Mid-Term Review Meeting in Dublin, Ireland

Hi guys!!

How have you been during this month? Hopefully, all of you had a wonderful Christmas and spent some quality time with your family and friends.

As we get closer to the end of 2016, I take advantage to write here about an important meeting that our TRUSS research group had at the beginning of this month, on the 1st and 2nd of December in Dublin, Ireland.

I'm talking about the Mid-Term Review (MTR) meeting that had the goal of bringing together all the ESR's, supervisors, representatives of partner organizations and project coordinator with a project officer from the Research Executive Agency (REA) and a scientific external expert. This MTR had the goal of assessing the fulfillment of the scientific, training, management and networking aspects that are part of the grant agreement that serves as the basis of this current European research project. Hence, not only the scientific progress was to be evaluated but also particular attention was to be given to the training activities and networking aspects including the topic of each ESR's secondment.

(Credits)

This meeting was held in the offices of Ove Arup and Partners, one of the global leading firms of structural design engineering.

Ove Arup & Partners offices in Dublin, Ireland (credits)

After an initial introduction of all the attendees,  the Project Coordinator, Prof. Arturo Gonzalez made an interesting presentation about the TRUSS project and its current situation. From this, I want to point out the information provided regarding the local training on complimentary skills received by the ESRs: "314 hours in 8 language courses, more than 110 hours in teaching activities -supervising, demonstrating or providing tutorials- and more than 150 hours in other taught courses on soft skills -bibliographical management, how to write an academic paper, communication skills, etc-." Furthermore, regarding more technical skills, the ESR's received "more than 500 hours in 19 laboratory/field tests and almost 1000 hours in 71 courses directly related to their research while also attending 37 conferences"

Moreover, details with reference to the already carried out dissemination of the overall project were shared with all the attendees of this meeting: "TRUSS has published 24 technical papers (3 in peer-reviewed journals and 21 in conferences), and 3 press releases in mainstream magazines or newspapers prior to November 2016".

Finally, each ESR made a very brief and small presentation regarding their scientific progress, local and network-wide received training in these past 14 months.

Presenting at Mid-Term Review Meeting in Dublin, Ireland (credits)

In conclusion, this was an incredibly enjoyable meeting where it was possible to observe the general good situation of the project and the great work being carried out not only by each of the ESRs but also by every person involved in this research program.

In addition and on a great final note, I conclude this post by informing you that in little less than 3 weeks our group is going to get together again, this time in Barcelona, for the second network-wide training week. Therefore, in the next post, surely I will write here plenty of enjoyable stories about this meeting, so please stay tuned!

I wish you all a wonderful year of 2017! 

Attendance and presentation at IALCCE' 16 in Delft, Netherlands

Hello everyone!

How is everything going with you guys? This month went flying but, at the same time, it was greatly productive. However, in this post, I will talk with you about my experience last month at IALCCE 2016.

The Fifth International Symposium on Life-Cycle Civil Engineering, IALCCE2016, was a conference held in the city of Delft, South Holland in Netherlands from the 16th to the 19th of October 2016.

IALCCE'16 logo (credits)

This was a conference organized by Infra Quest, a collaboration between the Delft University of Technology, TNO (the Netherlands Organization for Applied Scientific Research) and Rijkswaterstaat (government agency within the Dutch Ministry of Infrastructure and the Environment. Furthermore, this event was mainly held at TU Delft Aula Congress Centre, that can be seen here.

Venue of IALCCE'16 (credits)

The International Association for Life-Cycle Civil Engineering, or IALCCE, is an organization  that focus on the advocacy of the life-cycle assessment and study in the field of civil engineering through international cooperation for the society benefit. They sponsor this conference that is held every two years, being that the first was held in Varenna, Italy back in 2008.

In this conference, the theme of this year event was: Civil Engineering from a life-cycle perspective. In this way, and taking into account the topic of the project that we have been discussing in this blog, our research group at Barcelona, submitted a document with the title "Health Monitoring of real structures by distributed optical fiber". 

