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NDT.net Issue - 2007-09 - NEWS
NDT.net Issue: 2007-09
Publication: e-Journal of Nondestructive Testing (NDT) ISSN 1435-4934 (NDT.net Journal)

On-Line Bridge Monitoring: A Sound Based Sensor Fusion Technology for Preventing Failures

MISTRAS Products & Systems72, Princeton Junction, NJ, USA

August 2007 - Princeton, NJ – Physical Acoustics Corporation (PAC), a member of MISTRAS Group Inc., specializing in Nondestructive Testing (NDT) and Inspection, has developed digital wireless sensor technology that assists Bridge Operators in preventing bridge failures. Rising demand for ensuring the integrity and performance of our nation’s aging bridges and infrastructure may sometimes require more than typical visual inspection for evaluation of their structural conditions by using advanced inspection technologies. The additional information from NDT can provide input to authorities and assist in making informed and effective decisions with regards to planning for maintenance, repair, rehabilitation or replacement. While there are several factors that can lead to degradation and deterioration of a bridge, increased traffic on our nation’s bridges, coupled with corrosive environments, are the leading causes of deterioration for steel bridges. For concrete bridges, corrosion of reinforcement due to chloride ingress, vehicle impact, concrete cracking and fatigue are the major factors of degradation. On-line monitoring and sensor fusion can cover all possible failure mechanisms including unpredictable deterioration.

Remote AE Sensor
Since 1972, PAC has applied sound technology, called Acoustic Emission (AE), for “global” bridge monitoring while other sensors, such as vibration accelerometers, strain gages, corrosion gages, etc., are used by our staff and bridge engineers to assess the possible mechanism of failures and predict bridge life. AE testing is a technique used to detect “warning signals” forecasting defect formation and impeding failures in structural materials. Cracks can be heard from remote distances by using AE sensors similar to using geophones for earthquake detection and location or sonar devices to detect enemy submarines. Commonly used visual inspection to detect small cracks/defects, is like finding a needle in a haystack and impossible in areas that are inaccessible or hard to access.

Technicians Installing Sensors
Per the NY Times, “warning sounds were heard for months by neighbors prior to the I-95 CT bridge collapse 15 years ago” reports Dr. Sotirios J. Vahaviolos, Founder and Chairman/CEO of PAC and MISTRAS Group Inc. The airport manager at Charles De Gaulle airport reported to CNN that they also heard warning sounds a couple of years prior to the collapse of a terminal. In both these instances, PAC’s systems could have differentiated “crack sounds” from other normal daily sounds in a bridge structure including heavy rain. Since the early 1990’s bridge monitoring using AE has been investigated by the Federal Highway Administration (FHWA) that continues to fund development, testing and demonstrations on the use of AE for bridge inspection and monitoring. PAC has been awarded several FHWA contracts since the late 1980’s and has successfully monitored over 20 bridges. “It is only because of State DOT’s and government funding that has prevented wide scale deployment of on-line monitoring using sensor fusion and wireless technologies on bridges” states Dr. Vahaviolos. More recently, FHWA selected

PAC’s Sensor Highway II™ System for awarding and participation under the Steel Bridge Testing Program.

“AE can also be used by Homeland Security for prevention of vandalism” states PAC’s National Sales & Applications Director, Terry Tamutus. Recently youths with hacksaws cut dozens of wires from four main cables on a cable stay bridge. “It caused more than $2MM in repairs and a possible catastrophic bridge failure. An on-line AE system could have easily detected the start of a cable cutting and could have alerted authorities through wireless or internet based communication technology” states Tamutus.

“We have the technology for Bridge Health Monitoring now and are ready to team up with Bridge Operators in order to prevent catastrophic failures from naturally occurring structural flaws that are the result of an aging infrastructure” concludes Dr. Vahaviolos.

MISTRAS Group Inc. provides Nondestructive testing products and services under the well known brand names of CONAM Inspection and Engineering Services Inc., Physical Acoustics Corporation, Code Services, Quality Services Laboratories Inc., Caliber Inspection, PRI, NDT Automation, and Vibra-Metrics. MISTRAS Group provides Mechanical Asset Inspection and Integrity Solutions to the Energy, Aerospace, Manufacturing and Gas & Oil Sectors as well as strategic on-line instrumentation that facilitates Plant Asset Management decisions. In addition, MISTRAS is the leading provider of Enterprise Solution Software that aids in the safe and profitable operation of industrial facilities worldwide.

For more information, please visit the company’s website at www.mistrasgroup.com or contact the main office at 609-716-4000.

Keywords: Acoustic Emission (AE) (1358), civil engineering (1026), bridge (115), in-situ (133), instrumentation (454), structural health monitoring (SHM) (220),
*Keywords are freely formed keywords from the authors and thus you may Search also for similar terms.  

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