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  • 1.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Carlsson, Fredrik
    Lunds Tekniska Höskola.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Enochsson, Ola
    Luleå Tekniska Universitet.
    Karoumi (Redaktör), Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Plos, Mario
    Chalmers Tekniska Högskola.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE).
    Täljsten, Björn
    LuleåTekniska Universitet.
    Wiberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Ülker, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Modern mät- och övervakningsmetodik för bedömning av befintliga broar2007Report (Other academic)
  • 2.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Lessons Learned in Structural Health Monitoring of Bridges Using Advanced Sensor Technology2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Structural Health Monitoring (SHM) with emerging technologies like e.g. fibre optic sensors, lasers, radars, acoustic emission and Micro Electro Mechanical Systems (MEMS) made an entrance into the civil engineering field in last decades. Expansion of new technologies together with development in data communication benefited for rapid development. The author has been doing research as well as working with SHM and related tasks nearly a decade. Both theoretical knowledge and practical experience are gained in this constantly developing field.

    This doctoral thesis presents lessons learned in SHM and sensory technologies when monitoring civil engineering structures, mostly bridges. Nevertheless, these techniques can also be used in most applications related to civil engineering like dams, high rise buildings, off-shore platforms, pipelines, harbour structures and historical monuments. Emerging and established technologies are presented, discussed and examples are given based on the experience achieved. A special care is given to Fibre Optic Sensor (FOS) technology and its latest approach. Results from crack detection testing, long-term monitoring, and sensor comparison and installation procedure are highlighted. The important subjects around sensory technology and SHM are discussed based on the author's experience and recommendations are given.

    Applied research with empirical and experimental methods was carried out. A state-of-the art-review of SHM started the process but extensive literature studies were done continuously along the years in order to keep the knowledge up to date. Several SHM cases, both small and large scale, were carried out including sensor selection, installation planning, physical installation, data acquisition set-up, testing, monitoring, documentation and reporting. One case study also included modification and improvement of designed system and physical repair of sensors as well as two Site Acceptance Tests (SATs) and the novel crack detection system testing. Temporary measuring and testing also took place and numerous Structural Health Monitoring Systems (SHMSs) were designed for new bridges. The observed and measured data/phenomena were documented and analysed. 

    Engineers, researchers and owners of structures are given an essential implement in managing and maintaining structures. Long-term effects like shrinkage and creep in pre-stressed segmental build bridges were studied. Many studies show that existing model codes are not so good to predict these long-term effects. The results gained from the research study with New Årsta Railway Bridge are biased be the fact that our structure is indeed special. Anyhow, the results can be compared to other similar structures and adequately used for the maintenance planning for the case study.

    A long-term effect like fatigue in steel structures is a serious issue that may lead to structural collapse. Novel crack detection and localisation system, based on development on crack identification algorithm implemented in DiTeSt system and SMARTape delamination mechanism, was developed, tested and implemented. Additionally, new methods and procedures in installing, testing, modifying and improving the installed system were developed.

    There are no common procedures how to present the existing FOS techniques. It is difficult for an inexperienced person to judge and compare different systems. Experience gained when working with Fibre Optic Sensors (FOS) is collected and presented. The purpose is, firstly to give advice when judging different systems and secondly, to promote for more standardised way to present technical requirements. Furthermore, there is need to regulate the vocabulary in the field.

    Finally, the general accumulated experience is gathered. It is essential to understand the complexity of the subject in order to make use of it. General trends and development are compared for different applications. As the area of research is wide, some chosen, specific issues are analysed on a more detailed level. Conclusions are drawn and recommendations are given, both specific and more general. SHMS for a complex structure requires numerous parameters to be measured. Combination of several techniques will enable all required measurements to be taken. In addition, experienced specialists need to work in collaboration with structural engineers in order to provide high-quality systems that complete the technical requirement. Smaller amount of sensors with proper data analysis is better than a complicated system with numerous sensors but with poor analysis. Basic education and continuous update for people working with emerging technologies are also obligatory.

    A lot of capital can be saved if more straightforward communication and international collaboration are established: not only the advances but also the experienced problems and malfunctions need to be highlighted and discussed in order not to be repeated. Quality assurance issues need to be optimized in order to provide high quality SHMSs. Nevertheless, our structures are aging and we can be sure that the future for sensory technologies and SHM is promising.

    The final conclusion is that an expert in SHM field needs wide education, understanding, experience, practical sense, curiosity and preferably investigational mind in order to solve the problems that are faced out when working with emerging technologies in the real world applications.  The human factor, to be able to bind good relationship with workmanship cannot be neglected either. There is also need to be constantly updated as the field itself is in continuous development.

