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Cambridge Centre for Smart Infrastructure and Construction

An Innovation and Knowledge Centre funded by EPSRC and Innovate UK

Studying at Cambridge

 

The use and development of sensors

CSIC has substantial experience in the use of fibre optic sensing to monitor infrastructure with many successful installations in civil structures over the past five years.

CSIC’s strength is also in its analytical capabilities and its unbiased approach to testing and qualifying the technologies it uses. It is a pioneer and leader in distributed temperature and strain sensing in the UK, a field in which Cambridge University has been active since 2003. It is also developing the uses of high-density or quasi-distributed Fibre Bragg Grating (FBG) sensing systems.  Through the formalisation of design, installation and testing methodologies and the development of specifications for the use of fibre optic sensing in infrastructure, some of the applications implemented by CSIC have now reached full maturity.

Examples include:

  • concrete bored and CFA piles load tests,
  • steel piles lateral load tests,
  • monitoring of axial shortening of tall buildings,
  • pile monitoring during operation,
  • D-walls or sheet piles bending during excavation,
  • effect of heave on raft slabs bending,
  • tunnel monitoring during proximity works,
  • structural health monitoring of ageing tunnels,
  • performance monitoring of new tunnels and bridges,
  • monitoring at risk or historical buildings during proximity works,
  • masonry bridge arches monitoring, and
  • sewer monitoring for anomalous infiltration detections.

As a result, and because of its many practical advantages, fibre optic sensing is replacing electrical sensing in construction. As of 2017 optical strain sensing is included in the ICE Specification for Piling and Embedded Retaining Walls, Third edition.

Current 'Use and Development of Sensors' projects:

New sensor system development The following four projects are at an early research and development stage with the intent of being developed to commercial readiness in the future.

1. Development of combined strain and displacement wireless sensors

2. Fibre optic geogrid systems 

3. Wireless fatigue sensors 

4. Design and development of autonomous, low-cost and low-power wireless sensing technology for long-term, large-scale earthworks monitoring

 

Novel applications of sensors

The following projects are at varying stages of development from early stage to commercial readiness. Please contact us for more information on the stage of readiness for any particular application.

5. Rail track-bed stability monitoring (also under the 'Performance Based Design' theme)

6. Fibre optic temperature sensing in ground source heat pump boreholes (GSHP) (also under the 'Performance Based Design' theme)

7. Long-term deformation monitoring using photogrammetric techniques – CSattAR

8. Development of a remote-controlled boat for underwater surveying (also under the 'Data-driven Decision-making theme)

9. Measuring axial shortening of a high-rise building using distributed fibre optic sensing (DFOS)

10. Tram vibration and impact monitoring

11. Settlement monitoring of heritage structures during Bank station capacity upgrade (also under the 'Managing and Operating Infrastructure' theme)

12. Optimal monitoring of a masonry arch skew bridge (also under the 'Data-driven Decision-making theme)

13. Satellite monitoring for remote structural monitoring of infrastructure (also under the 'Managing and Operating Infrastructure' theme)  

Supporting industry uptake of sensors

12. Integrity testing of deep foundations using fibre optic methods

13. Collaborative training network to apply advanced distributed fibre optic sensor technology – (FINESSE) 

 

 

1. Development of combined strain and displacement wireless sensors

Civil engineers use strain sensors to measure precise, small-scale increases in extension of dimensions in structures including arches, foundations, tunnels, and bridge members. Displacement sensors are used to measure millimetre-to-centimetre movements in walls and arches. A gauge that delivers both high precision at the micro-scale and large-scale movement capability does not currently exist.

However, there is need for flexible, cost-effective measurement systems that are scalable from a few sensors to many, which can provide failure predictive information, such as strain, through to post-failure displacements in structures after cracking.

This project will incorporate optical transducers in a processing package with wireless data transmission to provide both precise micro-strain measurements up to centimetre displacement data. Project contact is Dr Cedric Kechavarzi, CSIC Operations Manager.

