Final Report Summary - MONICO (Fibre Optics-Based Intelligent MONItoring and Assessment System for Proactive Maintenance and Seismic Disaster Prevention in Reinforced COncrete Tunnel Linings)
Project context and objectives:
Fibre optic sensing is one of today's fastest developing technologies. One reason for this is that the costs of fibre sensors have been dropping steadily (in large part due to exceptional advances in fibre telecommunications technologies) and this trend will continue. Further, measurement capabilities and system configurations (such as wavelength multiplexed, quasi-distributed sensor arrays) that are not feasible with conventional technologies, are now possible with fibre sensors, enabling previously unobtainable information on structures to be acquired. One area where the above advanced technology can have an immediate impact in construction is in improving the current state-of-practice of structural monitoring systems. The importance of structural monitoring is growing due to a shift from construction costs to life cycle costs and lifetime performance including safety and use. This holistic approach in addition to monitoring technologies includes assessment methods. Fibre optic sensor technologies are finding growing application in the area of monitoring of civil structures. This has resulted in a growing field of fibre optic structural sensing in construction that is highly competitive and composed exclusively of small and medium-sized enterprises (SMEs). A study in the field by one of the SME proposers showed that 90 % of those interviewed from the construction industry and the administration would like to outsource structural monitoring. It follows that companies in the fibre optic structural sensing field need to develop advanced methodologies and computer programmes for specific applications that based on the sensor information will assess the structural condition of the monitored facility. For this, these companies need expertise in structural engineering, earthquake engineering (in seismic prone areas), and structural reliability since there are uncertainties in measurements from inspections, materials' parameters and geometric properties and errors in materials' and structural models. Such expertise is presently not available in the fibre optic sensing industries.
Tunnelling activity is on the increase around the world, but it is not just the volume of work which is rising. The demands of modern transport networks mean that tunnels are longer and wider than ever before and being driven through increasingly difficult ground conditions. Moreover, several planned tunnels are in countries of high seismicity and a good part of the tunnel kilometres will be under densely populated areas and require very high standards of safety. To the above one should add that today's tunnel environment is characterised by high user demands, stretched budgets, declining staff resources and greater operational complexity necessitating the development of asset management plans that are based on accurate and timely assessment of the structural health of tunnels. Accordingly, the new niche market of tunnel continuous monitoring and assessment should be among the first markets to be targeted by the SMEs in the fibre optic structural sensing field. There is an increasing awareness of the sensitivity of tunnels to seismic activity (tunnels have experienced significant damage in recent large earthquakes including the 1999 Kocacli, Turkey earthquake, the 1999 Chi-Chi, Taiwan earthquake and the 1995 Kobe, Japan, earthquake). Moreover, the damage to the tunnel structure is difficult to assess and a damaged tunnel that has survived the major earthquake might not have the capacity to survive consecutive seismic aftershocks. Such aftershocks take place within few hours of the earthquake and have been reported to have an intensity of up to 90 % of the earthquake intensity.
Tunnel primary linings are mostly constructed of reinforced concrete (r.c.). Most vulnerable are lining cross-sections under inhomogeneous loading, e.g. cross-sections located in regions of transition from one type of soil to another. Included are the tunnel entrance and exit. Included also in the old cities of the European Union (EU) are metro cross-sections that on one side step on ancient ruins. For instance in Athens such cross-sections can be found on the average every 200 metres. All structures undergo deformations under the effects of loads or changes in the constituent materials. The deformations of any structure (tunnels, bridges, etc.) contain a lot of information about its health state. By measuring these deformations, it is possible to analyse the loading and ageing behaviour of the structure and assess its safety. To ensure the safety of vulnerable tunnel cross-sections or sections where very high standards of safety are required, fibre optic sensors providing a real-time, wireless and remote deformation sensing capability, need to be integrated with software that will collect and process the signals and assess the structural reliability of the lining. In regards to proactive maintenance, measured deformations can be converted to strains, curvatures, deflections, stresses, bending moments and axial forces which can be monitored so that they do not exceed limit values. Regarding earthquakes, the philosophy of earthquake resistant design is to mitigate extensive damage rather than to prevent its occurrence. Elastic response provides a poor measure of susceptibility to damage. The damage done to a cross-section during strong motion excitation depends primarily on the energy transmitted and dissipated by the cross-section during inelastic cycling. Only by recording and analysing the structural response during the latter cycling can an accurate evaluation be made of the remaining dissipative energy capacity of the cross-section before the limit state is being reached.
In the EU funded project TUNNELLING, Tecnic developed an energy-based theory of seismic failure for reinforced concrete tunnel lining cross-sections based on the history of deformations during the earthquake derived from fibre optic measurements. It was deterministic and limited to local failure. Deterministic evaluations leave no room for tolerances for errors in data from non-destructive evaluations, variations in materials and the relevant geometry and errors in modelling material and structural behaviour. Hence, the deterministic evaluations obtained without consideration of uncertainty could lead to unreliable results. Accordingly, reliability-based evaluation methods are more appropriate. Furthermore, local failure does not necessarily result in global failure (collapse) of the monitored cross-section. Thus, the probabilities of both local and global failure need to be determined. New technologies are being developed continuously in the optical sensing area which is one of the fastest developing technologies. What is needed at this point is that existing and emerging fibre optic deformation monitoring technologies be evaluated and optimised so that alone or in combination can provide optimal performance in tunnel structural sensing under operating and seismic loads. The SMEs in the fibre optic sensing field do not have the extra manpower and facilities for the above.
The overall objective of the proposed research is to provide the SMEs in the group with an integrated package that will include an optimised fibre optics sensing system for the continuous monitoring of deformation and a decision support system (DSS) for the assessment of the structural condition of reinforced concrete, transportation, primary tunnel linings under operating and seismic loading.
To accomplish the above, specific scientific and technical objectives of this work are the following:
1. To provide optimised fibre optics based sensing system for r.c. tunnel linings that can be embedded in concrete for the life cycle measurement of deformation, that measures fast events (seismic disturbances) and that transmits information to a remote base using a wireless interface. A sensor data processing module (SDPM) will be developed that will be part of the monitoring system in order to filter out noise and erroneous data and present it in a way that is useful and convenient to the user. To elaborate further, the SDPM will be a software component to render the data to the appropriate format in order to be fed to the expert system. A processing of the sensors data will ensure the compatibility of the format for processing by the structural condition assessment software.
At the very minimum the following systems will be evaluated in regards to continuous tunnel monitoring, optimised and possibly combined:
- A Bragg grating fibre optic based monitoring system
This system will permit at least 2 × 8 gauges, each between 200 mm and 2000 mm long, to be put on the same fibre and each gauge will include at least 4 conventional, high reflectivity apodised fibre Bragg gratings (FBG). The resolution of each specific sensor is expected to be around 1 - 5 µe in strain terms or 1 - 5 pm in wavelength terms. Two about 30 m long systems will be installed inside the inner and outer linings of the tunnel. The environmental temperature of the sensors will be monitored and the measurements compensated accordingly. The remote interrogation system will perform, with the aid of a CCD, a spectrum analysis of the light reflected by the FBGs and decode the Bragg wavelength shifts in terms of the strain acting on the gauge. A broadband (about 75 nm) SLED light source will accomodate the full spectral range of FBG wavelengths. The interrogation system will support two channels, the inner and the outer sensor systems, simultaneously using an optical switch.
- A distributed fibre optics sensing system based on the principle of Brillouin scattering
Brillouin scattering is a fundamental process of inelastic light scattering which occurs due to the interaction of light with acoustic waves (phonons) of an optical medium. The backscattered light of the Brillouin process is red-shifted from the frequency of the incident light and this shift is proportional to the strain and temperature at the certain part of the medium from which the backscattered component arises. Using pulsed light and optical time domain reflectometry (OTDR) measurements, the Brillouin shift can be resolved in space along the fibre (medium) thus a distributed (almost continuous) sensing of strain and temperature along the fibre is possible. The interrogator of the Brillouin sensing system is a sophisticated coherent detection device that is able to measure the beat frequencies arising from the detuning between the incident and backscattered light. The space resolution of the system is proportional to the duration of the light pulses. It can be as low as 1m or even lower if a special mounting technique of the fibre is employed and the strain resolution can be as low as 5µe.
Both of the above approaches have certain advantages and disadvantages. They will be identified, evaluated and optimised, so that alone or in combination can provide optimal performance in structural sensing. Briefly, the main advantage of Brillouin technique is the capability of continuous strain and temperature measurements along a simple and inexpensive commercial fibre cable that runs along the entire structure to be monitored. Though, our proposed analysis, will refer to specific sections of the installed fiber, it gives the ability to monitor any point on the fibre line, allowing for the fine tuning of the section to be monitored. However, the spatial resolution of the Brillouin method is restricted by the pulse width to approximately 1m. Moreover due to the inherent characteristics of the Brillouin phenomenon (low backscattered light power) the rate at which measurements can be obtained is lower compared to an FBG system. On the other hand FBG sensing systems are more complicated in installation due to the multiple gauges required for monitoring different points of the same structure but lend themselves to high data acquisition rates. The complexity and the cost of a Brillouin interrogator is also considerably greater compared to the much simpler FBG interrogator.
2. To develop a methodology for the probabilistic assessment of the local structural condition of the r.c. monitored sections in the tunnel lining cross-section under operating loads based on measurements of deformation.
3. To extend the deterministic energy-based theory of local seismic failure for reinforced concrete structures devised by Tecnic to a probability-based assessment of local seismic structural reliability.
4. To develop a methodology for the probabilistic assessment of the global structural condition of the r.c. lining cross-section based on the local, probabilistically defined, conditions in the monitored lining sections.
5. To evaluate the methodology in '4' via non-linear finite element analyses.
In '2', '3' and '4' above account will be taken of errors in data from the fibre optic sensors, variations in materials' parameters and the relevant geometry and errors in the modelling of materials and structural behaviour.
6. To provide an integrated package for tunnels for health monitoring and safety assessment under routine operation and seismic forces. It will include the following:
- The system in'1'.
- The 'local structural condition' module. This module, which is a software implementation of the theory in '2', will receive as input from the sensing system measurements of deformation according to some schedule and will process it to derive the corresponding strains, curvatures, stresses, moments and the axial force and to assess the probability that defined limit states have not been exceeded..
- The 'local seismic capacity' module. This module, which is a software implementation of the theory in '3', will receive as input from the sensing system the deformation time history during an earthquake and will process it to assess, probabilistically, the remaining dissipative capacity of the monitored sections before the limit state is being reached.
- The 'global structural condition' module. This module, which is a software implementation of the theory in '4', will receive input on local conditions from the above modules in order to derive, probabilistically, the global structural condition of the tunnel cross-section. This module will signal a warning if the tunnel is unsafe or if, in the case of an earthquake, might not survive expected aftershocks.
- Deterministic versions of the above modules will also be provided. Moreover, these modules will be usable with the existing sensing systems of the SMEs in the group as well as with other sensing systems that can provide tunnel deformations.
- A data and knowledge base that will contain domain knowledge (represented in the domain modules) and system knowledge (i.e. rules governing the coordination of the system modules). The data base will include sensor data and data on tunnel records (e.g. amount and type of steel reinforcement).
- An expert system. This system will coordinate the other modules and sub-modules and will act as an intelligent intermediary between the users and the results that will be obtained.
7. To experimentally evaluate the sensing and data acquisition system in '1' and the predictive ability of the theory of seismic failure in '3'.
Project results:
Work package (WP)1 - Monitoring system. Wireless communication capability (ICCS)
General objectives
- Development and production of a fibre optics based deformation monitoring system that can be embedded in concrete and report at seismic frequencies.