Article (left) and Presentation (right) submitted to IALCCE'16

Here, as the title suggests, it was showcased the opportunities and enhancements that distributed optical fiber sensing can provide for Structural Health Monitoring of real world structures, with important saving costs for the structure's owner authorities (including, naturally, the tax payers) and the further assurance that can be granted to their everyday users.

Waiting to present at IALCCE'16 on the 19th of October 2016

As always, this was also an excellent opportunity to continuously get to know excellent work that is being conducted in areas similar and relevant to the one that I'm dealing with in my project, and also, to get to know the people behind those same studies.

As I'm writing this, the date of TRUSS's Mid-term Review Meeting at Dublin is approaching on the first two days of December. In this way, hopefully, I will be able to give you some information of what went on on this meeting on my next post.

I also, take this opportunity, to wish you all a happy and delightful Christmas. 

See you soon!

Beginning of secondment at COTCA

Hi guys, how's everything?

I hope your work is going well. As for me, a lot of work is being conducted with its inherent challenges but in the end I think everything will come out just fine.

As planned in the beginning of my project, the time to start my secondment at COTCA S.A. has arrived, so basically in this post I will talk with you about this important stage of my project within TRUSS.

This secondment is part of the training that, as an ESR in TRUSS project, we receive during our research that is a period between 3 and 6 months. ESR's that are hosted at universities are seconded to industry and vice versa. There's several benefits that we receive from this experience, such as a better perspective from industry of the topics of our researches and in this way provide us with knowledge that will aid us in our researches in order to provide work and information that will better tackle the real necessities of our current society. Moreover, it's a great way to provide personal experience in an industry wise environment, that for instance, in my personal case, I've never had experienced before, improving our curriculum and widening our future professional opportunities after the conclusion of our work within this ITN.

So, in this way, last September 12th I officially initiated my secondment at the company COTCA S.A. that is also located in the city of Barcelona, Spain. This secondment is done under the supervision of Dr. Sergi Villalba that is an employee of this company and is the overall co-supervisor of my project. 

COTCA S.A. logo

This is a company that was founded in 1979 and that is dedicated to the quality control of construction in civil and building structures. In this way, they have a large expertise in the instrumentation of structures for monitoring purposes with different types of sensors including, and this is very important, the use of distributed optical fiber sensors, more specifically the OBR based sensor that I've mentioned in previous posts. It's a relatively small company, with only 16 staff members but that has significant practical experience on structural monitoring, instrumentation, control and maintenance of structures.

Actually, I had the opportunity of working with Sergi before, as part of some short stays of my secondment back in January and February, when a two-span bridge was being monitored with OBR sensors and where I was able to acquire a lot of practical experience by witnessing in first hand the main adversities and difficulties that arise from the real world application of this technology.

In opposition to what happened with a lot of my fellow ESR's, the location of my secondment is not far away from where I am currently living. Actually it's closer to my home than the university, so in this way, my normal daily routine was not at all affected by this. This also allows me to easily and often visit UPC either to have a meeting with my supervisor, Prof. Joan Ramon Casas, or the laboratories of the Structures' department.

Now, as part of my long stay secondment, among several tasks, I'm analyzing the data collected in the aforementioned real world application as well as other experiments already conducted by me in the UPC laboratory. I'm also trying to thoroughly prepare further laboratory experiments which always provides different challenges such as the coordination with laboratory technicians and availability of loading test machines. Furthermore, it's required to buy and assemble several components in order to successfully prepare these experiments, such as new and different adhesives, concrete ingredients and last but not least, more optical fiber! For this I have to personally contact different commercial entities and carefully evaluate each option. Naturally, this process demands a considerable effort in order to overcome the usual inertia associated with these actions, but in the end, I think it provides me a valuable and unique kind of experience that otherwise I wouldn't be able to acquire.

