Structural Health Monitoring of Streicker Bridge

Prof. Branko Glisic and his team have recently installed a SHM system on the Streicker Bridge at Princeton University.

The project involves instrumenting the bridge with various sensors, and to transform it into an on-site laboratory for various research and educational purposes. The main aims of the instrumentation are to face the following challenges related to SHM:

• Education gap. In spite of its importance, the culture on SHM is not yet widespread. It is often considered as an accessory activity that does not require specific skills and detailed planning, while the facts are rather the opposite.
• Real structural behavior data sets. The complete data sets collected over long-terms are needed to fully understand real structural behavior and its interaction with environment. The SHM was applied to various types of structures, but the results of monitoring are frequently only partially disclosed or incomplete, thus the knowledge basis is rather deficient.
• Change in strain patterns caused by unusual behaviors. The patterns of degradation in performance and damage in monitoring results are often “masked” by environmental influences (temperature, wind, humidity, etc.) and human-made actions (live load fluctuations) and consequently, cannot be reliably identified in controlled laboratory conditions. More real data with unusual behaviors are needed in order to develop reliable detection algorithms.
• Characterization of SHM contribution to sustainability of built environment. SHM has promising potential to contribute to the sustainability of built environment since it provides with objective information concerning the real structural performance, which can be used as an input to optimize maintenance, extend structure’s life, increase safety, decrease life-cycle costs, reduce the use of construction material, minimize adverse impact on society that may occur in case of structural deficiency, and help reducing greenhouse gas emissions.
• Besides addressing above listed challenges, the Streicker Bridge will be used for full scale testing of new SHM methods, and newly developed monitoring systems.

The SHM of Streicker Bridge is a long-term project and it will be realized in several phases. The initial phase consists of instrumentation of main span and south-east leg. The instrumentation of main span was completed on August 14, 2009 with two fiber-optic sensing technologies:

(1) Discrete Fiber Bragg-Grating (FBG) long-gage sensing technology (average strain and temperature measurements);

(2) Truly distributed sensing technology based on Brillouin Optical Time Domain Analysis (average strain and temperature measurements).

The sensors were embedded in concrete during the construction.

More information can be found on the project website.

[Prof Glisic, SHM Lab,Princeton University]

The Economist reports on Smart Bridges

The Economist reports about smart bridges and the SHM system that was installed by Roctest and SMARTEC on the I35W bidge in Minneapolis.

Here are some interesting parts:

When an eight-lane steel-truss-arch bridge across the Mississippi River in Minneapolis collapsed during the evening rush hour on August 1st 2007, 13 people were killed and 145 were injured. There had been no warning. The bridge was 40 years old but had a life expectancy of 50 years. The central span suddenly gave way after the gusset plates that connected the steel beams buckled and fractured, dropping the bridge into the river.

In the wake of the catastrophe, there were calls to harness technology to avoid similar mishaps. The St Anthony Falls bridge, which opened on September 18th 2008 and replaces the collapsed structure, should do just that. It has an embedded early-warning system made of hundreds of sensors. They include wire and fibre-optic strain and displacement gauges, accelerometers, potentiometers and corrosion sensors that have been built into the span to monitor it for structural weaknesses, such as corroded concrete and overly strained joints.

Some civil engineers are sceptical about whether such instrumentation is warranted. Emin Aktan, director of the Intelligent Infrastructure and Transport Safety Institute at Drexel University in Philadelphia, points out that although the sensors generate a huge amount of data, civil engineers simply do not know what happened in the weeks and days before a given bridge failed. It will take a couple of decades to arrive at a point when bridge operators can use such data intelligently.

The last part is quite pessimistic. While more research is certainly needed in the field of data analysis, there is a lot of useful information that can be obtained today from a monitoring system such as the one installed on the I35 Bridge.

[The Economist]

Call for papers: NDE/NDT for Highways and Bridges

NDE/NDT for Highways and Bridges: Structural Materials Technology (SMT) 2010

16–20 August 2010, New York LaGuardia Airport Marriott, New York, NY, USA

The conference promotes the exchange of information among national and international researchers, practitioners and infrastructure stakeholders on the application of nondestructive evaluation (NDE) and nondestructive testing (NDT) technologies for condition assessment of highway infrastructure. Contributions focused on field applications, case studies, technology implementation, applied research, and practical experience are invited to submit abstracts. Through technical presentations and exhibits, infrastructure stakeholders, transportation officials, researchers, consultants, and contractors will be exposed to the state-of-the-practice in NDE methods. In addition, participants will have opportunities to discuss urgent problems faced by civil infrastructure stakeholders and the potential solutions utilizing available and emerging NDE technologies.