 

2. Fibre optic geogrid systems

Earthwork structures, including embankments, tailing dams, levees and railtrack beds, present a challenge to integrating a sensor such that the true strains or displacements taking place in the structure are accurately represented by the sensor outputs. It is problematic if the sensing system acts as a constraint on soil movement, and conversely, if soil movement takes place without being registered by the sensing transducer.

This project aims to integrate distributed and FBG-optical sensors into a two-dimensional geogrid that is integrated into soil structures in order to accurately respond to soil movement. This system will offer benefits to civil and geotechnical engineers who need to accurately measure strain in earthworks in order to determine margins of safety in structures. This information also enables the optimum designs of such structures. Project contact is Dr Cedric Kechavarzi, CSIC Operations Manager.

 

3. Wireless fatigue sensors

Fatigue is among the most common causes of damage occurring in steel structures. A great deal of research has been conducted to understand the effects of repetitive loadings to which steel structures are subjected and to formulate reliable fatigue-resistant design methodologies. However, fatigue life condition assessment is still a challenging and unsolved issue, mostly relying on visual inspection and wired sensing methods. CSIC is currently developing a novel wireless sensor solution that provides direct information about the cyclic fatigue behaviour of individual structural steel members. This solution is very low cost, ultra low-power, and has the ability to operate perpetually and autonomously. Project contact is Dr Xioamin Xu, CSIC Research Associate.

 

4. Design and development of autonomous, low-cost and low-power wireless sensing technology for long-term, large-scale earthworks monitoring

Incidents of instability and serviceability of existing (and future) transport infrastructure earthworks, such as embankment slopes or soil or rock cuttings, are a major concern for the UK’s infrastructure managers, especially after recent events of localised extreme weather leading to heavy rainfall and flooding. In the UK alone, there are over 17,500 km of earthworks assets on the railway network, – on average most of them are 150 years old. A failure in any of these assets, such as landslips on embankments or loss of support to the railway tracks (due to sink holes), can have dramatic consequences ranging from derailment to collisions with oncoming trains, or part of a train falling down an embankment or even into water. Current engineering practice depends mainly on periodic inspections by geotechnical engineers, a task which is labour intensive, costly and time consuming. This suggests that there is a strong need for an effective, streamlined strategy to monitor earthworks assets with as little effort as possible. Unfortunately, the installation and operation costs of current available monitoring solutions are key barriers to their large-scale adoption for earthworks monitoring in the civil industry.

This project aims to provide an autonomous, very low-power and scalable wireless sensor solution for remote monitoring of earthworks assets. The goal is to facilitate a better understanding of performance and safety of earthworks, particularly in terms of reliability of the subsoil, loading conditions and likelihood and seriousness of potential failures. The project is not intended to replace traditional engineering-led approaches but to provide the construction and infrastructure industries with a cost-efficient, easy-to-deploy, easy-to-use and multi-purpose alternative to those addressed by existing commercial solutions. Project contact is Dr David Rodenas Herráiz, CSIC Research Associate.

 

5. Rail track-bed stability monitoring

Rail track-bed construction techniques, such as slab-track (used for a range of constructions including tramlines and high speed rail), must support and maintain vertical and lateral rail position stability to ensure track operational safety and passenger comfort.

CSIC is investigating developing long-length shape and displacement sensors of several metres in length that dynamically detect and measure deformation in the track-bed under load with a high degree of sensitivity. The sensors are typically deployed during the early stages of construction where they are laid in the track-bed before the slab-track is deployed, or attached to the slab-track structure after construction. The sensor system would deliver data to confirm rail stability and assists in the validation of such construction methods for use in rail projects. This system will benefit construction companies developing and demonstrating new proposals for rail-track construction. Project contact is Phil Keenan, CSIC Business Development Manager.