So, this is basically it for now. Hopefully, next month I will be able to get back to you guys with more and exciting news.

Stay tuned and see you soon!

Presentation at 5th Workshop of COST TU1402 in Denmark

Hello, everyone!

How is the return to work have been for you? Hopefully with a lot of new and interesting ideas.

Well, I know that, at least for me, this has been a period with plenty of tasks and activities which sometimes makes it difficult to deal with each one at a time. Nonetheless, I hope that in the end, everything will come out nicely with productive results for my project. Surely I will speak about this with more detail in future posts.

In this post, I will talk about my experience, on the 5th Workshop of COST action TU 1402. For those of you that don't remember, back in my last April post, I mentioned that a workshop of this specific COST action had been held here at UPC in Barcelona back in March. Like I mentioned at that time, it had been very interesting to attend that workshop and I was looking forward to have the opportunity to attend or even participate in new meetings of this action. It so turns out that this opportunity indeed appeared  back in June when my supervisor received a call for presentations on the experience of the use of new structural health monitoring techniques to be made at the 5th Workshop to be held at the Technical University of Denmark in Kongens Lingby.

This event was held last month on the 24th and 25th of August. Here, we decided to present a review of the experience of our local research group at BarcelonaTech on the use of Distributed Optical Fiber Sensors (DOFS) in both laboratory and real-world applications. Thus, the title of our presentation was: "Concrete structures monitoring with Optical Backscatter Reflectometry based Distributed Optical Fiber Sensors". Here, you can see a photo taken during my presentation.

Presenting at 5th Workshop of COST TU1402

Since the title of this action is "Quantifying the Value of Structural Health Monitoring" the presentation was more focused on the added information and accuracy obtained by the use of this sensing technique on SHM applications. Furthermore, as in the last meeting, I got to meet several researchers working on incredibly interesting topics, even ones working on researches very similar to mine, allowing for fascinating and amusing conversations between presentations. You can see my presentation as well as any other made in this event here.

As always, this experience allowed the continuous learning of the most recent investigated topics in the SHM field as well as the prolific exchange of ideas and opinions regarding my own project which I believe can only improve the final quality of my work.

Group photo of 5th Workshop of COST TU1402 at TU Denmark

Furthermore, I take the opportunity to announce that I officially began my secondment at COTCA S.A. company as it was planned at the beginning of my project. In the next post, I will talk in more detail about this topic and its role in my research within the TRUSS group.

Stay tuned for more posts in the near future!

See you soon!

Attendance of the 8th European Workshop on Structural Health Monitoring

Hey guys!

Enjoying some of your vacation days? For me, I'm afraid they are coming to an end so it's time to get back to work with recharged batteries. But before, and like I said in my last post, I will tell you guys very briefly about my attendance of the 8th European Workshop on Structural Health Monitoring (EWSHM2016).

This was an event held at the Euskalduna Conference Center in the beautiful city of Bilbao, in the Basque country in Spain, from July 5-8, where the latest advances related with Structural Health Monitoring (SHM) were presented. At the same time, the 3th European Conference of the Prognostics and Health Management Society (PHME16) was organised jointly at the same building. As me, also my colleague JJ Moughty (ESR12) presented part of his work on EWSHM2016 and my colleague Matteo Vagnoli (ESR9) on PHME16.

Me with my colleagues JJ Moughty (ESR12) and Matteo Vagnoli (ESR9) at Bilbao

I made a presentation regarding my work on the literature review that I conducted in the first year of my research with the title: " Review of civil engineering applications with distributed optical fiber sensors".

Presenting at EWSHM2016

As always it was very pleasant and interesting to attend this event where I was able to meet and interact with new people and get to know more about the current researched topics related with Structural Health Monitoring and other relevant themes.

I wish you guys a good and energetic return to work.

Stay tuned for more developments regarding my project.