  • 3.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    New Årsta Railway Bridge: A case study on the long-term Structural Health Monitoring with Fibre Optic Sensors2011In: Nordic Concrete Research, ISSN 0800-6377, no 2/2011, 123-142 p.Article in journal (Refereed)
    Abstract [en]

    The New Årsta Railway Bridge was built in 2000-2005. The structure is a unique pre-stressed concrete girder bridge with slender and optimised design. Structural Health Monitoring System was installed on the bridge during construction. One characteristic span is mainly instrumented with several sensors and monitoring is still ongoing.This paper presents the Fibre Optic Sensor system including thermocouples; and their function. Observations, malfunctions and inconvenience during construction, testing and operation are collected, carefully documented and analysed. Strain and temperature data are collected from first casting up to date.Results are highlighted and conclusions are drawn. Recommendations are given, based on the experience gained so far. Furthermore, general, accumulated knowledge about monitoring is given.

  • 4.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    New Årsta Railway Bridge: A Long Term SHM Case Study with Fibre Optic Sensors2011In: Nordic Concrete Research: 30 September 2011, 2011Conference paper (Other academic)
  • 5.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    STRUCTURAL HEALTH MONITORING OF BRIDGES IN SWEDEN2007In: PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON STRUCTURAL HEALTH MONITORING & INTELLIGENT INFRASTRUCTURE: STRUCTURAL HEALTH MONITORING & INTELLIGENT INFRASTRUCTURE / [ed] Bakht B, Mufti A, MANITOBA: ISHMII-INT SOC STRUCTURAL HEALTH MONITORING INTELLIGENT INFRASTRUCTURE , 2007, U295-U303 p.Conference paper (Refereed)
    Abstract [en]

    Measuring insecure parameters in constructions has taken place in the past. However, the measuring was small in scale and aimed at pure verification of desired parameters rather than for economical, security or maintenance aspects. Organized Structural Health Monitoring (SHM) activities of bridges in Sweden have begun in recent years when some innovative bridges with complicated design were constructed. Several old and/or deteriorated bridges needed upgrading and classification and benefited from SHM. Both large scale and long-term projects were initiated; as well as some more moderate projects. Planning of data acquisition, installation of sensors, data storage and analysis were very demanding and a lot of heuristic knowledge was gathered. New techniques were also introduced and some preliminary fibre optic installations took place. A lot of practical experience was obtained when working in the field with fibre optic sensors, especially when handling distributed fibre optic sensors. This paper introduces some projects and results in short, and highlights conclusions. Special care is paid to reasons for monitoring, issues in planning, monitoring and practices in fibre optic installation procedures.

  • 6.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Structural health monitoring using modern sensor technology: long-term monitoring of the New Årsta Railway Bridge2006Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Structural Health Monitoring (SHM) is a helpful tool for engineers in order to control and verify the structural behaviour. SHM also guides the engineers and owners of structures in decision making concerning the maintenance, economy and safety of structures. Sweden has not a very sever tradition in monitoring, as countries with strong seismic and/or aerodynamic activities. Anyway, several large scale monitoring projects have taken place in recent years and SHM is slowly making entrance as an essential implement in managing structures by engineers as well as owners.

    This licentiate thesis presents a state-of-the art-review of health monitoring activities and over sensory technologies for monitoring infrastructure constructions like bridges, dams, off-shore platforms, historical monuments etc. related to civil engineering. The fibre optic equipment is presented with special consideration.

    The permanent monitoring system of the New Årsta Bridge consists of 40 fibre optic sensors, 20 strain transducers, 9 thermocouples, 6 accelerometers and one LVDT. The aims of the static study are: to control the maximal strains and stresses; to detect cracking in the structure; to report strain changes under construction, testing period and in the coming 10 years; and to compare conventional system with fibre optic system.

    The system installation started in January 2003 and was completed October 2003. The measurements took place from the very beginning and are suppose to continue for at least 10 years of operation. At the construction phase the measurements were performed manually and later on automatically through broad band connection between the office and central data acquisition systems located inside the bridge.

    The monitoring project of the New Årsta Railway Bridge is described from the construction phase to the testing phase of the finished bridge. Results of the recorded statistical data, crack detection and loading test are presented and a comparison between traditional techniques like strain transducers and fibre optic sensors is done.

    Various subjects around monitoring and sensor technologies that were found under the project are brought up in order to give the reader a good understanding, as well of the topics, techniques and of the bridge. Example of few applications is given with the aim of a deeper insight into monitoring related issues.

