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Sensors power next-generation Structural Health Monitoring in civil engineering applications

Friday, February 21st, 2014

Sherborne Sensors’ Mike Baker (guest writer) examines how field-proven sensor technology lies at the heart of Structural Health Monitoring (SHM) innovation.

Structural Health Monitoring (SHM) is an emerging field that provides information on demand about any significant change or damage occurring in a structure. It has been employed for many years in civil infrastructure in various forms, ranging from visual observation and assessment of structural condition, to technology-led approaches involving deployment of an array of sensors that can include accelerometers, inclinometers and strain measurement devices on site.  These sensors can be deployed on a permanent basis or moved on and off site each time a fresh set of data is required.

Conventional forms of inspection and monitoring are only as good as their ability to uncover potential issues in a timely manner. One of the major difficulties with SHM instruments for example, is managing the huge volumes of data that sensor arrays generate. Meanwhile, visual inspections and evaluations are insufficient for determining the structural adequacy of bridges or buildings.

With many civil structures throughout the world in urgent need of strengthening, rehabilitation, or replacement, SHM has seen renewed focus. There have been major advances in communications, data transmission and computer processing, which have enabled SHM solutions providing the ability to acquire vast volumes of data in relatively short periods of time and transfer it via high-speed fibre-optic or wireless connections to a central database. Subsequent analysis and modelling of this data can provide critical intelligence for maintenance and management strategies, as well as improved design.

Shoring-up civil structures

The immediacy and sensitivity of SHM enables it to serve a variety of applications. It can allow for short-term verification of new or innovative designs, as well as the early detection of problems and subsequent avoidance of catastrophic failures. When implemented as part of a maintenance strategy, it can assist with the effective allocation of resources, reducing both service disruptions and maintenance costs.

One of the core drivers however, is the growing requirement for refurbishment of critical transport infrastructure. Many owners and operators need timely information to ensure continued safe and economic operation of ageing infrastructure, while the construction and engineering industry faces a mounting challenge to shore-up supporting civil structures. Deterioration can be due to multiple factors, including the corrosion of steel reinforcement and consequent breakdown of concrete, or the fact that some structures may be sound, but have become functionally obsolete – e.g. a bridge that is no longer able to support growing traffic volumes, vehicle sizes and weights.

According to the American Society of Civil Engineers (ASCE), one in four bridges in the US is either structurally deficient or functionally obsolete. In Canada, more than 40 per cent of operational bridges were built over 30 years ago and have been impacted by the adverse climate and extensive use of de-icing salts. And in the UK, an increasing number of bridges and other structures need to be strengthened to comply with legal minimum requirements specified by European Community legislation. Efforts to reinforce the resilience of key infrastructure to extreme weather events are also ongoing.

Sensors in the loop

The aim of SHM is many fold, including monitoring the in-situ behaviour of a structure accurately and efficiently, to assess its performance under various service loads, to detect damage or deterioration, and to determine its health or condition in a timely manner.

Although a single definition has yet to be universally agreed, SHM describes the confluence of structural monitoring and damage detection, with the physical diagnostic tool being the integration of various sensing devices and ancillary systems. The latter can include data acquisition and processing, communications and networking, and damage detection and modelling software powered by sophisticated algorithms.

Field-proven technologies lie at the heart of SHM innovation. For the past few decades, closed loop sensors have proven to be highly robust, reliable, repeatable and accurate in a variety of applications where extremely precise measurements are required. Such devices include:

  • Inclinometers – measure horizontal and vertical angular inclination to very high levels of precision, and output the data in analogue or digital form. In SHM applications, inclinometers are employed to monitor movement over time of bridges, buildings and other large structures. In addition, customised products can offer specific performance specifications to meet exacting requirements.
  • Accelerometers – measure acceleration and deceleration of dynamic systems. Low ‘g’ range accelerometers are used within SHM to monitor accelerations induced into bridges and other structures to check design calculations and long-term critical safety. Accelerometers can also be used in the development phase of projects to ensure design calculations correlate with actual measurements in the application.
  • Load cells – transducers used to convert a force into an electrical signal and offer measurement of tension, compression and shear forces. Load cells are available in many physical shapes and forms to suit particular applications and types of loading. The majority of today’s designs employ precision strain gauges as the primary sensing element, whether foil or semiconductor, and feature low deflection and high frequency response characteristics. SHM applications for load cells include bridge lifting/weighing, vehicle/crane load monitoring, and earthquake force monitoring.

