Completed Research 1995 to 2006

Theme 3 Projects (1999-2002):
Remote Monitoring and Field Assessments

Director: Dr. Aftab Mufti, Dalhousie University

THEME 3 OVERVIEW

(All project descriptions are provided as proposed in 1998 as part of the NCE mid-term review)

The work is directed toward achieving remote monitoring capability that will allow a sensor system to detect significant events at a bridge, initiate communication via a telemetry link and deposit measured data associated with the event at some central and generally accessible site. Some initial success has been achieved with a dial in system as utilized on the Salmon River Field Demonstration Project [Mufti, A.A., et al., 1997]. The primary objective of this research is to continue to investigate methods of achieving effective remote monitoring of innovative structures through the following five tasks: wireless transmission; various sensor interfaces and data compression; dial out remote monitoring; remote connection to Internet and satellite; and microchip data acquisition system [Mufti, A.A., et al., 1997].

The remote monitoring system developed in this project will be able to communicate with various types of sensor, such as transducers, strain gauges, thermisters, corrosion sensors, vibration sensors, and fibre optic sensors. The project will investigate the various interfaces of these sensors with different types of data acquisition systems. Various types of digital filters will be developed to efficiently collect, filter and sample from different types of sensors and to transmit data with minimum loss in data quality. The devices developed will provide wireless transmission between sensor to data logger or data logger to remote monitoring site. Dynamic dial out capability, triggered by a special event, will be developed. The design of appropriate PC software structures will facilitate the connection of a sensor system via Internet and CDPD modem. The feasibility of transmitting data via satellite will also be studied. Finally, the project will integrate the technology into a complete, cost effective and portable integrated remote data.

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In the first phase of this project an intelligent processing framework was developed for analysis of signals obtained from permanently installed sensors in monitored structures (mainly bridges) [Karasaridis, A., et al., 1997]. The software developed is used to identify the prominent properties that characterize the condition of the structure and changes thereof that might signify the occurrence of damage. However, field application of the proposed methodology in bridge case studies has revealed that interpretation of the significance of the several recorded events requires a considerable amount of familiarity and expertise with the specific structure that is being monitored.

A knowledge based system is therefore required to establish, from the history of the structure, not just the important indices of state for the structure, but also other relevant variables such as the expected range of these indices for structures of the type under consideration, previous values of these indices over the service life of the structure, changes in the reference values observed in the past, and the relative significance of these on the condition of the structure.

During the first phase of Project T3.2 a powerful software package was developed to process collectively groups of signals obtained from each monitoring procedure conducted on a specific structure. To facilitate the development of a knowledge based system, the next phase of project T3.2 includes the task of assembling into a single database, processed information and interpretation results from several bridges of different type, size and location in Canada. The database will be continuously updated and expanded as the ISIS monitoring technologies are applied to additional case studies and as more data becomes available. The software package ESPAN along with the database will be integrated into a knowledge based intelligent expert system which will be designed to perform short term and long term evaluation of the available records of the structure analyzed.

The program will assist not only in quantifying and localizing changes of important structural parameters but will also supplement the user with information about the possible interpretation of the records from accumulated knowledge and expertise that the program will extract from its database for the same structure, as well as from structures of the same type. Because of storage considerations, particularly as the history of the structure increases, the compression of the signals becomes a key design consideration for the development of the database. Algorithms developed in the first phase of Project T3.2 will be refined to address the special needs of the database, particularly with regard to storage of additional information, such as heuristic data, threshold values, previous significant events, and experience from other structures of similar or related type and history. The new algorithms will be developed in close collaboration with all other ISIS teams that are directly or indirectly involved in field assessments across Canada.

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This feasibility study will identify the steps necessary to finalize a software program being developed for storing and archiving data collected from structures via remote monitoring systems.

Several bridge structures in Canada have been instrumented and are now being monitored with data collected at varying frequencies. Archival management is a vital component of structural monitoring. Soon, ISIS will have an online archiving system whereby authorized researchers submit raw data that will be accessible to users. In a user-friendly, worldwide web interface, the site will offer access to sensor characteristics and locations, and response measurements from static and dynamic load tests. The archive will enable interested parties to browse the content, view the relevant documentation and download data for their own analysis.