Attendance of IABMAS 2016 at Foz do Iguaçu, Brazil

Hello everyone!

How have you been doing in this lovely summer? I hope to find you well.

Like I mentioned in my last message, in this post I will talk about my trip to Brazil for the attendance of the 8th International Conference on Bridge Maintenance, Safety and Management. 

This conference was held in Foz do Iguaçu, Brazil, from June 26-30 and organized by the International Association for Bridge Maintenance and Safety (IABMAS). This is one of the biggest bridge monitoring conferences in the world and is organized every two years being that the first was held precisely here in Barcelona in 2002.

Like the title of the conference suggests, its main objective is to bring together academics and practicing professionals related to bridge maintenance, safety, and management for the dissemination of the latest developments in this field. 

The city of Foz do Iguaçu, located in the southwest interior of Brazil (at the border with both Paraguay and Argentina) is characterized for being the place where the Paraná and Iguaçu river converge. Near to the meeting of this two rivers the Iguaçu Falls are located, listed as one of the New 7 Wonders of Nature, with a flow of up to 45 milion liters per second! And as you can see from the following picture, it's astonishing beautiful. 

Overall perspective of Iguaçu Falls (credits)

A very happy ESR in front of the falls

In this event I presented a paper developed under the TRUSS project with the title: "Monitoring of shear cracking in partially prestressed concrete beams by distributed optical fiber sensors".

Presenting at IABMAS 2016

This was an extremely enticing and productive conference where I got to interact and discuss with several researchers from all around the world about several advances and topics of studies related with the structural monitoring of bridges. The next IABMAS conference is going to be in Melbourne, Australia in July 2018 and the deadline for the submission of the abstracts is May 2017. Hopefully, I will be able to attend it with further developments of my project together with more of my ESR colleagues.  

Next month, I will talk about another conference that I attended in the beginning of this month at Bilbao, so please stay tuned.

In the meantime, I'll leave you with this incredibly beautiful image of the new  European champions!!

TRUSS annual plenary meeting at Santander

Hello everyone!

How is the beginning of the summer been treating you? I hope you all have been enjoying it.

As for me, like I said in my last post, this has been a busy but also productive period of my project. In addition, to the work that I've been developing at the UPC laboratory (which I intend to talk about in a future post), I've been attending different meetings and conferences, which gives me plenty to talk about here. In this way, I will speak about these different events in different posts in this blog, starting by describing to you the 2nd meeting of our TRUSS ITN research group.

This meeting took place at Santander, Spain on the 16th and 17th of June. For those of you who don't know this city, Santander is the capital of the autonomous community region of Cantabria located in the north of Spain. Here you can see a few pictures of it (all of them were downloaded from the website of Santander tourism department).

In this meeting, all the ESRs presented their progress on there respective projects followed by separate meetings of each ESR with a small group of experts, by the name of doctoral studies panel (DSP) meetings, which provided feedback on the personal career development plan (PCPD) of each ESR.

Furthermore, we were presented by the local organization with different and interesting networking activities. From a visit to a factory of nuclear plant components, to boat rides through the Santander bay and also a visit to a historical  village in this region.

This was a incredibly fun and enjoyable meeting where it was good to see the development of all my colleagues and engage in these activities with them. I must refer that unfortunately, our colleague ESR 13 Federico Perrotta was not able to attend this meeting and in this way, he was greatly missed by all of us. But as you can see from his blog his project is going just fine.

Currently, I'm writing this post from Foz do Iguaçu in the beautiful country of Brazil, where I'm attending IABMAS 2016 conference and where I presented an article related with my PhD project. Here you can see a small preview of my time here in Brazil, which I will talk about in my next post.

Stay tuned for further developments of my work and if you want to know more of the meetings and conferences that I'm attending!

Workshop at Belfast and 1st Journal Publication

Hey everyone! How has this month been treating you?

Personally, this has been a busy period of my project but also very productive.