Topics of interest for the conference include NDE technologies for bridge superstructures, substructure and decks, pavement NDE and structural health monitoring. Quality control/quality assurance (QC/QA) practices, bridge inspection methods and the integration of inspection findings in bridge evaluation and management programs are also of interest.

Suggested Topics Include:

• Condition assessments of existing highway infrastructure

• Implementation of NDE technologies

• Quality control (QC) and forensic investigation of in-service structures

• Quality assurance (QA) during construction

• Inspections at the fabrication yards

• Bridge inspection challenges faced by State DOT’s

• Structural health monitoring (SHM) and load rating

• Foundation integrity and unknown depth

• Pavement integrity evaluations

• Bridge cable inspection

• Underwater inspection technologies

• Scour evaluation

• Long-term bridge monitoring

• Innovative sensors for civil infrastructure

• Embeddable sensors

• Tunnel and culvert inspection

• Inspection and evaluation of fiber reinforced polymer (FRP) material and FRP structures

• Inspection of light poles and sign supports

• Quantification of bridge deterioration

• Training and certification of inspection personnel

Deadlines

Abstracts submission: 1 February 2010

Acceptance notification: 15 March 2010

Final paper submission: 14 May 2010

More information: http://www.asnt.org/events/conferences/smt10/smt10.htm

Tobin Memorial Bridge Monitoring

In the next 18 months, the Massachusetts Port Authority’s (Massport) Tobin Memorial Bridge will be the state’s first bridge to have a wireless high-tech structural health monitoring system (SHM) in place to monitor stresses and strains in a real-time environment. In an effort to learn more about the behavior of the Tobin Bridge, Massport brought in an engineering consulting firm at a total project cost not to exceed $1 million. The firm will conduct structural modeling and analysis of forces and strains on the Tobin Bridge using a 3-D computer engineering model. Fay, Spofford & Thorndike (FST), located in Burlington, Mass., was chosen based on their overall qualifications and innovative approach. The firm’s knowledge base also is strengthened through an academic partnership with experts in the fields of structural engineering and computer analysis from Tufts University and the University of New Hampshire. A fourth member of the team, Geocomp of Boxborough, Mass., brings to the job worldwide expertise in placement and application of instrumentation. As a starting point, FST is working on the 3-D modeling, verification of results and recommendations for sensor and monitor placement on the Little Mystic truss and a six-span girder plate module on the Boston approach. These portions of the bridge were selected for their relatively simplified geometry in relation to the toll plaza and Big Mystic truss areas. A second phase for the Big Mystic truss also is under way. Further verification of the 3-D model results will be obtained by test loading of the Tobin Bridge once the sensors and monitors are installed. The test loading will consist of positioning fully loaded trucks along the bridge and recording the results. The test must be conducted when no other vehicle loading is on the portion of the span that is being tested. This will require that both decks of the Tobin Bridge be closed to traffic for a short period of time. The results of the test loading will help Massport engineers verify that the 3-D models are correctly predicting forces within the Tobin Bridge’s members and components. Once the verification process is complete, the models can then reliably be used to identify critical information points for sensor and monitor placement. These areas will include locations where elevated stress levels or unexpected deflections have been observed. At this writing, the initial 3-D models of the Tobin Bridge are still in development. Therefore, all key locations for sensor and monitor placement have not yet been finalized along with total project cost. [Roads and Bridges]

Dr. Bridge a new TV series on SHM

After the planetary success of Dr. House, another Princeton’s doctor is about to become the hero of a new TV series: Dr. Bridge.

BRIDGE, an innovative take on the structural drama, solves mysteries where the villain is a ill bridge and the hero is an irreverent, controversial doctor who trusts no one, least of all his patients.

Details on the new TV series can be found here.

U.S. Panel on Structural Control and Monitoring

An interesting intitiavie on SHM has an updated website.