Bridging old and new

Improvements in electronics packaging and assembly methods have allowed the sensing devices employed in SHM solutions to become smaller, more cost effective, and so sensitive that there is no longer a need to excite a structure in order to gain vital information about its integrity. By placing the right number of sensors in the appropriate positions on a bridge for example, analysts now have the raw data required via ambient sources such as wind gust loads, foot falls, and traffic flows.

Moreover, advanced algorithms have been developed that allow asset owners and managing authorities to acquire both short and long-term structural integrity assessments that prove essential in taking decisions regarding repairs and upgrades, strengthening projects, financing, insurance, and dispute resolution.

A long-span suspension bridge currently under construction in Asia employs a sensor network that includes Sherborne Sensors’ precision servo inclinometers and accelerometers. This sensor network enables the identification of structural problems at an early stage, prolonging the life of the structure, identifying areas of concern, and improving public safety.

SHM’s benefits have also been clearly demonstrated at a remote steel bridge in the heart of Brazil’s Amazon basin. Supporting freight trains carrying 10% of the world’s iron ore each year, the bridge had been rolling back and forth whenever an ore carrying heavy-laden train was crossing. A horizontal crack had also appeared in one of the supporting concrete girders, with train drivers returning to the mines reporting increasingly violent vibrations as they crossed – despite their cars being empty.

A sensors-based SHM solution was brought in to monitor the bridge over a period of time and, using its data collector devices and advanced analysis techniques, discovered that the crack in the concrete was not the cause. Rather, it was the frequency of the movement of the returning trains coupled with that of the bridge. The solution was simply to reduce the speed of the trains by 20km per hour when they crossed the bridge un-laden, and the vibration was eliminated, without the need for costly engineering works to the bridge.

Using conventional methods, a displacement sensor would have been placed over the crack to measure how it responded to ambient vibration over time. But such a device would not have told the bridge owners why the crack had come about, and whether it had anything to do with the movement in the structure.

In this scenario, an SHM solution takes raw vibration data from field-proven and trusted sensors, and turns it into valuable information enabling analysts to provide a holistic diagnosis of a structure. This ensures asset owners and management authorities are fully-equipped with the knowledge to establish the most appropriate strategy for modifying a structural system to repair current weaknesses, minimise further issues and thus prolong the life of the asset.

Wireless innovation

As more capable sensors are deployed, the opportunity exists for engineers to find even more efficient and effective ways to acquire data, analyse the vast volumes being stored, identify areas for improvement and most importantly, act on the information provided. Automated SHM for example, brings a number of benefits, such as enabling cost-effective, condition-based maintenance as opposed to conventional schedule-based approaches.

Current commercial monitoring systems suffer from various technological and economic limitations that prevent their widespread adoption. In particular, the fixed wiring used to route from system sensors to the centralised data hub represent one of the greatest limitations since they are physically vulnerable and expensive from an installation and subsequent maintenance standpoint. The introduction of wireless sensor networks in particular is attracting significant interest.

A wireless sensor network consists of ‘nodes’, which can range from a few to several hundred sensors, with each node connected to one or several sensors. This model provides a practical solution for bridging information systems and the physical world. One of the major potential benefits is that often a large number of individual wireless sensors can be monitored using a single display device, or with a wide variety of fixed base stations and hand-held readers that are already available.

Wireless solutions are shown to reduce installation costs and sensor installation times dramatically. They also increase safety levels because they can often be configured remotely or prior to installation, and exchanged easily for calibration and maintenance. Conversely, the more permanent a sensor installation, the more costly the maintenance requirement tends to be. In addition, a solution that combines both wireless data transmission and battery operation, together with low power consumption is preferable.

The Wireless Tilt System (WTS) developed by Sherborne Sensors for example, is designed to provide structural engineers with a complete measurement solution able to record and log data remotely without the cost and complexity of traditional wired methods. The engineer simply fits the low power inclinometers to strategic points on a given structure or component thus helping to determine range of motion, as well as any structural weaknesses and whether maintenance is required. This simple and cost-effective solution is extremely beneficial, especially when multiple readings must be obtained.

Building business intelligence

Although implementing change in the civil engineering and construction industry takes time, new approaches to SHM can deliver immediate benefits to asset owners, financiers, and public authorities in reducing the risk of litigation, improving public safety, and the sustainability of critical civil transport infrastructure. Using the latest SHM solutions, structural performance detection and monitoring can be performed continuously, on a periodic basis, or in direct response to an event that may have affected the structure.