Actually, I'm writing this post just after attending the 6th Workshop on Civil Structural Health Monitoring. This was an incredibly interesting event hosted by the School of Planning Architecture and Civil Engineering at Queen's University Belfast in Northern Ireland on 26 and 27th of May and organized in conjunction with the International Society for Structural Health Monitoring of Intelligent Infrastructure (ISHMII).

I was joined by my fellow TRUSS ESR's Farhad Huseynov (ESR7), John James Moughty (ESR10) and Daniel Martínez Otero (ESR12) at this event. Prof. James Brownjohn (Main supervisor of ESR7) and Prof. Eugene OBrien (Main Supervisor of ESR12) were also at this event where they made compelling and engaging presentations.

Here you can see a group photo of all the participants of this event.

6th Workshop on Civil Structural Health Monitoring attendees

And here you can see a photo of all present TRUSS fellows with Prof. Eugene OBrien at the Workshop.

TRUSS ESR fellows and Prof. Eugene OBrien at the Workshop

The workshop topics were mainly related with monitoring strategies for the evaluation of structures exceeding their design life; management of structures exceeding design life; geotechnical monitoring of civil infrastructure to extend life and improve safety, and finally, economic analysis of SHM for essential SHM strategies.

It was great to get to know the newest projects developed by our colleagues in this field and also the people behind it. I've even got to see some amazing works where distributed optical fiber sensors were applied with success and that gave me important and different perspectives of these sensors.

I also take this chance to happily announce that my first peer-reviewed journal article was published online this last week! This article is a result of my developed literature review and was published in the journal Sensors, an Open Access Journal from MDPI with an impact factor of 2.245. So if you want,  you can have a look at it here and hopefully, you'll find it interesting.

Published article in Sensors journal

Hopefully, this is the first of many more to come.

The following weeks are going to be insanely busy but I expect to be able to get back to you with more developments and exciting news anytime soon.

Stay tuned!

Attendance of meetings related with the developing topic

Hello everyone!

Well, in this post I will just talk about some activities that I've attended here at UPC that were related with topic of my project. 

In the past month of March, two different but compelling meetings occurred here in Barcelona where the thematic of Structural Health Monitoring was heavily discussed.

The first one was a summit organised by IABSE and the Finnish Association of Civil Engineers with the title of Global Risks in Structural Engineering. This was a two day event (10-11 March 2016) where the first day was held at Helsinki and the second one here at UPC, Barcelona. Here, different and engaging presentations were made by notable keynoters. 

As the title of this summit suggests its topic was focused on risk assessment and evaluation of civil engineering structures subjected to natural hazards. The presentations ranged from new risk-based wind design methods for bridges, probabilistic seismic risk evaluation of urban areas, damage modes of concrete structures in major earthquakes and state-of-the art and proposal of infrastructure for disaster hazards.

Here you can see two photos of the summit where unfortunately I was blocked on both of them... But since there aren't any better ones, I guess these will do just fine.

Well, anyway. It was definitely a productive meeting where interesting and relevant topics were examined, related with theme of the project that I'm developing and that has been discussed in this blog on the previous posts.

The second meeting was related with the COST Action TU1402. For those of you that like me didn't knew what a cost action is, it's basically an European Concerted Research Action that focus on a relevant field. You can find more about these actions in here.

This specific action has the objective of Quantifying the value of Structural Health Monitoring (SHM) by means of improving decision basis for design, operation and life-cycle integrity management of structures.

This action is involved with several other COST actions, other European projects and even a different Marie Curie Network (SmartEn).

This was a fascinating meeting since different SHM applications where presented and in which not only its relevance for the maintenance of the structure was debated but also the quantification of the procedure of implementing each SHM application and its value for the monitored structure. Unfortunately, I wasn't able to obtain photos of this meeting but you can see and read its presentations here.