The charter of the U.S. Panel on Structural Control and Monitoring is to accelerate the advancement of the science and practice of structural control and monitoring, by means of education, research and application of knowledge. This includes the response of large-scale structures to earthquakes, wind and man-made forces.  The U.S. Panel promotes and organizes activities including workshops, conferences and educational initiatives with the aim of fostering close collaboration between the academic and industrial communities.  In particular, the U.S. Panel has a proud tradition of assisting in the planning and execution of the International Workshop on Structural Control and Monitoring and the World Conference on Structural Control and Monitoring.

The website ca be found here: http://shm.engin.umich.edu/USPanel/index.html 

The Executive committe is chaired by prof. Shirley Dyke (Washington University) and prof. Jerome Lynch (University of Michigan, secretary). 

It contains useful information about SHM , conferences and test reports.

Using wireless sensors to monitor bridge safety

University of Texas (UT) professor, Dean Neikirk, will be field-testing a new bridge monitoring system within the year. The project is a collaboration between industry, government, and academia that will provide real-time monitoring of dangerous bridges and reduce inspection costs for all bridges.

"Most bridges have already been built," says Neikirk. "Our project will develop simple, low-cost equipment that can be used to retrofit existing construction as well as in new construction, but we are primarily concerned with ensuring that bridges do not fail without warning. Most aging bridges do not necessarily require replacement, they just need to be monitored for signs of corrosion and wear."

Neikirk and principal investigator and UT Civil, Architectural, and Environmental Engineering Chair Sharon L. Wood are developing a network of low-power wireless sensors capable of capturing and transmitting data to a central location. They already have working sensors, a data collection methodology, and specifications for sensor placement. Researchers are working on (1) powering sensors with solar, wind, or traffic vibrations instead of batteries, (2) ensuring the sensor output is compatible with National Instruments (NI) equipment that will be collecting the data and that NI equipment is rugged enough for outdoor use, and (3) preventing the steel structures from interfering with the radio signals used to transmit data.

[University of Texas at Austin]

SAMCO Library of documents

The thematic network SAMCO (Structural Assessment, Monitoring and Control) has become a focal point of reference for industries (especially for small and medium sized enterprises), consultants and other organisations interested in the transfer of knowledge and technology in the field of assessment, monitoring and control of structures of relevant civil and industrial interest, in particular the transportation infrastructure. The activities of the network are mostly related to bridges, buildings, power plants and industries under seismic and other environmental loads. The knowledge and technology transfer supports the research community but also brings benefit to owners of structures, consultants, suppliers and end users.

SAMCO has an interesting library of documents that cover different aspects of Structural Health Monitoring and Bridge Management, in particular:

• Monitoring Glossary
  
• Ambient Vibration Monitoring
  
• Guidelines for Structural Control 
  

Smart bridges Research Project

Engineering smart bridges that can thoroughly discuss their health with inspectors is the goal of a new $19-million project led by the University of Michigan.

A year and a half after the I-35 bridge collapse in Minneapolis, the five-year project aims to create the ultimate infrastructure monitoring system and install it on several test bridges whose precise locations are not yet determined.

The monitoring system is envisioned to include several different types of surface and penetrating sensors to detect cracks, corrosion and other signs of weakness. The system would also measure the effects of heavy trucks on bridges, which is currently impossible. And through enhanced antennas and the Internet, the system would wirelessly relay the information it gathers to an inspector on site or in an office miles away.

Funded in large part by nearly $9 million from the National Institute of Standards and Technology's (NIST) Technology Innovation Program (TIP), the project involves 14 U-M researchers with the College of Engineering and the U-M Transportation Research Institute (UMTRI). In addition, engineers at five private firms in New York, California and Michigan are key team members. The remaining funding comes from cost-sharing among the entities involved and the Michigan Department of Transportation. MDOT has offered unfettered access to state bridges to serve as high-visibility test-beds showcasing the project technology.

"This project will accelerate the field of structural health monitoring and ultimately improve the safety of the nation's aging bridges and other infrastructures," said Jerome Lynch, principal investigator on the project and assistant professor in the Department of Civil and Environmental Engineering. "We want to develop new technologies to create a two-way conduit of information between the bridge official and the bridge. We are excited to collaborate on these transformative technologies with partners like MDOT who could use them immediately to improve bridge inspection processes."