A variety of innovative structural integrity assessment solutions are being developed that provide the vital information that analysts use to compare the dissipation of vibrations with either the predicted behaviour of the structure given its design and materials, or with baseline measurements captured earlier. Customised servo accelerometers for example, are central to the data collector devices used to capture these baseline measurements and enable users to establish whether a structure transfers loads as designed.

When placed either singly or in an array on bridges or other structures for a period, data collector devices record a structure’s three-dimensional movement in extreme detail. Further successful applications include road deck frequency and mode shape determination; seismic structural monitoring; vertical, lateral and rotational acceleration measurements of decks, cables and bridge towers; and integration with GPS systems to improve deflection frequency response. However, determining the most appropriate sensor technology for the application, and also the interpretation of the data, is where the knowledge and experience of a specialist supplier of sensor technology comes to the fore.

NGA evolves

Wednesday, February 19th, 2014

From Federal News Radio

The National Geospatial-Intelligence Agency has experienced more changes over the past decade than all the other 16 intelligence agencies in the U.S. government.

Geospatial information intelligence was essentially spawned in the technology boom that led to big data, mobility and cloud computing raised the stature and importance of the NGA to both the intelligence and Defense Department Communities.

This was brought out in a recent press release about the NGA’s commitment to GIS at the ESRI Federal GIS Conference in Washington.

“We are no longer doing business as usual. The work around us is changing rapidly, and NGA is changing with it,” said Letitia Long, director of NGA, Tuesday at the ESRI Federal GIS Conference in Washington. “We are transforming from a traditional provider of products, static maps, charts and analytic products into a dynamic content and services provider. As the provider of this dynamic geospatial intelligence, we deliver advanced analysis. We drive integrated intelligence. We are constantly evolving our critical geospatial content and at the same time offering expert services to all of our many customers.”

Part of that transformation is entering phase three of the evolution of geospatial information services (GIS). Phase one according to Long, was all about coordinatino, where users could bring together disconnected data and systems to solve a problem. At this stage the data was still siloed and segmented and there was not much going on with information sharing.

The intelligence community moved into phase two called “connection” during the late 1990s.

Long said this is where the community moved past coordination by connecting the different disciplines and fostering mutual support among them. She said the data still wasn’t integrated, but at least there was collaboration.

The intelligence community, led by NGA, now is in the early stages of phase three, called “integration.” Long said these efforts and capabilities depend on the Intelligence Community Information Technology Enterprise (ICITE) initiative.

Long said all of these phases are part of a historic shift that NGA and the intel community are going through. She said the intel community could move into phase four over the next five years.

Meanwhile, NGA is leading the way in phase three with four new capabilities launched in the last six months.

All four are dependent on one another and integrated through ICITE.

Long said NGA moved first to open IT standards starting in 2011. This included operating in the cloud and focusing on customer satisfaction and efficiencies.

The second capability is called Map of the World. This is to be the home for all geoint related content, data, knowledge, reporting and analysis. It will provide a seamless, integrated environment for analysts to integrate all their data about anything.

The NGA Map of the World includes classified geospatial content about maritime and air safety and imagery data. Its content also is tailored for DoD and intelligence senior decision makers which differentiates it from other Map type approaches. Intelligence analysts can access the Map of the World through the Globe, a Web portal that will become the entry point for all intelligence data.


Google Goes to Antarctica

Thursday, February 13th, 2014

For those Antarctic enthusiasts, Google has been exploring Antarctica with its special Street View backpack carrying a special Trekker camera. It persuaded researchers at the Polar Geospatial Center to carry the trekker, a 42 pound backpack with 15 lenses. Starting with easy to obtain images using , Google has now added a range of hard to reach places.

Imagery courtesy of Google Street View Imagery


USGS investigates impacts of wind energy development on wildlife

Tuesday, February 11th, 2014

In response to the Department of Interior’s Powering Our Future initiative, the U.S. Geological Survey (USGS) has begun investigating how to assess the impacts of wind energy development on wildlife at a national scale.

This research differs from previous USGS energy assessments of wind energy. While in the past the USGS has looked at recoverable resources of such as gas, geothermal, oil or coal, the USGS is developing a method for determining the impacts of a type of energy production. Since wind energy is one of the fastest growing areas of renewable energy in the U.S., it is interesting that the USGS is looking at the creation of assessment methodologies that combine its past research in land change science, wildlife ecology and wind-wildlife research.