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The purpose of this project is to provide to the members of the ISIS Network a means of assessing the field performance of their innovative intelligent structures. A core group of investigators responsible for coordinating the field assessment projects and ensuring that consistent and effective evaluation is provided. Along with the general goal of field assessment, a specific objective will be to involve as many as possible of the Network participants, technicians and students in the field assessment projects, so as to maximize the benefits of the Network as a whole. Participants will be involved mainly in projects utilizing their own technologies.

The first phase of this project focused on two elements: the evaluation of the steel free bridge deck technology and the evaluation of fibre optic sensors in a bridge structure. The former used the Salmon River Bridge project as its field environment while the later used the Confederation Bridge [Doncaster et al., 1996].

The monitoring of the Confederation Bridge by fibre optic sensor will continue. The setback in collecting data was due to delay in obtaining the fibre optic data acquisition system, communication line from the bridge and easy access to the bridge. However, these problems are being addressed. The data from fibre optic sensors will be collected and compared to the conventional monitoring that is in progress.

The Salmon River bridge, the first bridge in the world that has no reinforcement in the concrete deck has been performing well. The data collected from fibre optic gauges and conventional gauges indicated that deck is participating in sharing of the live loads in the girders as per design assumptions. The fibre optic gauges have proven to be durable and resilient. The monitoring of the fibre reinforced concrete deck and fibre optic sensor will be continued to assess their durability.

See Salmon River Field Demo
See Confederation Bridge Field Demo

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Construction of the world's largest span bridge using CFRP as prestressing and shear reinforcement for four girders has been completed in Headingley, Manitoba, Canada. CFRP was also used to reinforce a part of the deck slab, while GFRP reinforcements were used in a part of the barrier wall. The bridge is instrumented with 63 fibre optic sensors coupled with 21 conventional electric strain gauges embedded in the bridge girders, deck slab, and barrier wall. Data is transmitted through two telephone lines for continuous monitoring of the performance of the bridge under traffic loads and extreme environmental conditions. The bridge, formally named the Taylor Bridge, was opened for traffic in October 1997 [Rizkalla et al., 1997].
The funds for the following years will be used to install a camera to provide video information synchronized with the optic sensor readings. The work on intelligent processing of the collected data will be in close collaboration with Project T3.2 to monitor the performance of the bridge. The monitor will be focused on evaluation of the behaviour of the carbon and glass fibre reinforced polymer reinforcements used in prestressing the main girder, the deck slab and the glass FRP for the barrier wall. The levels of prestress losses, possible initiation of crack, crack propagation and deflection will be used to evaluate the health of the bridge as a function of time.

See Field Demo

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The goal of the project is to remotely monitor the performance of the Chatham Bridge using a new sensing technology [Mufti et al., 1997]. The bridge performance would be evaluated based on static and dynamic response from the conventional and fibre optic gauges attached to the key structural elements, natural frequency readings from the accelerometers, stability of cracks under static and dynamic conditions, and monitoring of the changes in the concrete slab performance using piezoelectric/fibre optic transducers for acoustic and sonic measurements.

The existing instrumentation consists of resistive strain gauges attached to the steel flanges and webs of the steel girders, the steel straps, NEFMAC reinforcement embedded in concrete, and two fibre optic gauges embedded into the concrete slab.

This initial instrumentation was installed by the Ministry of Transportation, Ontario (MTO). The main shortcoming of the present system is that many of the monitoring instruments are located where deformations are minimal. Many of the gauges have failed, indicating the main problem of using such gauges in the field.

An instrumentation system complementary to that of the MTO is proposed for the Chatham Bridge for remote and non destructive testing of its performance. The key elements, which provide guidelines of structural and material integrity of a structure are strains, changes in the natural frequencies, stability of existing cracks and degradation of the slab due to the exposure to the aggressive environment.

See Field Demo

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The Crowchild Trail Bridge in Calgary, Alberta was rehabilitated by replacement of the existing superstructure made of concrete with a new superstructure consisting of steel girders and a fibre reinforced concrete bridge deck devoid of steel reinforcement. The bridge consists of three continuous spans and is the first continuous span bridge to utilize the fibre reinforced steel free deck system. External steel straps between girders and internal fibre reinforced plastic (FRP) bars in the cantilever portions were used to reinforce the deck. The bridge was instrumented using fibre optic sensors and conventional sensors. The performance of the steel free deck and fibre optic sensors has been very encouraging. This field assessment will continue to prove the durability and robustness of ISIS Canada technologies [Tadros et al., 1998].