- Development and production of interrogation equipment for the above system.
- Development and production of the sensor data processing module (SDPM) which will be part of the monitoring system.
- Provision of reliable wireless communication capability in supporting the project information transfer requirements under normal conditions and in the event of an earthquake.
Work progress towards objectives:
- Deformation sensors: The complete set of technical characteristics for the fabrication of FBG sensors was determined, meeting the requirements of the project, in terms of glass materials, grating parameters (pitch, strength, apodisation), wavelengths, side lobes level, strain and temperature sensitivity. A considerable effort was also devoted to the design of the gauges (SmartRod-style steel bars) that will enclose the FBG sensors. A redesign was required in order o increase the measurable strain range close to the concrete damage limit. This affected the number of sensors per line and the switching scheme.
- Sensor data processing module: Procedure and algorithm have been developed to transform Bragg wavelength shifts to strain information and compensation for the temperature dependence of measurements.
- Interrogation unit: The specifications of the light source (LED) that will illuminate the FBG arrays in terms of wavelength range and power have been developed. Analysis and details of the couplers directing the reflected light to the detecting unit has also been executed. Specifications of the CCD-based spectrum analysis of the reflected light in terms of resolution and sensitivity are complete.
- Wireless communication capability: The work has included hardware and software design: wireless modem, WiFi equipment, hub and router, protocol and interrogation routines between LabView environment and router. Two possible scenarios/options were developed regarding Ethernet or USB based connection of the interrogation unit.
- All objectives distributed among the tasks 1.1-1.4 were achieved as far as the design of the FBG sensors-based deformation monitoring system. The system was completely finalised and approved by the civil engineers partners.
- Problems related to the mounting of gauges to the lining so as to avoid techniques that may damage the sensors (welding) were solved through cooperation with partners experienced in civil structures.
- Special attention was given to the required triggering of data recording in the event of an earthquake ('awake' signal): survey on seismic switches and sensors, accelerometer and geophone technology. The discussion and survey concerning the required triggering of data-recording in the event of an earthquake ('awake' signal) has lead to this solution: the transient data provided the FBG sensors will be processed by the software (developed by RISA) in order to detect an abruptly increasing strain envelope. Thus, no additional earthquake triggering device (e.g. geophone) would be needed, which is beneficial in terms of cost and maximises the utility of our sensors.
- A wireless communication between FBG interrogator and the end user pc was established employing a USB extender. This module was chosen as the simplest solution for wireless communication, however error-free communication was achieved at a low data rate, inadequate to support continuous flaw of interrogator generated data. The well-established Ethernet technology is currently setup as the final solution for the wireless system communication.
- A first round of experimental calibration and validation of the FBG sensors completed to obtain essential results on the sensors performance. Full sensor characterisation in the material tester test-bed was completed.
- Regarding the Brillouin optical time domain reflectometry (BOTDR) fibre sensor types were selected and a preliminary coil-shaped sensor configuration was setup, in order to reduce the spatial resolution of the technique.
- The issues of the wireless communication data rate were solved in cooperation with AOS. USB-Ethernet solution was complete while a second pc-pc Ethernet communication was also evaluated as fall-back position.
- Intense collaboration between ICCS, AOS and UNITN allowed for an improved version of FBG sensors with better mounting features that exhibit increased tolerance to sensor deformation.
- Development of spiral shaped Brillouin sensors and (in-lab) characterisation.
- Completion of D1.2: 'The SDPM, the interrogation unit and the wireless transceiver module' (M22).
- BOTDR technology inherent restrictions were identified in spatial resolution, operational frequency and strain sensitivity / dynamic range. Custom configuration was accommodated in order to match/compensate for these operational characteristics. Please check D1.2 and D1.3.
- During the last reporting period, ICCS performed the characterization of the Brillouin sensors.
- ICCS (in cooperation with AOS) prepared the FBG and Brillouin sensors that were installed in the final test ring (in UNITN labs). Feedback was consolidated from the previous tests to improve and provide the optimal sensor solutions for the case.
- ICCS in cooperation with AOS and UNITN aided the installation of the sensorial (FBG and Brillouin) systems to the UNITN laboratory (final tunnel test ring).
- Completion of the deliverable D1.3 'Embedded deformation sensors evaluated at the structural lab and refined'.
Corrective actions taken / suggested:
- In the fourth MONICO meeting in Padova, partners agreed on taking a list of actions in order to solve the problem with OSMOS. Please refer to the MONICO meeting minutes. Partner OSMOS was formally removed from the consortium.
Contractors that worked in WP1: ICCS, Optronics, AOS, GHT, TECNIC, RISA
WP2 - The 'local structural conditions' module (RISA)
General objectives:
- Development of a methodology for the probabilistic assessment of the structural reliability of monitored reinforced concrete sections in a tunnel lining subjected to operating loads, based on measurements of deformation.
- Software implementation of the above in the 'local structural condition' module.
Work progress towards objectives:
- A methodology has been developed, as planned, for the assessment of the probabilistic, local, structural condition under normal, operating loads. It has been assumed that geometric properties (that is, the height of the cross section, distance between rebars and rebar covers) will be measured with a sufficient degree of accuracy when the sensors are installed. It has also been assumed that the measurement error of the sensors is negligible next to other uncertainties. Based on the above, the four following material variables are considered as random variables: yield strength of concrete in compression, ultimate strain of concrete in compression, yield strength of steel and modulus of elasticity of steel.
- A methodology has been developed, as planned, for the stochastic assessment of the local seismic capacity based on strain measurements. In this case in addition to the random variables above, DA, the allowable value of the energy ratio damage index D, has also been treated as a random variable.
- Requirements and specification of the module were successfully completed.
- Testing and refinement of the module was executed on time followed by the related documentation.
- Finishing task 2.3.4 documentation.
- Deliverable D2.2 finalisation.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP2: Optronics, AOS, GHT, Tecnic, RISA
WP3 - The 'local seismic capacity' module (RISA)
General objectives:
- Development of a methodology for the probabilistic assessment of the seismic structural reliability of monitored reinforced concrete sections in a tunnel lining subjected to seismic loads based on measurements of deformation.
- Software implementation of the above in the 'local seismic capacity' module.
- To develop a methodology for the stochastic assessment of the local seismic capacity based on strain measurements.
- Development of the requirements and specifications of the software package based on the methodology in D3.1.
- Start working on the design and implementation of the software package.
Work progress towards objectives:
- A methodology has been developed, as planned, for the stochastic assessment of the local seismic capacity based on strain measurements. In this case in addition to the random variables above, DA, the allowable value of the energy ratio damage index D, has also been treated as a random variable.
- Requirements and specification phases successfully completed during the second year of execution of the project while the design and implementation phases started immediately afterwards.
- The testing and refinement phases concluded the actual algorithms development phases.
- Documentation (task 3.3.4) has been completed.
- Finalisation of deliverable D3.2.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP3: Optronics, AOS, GHT, Tecnic, RISA
WP4 - The 'global structural condition' module (Tecnic):
General objectives:
- The objective of this WP is to assess, both deterministically and probabilistically, the degree of global damage of the monitored lining cross-section under normal operating and/or seismic loads
Work progress towards objectives:
- A methodology was developed and evaluated, as planned, that, based on local damage under operating conditions, can predict, deterministically and stochastically, the global stability of the monitored cross-section.
- While working in WP4 the research and technology development (RTD) performers realised that based on the measured deformations at specific points on the monitored tunnel cross-section under operating loads, they can, through back analysis, assess the applied external loads on the tunnel (that vary as a function of time and are unknown) and tunnel stability. This approach is novel and will provide invaluable information to tunnel owners and tunnel researchers. To this target the requirements and specifications were completely done and the design and implementation of the software package has started.
- The requirements and specification task was successfully completed while the design and design and implementation started on schedule.
- The testing and refinement task started and completed successfully including testing, integration, identification of problem areas and upgrading and refinement.
- The documentation task started also on time having as a major objective the contribution to system guide and user manual.
- During the last six months of the project the documentation task 4.3.4 was completed
- Completion of deliverable D4.2 'Module 3 evaluated at the structural lab and refined'.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP4: Optronics, AOS, GHT, Tecnic, RISA
WP5 - The expert system, the data base, the knowledge base and DSS and package integration (RISA)
General objectives:
- To design and deploy a system architecture that is flexible (so that it can be adapted to different types of fibre optic sensors), scalable (so that it can include into the future additional functions, e.g. selection of rehabilitation measures) and modular (so that that it can include additional type of measurements, e.g. corrosion measurements).
- To develop the expert system, the data base and the knowledge base.
- To integrate all modules in the DSS.
- To integrate the DSS with the sensing and data acquisition system. Moreover, to provide appropriate interfaces so that the proposed DSS can be used with the existing monitoring systems of the SMEs in the group.
Work progress towards objectives:
- The development of a common understanding of the system's scope and desired behaviour has been accomplished.
- A methodology has been defined, as planned. Having reviewed the available methodology, it has been decided that the overall development approach for the MONICO DSS will be the adopted adapted waterfall model, which includes analysis, design, development, testing and evaluation. The chosen data access application and programming language will be Microsoft Access and Java.
- A specification for the expert system and the data and knowledge bases has been set. The translation of the user requirements into specifications that describe the conceptual models for the expert system and the data and knowledge bases and how to implement them. The requirements have been transformed into a conceptual design and the best software architecture that is scalable and modular and permits future expansion of the expert system and the data and knowledge bases to accommodate additional applications.
- Design and implementation of the expert system and the data and knowledge bases. The purpose was to set out the design of the modules of the DSS. As the design has advanced with the clear longer-term goal of module integration, both it and the implementation methodology reflect an explicit preparation for the integration stage of the software development life-cycle.
- Software implementation and development of the prototypes of the expert system and the data and knowledge bases.
- The design and implementation task (5.3.3) was successfully finished towards the end of the second year of the project.
- The integration task started in the second year and by the end of the same year it was almost finished (90 %).
- System documentation started as planned during the second year.
- Finished integration: It involves integration of all modules in the DSS and integration of the DSS with the sensing and data acquisition system (task 5.4).
- Finished global system testing and consolidation: It involves testing and refinement of the overall DSS and includes test planning, global and extensive system testing, analysis of results and upgrading (task 5.5).
- Finished documentation (task 5.6).
- Finalisation of deliverables D5.3 and D5.4.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP5: ICCS, Optronics, AOS, GHT, Tecnic, RISA
WP6 - Laboratory evaluation of the performance of the condition monitoring system and the predictive capability of the theory of seismic failure (UNITN):
General objectives:
- To assess in a structural laboratory the performance of the condition monitoring system on reinforced concrete specimens (substructures) representative of a tunnel lining.
- To calibrate against novel monotonic, cyclic and dynamic test results the energy-based theory of seismic failure.
- To validate the predictive capability of the energy-based theory of seismic failure and the global structural condition module.
Work progress towards objectives:
- This WP officially was to start on month 16. However, an internal report on the design of specimens to be tested by UNITN was produced quite earlier. In detail, possible substructure and demonstration tests are presented devoted to the calibration of models and to the investigation of a typical design case where seismic forces can be greater than the ones obtained through static analysis.
- UNITN started parts of activities of WP6 after the coordinator of MONICO, in agreement with the remaining partners, proposed to test a full scale specimen of a tunnel lining in the UNITN laboratory. This test for its own nature is complex and risky, and unfortunately is unique. As a result in order to identify the optimal fibre attachment to the rebars, the plastic hinge length and the experimental material stress-strain constitutive laws as well as the moment curvatures diagrams, UNITN proposed to perform some preliminary tests on tunnel substructures, to be carried out.