Lovell Johns and SpatialTEQ announce partnership

Friday, February 7th, 2014


Map publishers Lovell Johns and SpatialTEQ Inc. announced a partnership designed to provide United Kingdom businesses with access to easy-to-use and affordable business mapping software.  There is a need for accessible business mapping in the UK which SpatialTEQ’s business mapping software, can address. The software has been modified to accommodate UK geographies in its latest version MBO 4.1 which was released in December 2013.


TerraGo and Carahsoft announce geospatial collaboration software

Tuesday, February 4th, 2014

George Demming, founding member of TerraGo Technology and CTO of TerraGo, talked in their recent webinar about the release of their Terrago v.6.0.4 geospatial collaboration software, including TerraGo Publisher, TerraGo Composer and TerraGo Toolbar.

TerraGo Publisher provides precise layer control and hyperlinking to documents, photos and files from within GeoPDF maps and imagery.


Blue Marble release of Global Energy Mapper v15.1

Friday, January 31st, 2014

Blue Marble Geographics released Global Energy Mapper version 15.1, a so called minor release that features the “Create Flattened Site Pad Plan” dialog box option and improved processing of IHS Well (297/298) files.

According to the press release, “Global Energy Mapper is not just a viewer capable of displaying the most popular raster, elevation, and vector datasets. It converts, edits, prints, tracks GPS, and allows users to utilize GIS functionality on a wide variety of datasets. With Global Energy Mapper users have access to the Blue Marble GeoCalc coordinate transformation, SpatialOnDemand subscription and custom industry tools like the pad site placement tool, seismic survey tools and built-in point types and symbols for the oil & gas industry.”

Additional features of the new release include added support for MS SQL Spatial databases, enabling Global Energy Mapper to support all available spatial database types and 3D support for displaying a path profile across separate terrain surfaces that allows users to easily compare the surface of multiple loaded terrain layers along a single path.

The value of flood mapping

Thursday, January 30th, 2014

According to the Fraser Coast Chronicle, of Queensland, Australia, the Bundaberg Regional Council embraced mapping technology in order to save lives of flood victims during the Bundaberg tornados a year ago in January 2013. This is now the anniversary of the disaster, when six tornados struck in and around Bundaberg. The GIS technology employed provided rescue teams with critical and timely information for evacuations, rescues, food drops, and the ensuing clean-up.

In the article, GIS Delivery and Support team leader Steven Bowden said the technology was a crucial part of its operation to evacuate more than 6,000 people from the areas of North and East Bundaberg. “Council has been working with Esri Australia in leveraging GIS technology across different business areas for the past five years,” Mr Bowden said.

Floods hit the regions in 2010 and 2013, when the technology delivered up-to-date information while the floods were happening. GIS was used for all tactical and operational decision-making, situational awareness, strategic planning and rescue efforts as well as engaging the public.


Sochi from the sky with a Pléiades satellite image

Tuesday, January 28th, 2014

Airbus Defense and Space satellite imagery of Sochi, Russia, displays the Russian town that was probably unknown to most of the world before the Olympics. Depicted are its sports complexes and natural setting. The Pléiades satellite image shows buildings — housing, and indoor sports complexes in the Adler district of Sochi, wheras the video depicts the town of Sochi, as well as nearby Adler and the Krasnaya Polyiana mountain cluster.

Airbus Defence and Space’s geo-information products – such as 3D elevation models drawing on satellite imagery – are useful for feasibility studies, risk modelling, environmental impact and cost evaluation in large civil engineering projects. Equipped with 3D data, construction projects are better able to gauge how much earth needs to be cleared or how much land needs to be filled on a building site.  


FME 2014 release offers more speed, graphics and formats

Friday, January 24th, 2014

In a discussion with Dale Lutz of Safe Software he talked about the latest version of FME, FME 2014.

“For every user we try hard to make the whole experience of using the product more effective and smooth, and that comes down to making use of streamed real estate,” said Lutz.

This has involved changing the interface out to new technology that is faster, with a nicer graphical look, and FME now works on the Mac as well as Linux.

“A lot of web developers work on Macs, and many want to work with spatial data, and in Europe especially there is a lot of interest in Linux, and they are happy to be able to use it directly. This isn’t a big commercial opportunity but many university people are Mac or Linux.”


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