In the future, I hope I'll be able to attend more of these meetings since it allows me to easily witness what have been the latest achievements in research related with the topic that I'm currently working on and also since it's a great way to network and interact with fellow researchers that, ultimately, can greatly contribute to the quality of my work.

Stay tuned for more posts in the near future!

See you soon!

Applications of DOFS in Civil Engineering

Hello everyone!

Hope you all had a great Easter. Now it's time to get to know a little more about Distributed Fiber Optic Sensors (DOFS).

As I mentioned last month, in this post I will talk a little bit about some recent applications of DOFS in civil engineering structures, focusing on the work being done by our research group at Universitat Politècnica de Catalunya (UPC).

The great majority of photonic sensing technology applied in the area of civil engineering is constituted by discrete sensors such as the Fiber Bragg Gratings (FBG). This topic has been extensively discussed in different publications in the past decades. 

Nowadays, DOFS sensors are an attractive technology that offers superior performances and advantages when compared with more conventional sensors applied in Structural Health Monitoring (SHM) practice, as explained in the previous posts. Despite their apparently high cost, they are ideal for applications where reliability in challenging environments is essential. Furthermore, they provide lower installation and maintenance costs.

However, this is still a recent and developing technology as it can be perceived by the relatively few number of DOFS applications in SHM projects. Notwithstanding, some different DOFS applications were made in the last two decades in various and very distinct civil engineering structures such as bridges, dams, tunnels, pipelines and slopes. Also, a great load of work was made, with the goal of improving these sensors capabilities by executing different laboratory experiments.

The ability to cover long distances, perform distributed measurements (both in space and time), immunity to electromagnetic interference and endurance, are some of the advantages of the DOFS over traditional discrete measuring sensors. For these reasons, these sensors have been initially and mostly instrumented in large structural systems. As discussed in the previous post, the Brillouin optical time domain analysis (BOTDR) has been the most applied technique of DOFS based sensors due to their wide range of measurement capability. In order to get to know with more detail examples of the application of this technique on bridges monitoring, for example, the reading of the following documents is advised: (Bastianini et al 2005a), (Bastianini et al 2005b), (Minardo et al 2012a), (Minardo et al 2012b), (Glisic et al 2011), (Glisic et al 2013).

When a better spatial resolution is necessary (for crack detection for example) in a relatively cost-effective way, the most sought-out technique is the Rayleigh based optical frequency reflectometry (OFDR) or as is also known, optical backscattered reflectometer (OBR) and this is the equipment that we mostly have been working with at UPC - Barcelonatech.

One of the first conducted experiments with the goal of exploring the capabilities of crack detection in concrete elements was conducted by Villalba & Casas, 2013 by instrumenting a concrete slab with OBR based DOFS that was then subjected to a load test .

Since then, various and different applications have been made by this group with engaging and promising results. From those, we can highlight the experiments done in Viaduct Road BP-1413 and a concrete cooling tower in Spain, that are described in greater detail in the following publication (Casas et al 2014).

Viaduct Road BP-1413 and Concrete Cooling Tower

Another impressive experiment was conducted in the extraordinary historical building of Hospital de la Sant Creu i Sant Pau. This building, one of the most outstanding examples of the Modernism movement in Barcelona of the beginning of the 20th Century and a UNESCO World Heritage Site. The OBR system was implemented, during the replacement of two deteriorated columns, on the adjacent upper slab where it successfully monitored the stress redistribution of this structural element due to this process.

Hospital de la Santa Creu i Sant Pau and implemented DOFS

More recently, this research group has been working on two experiments which have yet to be published. The first one is the attempt to detect and map shear induced cracks on partially prestressed concrete beams (PPC). This is of extreme relevance since that contrary to what happens with bending cracking, where the cracks appear orthogonally to the beam axis, in the case of shear action, the inclination of the cracking pattern is previously unknown and may even change depending on the prestressing force and the location along the element. For this, a two‑dimensional DOFS grid was proposed that monitored the crack initiation, location, inclination and evolution during a beam load (Rodríguez 2016).