Four types of sensors will contribute to gathering data. Victor Li, E. Benjamin Wylie Collegiate Professor of Civil and Environmental engineering, has developed a high-performance, fiber-reinforced, bendable concrete that's more durable than traditional concrete and also conducts electricity. Researchers would measure changes in conductivity, which would signal weaknesses in the bridge. On test bridges, the deck would be replaced with this concrete.

A carbon nanotube-based "sensing skin" that Lynch and a colleague in chemical engineering are developing would be glued or painted on to "hot spots" to detect cracks and corrosion invisible to the human eye. The skin's perimeter is lined with electrodes that run a current over the skin to read what's happening underneath based on changes in the electrical resistance.

Low-power, low-cost wireless nodes could look for classical damage responses like strain and changes in vibration. These nodes would harvest energy from vibrations on the bridge or even radio waves in the air. They are being developed by Dennis Sylvester, an associate professor in the Department of Electrical Engineering and Computer Science; and Khalil Najafi, Schlumberger Professor of Engineering, Arthur F. Thurnau Professor and chair of the Electrical and Computer Engineering division.

The fourth type of sensor would be housed in the vehicles that travel on the bridge. UMTRI researchers will outfit a test vehicle to measure the bridge's reaction to the strain the vehicle imposes. This information is not available today. But how vehicles, especially trucks, affect bridges is a critical piece of information that could help predict the structure's lifetime. Leading this effort is Research Professor Tim Gordon, head of UMTRI's Engineering Research Division.

[University of Michigan]

Wireless Monitoring of Highway Bridges

The nation's aging highway bridges could become safer structures using state-of-the-art wireless monitoring and inspection systems being developed through a multi-million-dollar grant to an engineering team from The University of Texas at Austin, National Instruments and Wiss, Janney, Elstner Associates, an engineering firm based in Northbrook, Ill.

The National Institute of Standards and Technology recently awarded the research team $3.4 million to develop the bridge monitoring systems. Including matching funds, the budget for the five-year research project doubles to about $6.8 million.

Civil, electrical and mechanical engineers from the Cockrell School of Engineering will work with engineers from the collaborating companies to develop two wireless monitoring systems. The work will draw on strengths in structural engineering and innovation in the school where faculty have an international reputation for successful large-scale laboratory testing and field monitoring of bridges.

The United States has about 600,000 highway bridges. Twenty-five percent were rated as structurally deficient or functionally obsolete in 2007, according to the Federal Highway Administration. About one-third of all bridges are 50 years or older.

Sharon L. Wood, the principal investigator and the chair of the Department of Civil, Architectural and Environmental Engineering, said the award will allow for the development of two wireless network systems that together will address a critical issue for bridge safety—the monitoring of cracks or defects and corrosion in key structural components.

"This project will not only transform the evaluation practices used for highway bridges today, but will dramatically advance the state of the art in wireless sensing technology," Wood said.

The group will first develop a system for existing bridges consisting of a network of low-power, wireless sensors designed to continuously monitor bridges deemed fracture-critical—those susceptible to collapse from the failure of a single critical component. The sensor nodes will harvest their own energy via solar or wind energy or vibrations in the bridge structure, Wood said, freeing them from the electric power grid. The nodes will be capable of supporting multiple sensors and will have sufficient computing power to process raw sensor data, detect events, and send notifications to a central, off-site location when a level of damage occurs.

"What we'll be doing is real-time monitoring of the bridge," Wood said.

The researchers will develop a second system to embed in new bridges as they are built. This system will consist of passive sensors designed to detect early signs of corrosion—the most common type of damage which cannot be seen by visual inspection—in reinforced concrete bridge decks. The sensors can be read using a wireless connection during regular bridge inspections. These robust sensors are inexpensive to produce, require no power source other than the wireless signal, can easily be dispersed throughout the entire structure during construction and will function for the lifetime of the bridge.

[University of Texas at Austin]

Weigh-In-Motion system for Stonecutters Bridge

International Road Dynamics Inc said it was awarded a contract by Lucky Engineering Co. Ltd. in Hong Kong to supply and install a Weigh-In-Motion system for Bridge Monitoring/Protection on the Stonecutters Bridge in Hong Kong. 

IRD's total contract value is approximately C$806 thousand. The bridge construction and Weigh-in-Motion installation are to be completed by the end of June 2009. 