 

6. Fibre optic temperature sensing in ground source heat pump boreholes (GSHP)

A distributed fibre optic temperature sensing system has been installed in GSHP boreholes as well as in the ground in dedicated boreholes at the new Papworth Hospital and the Cambridge University new Civil Engineering buildings both under construction in Cambridge. The distributed temperature data in the selected GSHP boreholes and in the soil will be used to assess the long-term performance of the ground source heat pump system and feedback into its efficient operation. It will also allow the detection of possible long-term heat imbalance and associated system efficiency loss as well as potential environmental issues.

The distributed data will be used to calibrate heat transfer models and estimate the thermal properties of individual geological strata. The data associated with the numerical simulations will be used to investigate the ground and closed loops thermal response as well as boreholes interaction. This will help optimise future system design by, for example, optimising the number of loops per boreholes, the boreholes depth, spacing, and layout. Project contact is Dr Cedric Kechavarzi, CSIC Operations Manager.

 

7. Long-term deformation monitoring using photogrammetric techniques – CSattAR

The aim of this project is to investigate the application of photogrammetric techniques for structural health monitoring purposes and to encourage industry to use photogrammetric monitoring when it is more advantageous, safer and more economical to do so. This project is a continuation of PhD research by Medhi Alhaddad, in which he developed CSattAR (a photogrammetric monitoring system) as a member of CSIC while a PhD student at CSIC. CSattAR has been applied successfully in numerous tunnel environments, including tunnels influenced by Crossrail work.  This project aims to trial and further develop the system to improve performance in outdoor environments.

Currently CSattAR runs on scripts written in Python and uses Raspberry Pi and off the shelf DSLR cameras and camera housings. The trial will include evaluation of the robustness of the equipment and the system performance for outdoor trials.  The system will also provide better understanding of the behaviour of the monitored assets when they are subjected to movements.

A best practice guide or a specification guidance document on photogrammetric monitoring of infrastructure elements will also be produced and disseminated to industry. The format of this document will be agreed subsequently.  This project is supervised by Dr Matthew DeJong from CSIC and Michael Devriendt from Arup and is led by Dr Mehdi Alhaddad Researcher on secondment to CSIC from ARUP.

 

8. Development of a remote-controlled boat for underwater surveying

Although great progress has been made in unmanned aerial vehicles (drones), the technology concerning the underwater or water-surface vehicles have been lacking. This project aims to develop a remote-controlled boat prototype to map underwater elevations. Such a device will be useful in the future for measuring the georeferenced river cross-sectional shapes for flood risk analysis. A twin-hulled boat has been built, with connecting framework and top platform providing room for mounting various instruments. The hulls are hollow, which act as the battery compartment. The heavy battery units placed at the bottom of the boat increase the stability of the boat. Most of the electronic devices are housed in a sealed plastic box on top of the middle platform, including a Raspberry Pi for data logging and a GPS sensor. In order to achieve desired accuracy, single frequency differential GPS operation is used, with an accuracy of a few centimetres. A second GPS sensor sits on a tripod at the base station, which supplies real-time satellite correction to the rover GPS sensor. The sonar is capable of measuring depths of up to 1000 feet. Power supply and extra room are provided to attach an Acoustic Doppler Velocimetry (ADV) to the boat, so that flow velocities can be measured. A Leica single prism precision reflector can be mounted on top of the boat, so that the boat’s position will be double-checked by a total station on the bank. The boat is controlled via a handheld 2.4Ghz remote control, and steering is achieved via the differential thrust. We will further test the boat’s performance, and will use it to measure the bathymetry of the River Cam. Project contacts are Dr Dongfang Liang, CSIC Investigator, and Nathanael West UROP student.

 

9. Measuring axial shortening of a high-rise building using distributed fibre optic sensing (DFOS) This project involves a novel application of DFOS to continuously measure the progressive axial displacement of reinforced concrete columns and walls in a high-rise building during construction.  The approach is being trialled for the first time in the 50-storey Principal Tower, in London, with the monitoring ongoing throughout the building’s 17-month construction programme. Fibre optic (FO) installation is carried out by the contractor’s operatives, trained by CSIC, while CSIC analyses the data and provides the required information to the contractors and design engineers. The axial shortening data provided allows the contractor to adjust the column height presets in the reinforced concrete structure if necessary. No other monitoring technology is able to provide this information with such a spatial and temporal density.