Finally, this research group, instrumented one span of a bridge in Barcelona with a OBR system in order to monitor this structure during a deck enlargement rehabilitation. This process was conducted through several months, spanning from summer to winter, so consequently the topic of temperature influence in the measurements was a relevant issue that needed to be addressed.

Sarajevo Bridge, Barcelona

Well, I hope you have enjoyed these examples and hopefully in the future you will be able to read more about these ones and more in developing publications.

For more developments tune in again at the end of next month!

Now I have other matters to attend to :)


Greetings from Barcelona! See you guys soon!



Bibliography

Bastianini F., Corradi M., Borri A. and di Tomasso A. (2005a), "Retrofit and monitoring of an historical building using "Smart" CFRP with embedded fibre optic Brillouin sensors". Construction and Building Materials, 19, 525-535

Bastianini F., Matta, F., Galati, N., Nani A. (2005b) "A Brillouin smart FRP material and strain data post processing software for structural health monitoring through laboratory testing and field application on a highway bridge" Proc. SPIE, 5765, 600-611

Minardo A., Bernini R., Amato L. and Zeni L. (2012a), "Bridge monitoring using Brillouin fiber-optic sensors", IEEE Sensors Journal, 12(1), 145-150

Minardo A, Persichetti G, Testa G and Zeni L. (2012b), "Long term structural health monitoring by Brillouin fibre-optic sensing: a real case", Journal of Geophysics and Engineering, 9, S64-S68

Glisic B., Chen J. and Hubbell D. (2011), "Streicker Bridge: A comparison between Bragg-gratting long-gauge strain and temperature sensors and Brillouin scattering-based distributed strain and temperature sensors", Proc. of SPIE, 7981, 1-10

Glisic B., Hubbell D., Hoeg S. D. and Yao Y. (2013), "Damage detection and characterization using long-gauge and distributed fiber optic sensors", Optical Engineering, 52(8), 1-12

S. Villalba and J. R. Casas, "Application of optical fiber distributed sensing to health monitoring of concrete structures" Mech. Syst. Signal Process., vol. 39, no.1, pp. 441-451, 2013

Casas J. R., Villalba S and Villalba V. (2014) "Management and safety of existing concrete structures via optical fiber distributed sensing". Chapter of the book "Maintenance and Saftey of Aging Infrastructure". Dan M. Frangopol and Yiannis Tsompanakis, Editors. CRC Press. Taylor and Francis 

G. Rodríguez, J. R. . Casas, S. Villalba, and A. Barrias, “Monitoring of shear cracking in partially prestressed concrete beams by distributed optical fiber sensors,” in Proceedings 8th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2016, 2016 (Acepted)

What is Structural Health Monitoring (SHM)? Distributed Fiber Sensors (DOFS)?

Hello everyone!

So, from my last publication you got to know me little bit and the process of how I ended up in this project entitled: Development of optical fibre distributed sensing for SHM of bridges and large scale structures. 

But, what is in fact SHM and DOFS?

Well, everything has a lifetime period, from living organisms to inanimate objects. Deterioration and decay is a constant all around us and engineering structures are not an exception. In the United States alone, over 11% of the nation’s 607 380 bridges are structurally deficient and the cost to repair these deficient bridges is estimated to be $76 billion (ASCE 2013). Well maintained civil infrastructure can substantially increase a country’s competitiveness in a global economy and enhance resilience to adverse circumstances. Therefore, a structure, especially in the present days, must be able to reliably produce information regarding the alterations in its structural health condition and communicate it to the responsible operators and decision makers both in time and either automatically or on-demand in order to decrease these costs. 