- WP6 started to analyse the structural behaviour of typical circular tunnel linings according to recent research works. The determination of actions, which the structure is subjected to, as well as their distribution represent main steps towards an adequate and significant specimen design. Thus, both static and seismic analyses were performed, by using common realistic size and materials for the lining and typical soil, depth and water table level values. Since the project is devoted to the detection of damage owing to seismic events, we designed the tunnel lining so that seismic loadings result to be critical. We found that actions are sinusoidal along the curvilinear coordinate of the transverse section; moreover, we identified that in correspondence of the maxima, tunnel portions of about 1 m long could be considered subjected to constant bending moment. Hence, specimens representative of tunnel lining substructures to be subjected to monotonic and cyclic four-point bending tests were reckoned to be suitable for our purposes.
- Due to the concrete flexural behaviour associated with high levels of stress distribution, e.g. owing to an earthquake, plastic hinges may form entailing large localised deformation associated with damage. The plastic hinge length depends on many factors and, therefore, it is important that FBGs be located within this length. Furthermore, cracking also occurs and this causes the so-called tension stiffening effect, i.e. tension peaks in the rebars in correspondence to cracks. This means that a FBG bonded to the concrete may be affect by this local phenomenon. Hence, the material characterization plays a central role in the FBG packaging design. Since, the preliminary tests also aims at identifying the optimal fiber attachment, two FBG packages have been conceived on the basis of the plastic hinge length estimate and employed in each instrumented specimen in order to measure strains at the two longitudinal rebar levels: i) FBGs bonded to the concrete and ii) FBGs unbounded to concrete. The latter system allows measuring mean strains in the plastic hinge zone, by eliminating any tension stiffening effect. Moreover, the packaging has been designed in order to be easily attached to the rebar cage.
- Through the structural analysis we designed the substructure specimens and we chose the test typology.
- In order to identify the optimal fibre attachment, we designed the FBG packing on the basis of material characterisation.
On the basis of the numerical analyses carried out in first year, UNITN found that actions are sinusoidal along the curvilinear coordinate of the lining tunnel transverse section; moreover, UNITN identified that in correspondence of the maxima, tunnel portions of about 1 m long could be considered subjected to constant bending moment. Hence, specimens representative of tunnel lining substructures to be subjected to monotonic and cyclic four-point bending tests were reckoned to be suitable for our purposes. Since, the material characterisation plays a central role in the FBG packaging design, we decided to perform three preliminary tests with also the aim of identifying the optimal fibre attachment. In detail, only one specimen was instrumented with FBGs, the other two were exploited to set the parameters of the loading protocol and to establish an optimised traditional instrumentation, whose data were compared with those obtained through the fibre sensors. Two FBG packages were conceived on the basis of the plastic hinge length estimate and employed in the instrumented specimen in order to measure strains at the two longitudinal rebar levels:
i) FBGs bonded to the concrete and
ii) FBGs unbonded to concrete.
At the end of September 2009 UNITN received from AOS the fibre packaging and casted the specimens. At the end of November 2009 UNITN performed the tests:
1) monotonic without fibres;
2) cyclic according to the ECCS (1986) protocol without fibres and
3) cyclic according to the ECCS (1986) protocol with optical fibres.
After the tests, we elaborated the data and the main findings related to the fibre optic sensor system are summarised below:
- The substructures exhibited ductile behaviour with large deformations in the plastic range associated with high energy dissipation. This implies that the structural design is suitable for seismic loading.
- Though both unbonded and bonded packaging solution should allow fibres to measure 1 % strain, from the results we noted that fibre optic sensors were not capable to measure reliable strains after reaching about 0.2 % strain. In fact, the bonded solution with increasing displacements unexpectedly read decreasing strains. From measurements we did not have accurate information on the performance of the unbonded solution, hence, it is recommended to test the unbonded solution or another packaging solution.
- In addition, the measurement of strain on short lengths can prevent an effective measure of the mechanical behaviour, i.e. the strain measure may occur in an uncracked concrete portion that entails smaller deformation values than the actual average ones. In this respect, unbonded fibres might provide more accurate values. Needless to say that steel deformation values less than 1 % are expected in tunnel linings out of fault regions.
These preliminary outcomes aided the partners to select optimal solutions in terms of optical sensors and type of packaging to be installed in the next three tests.
During the second semester of the second reporting period, UNITN designed and cast three substructures 3000 mm long and 1000 m wide characterised by a section of 200 mm. In detail, these specimens will be subject to:
- a cyclic test with FBGs fibre sensors (CF1), where the fibres will be externally installed;
- a cyclic test with FBGs fibre sensors (CF2), where the fibres will be both embedded in the specimen and externally installed;
- a cyclic test with Brillouin fibre sensors (CB1) that will be externally installed.
The design of the concrete ring was made too. The specimen was characterised by a ring endowed with 4800 mm diameter and a section of 200 mm. The specimen will be endowed with 32 FBG and 16 Brillouin fibres. Eight sections will be monitored and, in each of them, both technologies will be adopted. Cyclic loading was considered with a dy of about 6 mm.
During the last six months of the project, three tests on substructures 3000 mm long and 1000 m wide characterised by a section of 200 mm were executed as follows:
- a cyclic test with FBGs fibre sensors (CF1), where the fibres were externally installed;
- a cyclic test with FBGs fibre sensors (CF2), where the fibres where both embedded in the specimen and externally installed;
- a cyclic test with Brillouin fibre sensors (CB1) that were externally installed.
For the CF1 specimen, the maximum strain was almost 1 %; AEP and fiber sensors showed that the substructure reached the plastic range, whilst standard strain gauges were broken.
For the CF2 specimen, the maximum strain was almost 0,8% for the external fibres, whilst almost 1,3 % for the internal fibres. This time AEPs, fibres and strain gauges showed that the substructure didn't reach the plastic range but remained in the elastic range.
With regard to CB1, the specimen reached displacements values at about 4 y, i.e. 76 mm, with curvatures of about 0.5 1/m. Brillouin fibres performed significantly well.
In general, the fibre optic system externally installed in test CF1 allowed the plastic moment to be identified. In fact, the fibres read up to the 3rd cycle at a displacement of 2 y - i.e. 38 mm - measuring strains up to 1 %, thus detecting a hysteretic behaviour. However, in the CF2 test, the external fibres reached lower strain values. The method used to unbond the rebar of the second test campaign resulted to be more suitable for characterising the average strain in the plastic hinge zone with respect the one employed in the first test campaign.
Finally, it was decided that the sensor configuration for the ring test should include both fibre technologies, i.e. FBGs and Brillouin, in each monitored section.
The final test on the concrete ring was carried out the 3 February 2011. The specimen was characterised by a ring endowed with 4800 mm diameter and a section of 200 mm. The specimen was endowed with 32 FBG and 16 Brillouin fibres. Eight sections were monitored and, in each of them, both technologies were adopted. Cyclic loading was considered with a dy of about 6 mm. The concrete failure was reached at section 8; in detail this failure happened at the first cycle of 4dy, i.e. almost 25 cm. The ring exhibited a ductile behaviour associated with a high energy dissipation. Both FBGs and Brillouin sensors worked well and were capable to trace the evolution of inelastic mechanisms.
The data provided by the overall test program allowed the methodology for the deterministic and probabilistic assessment of the structural condition of a monitored tunnel reinforced concrete cross-sections to be calibrated and validated. This methodology based on the recorded strains of sensors installed both on the inner and outer transversal reinforcing bars in the eight critical sections will generally involve: the estimation of section internal forces; the external loads applied on a tunnel lining; the actual values of estimated damage indices. The structural assessment will concerns the behaviour under seismic loadings and the long term behaviour under normal operating conditions.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP6: AOS, GHT, Tecnic
WP7 - Knowledge management and intellectual property rights (IPR) protection (GHT):
General objectives:
- To secure by copyright protection the software that will be developed in the project.
- To file for patents for the optimised sensing system.
- To produce the plan for the use of the foreground
- To produce a brochure and a CD demo for the DSS and the monitoring system that will be used to present the results to major potential customers
- To present the results to major potential customers.
Objectives for the current period:
- Identifying the team in charge of WP
- Setting up the deliverables, the plan for the use of foreground and market analysis template
- Releasing of actual version of market analysis template to partners.
- Collecting exploitation input from partners;
- Releasing of draft version of plan for the use of foreground.
Work progress towards objectives:
- WP7 started handling IPR issues including securing by copyright protection either for software which will be developed and for optimised sensing system which will be produced. GhT also started to set a plan for the use of foreground together with the other SMEs. Moreover, we've started to talk with some major customers about the results of this project for mutual benefits.
- During the first year of the execution, the draft version of the plan for the use of foreground was implemented. The document reports either the dissemination and exploitation activities to be carried by consortium members, including the different channel to diffuse as much as possible the knowledge of project results toward scientific and industrial community. We've also put a list of potential target groups which could be the final users of the project. Finally, WP7 started to build a brochure and CD demo for customer presentations.
- The plan and the dissemination activities realised so far are reported in D7.1 'Plan for the use of the foreground'.
- The draft version of plan for the use of the foreground has been produced during the second semester by the WP7 leader, with the support of SMEs. In the last third semester, the involved partners added other targets for the dissemination activities and also potential customers in the data base of the plan for the exploitation of the project results.
- In the last semester GHT also proceeded in defining the different issues which will take to the final version of plan for the use of the foreground, i.e. adding new references regarding potential customers and also identifying strategies for an agreement between SMEs addressed to the ownership of the monitoring system and for DSS.
- During the second year, the design of the CD demo for the DSS and monitoring system to present the results to major potential customers started. Also, the brochure was to be designed for same purposes.
- SMEs started to disseminate the preliminary results of MONICO to the most relevant potential customers included in the data base of the draft of plan for the use of the foreground, through periodical updates via mail and newsletter. Also, the suggestions raised by these contacts help us in identifying new potential markets for MONICO results.
- Through conferences and symposia attending during the project duration, MONICO partners have been able to increase the knowledge of project outcomes, either towards industrial users, researchers and designers.
- During the second year of the project, the WP7 leader has been collecting from the other project partners new improvements, remarks and ideas for producing the final version of the plan for the use of the foreground. Besides, the feedback from potential customers has been quite positive and we're confident about the continuity of such interest also for the new results obtained by RTD performers which are added continuously.
- The drafting of other dissemination tools, like CD demo, brochure and also next newsletters also started during the second year.
- The collection of fundamental outcomes by the RTDs involved in the project has pushed the knowledge management activity towards potential customers it was quite sure that the interest of potential customers would increase more and more.
- A dissemination plan for the whole duration of the project has been drawn. The plan and the dissemination activities realised so far are reported in D7.1 'Plan for the use of the foreground (draft)'.
- Creation of SME's agreement report on the ownerships of the MONICO results. Please refer to deliverable D7.2. (Action executed in collaboration with all project SMEs).
- Creation of deliverable D7.2 - use of foreground - final version.
- Circulation of MONICO results to potential customers as these reported in D7.2.
- Development of MONICO demo-CD.
- Design and development of the MONICO final brochure.
- Development of MONICO demonstration video to be included in the demo CD.