SHM Shows Savings Potential in Excess of 30%

LifeSpan Technologies, announces the availability of its second White Paper that describes a simple four step process, allowing repair and replacement bridge projects to be based on risk priorities and precise engineering data.

If Congress were to implement this proposed process, bridge cost savings at the federal and the state level could be in excess of thirty percent. Federally mandated visual inspection techniques have been used on bridges for over 35 years. The Federal Highway Administration acknowledges that the visual process produces results that are subjective, highly variable and not sufficiently reliable for optimal long-term bridge management. Because of the inherent variability, allowing visual inspection assessments to control bridge repair and replacement projects can lead to significant unnecessary expense.

"Our proposed process, calling for the use of proven condition assessment technologies, can easily provide billions of dollars in savings," commented Peter Vanderzee, CEO of LifeSpan Technologies. "In this era of severely limited federal and state funding, we are convinced that every bridge classified as structurally deficient, or that has a sufficiency rating less than fifty (the threshold for replacement), should have a technically appropriate advanced condition assessment solution deployed prior to repair or replacement funding authorization."

Adopting advanced condition assessment technologies is the most effective means for DOTs, railroads, toll roads, counties, cities and other bridge owners to gather the crucial information on structurally deficient bridges to more accurately diagnose deficiencies, define safe operating parameters, and objectively plan/prioritize repair projects. Advanced bridge monitoring systems can help keep the traveling public safe and provide information which can be used to optimize long-term bridge management.

The White Paper can be ordered by emailing whitepaper@lifespantechnologies.com 

[Insurance News Net]

Sensors Deliver Real-Time Info on New Minnesota Bridge

Using a complex array of more than 300 sensors, engineers say they can now remotely monitor the structural health of the new I-35W bridge in Minneapolis. The concrete bridge, which replaces the steel spans of the old bridge that collapsed and killed 13 people in 2007, incorporates sensors in the foundation elements, sub-structure columns, main span, box girders, expansion joints, bridge deck and bearings. The bridge's engineers, Figg Engineering Group, Inc., say they outfitted the new structure with the sensor system because they wanted to monitor its "health" and because they wanted to participate in advanced engineering research on the new structure with the University of Minnesota's Institute of Technology.

"It's unusual to do this on a new bridge, even today," says Alan Phipps, design manager for the I-35W project at Figg Engineering. "Structural health monitoring systems are typically applied to older structures." Figg outfitted the new bridge with at least six different types of sensors. In all, the company embedded 323 sensors, including: vibrating wire strain gauges in the concrete; temperature sensors on the top of the bridge deck and on the underside of the bridge; accelerometers to measure forces near the center of each box girder span; long-gauge strain gages in the main span; linear potentiometers to monitor movement of the expansion joints and bearings and embedded corrosion sensors to monitor corrosion to the reinforcing bars at various depths of the concrete.

"Minnesota uses a lot of salt, so the top 2.5 inches of the wearing surface is intended to be replaceable," Phipps says. "It's like the shingles on your house; eventually you have to put a new roof on.". Figg worked with sub-contractors to outfit the bridge with the sensors. Roctest Telemac provided wire strain gauges, temperature sensors and corrosion sensors. Accelerometers came from Minnesota Measurement Engineering.

Engineers can monitor the strains in the bridge in real-time over the Internet. All 323 of the sensors are connected by wire to a central computer, which collects data and stores it. The sensors made their debut recently when the Department of Transportation placed eight 25-ton trucks in various patterns atop the bridge deck and then monitored strains on the central computer. University of Minnesota engineering professors are said to be interested in examining the effect of temperature differentials between the top of the bridge – which can be exposed to sunlight – and the structure's underside, which is in the shade and faces down at the river below.

"This is just a way of starting off on the right foot with this new bridge," Phipps said. "It provides information on how to maintain the bridge, starting with Day One. We think this kind of structural health monitoring is going to become more and more common in the future."

[Design News]

SHM Research at University of Michigan

Professor Jerry Lynch, in his lab at the University of Michigan Laboratory for Intelligent Structural Technology in Ann Arbor, holds up a sensor that can help detect damage to a bridge before it becomes visible.

"We're aware that bridges are really difficult to maintain over their life, and we're sensitive to that," said Jerry Lynch, U-M professor of engineering and author of a paper on the research.