See Field Demo

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The Waterloo Creek Bridge is part of the new Vancouver Island Highway. The bridge consists of two separate single span decks with integral abutments. The north bound structure was constructed using the innovative steel free bridge deck technology of Project T4.1 and is the main study of this field assessment project. The bridge has been instrumented with conventional and fibre optic sensors. As well, several smart reinforcement bars developed in Project T3.4 have been embedded in the concrete deck.

The instrumentation will be used to monitor the strains and cracks at various locations in both the steel free deck and the conventional concrete deck. This will permit a direct comparison of the performance of both structural systems under serviceability conditions. The strains in the girders will be monitored to assess the load sharing characteristics of the steel free bridge deck system. The south abutment wall will also be monitored to determine load transmitted to the substructure from both the girders and the backfill pressure. The project will allow for an assessment of the effectiveness of the steel free bridge deck in the an integral deck girder abutment system. The monitoring database will also be used to perform reliability analysis of the steel free bridge deck system.

See Field Demo

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The proposed field assessment project will demonstrate the usefulness of smart and noncorrosive reinforcements [Benmokrane et al., 1997]. Over 180 permanent monitoring instruments have been installed at critical locations and will be connected to a telephone line for remote monitoring of the structure's behaviour. The purpose of the research program is to determine the static and key dynamic characteristics of the bridge. The dynamic response of the bridge will be evaluated under normal traffic and with a calibrated highway truck. The findings will be used to calibrate a finite element program.

The most important aspect of the concrete deck slab reinforced with CFRP is the durability of the concrete deck. A special instrumentation strategy has been implemented with special attention being given to possible material degradation. In order to evaluate the material degradation, several locations of the concrete deck slab have been reinforced with FRPs. Long term assessment of the FRP reinforcement durability will be conducted using coring directly in the concrete deck slab.

See Field Demo

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Hall's Harbour is located on the Bay of Fundy in Nova Scotia and as such is subjected to the extreme tides and severe marine storms of the area. The community currently relies on an existing timber wharf breakwater for protection from these conditions. This existing wharf is a typical timber wharf constructed with a concrete deck slab and a large armour stone embankment on the exposed face. A large section of this wharf has failed due to the severe pounding from storms and the remainder of the wharf is expected to deteriorate with time. A repair scheme has been designed which consists of steel piles, spaced approximately 2.0 m apart, anchored back through the existing wharf. Between the piles are reinforced concrete panels which both retain the fill in the wharf and protect the existing structure from wave action. A design is being developed to utilize glass FRP reinforcement instead of steel reinforcement in these panels to substantially increase the life span of this structure. Other innovative technologies are being investigated such as the use of CFRP tie rods as anchors for the piles and the use of GFRP reinforced concrete piles in place of the steel piles.

The purpose of this project, is to provide a field assessment of the durability and structural performance of the glass FRP reinforced concrete panels in a marine application. The site will be monitored through physical assessment and instrumentation. A unique feature of this wharf is its entire height is within the tidal zone of the Bay of Fundy. Visual inspection of the entire face of the wharf is thereby possible on a daily basis. As major storm events are the critical load parameter for the panels, monitoring will coincide with the occurrence of major storm events. The visual inspection will focus on the general condition of the panels and the extent of cracking which occurs. Cores will be taken at predetermined locations on a periodic basis to determine if any strength or physical deterioration of the FRP occurs. If required, specific laboratory simulations will be developed to assist in the assessment of the actual field performance of the panels. A series of beams will be designed and positioned at the site which will be exposed to the same environmental loads as the panels. At periodic intervals these beams will be taken to the lab for testing.

In addition to the physical testing the panels will utilize a number of FRP bars instrumented with embedded fibre optic sensors from the research conducted by Project T3.4. These instrumenting bars will serve a two fold purpose. Firstly, they will be a field assessment of the performance of the instrumented bars in a marine environment. Secondly, they will provide field data on the stress levels in the bars, particularly during major storm events.