- Distribution of dissemination and demonstration material to potential customers.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP7: Optronics, AOS, GHT
WP8 - Training and dissemination of results (GHT)
General objectives:
- To disseminate the existence of the project and its results and achievements to the scientific community but mostly, through a market oriented approach to companies that provide structural monitoring services, agencies that own and operate tunnel facilities, tunnel rehabilitation contractors, tunnel designers, tunnel contractors, providers of fibre optic sensing services, insurers, officers in public safety agencies, representatives of relevant associations and societies, such as the Fibre Optic Association, the Optical industry Development Association, the International Tunnel Association, the Construction Management Association, the International Tunneling Insurance Group and others.
- To develop an interactive and user friendly web site to inform the general public and all stakeholders about MONICO.
- To organise a workshop that will focus on the application and end-users.
- To train the technical and managerial staff from the participating SMEs on the use of the DSS and the monitoring system.
Objectives for the current period:
- To disseminate the existence of the project and its results and achievements to the scientific community.
- To develop an interactive and user friendly web site to inform the general public and all stakeholders about MONICO.
Work progress towards objectives:
- The MONICO logo was developed and approved by the consortium. The logo is used to identify all project results including deliverables, dissemination material, scientific posters, etc.
- In order to facilitate the data communication among partners an ftp site was implemented restricted only to the consortium members. The ftp server will also serve as a storage place for all internal reports, deliverables, milestones and other project documents / files.
- The project's website was designed and implemented at http://www.monico-eu.org. The website includes information over the project's mission, objectives, technological approach, deliverables, latest news and contact information. The website will be continuous updated throughout the project's lifetime. Partners' logo, website and any other supportive material to be included in the project web site and dissemination material was gathered.
- Two issues of MONICO electronic newsletter were issued, at month 6 and 12 of the project, introducing MONICO project and presenting the work progress during the first year of project lifetime. The necessary material was requested and gathered from the relevant partners. The newsletters have been uploaded at the web-site.
- A mailing list has been implemented which is composed of people interested on the project's activities. The mailing list members will regularly receive updates on the project in the form of newsletters.
- MONICO leaflet and poster were developed. The design and graphical elements used were in line with the logo and the ones used for the website. The leaflet and poster were handed-out at conferences, workshops as well as important related events.
- In order to facilitate the selection of the appropriate edition or event to publish the project's results the dissemination responsible periodically issues an event calendar which includes events of special interest to the project.
- Our first aim, to disseminate the awareness of existence of MONICO both toward scientific community and potential industrial users, is pursuing continuously, being one of the first objectives of WP8. That was carried out through different ways, but all of them are with a market oriented approach. Also, the consortium set the conferences, workshop and exhibits to attend for dissemination purposes; further it created the basis for organising a final workshop which will release the final outcomes to potential end-users.
- The last newsletter has been released at the end of 2010, so all the potential customers included in the mailing list have been able to realise the valuable developments obtained during the last period. The document describes the MONICO proposal, giving an overview of monitoring technologies implemented in the project, introducing the DSS which is compound by the expert system and the data base of sensor data and tunnel records and finally an approach for deterministic and probabilistic assessment. We've also examined sensor and material performances used in the project and finally described some tests on small scale specimen.
- The final newsletter and project brochure were distributed to the list of potential customers.
- Further potential customer opportunities (in cooperation with all SMEs) and improvement of customer data base were investigated and improved.
- Towards the end of the project the MONICO workshop was organised.
- The RTD partners performed training of the monitoring technologies and software modules, through on-site meetings during the pre-final and final tests and other meetings, workshop etc.
- Website updates regarding project deliverables, recent outcomes, publications and recent updates were performed during the last period of the project.
- Following activities to submit project results into related conferences and journals (please refer to D7.2 for details).
Corrective actions taken / suggested:
No corrective actions needed as the delay was not crucial.
Contractors that worked in WP8: ICCS, Optronics, AOS, GHT, Tecnic, RISA
WP9 - Consortium management and assessment of progress results (ICCS)
- Overall project coordination. Communication with partners at all levels (WP leaders, task leaders, and partners).
- Overview of all technical activities.
- Coordination of the subcontracting procedure between project SMEs and RTDs. A template for subcontracting was prepared and distributed to the SMEs. The SMEs provided feedback and the template was agreed and signed by the three SMEs. The actual agreement has been included in deliverable D7.2.
- Regarding the issues with the defaulting partner (OSMOS), ICCS as the project coordinator and in cooperation with the Project Officer (European Commission (EC)), has followed all the legal and formal steps to exclude the partner and replace it by Optronics SA. The coordinator closely collaborating with the project SMEs have analysed various alternatives and the most proper partner was identified always ensuring high expertise as needed and fitting into the project needs as well.
- Preparation of agenda, organisation and coordination plenary meeting on the 10 - 11 March 2010.
- Preparation of agenda, organisation and coordination of kick-off and first plenary meetings.
- Preparation of kick-off and first plenary meetings minutes.
- Coordination of financial and technical contributions for the preparation of the first, second and third interim activity reports. Preparation of the relevant templates and distribution to partners.
- Close follow-up of reports / activities / deliverables deadlines and responsible partners.
- The quality control procedure for the project is defined from the beginning of the project. The quality manual sets the rules and procedures for document and data control, reporting and scheduling of dissemination events and reviewing of project deliverables. The manual includes templates for official MONICO documents and naming conventions.
- Coordination of review process (executed off-line), final review (also executed off-line) and submission of deliverables.
- Preparation of the technical meeting in Dresden (27 July 2010).
- Initial organisation for the next plenary meeting (9 - 10 November 2010).
- Close follow-up of reports / activities / deliverables deadlines and responsible partners.
- Preparation and organisation of the GA in Berlin (9 - 10 November 2010).
- Preparation above Berlin GA meeting minutes.
- General organisation of the small and large scale tests as executed in Trento.
- Following the quality control procedure for the project that was defined from the beginning of the project.
- After the quality review, all project deliverables were sent to the EU within the project execution:
D1.1: Specifications for the sensing system, the interrogation unit, the communication system and the SDPM. Sent to EC on 15 April 2009.
D2.1: Methodology for the deterministic and probabilistic assessment of structural condition under normal operating loads. Sent to EC on 15 April 2009.
D3.1: Methodology for the deterministic and probabilistic assessment of structural condition under seismic loads. Sent to EC on 15 April 2009.
D4.1: Methodology for the deterministic and probabilistic assessment of the global structural condition. Sent to EC on 11 June 2009
D5.1: The expert system, the data base and the knowledge base (Prototype V1) (D5.1) - Accompanying report. Sent to EC on 12 November 2009.
D7.1: Plan for the use of the foreground (Draft). Sent to EC on 12 November 2009.
D8.1: Website for the project - Accompanying report. Sent to EC on 1 December 2009.
D5.2: The expert system, the data base and the knowledge base v2 - sent to EC on 25 March 2010.
D1.2: The SDPM, the interrogator unit and the wireless transceiver module - sent to EC on 30 September 2010.
D1.3: Embedded deformation sensors evaluated at the structural lab and refined - sent to EC on 31 March 2011.
D7.3: Brochure and demo of the monitoring system and the DSS (Final) - Demo CD and brochure distributed at the final workshop (18 March 2011) - snapshots and content have been included in the D7.2 deliverable.
D2.2 D3.2 D4.2: 2.2. Module 1, evaluated at the structural lab and refined, 3.2. Module 2, evaluated at the structural lab and refined, 4.2. Module 3, evaluated at the structural lab and refined - Sent to EC on 9 May 2011.
D6.1: Report on the whole simulation tests and the calibration and validation of the theory of seismic failure. Sent to EC on 18 May 2011.
D7.2: Plan for the use of the foreground (Final). Sent to EC on 26 May 2011.
D5.3: The integrated DSS and package (Final). Sent to EC on 1 June 2011.
D5.4: The system guide and user manual. Sent to EC on 2 June 2011.
Corrective actions taken / suggested:
During the first year of execution, the partner OSMOS was removed from the consortium and replaced by the partner Optronics.
Project meetings:
- Kick-off meeting, Athens, 30 - 31 October 2008
- Plenary meeting, Rome, 26 - 27 February 2009
- Plenary meeting, Santorini, 25 - 26 June 2009
- Plenary meeting, Padova, 8 - 9 October 2009
- Plenary meeting, Athens, 10 - 11 March 2010
- Plenary meeting, Berlin, 9 - 10 November 2010
- Final meeting (and workshop), Athens 17 - 18 March 2011.
Technical meetings:
- Civil technical meeting, Athens, 27 January 2010
- Technical meeting, Dresden, 27July 2010.
Potential impact:
Socio-economic impact:
The assessment of operating life of civil structures has recently become crucial, because in the first place it takes to a better environmental impact due to the life extension of the structure and secondly it reduces the overall costs for demolition and rehabilitation of damaged segments.
The deployment of monitoring systems based on the MONICO project, which normally allow control of the structure in a continuous way, will strongly help both to increase its working life, leading to improvements on environmental conditions and cost reductions.
MONICO will introduce also a new concept on tunnel structural maintenance. Presently the verification of structural conditions is still based on periodic visual inspection, carried out by trained experts. This procedures are usually very expensive, time consuming, due to structure complexity, subjective, because the technicians normally cannot rely on historical data on structure and finally unreliable, because it cannot detect damages that are not yet visible.
Moreover, when the degradation is getting visible, it might be that the damage has already got to a level which could require huge costs for restoring. Indirect costs are also to be considered, due to tough access to the structure, which takes to delays and inefficiency suffered by the users.
At present, the most used method to prevent tunnel damages is normally called 'corrective maintenance'. According to this procedure, the damaged tunnel section is simply replaced with new one; this takes to high cost levels, either direct or indirect, reduced safety levels and high environmental impact.
An alternative method which is becoming more and more used is called 'proactive condition-based maintenance'. With this approach, the monitoring system which reads the data continuously provides the potential warning conditions of structure on the first stages; as consequence there's a lower maintenance level cost, because the inspections can be carried only after a real request, an increase of safety level and a better management of structure.
The actual importance of the MONICO project will evolve in cases where it's necessary to evaluate the tunnel structural conditions after an earthquake. Normally, the seismic event can cause asymmetric loads so that the structure can exceed its functional limits. If that overcoming does not take to evident signs of damage, it's necessary to carry a deep structural analysis. The problem is even more complex because there's in first place a shortage of experienced technicians to perform these analysis and secondly the need to close the structure accesses for enough time, just in those periods for which it would be necessary to have as many road links as possible.
The monitoring system based on MONICO will give on the contrary an immediate and reliable evaluation of suffered damages, allowing the operators to decide if the structure has to be shut down or not and thus aiding civilian safety, injuries or other unfortunate events that may be caused due to any earthquake aftermath.
Contribution to standards and policies
MONICO is a project based on using of fibre optic sensors, presently one of the most promising market segments. It is then in full accordance with EU policies which aid to adopt all the efforts to increase within EU the share of growing markets.
The high technological profile of MONICO will help to form expert technicians on fibre optic technology, following those recommendations of treaty of Amsterdam which concern social affairs and employment policies.
As we know, one of the main features of the project is the ability to monitor a structure continuously for its whole operating life; for that it will be possible to obtain both helpful details for a better standardisation of ways to design a tunnel and more complete understanding of the behaviour of structure in non-linear conditions.
Within the efforts for decreasing of civil structure environmental impact, MONICO is pursuing the environmental technologies action plan (ETAP) objectives, because it allows both to reduce the operating costs and consumption of resources and makes to grow the EU role within the development of environmental technologies.
The European Commission Transport Policy (ECTP) points out as primary target the reduction of deaths on the road by at least 50 %; MONICO will give its contribution by means of its new safety concepts.
Finally, other SMEs active in the optical monitoring technologies will benefit from MONICO outcomes, through the purchasing or licensing the MONICO results. This follows the EU objectives towards increasing SME competitiveness in Europe.