The control and monitoring of the aging process of civil engineering structures is of extreme importance for their quality and safety. Furthermore, there are different external events that can induce damage to a structure. The process of employing a damage identification strategy for engineering and aerospace infrastructures is referred to as structural health monitoring (SHM). The early detection of structural malfunctions allows the increase of the service life-time of the structure at the same time that decreases the maintenance costs associated with every infrastructure and the economic losses related with repair/reconstruction in the case of structural failure being critical for the emergence of sustainable civil and environmental engineering.

The act of damage identification has been around probably, in a qualitative manner, since modern man has used tools. Notwithstanding, SHM has been recently a fast-developing area in aerospace and engineering disciplines especially in the civil engineering field. The innovation in the SHM technologies as well as the development of the large‑scale SHM systems has been a great subject of interest within the engineering and academic communities over the last two decades. However, despite its great potential, SHM has not been applied in large scale and in a systematic manner to civil infrastructures. One significant reason for this is the deficit of reliable and affordable generic monitoring solutions. 

Currently, evaluations of buildings, bridges, dams, tunnels and other vital infrastructures are usually carried out by engineers trained in visual inspection, which sometimes can be inaccurate due to differences in their personal experience with safety condition assessment. In order to improve the inspection accuracy and efficiency, optical fiber sensors (OFS) are one of the fastest growing and most promising researched topic, due to their features of durability, stability, small size and insensitivity to external electromagnetic perturbations, which makes them ideal for the long-term health assessment of built environment. 

Different kinds of sensors, embedded or attached to the structure, can be used in SHM systems but only those based on fiber technology provide the ability to accomplish integrated, quasi-distributed, and truly distributed measurements on or even inside the structure, along extensive lengths. Standard monitoring practice is normally based on the choice of a limited and relatively small number of points that are supposed to be illustrative of the structural behavior. For a large scale structure, the number of point sensors needed to generate complete strain information can grow rapidly. Discrete short‑gauge sensors provide useful and interesting data of the structure related with local behavior but might omit important information in locations where degradation occurs but that not is instrumented. 

Distributed optical fiber sensors (DOFS) offer an advantage over point sensors for global strain measurements. The thousands of sensing points that the DOFS provides enables mapping of strain distributions in two or even three dimensions. Thus, real measurements can be used to reveal the global behavior of a structure rather than extrapolation from a few point measurements. A truly distributed optical sensor is expected to measure temperature, strain and vibration data at any point along an entire fiber trough light scattering. The great challenge has been to develop these sensors in a way that they can achieve appropriate sensitivity and spatial resolution. Fortunately, great advances have been made in the last decades in order to improve this area.

Scattering is at the origin of DOFS and it can be defined, in a simple way, as the interaction between the light and an optical medium. Three different scattering processes may occur in a DOFS, namely: Raman, Brillouin and Rayleigh scattering. Distributed fiber optic sensors can depend on different techniques and principles. For different SHM applications, different DOFSs sensors can be developed and so different techniques are applied.

Nevertheless, the DOFS that have been mostly applied in civil engineering SHM applications are based on the following techniques: Brillouin optical time domain reflectometer (BOTDR), Brillouin optical time domain analysis (BOTDA) and Rayleigh based optical frequency reflectometry that is better know by the optical backscattered reflectometer (OBR) designation.

BOTDR based sensors have been the most studied and applied measuring systems in civil structures SHM due to their extended measurement range potential that makes them very useful for the application on large structures, such as dams, pipelines, tunnels and long span bridges. Notwithstanding, some applications require a better spatial resolution than the one provided by these sensors. The BOTDA sensing technique, through the application of advanced and complex algorithms, can address this point but in the process increases the price of this technology. OBR technique (Rayleigh OFDR) offers a more cost-effective way of achieving high spatial resolution limiting, nonetheless, the sensing range to 70 meters.

In the next, publication , I will present some recent applications of these sensors on civil engineering structures, including some developments carried out by our research group at UPC. As a preview, I share with you a photo of me on one of those carried experiments :)

More updates next month, stay tuned!

Greetings from Barcelona!