Temperature and strain sensing fibre optic cables are embedded in vertical load-bearing concrete elements, in four locations, as the building is constructed level by level.  Automated measurements of strain and temperature are taken twice every hour, which are then analysed by CSIC researchers to derive the axial shortening of the instrumented elements, along the whole height of the building, with sub-millimetre precision.  This process is planned to continue throughout the construction, following which the embedded system will become a permanent installation within the building structure, thus making it possible to assess the axial deformation of this tall building throughout its lifetime.

This is a demonstrator project intended to (a) help CSIC fine-tune the DFOS system design, installation and data processing techniques for monitoring tall buildings, and (b) give the construction industry confidence in using DFOS for similar applications. The trial at Principal Tower has enabled CSIC to develop this application of DFOS to a commercial readiness level, making it possible for tall building assets to be monitored both during their construction and throughout their lifetime. Project contact is Dr Nicky de Battista, CSIC Research Associate.  

 

10. Tram vibration and impact monitoring

The Vibration and Impact Monitoring of Tram Operations (VIMTO) project aims to develop a vehicle-based automated system for track monitoring that may be permanently installed on service trams running on an operational network. This novel form of track vibration monitoring uses the trams themselves as the primary monitoring instrument. Low-cost instrumentation mounted on tram axle-boxes records vibration signatures simultaneously with positioning data to produce a map of the network in terms of its propensity to generate ground-borne vibration. The map offers real-time continuous monitoring of the network allowing asset managers to observe the rate of deterioration. This data is key to the formulation of an optimised maintenance strategy that eliminates costly track failures.

There are more than 290km of modern tramway in the UK alone, the majority of which runs through densely populated urban areas. The disturbance to building occupants caused by tram-generated ground-borne vibration presents a significant barrier to the expansion of tram networks in our cities. Improved track monitoring leading to lower maintenance costs and increased public acceptability of trams directly supports the expansion of this more environmentally sustainable mode of transport in both domestic and international markets.  Although the current focus of VIMTO is on tram operations, the proposed monitoring methodology is broadly applicable to other rail transport systems, including underground railways. Project contact is Dr James Talbot, CSIC Investigator.

 

11. Settlement monitoring of heritage structures during Bank station capacity upgrade CSIC is applying new-generation sensing techniques, including fibre optic strain sensing, point cloud and satellite displacement monitoring, to monitor the structural response of heritage buildings during tunnelling work for the Bank station capacity upgrade

The proposed tunnels are in close proximity to Christopher Wren’s St Mary Abchurch and George Dance’s Mansion House. There are significant uncertainties regarding the behaviour of the ground and building during the tunnelling works taking place between 2017 and 2021, making monitoring a necessary mitigation measure. Sensing data will be used to provide a critical assessment of analysis methods for tunnelling-induced damage in historic buildings and offer reassurance to asset owners and managers. Detailed data will allow informed assessment and timely intervention, if necessary, to avoid potential costly remedial action. Project contacts are Dr Sinan Açikgöz, Brunel Research Fellow and Dr Matthew DeJong, CSIC Investigator.

 

12. Optimal monitoring of a masonry arch skew bridge

Many ageing masonry bridges are in need of continuous assessment; this is typically completed through visual inspection, though in some cases crown displacements are monitored. This project seeks to monitor a specific masonry arch skew railway bridge with several techniques, with the specific aim of identifying pros and cons of various monitoring techniques for masonry bridge typologies. Specifically, CSIC, in collaboration with AECOM and Network Rail, will monitor a masonry arch skew bridge that has experienced severe distress. Numerous sensors will be deployed, including fibre-optic sensing and videogrammetry.

