of SHM for aircrafts:

Future Inspection Technologies (from avitaion week)

Here are a few interesting quotes:

Posit for a moment the airplane of the future, a flying machine all but freed from scheduled inspections, able to keep flying because of sets of sophisticated sensors imbedded within it.
Behold, the monitored machine.
In perhaps a decade or so, a mechanic might do a walk around inspection, much as the first officer does at pre-flight, just before departure. But this walkaround would be far more probing. Armed with a wireless ultrasound device, "your technician walks past the airplane and a little chip beeps at him," envisions Michael Moles, senior technology manager for Olympus NDT. "He knows then and there whether there's a problem." This, contends the veteran NDT executive, "will tend to be the future," a future predicated not so much on periodic inspection, as on structural health monitoring.

The irreducible criteria regulators will consider whether the in-situ sensor "works as [well] or better than my current hand-held inspection technique," said Roach. That's step one, a step that conceivably could lead to what Roach and Rackow write terms, "Condition-based maintenance practices ... substituted for the current time-based maintenance approach." At the very least, the Sandia researchers contend in-situ sensors render it "possible to produce an aircraft prognostic health architecture that can assist in maintenance scheduling and tracking."

Bridge Inspection and Conditions Maps

MSMBC has created a nice tool to map the conditions and inspection record of all US bridges in the national inventory.

You can find it here.

Sustainable bridges

Sustainable bridges is a EU project which assesses the readiness of railway bridges to meet the demands of the 2020 scenario and provides the means for up-grading them if they fall short. The 2020 scenario requires increased capacities with heavier loads to be carried and bigger forces to be absorbed due to longer faster trains and mixed traffic. All type of bridges are being considered.

The project has been recently concluded. On their website http://www.sustainablebridges.net/ you can find several interesting presentations and reports.

Bridge moved to the lab

A Teddington-based Government laboratory has taken on its biggest sample for analysis to date, a 14-tonne bridge which is 20 metres long and five metres high.
Scientists at the National Physical Laboratory (NPL), in Hampton Road, are set to use the bridge, which has been used to allow access from one side of the NPL site to the other for the last 46 years, as a demonstrator to try out different techniques for monitoring structures and will see it loaded until it cracks, repaired using new composite repair methods and then retested.
It will be part of a three-year Government project to encourage UK industry and UK infrastructure to use monitoring to maximise the lifetime and minimise maintenance costs for civil engineering structures.
Prior to the commencement of testing the bridge had to be moved across the site away from the demolition zone by Burton Smith and Beck and Pollitzer which used a 250-tonne capacity crane that extended nearly 50 metres into the sky earlier this month.
A spokesperson said: "It was then trailered across the NPL site, with essential co-operation from LGC, taking an hour to travel the quarter mile on Sunday, January 6, squeezing around tight turns and under trees before being lifted above existing buildings to its final resting place. The opportunity to have a large scale structure that can be abused in this way whilst being monitored is a once in a lifetime event and will provide evidence for the cost saving benefits of structural health monitoring."

Source: richmondandtwickenhamtimes.co.uk

Preliminary results on 35W bridge collapse

A design error in the Minneapolis bridge that collapsed Aug. 1 prompted Minnesota officials to look at the original plans of 59 similar bridges.
The $500,000 re-evaluation follows Tuesday’s preliminary report blaming gusset plates that connect bridge beams for the Interstate 35W bridge collapse.
Bridges Minnesota officials gave priority status for the re-evaluation include U.S. 61 over Mississippi River at Hastings, U.S. 63 over Mississippi River at Red Wing and the Blatnik Bridge in Duluth. Bridges throughout the state will be examined.
State transportation officials said inspectors most likely will not have to physically examine most of the bridges, but consultants will re-evaluate their design to make sure they were properly designed. Bridges whose design is being examined were built anywhere from 1889 to 1987.
No problems were found in the 56 bridges similar to the one that collapsed, but State Bridge Engineer Dan Dorgan said problems such as occurred on the 35W bridge would not have been discovered during an inspection.
Chairman Mark Rosenker of the National Transportation Safety Board said in Washington that some 35W gusset plates were too thin for the 35W bridge; they were a half-inch thick instead of an inch like they should have been.
Dorgan said gusset plates generally are the strongest part of a bridge and inspectors don’t look at their thickness once a bridge is built. However, he said, had a re-evaluation like now is being done on the 56 bridges been done on the 35W structure, the problem would have been discovered.
The problem was in the bridge’s design, Rosenker said, and there is no evidence other bridges have the same problem.
“The design process led to a serious error,” Rosenker told a news conference. “The bridge inspections would not have identified the error in the design of the gusset plates.”
The NTSB will take several more months to complete its investigation.