  • 7.
    Enckell, Merit
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Egede Andersen, Jacob
    Glisic, Branko
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    New and Emerging Technologies in Structural Health Monitoring2013In: Handbook of Measurement in Science and Engineering: Volume 1 / [ed] Myer Kutz, Hoboken, New Jersey: Wiley , 2013, 3-78 p.Chapter in book (Other academic)
  • 8.
    Enckell, Merit
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Glisic, Branko
    Princeton University, USA.
    Myrvoll, Frank
    Norwegian geotechnical Institute (NGI).
    Bergstand, Benny
    Traffic and Public Transport Authority, Gothenburg.
    Evaluation of a large-scale bridge strain, temperature and crack monitoring with distributed fibre optic sensors2011In: Journal of Civil Structural Health Monitoring, ISSN 2190-5452, Vol. 1, no 1-2, 37-46 p.Article in journal (Refereed)
    Abstract [en]

    Many structures like bridges are ageing and the necessity to measure the uncertain parameters is relevant. Crack-related parameters can be measured with traditional  techniques like crack gauges and displacement transducers. A method that can detect and localise cracks as well as measure crack width is most favourable. Several distributed and quasi-distributed systems were introduced to the market and tested in recent years. This paper presents a large-scale Structural Health Monitoring project based on stimulated Brillouin scattering in optical fibres for an old bridge. The Go¨taa¨lv Bridge is a continuous steel girder bridge with concrete bridge deck. Steel girders suffer from fatigue and mediocre steel quality and some severe cracking and also a minor structural element collapse have taken place. The system installed on the bridge measures strain profiles along the whole length of the bridge and detects cracks that are wider than 0.5 mm. Procedures like factory acceptance test, site acceptance test, laboratory testing and field testing are presented and analysed. Innovative technology was developed, tested and applied on the bridge. Heuristic knowledge was collected; conclusions are presented and discussed for future development.

  • 9.
    Enckell, Merit
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Larsson, Hans
    Monitoring the behaviour of the Traneberg Bridge during retrofitting2006In: Structural Health Monitoring and Intelligent Infrastructure, Vols 1 and 2 / [ed] Ou, JP; Li, H; Duan, ZD, 2006, 1631-1635 p.Conference paper (Refereed)
    Abstract [en]

    Monitoring structures under retrofitting and strengthening is an ideal way to verify and control their behaviour and also to confirm and calibrate the calculation models. The Traneberg Bridge is a combined road and suburban railway bridge. The retrofitting and strengthening of the bridge started in 1999 in order to accommodate the increasing traffic and the need for heavy vehicles. It is a concrete bridge where only the deck support girders are made of steel. The main span is 191 meters and at the time of its completion in 1934 was the longest concrete arch bridge in the world. The vertical clearance is 26 meters. The old concrete arches seemed to be in good condition and the concrete samples taken confirmed high values of Young's modulus. It was decided that the old arch would be kept but the pillars and the deck were to be reconstructed. Monitoring the old arch during the retrofitting was significant in order to control the behaviour of the arch during demolition and reconstruction. The monitoring system consisted of seven fibre optic SOFO sensors and five thermocouples. The monitoring started in November 2003 and was completed in February 2005. The bridge was checked on a weekly and monthly basis and the modelling of the construction steps was compared to real values from measurements. This paper presents the results during reconstruction and highlights the benefits of the monitoring project when reconstructing the old structure.

  • 10.
    Enckell, Merit
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Silfwerbrand, Johan L.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Gathered Knowledge of Structural Health Monitoring of Bridges with Fibre Optic Sensors2011In: Proceedings of the ICE - Bridge Engineering: on 13 October 2011, 2011Conference paper (Other academic)
  • 11.
    Enckell, Merit
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Wiberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Monitoring of the New Årsta Railway Bridge: Instrumentation and preliminary results from the construction phase2005Report (Other academic)
  • 12.
    Enckell, Merit
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Wiberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Monitoring of the New Årsta Railway Bridge. Presentation of measured data and report on the monitoring system over the period 2003-20072008Report (Other academic)
  • 13. Glisic, B.
    et al.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Myrvoll, F.
    Tuvert, J.
    Distributed sensors for damage detection and localization2009In: 4th International Conference on Structural Health Monitoring on Intelligent Infrastructure (SHMII-4), 2009Conference paper (Refereed)
    Abstract [en]

    Distributed fiber optic sensing technology based on Brillouin scattering effect hasbeen proven as a mean to assess average strain and average temperature distributions instructures. However, detection of damage such as crack is very challenging, since only a shortportion of sensor, much shorter than spatial resolution of the system, is exposed to very highconcentrated strain. Beside this, the sensing fiber itself suffers from concentrated stresses andmay be broken. In order to resolve above mentioned issues, first the detection algorithm wasimproved in order to make system sensitive to measurand changes occurring over length shorterthan spatial resolution, and second a special manner of sensor installation is developed in orderto make possible for optical fiber to survive high concentrated stresses. The system is applied onGota Bridge, Gothenburg, Sweden, for the first time at a large scale. Number of reduced and fullscale tests were performed in order to assess performance of the system. The system, itsimplementation method and results of the tests are presented in this paper.

  • 14. Myrvoll, F.
    et al.
    Bergstrand, B.
    Glisic, B.
    Enckell, Merit
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Extended operational time for an old bridge in Sweden using instrumented integrity monitoring2009In: The 5th Symposium of  Srait Crossings, Trondheim Norway, 2009Conference paper (Refereed)
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