Fibre optic sensing is one of today's fastest developing technologies. One reason for this is that the costs of fibre sensors have been dropping steadily (in large part due to exceptional advances in fibre telecommunications technologies) and this trend will continue. Further, measurement capabilities and system configurations (such as wavelength multiplexed, quasi-distributed sensor arrays) that are not feasible with conventional technologies, are now possible with fibre sensors, enabling previously unobtainable information on structures to be acquired. One area where the above advanced technology can have an immediate impact in construction is in improving the current state-of-practice of structural monitoring systems. The importance of structural monitoring is growing due to a shift from construction costs to life cycle costs and lifetime performance including safety and use. This holistic approach in addition to monitoring technologies includes assessment methods. Fibre optic sensor technologies are finding growing application in the area of monitoring of civil structures. This has resulted in a growing field of fibre optic structural sensing in construction that is highly competitive and composed exclusively of small and medium-sized enterprises (SMEs). A study in the field by one of the SME proposers showed that 90 % of those interviewed from the construction industry and the administration would like to outsource structural monitoring. It follows that companies in the fibre optic structural sensing field need to develop advanced methodologies and computer programmes for specific applications that based on the sensor information will assess the structural condition of the monitored facility. For this, these companies need expertise in structural engineering, earthquake engineering (in seismic prone areas), and structural reliability since there are uncertainties in measurements from inspections, materials' parameters and geometric properties and errors in materials' and structural models. Such expertise is presently not available in the fibre optic sensing industries.
Tunnelling activity is on the increase around the world, but it is not just the volume of work which is rising. The demands of modern transport networks mean that tunnels are longer and wider than ever before and being driven through increasingly difficult ground conditions. Moreover, several planned tunnels are in countries of high seismicity and a good part of the tunnel kilometres will be under densely populated areas and require very high standards of safety. To the above one should add that today's tunnel environment is characterised by high user demands, stretched budgets, declining staff resources and greater operational complexity necessitating the development of asset management plans that are based on accurate and timely assessment of the structural health of tunnels. Accordingly, the new niche market of tunnel continuous monitoring and assessment should be among the first markets to be targeted by the SMEs in the fibre optic structural sensing field. There is an increasing awareness of the sensitivity of tunnels to seismic activity (tunnels have experienced significant damage in recent large earthquakes including the 1999 Kocacli, Turkey earthquake, the 1999 Chi-Chi, Taiwan earthquake and the 1995 Kobe, Japan, earthquake). Moreover, the damage to the tunnel structure is difficult to assess and a damaged tunnel that has survived the major earthquake might not have the capacity to survive consecutive seismic aftershocks. Such aftershocks take place within few hours of the earthquake and have been reported to have an intensity of up to 90 % of the earthquake intensity.
Tunnel primary linings are mostly constructed of reinforced concrete (r.c.). Most vulnerable are lining cross-sections under inhomogeneous loading, e.g. cross-sections located in regions of transition from one type of soil to another. Included are the tunnel entrance and exit. Included also in the old cities of the European Union (EU) are metro cross-sections that on one side step on ancient ruins. For instance in Athens such cross-sections can be found on the average every 200 metres. All structures undergo deformations under the effects of loads or changes in the constituent materials. The deformations of any structure (tunnels, bridges, etc.) contain a lot of information about its health state. By measuring these deformations, it is possible to analyse the loading and ageing behaviour of the structure and assess its safety. To ensure the safety of vulnerable tunnel cross-sections or sections where very high standards of safety are required, fibre optic sensors providing a real-time, wireless and remote deformation sensing capability, need to be integrated with software that will collect and process the signals and assess the structural reliability of the lining. In regards to proactive maintenance, measured deformations can be converted to strains, curvatures, deflections, stresses, bending moments and axial forces which can be monitored so that they do not exceed limit values. Regarding earthquakes, the philosophy of earthquake resistant design is to mitigate extensive damage rather than to prevent its occurrence. Elastic response provides a poor measure of susceptibility to damage. The damage done to a cross-section during strong motion excitation depends primarily on the energy transmitted and dissipated by the cross-section during inelastic cycling. Only by recording and analysing the structural response during the latter cycling can an accurate evaluation be made of the remaining dissipative energy capacity of the cross-section before the limit state is being reached.
In the EU funded project TUNNELLING, Tecnic developed an energy-based theory of seismic failure for reinforced concrete tunnel lining cross-sections based on the history of deformations during the earthquake derived from fibre optic measurements. It was deterministic and limited to local failure. Deterministic evaluations leave no room for tolerances for errors in data from non-destructive evaluations, variations in materials and the relevant geometry and errors in modelling material and structural behaviour. Hence, the deterministic evaluations obtained without consideration of uncertainty could lead to unreliable results. Accordingly, reliability-based evaluation methods are more appropriate. Furthermore, local failure does not necessarily result in global failure (collapse) of the monitored cross-section. Thus, the probabilities of both local and global failure need to be determined. New technologies are being developed continuously in the optical sensing area which is one of the fastest developing technologies. What is needed at this point is that existing and emerging fibre optic deformation monitoring technologies be evaluated and optimised so that alone or in combination can provide optimal performance in tunnel structural sensing under operating and seismic loads. The SMEs in the fibre optic sensing field do not have the extra manpower and facilities for the above.
The overall objective of the proposed research is to provide the SMEs in the group with an integrated package that will include an optimised fibre optics sensing system for the continuous monitoring of deformation and a decision support system (DSS) for the assessment of the structural condition of reinforced concrete, transportation, primary tunnel linings under operating and seismic loading.
To accomplish the above, specific scientific and technical objectives of this work are the following:
1. To provide optimised fibre optics based sensing system for r.c. tunnel linings that can be embedded in concrete for the life cycle measurement of deformation, that measures fast events (seismic disturbances) and that transmits information to a remote base using a wireless interface. A sensor data processing module (SDPM) will be developed that will be part of the monitoring system in order to filter out noise and erroneous data and present it in a way that is useful and convenient to the user. To elaborate further, the SDPM will be a software component to render the data to the appropriate format in order to be fed to the expert system. A processing of the sensors data will ensure the compatibility of the format for processing by the structural condition assessment software.
At the very minimum the following systems will be evaluated in regards to continuous tunnel monitoring, optimised and possibly combined:
- A Bragg grating fibre optic based monitoring system
This system will permit at least 2 × 8 gauges, each between 200 mm and 2000 mm long, to be put on the same fibre and each gauge will include at least 4 conventional, high reflectivity apodised fibre Bragg gratings (FBG). The resolution of each specific sensor is expected to be around 1 - 5 µe in strain terms or 1 - 5 pm in wavelength terms. Two about 30 m long systems will be installed inside the inner and outer linings of the tunnel. The environmental temperature of the sensors will be monitored and the measurements compensated accordingly. The remote interrogation system will perform, with the aid of a CCD, a spectrum analysis of the light reflected by the FBGs and decode the Bragg wavelength shifts in terms of the strain acting on the gauge. A broadband (about 75 nm) SLED light source will accomodate the full spectral range of FBG wavelengths. The interrogation system will support two channels, the inner and the outer sensor systems, simultaneously using an optical switch.
- A distributed fibre optics sensing system based on the principle of Brillouin scattering
Brillouin scattering is a fundamental process of inelastic light scattering which occurs due to the interaction of light with acoustic waves (phonons) of an optical medium. The backscattered light of the Brillouin process is red-shifted from the frequency of the incident light and this shift is proportional to the strain and temperature at the certain part of the medium from which the backscattered component arises. Using pulsed light and optical time domain reflectometry (OTDR) measurements, the Brillouin shift can be resolved in space along the fibre (medium) thus a distributed (almost continuous) sensing of strain and temperature along the fibre is possible. The interrogator of the Brillouin sensing system is a sophisticated coherent detection device that is able to measure the beat frequencies arising from the detuning between the incident and backscattered light. The space resolution of the system is proportional to the duration of the light pulses. It can be as low as 1m or even lower if a special mounting technique of the fibre is employed and the strain resolution can be as low as 5µe.
Both of the above approaches have certain advantages and disadvantages. They will be identified, evaluated and optimised, so that alone or in combination can provide optimal performance in structural sensing. Briefly, the main advantage of Brillouin technique is the capability of continuous strain and temperature measurements along a simple and inexpensive commercial fibre cable that runs along the entire structure to be monitored. Though, our proposed analysis, will refer to specific sections of the installed fiber, it gives the ability to monitor any point on the fibre line, allowing for the fine tuning of the section to be monitored. However, the spatial resolution of the Brillouin method is restricted by the pulse width to approximately 1m. Moreover due to the inherent characteristics of the Brillouin phenomenon (low backscattered light power) the rate at which measurements can be obtained is lower compared to an FBG system. On the other hand FBG sensing systems are more complicated in installation due to the multiple gauges required for monitoring different points of the same structure but lend themselves to high data acquisition rates. The complexity and the cost of a Brillouin interrogator is also considerably greater compared to the much simpler FBG interrogator.
2. To develop a methodology for the probabilistic assessment of the local structural condition of the r.c. monitored sections in the tunnel lining cross-section under operating loads based on measurements of deformation.
3. To extend the deterministic energy-based theory of local seismic failure for reinforced concrete structures devised by Tecnic to a probability-based assessment of local seismic structural reliability.
4. To develop a methodology for the probabilistic assessment of the global structural condition of the r.c. lining cross-section based on the local, probabilistically defined, conditions in the monitored lining sections.
5. To evaluate the methodology in '4' via non-linear finite element analyses.
In '2', '3' and '4' above account will be taken of errors in data from the fibre optic sensors, variations in materials' parameters and the relevant geometry and errors in the modelling of materials and structural behaviour.
6. To provide an integrated package for tunnels for health monitoring and safety assessment under routine operation and seismic forces. It will include the following:
- The system in'1'.
- The 'local structural condition' module. This module, which is a software implementation of the theory in '2', will receive as input from the sensing system measurements of deformation according to some schedule and will process it to derive the corresponding strains, curvatures, stresses, moments and the axial force and to assess the probability that defined limit states have not been exceeded..
- The 'local seismic capacity' module. This module, which is a software implementation of the theory in '3', will receive as input from the sensing system the deformation time history during an earthquake and will process it to assess, probabilistically, the remaining dissipative capacity of the monitored sections before the limit state is being reached.
- The 'global structural condition' module. This module, which is a software implementation of the theory in '4', will receive input on local conditions from the above modules in order to derive, probabilistically, the global structural condition of the tunnel cross-section. This module will signal a warning if the tunnel is unsafe or if, in the case of an earthquake, might not survive expected aftershocks.
- Deterministic versions of the above modules will also be provided. Moreover, these modules will be usable with the existing sensing systems of the SMEs in the group as well as with other sensing systems that can provide tunnel deformations.
- A data and knowledge base that will contain domain knowledge (represented in the domain modules) and system knowledge (i.e. rules governing the coordination of the system modules). The data base will include sensor data and data on tunnel records (e.g. amount and type of steel reinforcement).
- An expert system. This system will coordinate the other modules and sub-modules and will act as an intelligent intermediary between the users and the results that will be obtained.
7. To experimentally evaluate the sensing and data acquisition system in '1' and the predictive ability of the theory of seismic failure in '3'.
Project results:
Work package (WP)1 - Monitoring system. Wireless communication capability (ICCS)
General objectives
- Development and production of a fibre optics based deformation monitoring system that can be embedded in concrete and report at seismic frequencies.
- Development and production of interrogation equipment for the above system.