"But what we'd like to do is give (inspectors) a way to monitor those structures in a better way."

Lynch helped develop a structural coating, made of carbon nanotubes, that uses electrical currents to find damage like strain and corrosion. The idea behind the coating technology is to avoid catastrophes like the August 2007 collapse of the I-35 bridge in Minneapolis, Minn., that killed 13 people. The recent one-year anniversary of the collapse has again drawn attention to bridge safety and monitoring techniques. Faulty design is being investigated as the cause.

"These sorts of failures are very intimidating psychologically. It sort of violates that notion of terra firma," Lynch said. " ... Bridges are not supposed to fail." The breakthrough sensing skin is made of layers of the nanotubes mixed with polymers, and is sprayed as a permanent coating on the structure. A carbon nanotube is microscopic and shaped like a long, hollow strand of spaghetti, said U-M engineering professor Nicholas Kotov, a key developer of the technology. 

It's one of the strongest materials available and, when mixed with the polymers, lends that strength to the coating. When technicians flow electricity through the skin, it produces a two-dimensional image via a central computing device. Electrical resistance shown in the image will indicate structural damage. The hundreds of micro-layers in the coating allow it to sense structural strain, corrosion, pH levels and other indicators of damage. The technology is the first to provide comprehensive data on the entire structure, Lynch said. In traditional bridge monitoring, engineers use data from points of concern, like the structure's joints, to calculate data for the entire bridge. The coating costs about $1 per square inch and is engineered to last decades, Kotov said. "Presumably the carbon nanotube coating won't corrode over the lifetime of the bridge," he said. The sensing skin is set to be tested in Korea or Taiwan next summer. Several Asian countries - particularly those in high seismic areas - are interested in the technology. The technology also is important to U.S. bridges, which are aging. In two or three years, the coating could be ready for commercial use.

In the meantime, Lynch has helped create wireless sensing devices to send bridge monitoring data more cheaply. One of his devices, although only a few inches in diameter, costs $100-$200. Data-sending cables could cost more than $1,000 a piece.

The wireless device, called the Narada wireless sensor, is already installed on 15 bridges worldwide, on a U.S. naval ship and on wind turbines in Germany.

Lynch said he hopes to be able to combine the sensing skin and wireless technologies "for use somewhere down the line." It's important to monitor the country's bridges to prevent disasters like the Minneapolis bridge collapse, Lynch said. And because most bridges fail slowly instead of without warning, sophisticated monitoring techniques are vital. "I think it's critically important, there's no doubt about it," Lynch said. "There's room for improvement when it comes to monitoring bridges. ... it's like medicine. There are always challenges out there."

[Ann Arbor News]

Clarkson University’s Sazonov Performs Bridge Experiments In Malaysia

Edward Sazonov, assistant professor of electrical and computer engineering at Clarkson University, recently collaborated with faculty from the National University of Malaysia (Universiti Kebangsaan Malaysia, UKM) to perform bridge experiments on location in Malasia. UKM sponsored Sazonov’s visit, which focused on wireless bridge monitoring technologies that he has developed at Clarkson with substantial funding from the New York State Energy Research and Development Authority (NYSERDA).

The task of structural health monitoring of highway bridges and overpasses has gained significant attention in recent years. Monitoring the health status of bridges is not only a matter of preventing economic losses from traffic delays and detours, but also an issue of preventing catastrophic failures and loss of human life as occurred in Minneapolis just a year ago. Unfortunately, this has become a worldwide problem as many countries recently have realized a significant increase in the number of aging bridges constructed 50 years ago and more.

Sazonov’s group has developed a wireless system, which provides utility similar to a conventional wired system, but does not need wires. The wireless sensors are capable of time-synchronous data acquisition and 100 percent data delivery in a scalable system that can include hundreds of distributed sensors. Sazonov’s research shows that synchronization on the level of microseconds is required for vibration analysis of highway structures. Sazonov’s system satisfies such stringent requirements and can serve as a platform for applications of structural health monitoring that use vibration.

The experiments in Malaysia followed earlier experiments in New York State in which 44 wireless sensors were deployed on a steel girder bridge. The goal of the joint experiments with UKM was to test the system’s applicability to different construction technologies and different environments. In the experiment, the sensor network was installed on a pre-stressed concrete bridge. Then, the vibration response of the structure, due to passing traffic, was analyzed to provide information useful for damage detection.