See Field Demo

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In 1997, ISIS-Sherbrooke obtained a research contract with the Ministry of Transportation of Québec to identify a potential bridge-strengthening scheme with composite materials, and to conduct an analytical study of such a repair. The selected structure was a single-span, simply supported bridge with T-section, which is characteristic of many bridges currently in use in Québec.

It would thus be eventually possible to apply the same strengthening method to other bridges presenting similar structural deficiencies. Test beams were fabricated to evaluate various reinforcing schemes in bending and in shear, and were used to check the validity of the analytical procedures developed for this project. The four T-beams were reinforced in order to demonstrate the potential increase in strength as was requested for the reference bridge proposed by the MTQ. Special attention was paid to the scale effect in order to demonstrate acceptable correlation between the laboratory results and the actual structure being considered.

Durability of the composite material reinforcement was also included in the study. Specimens were tested to evaluate the influence of freeze-thaw or wet-dry cycles on both the composite materials and the concrete-composite interface. Preliminary results obtained in this project confirm that the two kinds of cycles have a negligible effect on the composites themselves and on their bond to the support surface. Long-term durability tests continue.

The experimental study was followed, in the fall of 1998, by the strengthening of the actual reference bridge. Preparation of the site, including curing of some concrete used in the repair, took three weeks. Installation of the composites took five days over a two-week period.

Sensing devices were installed on the bridge in order to monitor its behaviour. The 66 instruments on the bridge include 28 strain gauges, 10 thermocouples, 20 optic fibres with Bragg sensors and 8 with Fabry-Perot sensors. Positions of the sensors were selected in such a way that complementary readings can be obtained from the various types of instruments, and to validate the data obtained from the experimental optic fibre sensors. The repair work was done under close supervision of the Ministry of Transportation, which conducted the loading tests before and after the repair work. Additional loading tests will be conducted in the future in order to evaluate the behaviour of the repaired structure, and to validate the optic fibre technology for this type of application.

See Field Demo

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The objective of this project is to investigate the feasibility of using FRP rods as reinforcement for underground concrete chambers, to develop design procedures, to study the durability, and to predict the service life of such FRP reinforced concrete structures.

A consortium has been created for this research program which includes Hydro-Quebec, Lecuyer et Fils Ltée, Pultrall Inc., Speco Engineering Ltd., and ISIS Canada. In all, 10 experimental FRP reinforced underground chambers are proposed to be undertaken. Two of them will be tested at the Unviersité de Sherbrooke under static and cyclic loadings. The remaining eight chambers will be installed at different locations in Quebec to simulate different terrain environmental characteristics.

All experimental chambers will be instrumented with gauges and fibre optic sensors to monitor structural performance and long term behaviour.

Taking into account the work involved both in the laboratory and field, the program is planned to last two years. Monitoring will continue for a longer period to collect data. The research program will produce a working manual including design procedures and construction methods for the use of FRP reinforcement.

All the chambers under investigation will be reinforced by new FRP ISOROD rebars produced by Pultrall Inc.

Underground concrete chambers reinforced with steel bars are used frequently in construction and civil engineering. In Quebec, more than 50,000 of these structures measuring 2,000 x 3,500 x 3,000 mm have been installed by Hydro-Quebec during the last 30 years to house special devices used for electric transmission lines. However, like other conventionally reinforced concrete structures, corrosion of the steel reinforcement is a major problem. Each year, two percent (approximately 1,000) of Hydro-Quebec's steel-reinforced underground concrete chambers become corroded and must be replaced with new ones.

The use of FRP reinforcement for such underground chambers has advantages such as non-corrosiveness, electrical non-conductivity and overall light weight. Research performed by ISIS Sherbrooke on FRP reinforcements for concrete structures demonstrates that there are numerous benefits to using FRP in underground chambers. At the Université de Sherbrooke, studies have been conducted with respect to physical and mechanical properties of FRP rods, bond properties of FRP to concrete, flexural behaviour of FRP-reinforced concrete elements and durability of FRP reinforcements.

The objectives of the research program are:

• To investigate the feasibility of using FRP reinforcements in underground concrete chambers
• To develop design procedures suitable for FRP-reinforced underground concrete chambers (straight and bent FRP rebars)
• To examine and monitor the structural performance and long term behaviour
• To prepare a working manual from the results of the research and to predict the service life of FRP-reinforced underground concrete chambers.