- Development and production of the sensor data processing module (SDPM) which will be part of the monitoring system.
- Provision of reliable wireless communication capability in supporting the project information transfer requirements under normal conditions and in the event of an earthquake.
Work progress towards objectives:
- Deformation sensors: The complete set of technical characteristics for the fabrication of FBG sensors was determined, meeting the requirements of the project, in terms of glass materials, grating parameters (pitch, strength, apodisation), wavelengths, side lobes level, strain and temperature sensitivity. A considerable effort was also devoted to the design of the gauges (SmartRod-style steel bars) that will enclose the FBG sensors. A redesign was required in order o increase the measurable strain range close to the concrete damage limit. This affected the number of sensors per line and the switching scheme.
- Sensor data processing module: Procedure and algorithm have been developed to transform Bragg wavelength shifts to strain information and compensation for the temperature dependence of measurements.
- Interrogation unit: The specifications of the light source (LED) that will illuminate the FBG arrays in terms of wavelength range and power have been developed. Analysis and details of the couplers directing the reflected light to the detecting unit has also been executed. Specifications of the CCD-based spectrum analysis of the reflected light in terms of resolution and sensitivity are complete.
- Wireless communication capability: The work has included hardware and software design: wireless modem, WiFi equipment, hub and router, protocol and interrogation routines between LabView environment and router. Two possible scenarios/options were developed regarding Ethernet or USB based connection of the interrogation unit.
- All objectives distributed among the tasks 1.1-1.4 were achieved as far as the design of the FBG sensors-based deformation monitoring system. The system was completely finalised and approved by the civil engineers partners.
- Problems related to the mounting of gauges to the lining so as to avoid techniques that may damage the sensors (welding) were solved through cooperation with partners experienced in civil structures.
- Special attention was given to the required triggering of data recording in the event of an earthquake ('awake' signal): survey on seismic switches and sensors, accelerometer and geophone technology. The discussion and survey concerning the required triggering of data-recording in the event of an earthquake ('awake' signal) has lead to this solution: the transient data provided the FBG sensors will be processed by the software (developed by RISA) in order to detect an abruptly increasing strain envelope. Thus, no additional earthquake triggering device (e.g. geophone) would be needed, which is beneficial in terms of cost and maximises the utility of our sensors.
- A wireless communication between FBG interrogator and the end user pc was established employing a USB extender. This module was chosen as the simplest solution for wireless communication, however error-free communication was achieved at a low data rate, inadequate to support continuous flaw of interrogator generated data. The well-established Ethernet technology is currently setup as the final solution for the wireless system communication.
- A first round of experimental calibration and validation of the FBG sensors completed to obtain essential results on the sensors performance. Full sensor characterisation in the material tester test-bed was completed.
- Regarding the Brillouin optical time domain reflectometry (BOTDR) fibre sensor types were selected and a preliminary coil-shaped sensor configuration was setup, in order to reduce the spatial resolution of the technique.
- The issues of the wireless communication data rate were solved in cooperation with AOS. USB-Ethernet solution was complete while a second pc-pc Ethernet communication was also evaluated as fall-back position.
- Intense collaboration between ICCS, AOS and UNITN allowed for an improved version of FBG sensors with better mounting features that exhibit increased tolerance to sensor deformation.
- Development of spiral shaped Brillouin sensors and (in-lab) characterisation.
- Completion of D1.2: 'The SDPM, the interrogation unit and the wireless transceiver module' (M22).
- BOTDR technology inherent restrictions were identified in spatial resolution, operational frequency and strain sensitivity / dynamic range. Custom configuration was accommodated in order to match/compensate for these operational characteristics. Please check D1.2 and D1.3.
- During the last reporting period, ICCS performed the characterization of the Brillouin sensors.
- ICCS (in cooperation with AOS) prepared the FBG and Brillouin sensors that were installed in the final test ring (in UNITN labs). Feedback was consolidated from the previous tests to improve and provide the optimal sensor solutions for the case.
- ICCS in cooperation with AOS and UNITN aided the installation of the sensorial (FBG and Brillouin) systems to the UNITN laboratory (final tunnel test ring).
- Completion of the deliverable D1.3 'Embedded deformation sensors evaluated at the structural lab and refined'.
Corrective actions taken / suggested:
- In the fourth MONICO meeting in Padova, partners agreed on taking a list of actions in order to solve the problem with OSMOS. Please refer to the MONICO meeting minutes. Partner OSMOS was formally removed from the consortium.
Contractors that worked in WP1: ICCS, Optronics, AOS, GHT, TECNIC, RISA
WP2 - The 'local structural conditions' module (RISA)
General objectives:
- Development of a methodology for the probabilistic assessment of the structural reliability of monitored reinforced concrete sections in a tunnel lining subjected to operating loads, based on measurements of deformation.
- Software implementation of the above in the 'local structural condition' module.
Work progress towards objectives:
- A methodology has been developed, as planned, for the assessment of the probabilistic, local, structural condition under normal, operating loads. It has been assumed that geometric properties (that is, the height of the cross section, distance between rebars and rebar covers) will be measured with a sufficient degree of accuracy when the sensors are installed. It has also been assumed that the measurement error of the sensors is negligible next to other uncertainties. Based on the above, the four following material variables are considered as random variables: yield strength of concrete in compression, ultimate strain of concrete in compression, yield strength of steel and modulus of elasticity of steel.
- A methodology has been developed, as planned, for the stochastic assessment of the local seismic capacity based on strain measurements. In this case in addition to the random variables above, DA, the allowable value of the energy ratio damage index D, has also been treated as a random variable.
- Requirements and specification of the module were successfully completed.
- Testing and refinement of the module was executed on time followed by the related documentation.
- Finishing task 2.3.4 documentation.
- Deliverable D2.2 finalisation.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP2: Optronics, AOS, GHT, Tecnic, RISA
WP3 - The 'local seismic capacity' module (RISA)
General objectives:
- Development of a methodology for the probabilistic assessment of the seismic structural reliability of monitored reinforced concrete sections in a tunnel lining subjected to seismic loads based on measurements of deformation.
- Software implementation of the above in the 'local seismic capacity' module.
- To develop a methodology for the stochastic assessment of the local seismic capacity based on strain measurements.
- Development of the requirements and specifications of the software package based on the methodology in D3.1.
- Start working on the design and implementation of the software package.
Work progress towards objectives:
- A methodology has been developed, as planned, for the stochastic assessment of the local seismic capacity based on strain measurements. In this case in addition to the random variables above, DA, the allowable value of the energy ratio damage index D, has also been treated as a random variable.
- Requirements and specification phases successfully completed during the second year of execution of the project while the design and implementation phases started immediately afterwards.
- The testing and refinement phases concluded the actual algorithms development phases.
- Documentation (task 3.3.4) has been completed.
- Finalisation of deliverable D3.2.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP3: Optronics, AOS, GHT, Tecnic, RISA
WP4 - The 'global structural condition' module (Tecnic):
General objectives:
- The objective of this WP is to assess, both deterministically and probabilistically, the degree of global damage of the monitored lining cross-section under normal operating and/or seismic loads
Work progress towards objectives:
- A methodology was developed and evaluated, as planned, that, based on local damage under operating conditions, can predict, deterministically and stochastically, the global stability of the monitored cross-section.
- While working in WP4 the research and technology development (RTD) performers realised that based on the measured deformations at specific points on the monitored tunnel cross-section under operating loads, they can, through back analysis, assess the applied external loads on the tunnel (that vary as a function of time and are unknown) and tunnel stability. This approach is novel and will provide invaluable information to tunnel owners and tunnel researchers. To this target the requirements and specifications were completely done and the design and implementation of the software package has started.
- The requirements and specification task was successfully completed while the design and design and implementation started on schedule.
- The testing and refinement task started and completed successfully including testing, integration, identification of problem areas and upgrading and refinement.
- The documentation task started also on time having as a major objective the contribution to system guide and user manual.
- During the last six months of the project the documentation task 4.3.4 was completed
- Completion of deliverable D4.2 'Module 3 evaluated at the structural lab and refined'.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP4: Optronics, AOS, GHT, Tecnic, RISA
WP5 - The expert system, the data base, the knowledge base and DSS and package integration (RISA)
General objectives:
- To design and deploy a system architecture that is flexible (so that it can be adapted to different types of fibre optic sensors), scalable (so that it can include into the future additional functions, e.g. selection of rehabilitation measures) and modular (so that that it can include additional type of measurements, e.g. corrosion measurements).
- To develop the expert system, the data base and the knowledge base.
- To integrate all modules in the DSS.
- To integrate the DSS with the sensing and data acquisition system. Moreover, to provide appropriate interfaces so that the proposed DSS can be used with the existing monitoring systems of the SMEs in the group.
Work progress towards objectives:
- The development of a common understanding of the system's scope and desired behaviour has been accomplished.
- A methodology has been defined, as planned. Having reviewed the available methodology, it has been decided that the overall development approach for the MONICO DSS will be the adopted adapted waterfall model, which includes analysis, design, development, testing and evaluation. The chosen data access application and programming language will be Microsoft Access and Java.
- A specification for the expert system and the data and knowledge bases has been set. The translation of the user requirements into specifications that describe the conceptual models for the expert system and the data and knowledge bases and how to implement them. The requirements have been transformed into a conceptual design and the best software architecture that is scalable and modular and permits future expansion of the expert system and the data and knowledge bases to accommodate additional applications.
- Design and implementation of the expert system and the data and knowledge bases. The purpose was to set out the design of the modules of the DSS. As the design has advanced with the clear longer-term goal of module integration, both it and the implementation methodology reflect an explicit preparation for the integration stage of the software development life-cycle.
- Software implementation and development of the prototypes of the expert system and the data and knowledge bases.
- The design and implementation task (5.3.3) was successfully finished towards the end of the second year of the project.
- The integration task started in the second year and by the end of the same year it was almost finished (90 %).
- System documentation started as planned during the second year.
- Finished integration: It involves integration of all modules in the DSS and integration of the DSS with the sensing and data acquisition system (task 5.4).
- Finished global system testing and consolidation: It involves testing and refinement of the overall DSS and includes test planning, global and extensive system testing, analysis of results and upgrading (task 5.5).
- Finished documentation (task 5.6).
- Finalisation of deliverables D5.3 and D5.4.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP5: ICCS, Optronics, AOS, GHT, Tecnic, RISA
WP6 - Laboratory evaluation of the performance of the condition monitoring system and the predictive capability of the theory of seismic failure (UNITN):
General objectives:
- To assess in a structural laboratory the performance of the condition monitoring system on reinforced concrete specimens (substructures) representative of a tunnel lining.
- To calibrate against novel monotonic, cyclic and dynamic test results the energy-based theory of seismic failure.
- To validate the predictive capability of the energy-based theory of seismic failure and the global structural condition module.
Work progress towards objectives:
- This WP officially was to start on month 16. However, an internal report on the design of specimens to be tested by UNITN was produced quite earlier. In detail, possible substructure and demonstration tests are presented devoted to the calibration of models and to the investigation of a typical design case where seismic forces can be greater than the ones obtained through static analysis.
- UNITN started parts of activities of WP6 after the coordinator of MONICO, in agreement with the remaining partners, proposed to test a full scale specimen of a tunnel lining in the UNITN laboratory. This test for its own nature is complex and risky, and unfortunately is unique. As a result in order to identify the optimal fibre attachment to the rebars, the plastic hinge length and the experimental material stress-strain constitutive laws as well as the moment curvatures diagrams, UNITN proposed to perform some preliminary tests on tunnel substructures, to be carried out.