The data will first be used to reveal the in-plane flow of force through the skew arch, which until now has not been well understood. Second, local strain and displacement measurements will be correlated to global (3D) movements obtained from fibre-optic and videogrammetry monitoring. This will facilitate the decision-making on how to optimally monitor to detect the specific service performance that may be a concern. Interpretation of these results will be complemented by modelling of the bridge, so that the monitoring data can be benchmarked against currently applied modelling techniques. Project contacts are Dr Matthew DeJong, CSIC Investigator and Sam Cocking, PhD Researcher.

 

13. Satellite monitoring for remote structural monitoring of infrastructure

The widespread deterioration and recent collapses of bridges, dams, tunnels and other key services have highlighted the importance of structural health monitoring as a tool to aid infrastructure asset owners and managers. This research investigates advances in satellite measurement technologies and understand their relevance, utilisation, and limitations to civil engineering applications, such as bridge or embankment monitoring. These data sets are then compared with traditional measurement techniques from sensors installed on existing bridges (including fibre optic sensors, wireless sensor networks, traditional surveying techniques etc.). From this, they can be complemented with traditional measurement techniques to provide a more effective strategy for interpreting data to provide useful information and value to asset owners. This research aims to address the following research questions:

- Can satellite measurement technology provide remote measurement and monitoring such that it is able to replace or complement traditional forms of physical measurement and monitoring infrastructure assets?

- Can satellite measurement and imagery be used to indicate signs or precursors of failure in infrastructure assets?

The primary method of satellite measurement used in this research is Interferometric Synthetic Aperture Radar (InSAR) which has the capability to provide wide-area, high-density, remote measurements of movement. Situations for which satellite measurement technology could potentially be useful include identifying impending structural failures by detecting small movements in advance of, or prior to, collapse; identifying unusual movement that would indicate potential problems (e.g. seized bridge bearings); and, looking at bridges and other assets before and after significant events (e.g. flooding). Project contact is Sakthy Selvakumaran, PhD Researcher.

 

14. Integrity testing of deep foundations using fibre optic methods
CSIC has been testing the use of distributed fibre optic sensing (DFOS) as a thermal method to assess the quality of cast in situ concrete foundations. Thermal methods, which use the temperature generated during cement hydration to provide a continuous temperature profile, are an alternative to conventional point sensors. With DFOS, low-cost standard telecommunication fibre optic cables can be attached to several sides of the reinforcement cage of a foundation element in continuous loops. Several elements can be monitored at the same time on a single fibre optic circuit (single channel). Temperature measurements are obtained at close spatial intervals along the cage, and regular time intervals to record the evolution of the temperature profile of the element during concrete curing.

This approach has been put into practice on a number of projects with Cementation Skanska and the method reached commercial readiness in 2015, when Cementation Skanska’s own fibre optic technology system, CemOptics, was launched. The technique continues to be used by the company on an unprecedented scale for pile and wall integrity testing. Project contacts are Dr Mohammed Elshafie, CSIC Investigator and Dr Cedric Kechavarzi, CSIC Operations Manager.

 

15. Collaborative training network to apply advanced distributed fibre optic sensor technology – (FINESSE)

FINESSE (Fibre Nervous Sensing Systems) is a collaborative research and training network comprising 26 European universities, research centres and industrial partners with the shared aim of implementing distributed fibre optic sensor (DFOS) systems for a safer and more sustainable society. In recent years fibre optic sensing has created sustained market growth and attracted the interest of a diverse range of end-users including pipeline protection, oil and gas well exploitation, electricity, transport and fire alarms. However, the full potential of DFOS is restricted due to the lack of trained scientific personnel capable of creating the link between the sensors and potential applications. This challenge will be addressed by the Innovative Training Network that aims to educate and train 15 Early Stage Researchers (ESRs) in the development of new optical ‘artificial nervous systems’ and to boost industry uptake of DFOS by technology transfer from academic research to the European optical fibre sensor industry. A substantial part of training will be dedicated to field experience in the private sector with the aim to drive business concepts and entrepreneurship and to encourage widespread industry adoption of the technology. Project contact is are Dr Mohammed Elshafie, CSIC Investigator.