During the summer of 1998, two chambers were constructed with FRP reinforcement as part of a preliminary feasibility study and were installed at Longueuil and Valleyfield, Quebec. From this study, information was gained regarding fabrication of FRP reinforcement cages, installation of the cages into formwork and casting of the concrete.

In this research program, 10 underground chambers are to be evaluated. Two of the 10 chambers, measuring 2,000 x 3,500 x 3,000 mm, will be tested by using a newly-built reaction wall at the Université de Sherbrooke. Static and cyclic loadings will be used (static loading for one chamber and cyclic loading for the second chamber) to simulate field conditions such as weight of tracks and soil and water pressure.

The remaining eight chambers will be located in different parts of Quebec taking into account terrain and environmental conditions. Hydro-Quebec will advise the exact locations and they will extend all cooperation regarding installation.

All chambers under investigation will be instrumented with gauges and fibre optic sensors for monitoring. The research program will be executed with collaboration from the consortium. Fabrication of the FRP reinforced underground concrete chambers will take place at the Lecuyer et Fils plant, FRP reinforcement will be provided by Pultrall, and Speco Engineering will assist in the design of the underground concrete chambers. The research team at the Université de Sherbrooke will lead this research endeavour.

See Field Demo

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It is one of the largest strengthening projects of its kind. Carbon fibre reinforced polymer (CFRP) sheets have been used to upgrade the shear capacity of the John Hart Bridge in Prince George, British Columbia. The bridge, owned by B.C.'s Ministry of Transportation Central Northeast Region, required shear strengthening in order to support heavier truck loads.

It consists of seven simply supported spans with six prestressed concrete girders per span. The 42girders are 1500 mm deep with a typical I-shaped AASHTO cross-section. They were strengthened with FRP sheets covering a four-m length at each end of the girder. By strengthening 64 girder ends, shear capacity was increased by 15 to 20 percent.

Similar to the Maryland Street Bridge in Winnipeg, Manitoba, the John Hart bridge was strengthened by applying diagonal CFRP sheets. Dave Scouten, a principal of Scouten and Associates Ltd., located in Prince George, British Columbia, consulted with ISIS Canada on the design. Replark sheets manufactured by Mitsubishi Chemical Corporation were chosen and then installed by specialty contractor Retro, of Vancouver. The project was completed in six weeks with the assistance of the general contractor, SureSpan, also of Vancouver. During this time the bridge remained completely accessible to traffic.

Phase II of the project involves a monitoring program to collect data on the long-term performance of CFRP sheets for shear strengthening this particular type of cross-section. The bridge was instrumented to monitor its behaviour under dynamic vertical and service load conditions. Periodic site visits and visual inspections are conducted to assess the bridge's long term performance. In the future, a twin bridge will be constructed and, upon opening of the new lanes, the existing bridge will undergo further rehabilitation. The existing high density overlay will be replaced with a reinforced concrete deck topping, and the use of CFRP reinforcing bars has been proposed.

See Field Demo

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The project's major objective during the second phase is to refine the current technology and to accomplish a large volume program of laboratory testing and field assessment, as well as to complete the product specification and manufacturing guidelines for the smart FRP reinforcements incorporating the fibre optic sensors. The product under development and assessment is the smart FRP composite reinforcement which incorporates one or a number of fibre optic sensors embedded into the host composite material during the pultrusion process [Kalamkarov et al., 1997]. A new direction in the proposed research program will focus on the design, manufacturing, testing and application of the innovative strain gauges using composite materials to encapsulate optical fibre sensors. Composite materials have the unique ability to be designed and manufactured with a very wide range of mechanical and thermo mechanical properties. Embedment of the fibre optic sensors into the specially tailored composite host material will ensure the sensor protection, thermal compatibility with the host material, and the proper integration into the concrete structures.

The smart FRP reinforcements and innovative strain gauges will be used for the monitoring of concrete bridges. This work will constitute an important part of the future effort of this project. During the first stage of the project, it has been established that it is possible to incorporate fibre optic sensors into the FRP composite reinforcements during the pultrusion process. This work will be continued to refine the technology and the machinery from one side, and to commercialize and transfer the developed technology to the large scale manufacturing for the commercial use.

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Completed Research 1995 to 2006