- WP6 started to analyse the structural behaviour of typical circular tunnel linings according to recent research works. The determination of actions, which the structure is subjected to, as well as their distribution represent main steps towards an adequate and significant specimen design. Thus, both static and seismic analyses were performed, by using common realistic size and materials for the lining and typical soil, depth and water table level values. Since the project is devoted to the detection of damage owing to seismic events, we designed the tunnel lining so that seismic loadings result to be critical. We found that actions are sinusoidal along the curvilinear coordinate of the transverse section; moreover, we identified that in correspondence of the maxima, tunnel portions of about 1 m long could be considered subjected to constant bending moment. Hence, specimens representative of tunnel lining substructures to be subjected to monotonic and cyclic four-point bending tests were reckoned to be suitable for our purposes.
- Due to the concrete flexural behaviour associated with high levels of stress distribution, e.g. owing to an earthquake, plastic hinges may form entailing large localised deformation associated with damage. The plastic hinge length depends on many factors and, therefore, it is important that FBGs be located within this length. Furthermore, cracking also occurs and this causes the so-called tension stiffening effect, i.e. tension peaks in the rebars in correspondence to cracks. This means that a FBG bonded to the concrete may be affect by this local phenomenon. Hence, the material characterization plays a central role in the FBG packaging design. Since, the preliminary tests also aims at identifying the optimal fiber attachment, two FBG packages have been conceived on the basis of the plastic hinge length estimate and employed in each instrumented specimen in order to measure strains at the two longitudinal rebar levels: i) FBGs bonded to the concrete and ii) FBGs unbounded to concrete. The latter system allows measuring mean strains in the plastic hinge zone, by eliminating any tension stiffening effect. Moreover, the packaging has been designed in order to be easily attached to the rebar cage.
- Through the structural analysis we designed the substructure specimens and we chose the test typology.
- In order to identify the optimal fibre attachment, we designed the FBG packing on the basis of material characterisation.
On the basis of the numerical analyses carried out in first year, UNITN found that actions are sinusoidal along the curvilinear coordinate of the lining tunnel transverse section; moreover, UNITN identified that in correspondence of the maxima, tunnel portions of about 1 m long could be considered subjected to constant bending moment. Hence, specimens representative of tunnel lining substructures to be subjected to monotonic and cyclic four-point bending tests were reckoned to be suitable for our purposes. Since, the material characterisation plays a central role in the FBG packaging design, we decided to perform three preliminary tests with also the aim of identifying the optimal fibre attachment. In detail, only one specimen was instrumented with FBGs, the other two were exploited to set the parameters of the loading protocol and to establish an optimised traditional instrumentation, whose data were compared with those obtained through the fibre sensors. Two FBG packages were conceived on the basis of the plastic hinge length estimate and employed in the instrumented specimen in order to measure strains at the two longitudinal rebar levels:
i) FBGs bonded to the concrete and
ii) FBGs unbonded to concrete.
At the end of September 2009 UNITN received from AOS the fibre packaging and casted the specimens. At the end of November 2009 UNITN performed the tests:
1) monotonic without fibres;
2) cyclic according to the ECCS (1986) protocol without fibres and
3) cyclic according to the ECCS (1986) protocol with optical fibres.
After the tests, we elaborated the data and the main findings related to the fibre optic sensor system are summarised below:
- The substructures exhibited ductile behaviour with large deformations in the plastic range associated with high energy dissipation. This implies that the structural design is suitable for seismic loading.
- Though both unbonded and bonded packaging solution should allow fibres to measure 1 % strain, from the results we noted that fibre optic sensors were not capable to measure reliable strains after reaching about 0.2 % strain. In fact, the bonded solution with increasing displacements unexpectedly read decreasing strains. From measurements we did not have accurate information on the performance of the unbonded solution, hence, it is recommended to test the unbonded solution or another packaging solution.
- In addition, the measurement of strain on short lengths can prevent an effective measure of the mechanical behaviour, i.e. the strain measure may occur in an uncracked concrete portion that entails smaller deformation values than the actual average ones. In this respect, unbonded fibres might provide more accurate values. Needless to say that steel deformation values less than 1 % are expected in tunnel linings out of fault regions.
These preliminary outcomes aided the partners to select optimal solutions in terms of optical sensors and type of packaging to be installed in the next three tests.
During the second semester of the second reporting period, UNITN designed and cast three substructures 3000 mm long and 1000 m wide characterised by a section of 200 mm. In detail, these specimens will be subject to:
- a cyclic test with FBGs fibre sensors (CF1), where the fibres will be externally installed;
- a cyclic test with FBGs fibre sensors (CF2), where the fibres will be both embedded in the specimen and externally installed;
- a cyclic test with Brillouin fibre sensors (CB1) that will be externally installed.
The design of the concrete ring was made too. The specimen was characterised by a ring endowed with 4800 mm diameter and a section of 200 mm. The specimen will be endowed with 32 FBG and 16 Brillouin fibres. Eight sections will be monitored and, in each of them, both technologies will be adopted. Cyclic loading was considered with a dy of about 6 mm.
During the last six months of the project, three tests on substructures 3000 mm long and 1000 m wide characterised by a section of 200 mm were executed as follows:
- a cyclic test with FBGs fibre sensors (CF1), where the fibres were externally installed;
- a cyclic test with FBGs fibre sensors (CF2), where the fibres where both embedded in the specimen and externally installed;
- a cyclic test with Brillouin fibre sensors (CB1) that were externally installed.
For the CF1 specimen, the maximum strain was almost 1 %; AEP and fiber sensors showed that the substructure reached the plastic range, whilst standard strain gauges were broken.
For the CF2 specimen, the maximum strain was almost 0,8% for the external fibres, whilst almost 1,3 % for the internal fibres. This time AEPs, fibres and strain gauges showed that the substructure didn't reach the plastic range but remained in the elastic range.
With regard to CB1, the specimen reached displacements values at about 4 y, i.e. 76 mm, with curvatures of about 0.5 1/m. Brillouin fibres performed significantly well.
In general, the fibre optic system externally installed in test CF1 allowed the plastic moment to be identified. In fact, the fibres read up to the 3rd cycle at a displacement of 2 y - i.e. 38 mm - measuring strains up to 1 %, thus detecting a hysteretic behaviour. However, in the CF2 test, the external fibres reached lower strain values. The method used to unbond the rebar of the second test campaign resulted to be more suitable for characterising the average strain in the plastic hinge zone with respect the one employed in the first test campaign.
Finally, it was decided that the sensor configuration for the ring test should include both fibre technologies, i.e. FBGs and Brillouin, in each monitored section.
The final test on the concrete ring was carried out the 3 February 2011. The specimen was characterised by a ring endowed with 4800 mm diameter and a section of 200 mm. The specimen was endowed with 32 FBG and 16 Brillouin fibres. Eight sections were monitored and, in each of them, both technologies were adopted. Cyclic loading was considered with a dy of about 6 mm. The concrete failure was reached at section 8; in detail this failure happened at the first cycle of 4dy, i.e. almost 25 cm. The ring exhibited a ductile behaviour associated with a high energy dissipation. Both FBGs and Brillouin sensors worked well and were capable to trace the evolution of inelastic mechanisms.
The data provided by the overall test program allowed the methodology for the deterministic and probabilistic assessment of the structural condition of a monitored tunnel reinforced concrete cross-sections to be calibrated and validated. This methodology based on the recorded strains of sensors installed both on the inner and outer transversal reinforcing bars in the eight critical sections will generally involve: the estimation of section internal forces; the external loads applied on a tunnel lining; the actual values of estimated damage indices. The structural assessment will concerns the behaviour under seismic loadings and the long term behaviour under normal operating conditions.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP6: AOS, GHT, Tecnic
WP7 - Knowledge management and intellectual property rights (IPR) protection (GHT):
General objectives:
- To secure by copyright protection the software that will be developed in the project.
- To file for patents for the optimised sensing system.
- To produce the plan for the use of the foreground
- To produce a brochure and a CD demo for the DSS and the monitoring system that will be used to present the results to major potential customers
- To present the results to major potential customers.
Objectives for the current period:
- Identifying the team in charge of WP
- Setting up the deliverables, the plan for the use of foreground and market analysis template
- Releasing of actual version of market analysis template to partners.
- Collecting exploitation input from partners;
- Releasing of draft version of plan for the use of foreground.
Work progress towards objectives:
- WP7 started handling IPR issues including securing by copyright protection either for software which will be developed and for optimised sensing system which will be produced. GhT also started to set a plan for the use of foreground together with the other SMEs. Moreover, we've started to talk with some major customers about the results of this project for mutual benefits.
- During the first year of the execution, the draft version of the plan for the use of foreground was implemented. The document reports either the dissemination and exploitation activities to be carried by consortium members, including the different channel to diffuse as much as possible the knowledge of project results toward scientific and industrial community. We've also put a list of potential target groups which could be the final users of the project. Finally, WP7 started to build a brochure and CD demo for customer presentations.
- The plan and the dissemination activities realised so far are reported in D7.1 'Plan for the use of the foreground'.
- The draft version of plan for the use of the foreground has been produced during the second semester by the WP7 leader, with the support of SMEs. In the last third semester, the involved partners added other targets for the dissemination activities and also potential customers in the data base of the plan for the exploitation of the project results.
- In the last semester GHT also proceeded in defining the different issues which will take to the final version of plan for the use of the foreground, i.e. adding new references regarding potential customers and also identifying strategies for an agreement between SMEs addressed to the ownership of the monitoring system and for DSS.
- During the second year, the design of the CD demo for the DSS and monitoring system to present the results to major potential customers started. Also, the brochure was to be designed for same purposes.
- SMEs started to disseminate the preliminary results of MONICO to the most relevant potential customers included in the data base of the draft of plan for the use of the foreground, through periodical updates via mail and newsletter. Also, the suggestions raised by these contacts help us in identifying new potential markets for MONICO results.
- Through conferences and symposia attending during the project duration, MONICO partners have been able to increase the knowledge of project outcomes, either towards industrial users, researchers and designers.
- During the second year of the project, the WP7 leader has been collecting from the other project partners new improvements, remarks and ideas for producing the final version of the plan for the use of the foreground. Besides, the feedback from potential customers has been quite positive and we're confident about the continuity of such interest also for the new results obtained by RTD performers which are added continuously.
- The drafting of other dissemination tools, like CD demo, brochure and also next newsletters also started during the second year.
- The collection of fundamental outcomes by the RTDs involved in the project has pushed the knowledge management activity towards potential customers it was quite sure that the interest of potential customers would increase more and more.
- A dissemination plan for the whole duration of the project has been drawn. The plan and the dissemination activities realised so far are reported in D7.1 'Plan for the use of the foreground (draft)'.
- Creation of SME's agreement report on the ownerships of the MONICO results. Please refer to deliverable D7.2. (Action executed in collaboration with all project SMEs).
- Creation of deliverable D7.2 - use of foreground - final version.
- Circulation of MONICO results to potential customers as these reported in D7.2.
- Development of MONICO demo-CD.
- Design and development of the MONICO final brochure.
- Development of MONICO demonstration video to be included in the demo CD.
- Distribution of dissemination and demonstration material to potential customers.
Corrective actions taken / suggested:
No corrective actions needed.
Contractors that worked in WP7: Optronics, AOS, GHT
WP8 - Training and dissemination of results (GHT)
General objectives:
- To disseminate the existence of the project and its results and achievements to the scientific community but mostly, through a market oriented approach to companies that provide structural monitoring services, agencies that own and operate tunnel facilities, tunnel rehabilitation contractors, tunnel designers, tunnel contractors, providers of fibre optic sensing services, insurers, officers in public safety agencies, representatives of relevant associations and societies, such as the Fibre Optic Association, the Optical industry Development Association, the International Tunnel Association, the Construction Management Association, the International Tunneling Insurance Group and others.