The results of the experiments demonstrated that the system can be deployed successfully on structures constructed using different technologies. This was good news to Muhammad Fauzi Mohd Zain, who is deputy dean and co-director, Advanced Engineering Centre, Faculty of Engineering at UKM and Sazonov’s Malasian host. "In Malaysia, commonly we use visual inspection routinely to detect small cracks or defects. It is like finding a needle in a haystack and impossible in areas that are inaccessible or hard to access," said Zain. "Gradually such constraints are being overcome with emerging new technologies... for vibration based monitoring of structures."

[Clarkson University]

Bridges on I-80 monitored for stress, strain during move

Sensors that dotted and crisscrossed the seven bridges that were lifted, driven, launched and lowered into place along I-80 have told officials in charge of the project that the structures responded as they were designed to.

In past bridge projects around the nation, prefabricated decks haven't been lifted and transported to the extent the replacements along I-80 were, so monitoring the integrity of the structures was important, Utah Department of Transportation officials said.

"We had real-time data during the moves that let us monitor the stress and strain on the girders and the bridge deck," said Shana Lindsey, director of research and bridge operation for UDOT. "The sensors allowed us to see if we went beyond the tolerance levels of the materials, and we didn't."

As each bridge moved from the farm to its final location, 28 long-strand fiber optic sensors sent out more than 100 readings per second on the state of the structure. In real-time, a crew of engineers and specialists analyzed the data on-site to gauge the strain on points of stress for each portion of the transport. The readings alerted the observers to potholes or bumps in the route, telling them how the bridge responded.

"If you can pick up the movement of a structure while they're still in their embryonic stages, you can prevent repairs and problems before they happen," said Tom Winant, vice president of technical sales and marketing for Osmos USA.

The bridges were designed to allow for up to three to four inches of deflection on either end and still be able to return to their original state, Lindsey said. According to the sensors and the analysis of engineers, the bridges did not deflect to those levels, but some hairline cracks did appear on the structures.

The cracks were expected, though, because it is concrete's nature to crack even without being transported, Lindsey said. To prevent salt and water from entering into the cracked areas, UDOT has scheduled a polymer overlay to coatthe structures to protect them from early erosion or deterioration.

Lindsey said the massive amount of data compiled from each move will help UDOT refine its techniques and designs for future projects.

The results from the move verified the assumptions designers made when they began fabricating the bridges and planned the launch, said Roy A. Imbsen, an engineer and consultant to the project. With the data, Imbsen said UDOT would be able to implement specifications to the accelerated bridge construction process so other agencies could begin to use it, too.

[Desert News]

New Minnesota laws on Bridge Inspection

Four DFL lawmakers stood before the press and proposed a 10-point package of bridge safety reforms that they say is a first step toward a bill they will introduce during next year’s legislative session.

The package has been in the works for weeks, and is in direct response to reports and recommendations contained in two independent studies on bridge safety that have been concluded in response to the I-35 bridge collapse last August — by the Office of the Legislative Auditor in February and the law firm of Gray Plant Mooty in May. But the harrowing incident over the weekend — in which a six-foot-by-nine-foot slab of concrete tore away from the underside of Maryland Avenue and fell into Highway 35E, damaging two vehicles and snarling traffic for eight hours — added urgency and gravitas to the legislators’ recommendations.

Among the more prominent recommendations set forth on Monday was the necessity for bridges to be inspected at least every 12 months, and the setting and followup of specific performance targets at MnDOT, including the stipulation that an analysis be done by the agency whenever any of their goals or forecasts aren’t met. The package also recommends that the state salary cap be lifted for MnDOT engineers in order to assist with recruitment and retain quality personnel, and that either the commissioner or deputy commissioner of MnDOT be a professional engineer.

Read more here. [minnesotaindependent.com]

US Sweeping bridge safety bill includes fiber optic

U.S. Rep. Steven C. LaTourette (R-Bainbridge Township) today announced that a sweeping bridge safety bill approved by the House includes a study of fiber optic sensors like those developed by companies with offices in Twinsburg and Mentor that can detect stresses on bridges before they collapse or fail.

The House of Representatives today approved H.R. 3999, the Highway Bridge Reconstruction and Inspection Act, by a vote of 367-55. LaTourette said the measure authorizes $2 billion over two years for bridge reconstruction nationwide and requires the Federal Highway Administration (FHWA) to update national bridge inspection standards. It also calls on the FHWA to improve training for highway bridge inspectors. The bill was introduced after the August 2007 bridge collapse in Minneapolis that killed 13 people.

LaTourette said the bill includes language he supported that will authorize the FHWA to study the effectiveness of fiber optic sensors and other sensors in detecting deficiencies in bridges, particularly those under construction or renovation. LaTourette said he believes fiber optic sensors marketed by companies in Twinsburg and Mentor might have detected extreme stresses on the 35W Bridge in Minneapolis before it collapsed. It was loaded with heavy equipment and traffic had been shifted to accommodate construction, he said.

LaTourette said two 14th District companies are marketing cutting edge products that might have been able to avert the tragedy in Minneapolis. Cleveland Electric Laboratories Co. in

Twinsburg is marketing fiber-optic sensors that are attached to bridges to detect and monitor stress loads, and its product is being used on a project in Albany, NY. Roctest Ltd. of Quebec, which has its U.S. office in Mentor, is also marketing a fiber optic sensor system to detect stresses on bridges, and it will be used as the 35W Bridge in Minneapolis is rebuilt.

“We’re lucky that inspectors almost always catch problems and avert tragedies, but there are situations where unusual stresses on a bridge can lead to catastrophe. I think this technology

certainly merits more study so we never experience another disaster like the one in Minneapolis. It’s exciting to have two Northeast Ohio companies right in the mix,” LaTourette said.

LaTourette said construction can place unusual stresses on a bridge, and the small fiber optic sensors can monitor and record the level of stress.

“Who hasn’t been on a bridge where all the traffic is shifted to one side while the other is filled with workers and heavy equipment?” LaTourette said. “If a tiny sensor can detect when stress becomes so great that it makes a bridge susceptible to collapse, that’s a tremendous safety benefit not only for motorists but the workers renovating the bridge.”

[latourette.house.gov]

Roctest Introduces New SensCore System

Roctest Ltd. announced the introduction of the new SensCore product line, dedicated to the monitoring of corrosion in reinforced concrete structures. The SensCore system is a wireless sensor network, designed to detect and predict the onset of steel corrosion in concrete. The system consists of sensors, dataloggers and a measurement hub that concentrates the data from several dataloggers and transmits it to a central database, where it can be accessed by the authorized users. The sensors are able to measure several parameters, which are critical to evaluate the present and future risk of rebar corrosion in concrete. In particular the corrosion current and the concrete humidity are measured at several depths between the concrete surface and the rebar depth, to analyze the progression of the corrosion front as well as evaluate the performance of hydrophobic coatings.

The sensors are extremely simple to deploy and can transmit their data wirelessly to the measurement hub, thus eliminating the need to install any wiring in the structure to be monitored. Because of its modular design, this system is adapted to structures of all sizes, from a small overpass to a long tunnel and can be installed in both new and existing structures. The SensCore system integrates seamlessly with all present Roctest, Télémac and SMARTEC product lines, based on electrical, vibrating wire or fiber optics technologies. It is therefore possible to combine several technologies in order to implement an optimal monitoring network for any type of structure, being it a bridge, a building, a tunnel, a dam or any other concrete structure. The SensCore System ties into Roctest’s SDB database system, providing a unified

display and interface to all monitoring data, regardless of the underlying sensing technologies.

The SensCore system has been developed in cooperation with a leading Swiss University and has already being deployed on tens of structures, including the I35 St. Antony Falls Bridge in Minneapolis recently instrumented by Roctest. “Corrosion is one of the leading concerns in reinforced concrete structures and often limits their durability” said Daniele Inaudi, Roctest’s CTO, “it is therefore advantageous to complement the current monitoring strategies with a direct measurement of the corrosion progression”.

“The SensCore system ideally expands our growing toolbox of sensing systems” added François Cordeau, Roctest’s CEO, “further positioning our Company as the leading provider of Structural Health Monitoring solutions”.

Roctest Press Release [Roctest]

Bridge Doctors Podcast

Structural engineer Michael Todd describes the state of bridge monitoring around the world in this podcast. Interview by Rima Chaddha. Edited by David Levin. 

[NOVA]