- To develop an interactive and user friendly web site to inform the general public and all stakeholders about MONICO.
- To organise a workshop that will focus on the application and end-users.
- To train the technical and managerial staff from the participating SMEs on the use of the DSS and the monitoring system.
Objectives for the current period:
- To disseminate the existence of the project and its results and achievements to the scientific community.
- To develop an interactive and user friendly web site to inform the general public and all stakeholders about MONICO.
Work progress towards objectives:
- The MONICO logo was developed and approved by the consortium. The logo is used to identify all project results including deliverables, dissemination material, scientific posters, etc.
- In order to facilitate the data communication among partners an ftp site was implemented restricted only to the consortium members. The ftp server will also serve as a storage place for all internal reports, deliverables, milestones and other project documents / files.
- The project's website was designed and implemented at http://www.monico-eu.org. The website includes information over the project's mission, objectives, technological approach, deliverables, latest news and contact information. The website will be continuous updated throughout the project's lifetime. Partners' logo, website and any other supportive material to be included in the project web site and dissemination material was gathered.
- Two issues of MONICO electronic newsletter were issued, at month 6 and 12 of the project, introducing MONICO project and presenting the work progress during the first year of project lifetime. The necessary material was requested and gathered from the relevant partners. The newsletters have been uploaded at the web-site.
- A mailing list has been implemented which is composed of people interested on the project's activities. The mailing list members will regularly receive updates on the project in the form of newsletters.
- MONICO leaflet and poster were developed. The design and graphical elements used were in line with the logo and the ones used for the website. The leaflet and poster were handed-out at conferences, workshops as well as important related events.
- In order to facilitate the selection of the appropriate edition or event to publish the project's results the dissemination responsible periodically issues an event calendar which includes events of special interest to the project.
- Our first aim, to disseminate the awareness of existence of MONICO both toward scientific community and potential industrial users, is pursuing continuously, being one of the first objectives of WP8. That was carried out through different ways, but all of them are with a market oriented approach. Also, the consortium set the conferences, workshop and exhibits to attend for dissemination purposes; further it created the basis for organising a final workshop which will release the final outcomes to potential end-users.
- The last newsletter has been released at the end of 2010, so all the potential customers included in the mailing list have been able to realise the valuable developments obtained during the last period. The document describes the MONICO proposal, giving an overview of monitoring technologies implemented in the project, introducing the DSS which is compound by the expert system and the data base of sensor data and tunnel records and finally an approach for deterministic and probabilistic assessment. We've also examined sensor and material performances used in the project and finally described some tests on small scale specimen.
- The final newsletter and project brochure were distributed to the list of potential customers.
- Further potential customer opportunities (in cooperation with all SMEs) and improvement of customer data base were investigated and improved.
- Towards the end of the project the MONICO workshop was organised.
- The RTD partners performed training of the monitoring technologies and software modules, through on-site meetings during the pre-final and final tests and other meetings, workshop etc.
- Website updates regarding project deliverables, recent outcomes, publications and recent updates were performed during the last period of the project.
- Following activities to submit project results into related conferences and journals (please refer to D7.2 for details).
Corrective actions taken / suggested:
No corrective actions needed as the delay was not crucial.
Contractors that worked in WP8: ICCS, Optronics, AOS, GHT, Tecnic, RISA
WP9 - Consortium management and assessment of progress results (ICCS)
- Overall project coordination. Communication with partners at all levels (WP leaders, task leaders, and partners).
- Overview of all technical activities.
- Coordination of the subcontracting procedure between project SMEs and RTDs. A template for subcontracting was prepared and distributed to the SMEs. The SMEs provided feedback and the template was agreed and signed by the three SMEs. The actual agreement has been included in deliverable D7.2.
- Regarding the issues with the defaulting partner (OSMOS), ICCS as the project coordinator and in cooperation with the Project Officer (European Commission (EC)), has followed all the legal and formal steps to exclude the partner and replace it by Optronics SA. The coordinator closely collaborating with the project SMEs have analysed various alternatives and the most proper partner was identified always ensuring high expertise as needed and fitting into the project needs as well.
- Preparation of agenda, organisation and coordination plenary meeting on the 10 - 11 March 2010.
- Preparation of agenda, organisation and coordination of kick-off and first plenary meetings.
- Preparation of kick-off and first plenary meetings minutes.
- Coordination of financial and technical contributions for the preparation of the first, second and third interim activity reports. Preparation of the relevant templates and distribution to partners.
- Close follow-up of reports / activities / deliverables deadlines and responsible partners.
- The quality control procedure for the project is defined from the beginning of the project. The quality manual sets the rules and procedures for document and data control, reporting and scheduling of dissemination events and reviewing of project deliverables. The manual includes templates for official MONICO documents and naming conventions.
- Coordination of review process (executed off-line), final review (also executed off-line) and submission of deliverables.
- Preparation of the technical meeting in Dresden (27 July 2010).
- Initial organisation for the next plenary meeting (9 - 10 November 2010).
- Close follow-up of reports / activities / deliverables deadlines and responsible partners.
- Preparation and organisation of the GA in Berlin (9 - 10 November 2010).
- Preparation above Berlin GA meeting minutes.
- General organisation of the small and large scale tests as executed in Trento.
- Following the quality control procedure for the project that was defined from the beginning of the project.
- After the quality review, all project deliverables were sent to the EU within the project execution:
D1.1: Specifications for the sensing system, the interrogation unit, the communication system and the SDPM. Sent to EC on 15 April 2009.
D2.1: Methodology for the deterministic and probabilistic assessment of structural condition under normal operating loads. Sent to EC on 15 April 2009.
D3.1: Methodology for the deterministic and probabilistic assessment of structural condition under seismic loads. Sent to EC on 15 April 2009.
D4.1: Methodology for the deterministic and probabilistic assessment of the global structural condition. Sent to EC on 11 June 2009
D5.1: The expert system, the data base and the knowledge base (Prototype V1) (D5.1) - Accompanying report. Sent to EC on 12 November 2009.
D7.1: Plan for the use of the foreground (Draft). Sent to EC on 12 November 2009.
D8.1: Website for the project - Accompanying report. Sent to EC on 1 December 2009.
D5.2: The expert system, the data base and the knowledge base v2 - sent to EC on 25 March 2010.
D1.2: The SDPM, the interrogator unit and the wireless transceiver module - sent to EC on 30 September 2010.
D1.3: Embedded deformation sensors evaluated at the structural lab and refined - sent to EC on 31 March 2011.
D7.3: Brochure and demo of the monitoring system and the DSS (Final) - Demo CD and brochure distributed at the final workshop (18 March 2011) - snapshots and content have been included in the D7.2 deliverable.
D2.2 D3.2 D4.2: 2.2. Module 1, evaluated at the structural lab and refined, 3.2. Module 2, evaluated at the structural lab and refined, 4.2. Module 3, evaluated at the structural lab and refined - Sent to EC on 9 May 2011.
D6.1: Report on the whole simulation tests and the calibration and validation of the theory of seismic failure. Sent to EC on 18 May 2011.
D7.2: Plan for the use of the foreground (Final). Sent to EC on 26 May 2011.
D5.3: The integrated DSS and package (Final). Sent to EC on 1 June 2011.
D5.4: The system guide and user manual. Sent to EC on 2 June 2011.
Corrective actions taken / suggested:
During the first year of execution, the partner OSMOS was removed from the consortium and replaced by the partner Optronics.
Project meetings:
- Kick-off meeting, Athens, 30 - 31 October 2008
- Plenary meeting, Rome, 26 - 27 February 2009
- Plenary meeting, Santorini, 25 - 26 June 2009
- Plenary meeting, Padova, 8 - 9 October 2009
- Plenary meeting, Athens, 10 - 11 March 2010
- Plenary meeting, Berlin, 9 - 10 November 2010
- Final meeting (and workshop), Athens 17 - 18 March 2011.
Technical meetings:
- Civil technical meeting, Athens, 27 January 2010
- Technical meeting, Dresden, 27July 2010.
Potential impact:
Socio-economic impact:
The assessment of operating life of civil structures has recently become crucial, because in the first place it takes to a better environmental impact due to the life extension of the structure and secondly it reduces the overall costs for demolition and rehabilitation of damaged segments.
The deployment of monitoring systems based on the MONICO project, which normally allow control of the structure in a continuous way, will strongly help both to increase its working life, leading to improvements on environmental conditions and cost reductions.
MONICO will introduce also a new concept on tunnel structural maintenance. Presently the verification of structural conditions is still based on periodic visual inspection, carried out by trained experts. This procedures are usually very expensive, time consuming, due to structure complexity, subjective, because the technicians normally cannot rely on historical data on structure and finally unreliable, because it cannot detect damages that are not yet visible.
Moreover, when the degradation is getting visible, it might be that the damage has already got to a level which could require huge costs for restoring. Indirect costs are also to be considered, due to tough access to the structure, which takes to delays and inefficiency suffered by the users.
At present, the most used method to prevent tunnel damages is normally called 'corrective maintenance'. According to this procedure, the damaged tunnel section is simply replaced with new one; this takes to high cost levels, either direct or indirect, reduced safety levels and high environmental impact.
An alternative method which is becoming more and more used is called 'proactive condition-based maintenance'. With this approach, the monitoring system which reads the data continuously provides the potential warning conditions of structure on the first stages; as consequence there's a lower maintenance level cost, because the inspections can be carried only after a real request, an increase of safety level and a better management of structure.
The actual importance of the MONICO project will evolve in cases where it's necessary to evaluate the tunnel structural conditions after an earthquake. Normally, the seismic event can cause asymmetric loads so that the structure can exceed its functional limits. If that overcoming does not take to evident signs of damage, it's necessary to carry a deep structural analysis. The problem is even more complex because there's in first place a shortage of experienced technicians to perform these analysis and secondly the need to close the structure accesses for enough time, just in those periods for which it would be necessary to have as many road links as possible.
The monitoring system based on MONICO will give on the contrary an immediate and reliable evaluation of suffered damages, allowing the operators to decide if the structure has to be shut down or not and thus aiding civilian safety, injuries or other unfortunate events that may be caused due to any earthquake aftermath.
Contribution to standards and policies
MONICO is a project based on using of fibre optic sensors, presently one of the most promising market segments. It is then in full accordance with EU policies which aid to adopt all the efforts to increase within EU the share of growing markets.
The high technological profile of MONICO will help to form expert technicians on fibre optic technology, following those recommendations of treaty of Amsterdam which concern social affairs and employment policies.
As we know, one of the main features of the project is the ability to monitor a structure continuously for its whole operating life; for that it will be possible to obtain both helpful details for a better standardisation of ways to design a tunnel and more complete understanding of the behaviour of structure in non-linear conditions.
Within the efforts for decreasing of civil structure environmental impact, MONICO is pursuing the environmental technologies action plan (ETAP) objectives, because it allows both to reduce the operating costs and consumption of resources and makes to grow the EU role within the development of environmental technologies.
The European Commission Transport Policy (ECTP) points out as primary target the reduction of deaths on the road by at least 50 %; MONICO will give its contribution by means of its new safety concepts.
Finally, other SMEs active in the optical monitoring technologies will benefit from MONICO outcomes, through the purchasing or licensing the MONICO results. This follows the EU objectives towards increasing SME competitiveness in Europe.
