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!

Introduction

Hello everyone!

So, since this is my first message on this blog, I thought I should start by making a presentation of myself and my background.

In this way, my name is António Barrias, I’m 25 years old and I’m currently working towards a PhD degree on the project in the title, under the TRUSS ITN initiative in Universitat Politècnica de Catalunya in Barcelona since September 2015. I was born in a small but beautiful city in the north of Portugal called Vila Real in the unique Douro region. From a very young age, I was impressed by structural engineering, especially bridges. The first time I saw bridges like D. Luiz and Arrábida in Porto or 25 de Abril in Lisbon I was very intrigued and fascinated with such works of art as we call them in Portuguese. When the Vasco da Gama bridge in Lisbon, the longest bridge in Europe, was completed in 1998 and I crossed it for the first time with some family members, I asked them who were the amazing persons responsible by the astonishing feat of “making bridges”. When they told me that these structures were possible thanks to structural engineers, I decided right then, that I had to be one someday.

Vasco da Gama bridge in Lisbon, Portugal

Therefore, in 2008, after high school I enrolled at Faculty of Engineering of University of Porto (FEUP) in Civil Engineering where, when starting to learn more about this fascinating area, I realized I had made the correct decision despite the hard recession that was starting to develop in Portugal and that was taking a big toll in the construction business.

During this period, I participated in the Erasmus programme in the Czech Technical University in Prague for one semester where I was able to meet different people and different cultures but also a different way of looking to and solving civil engineering challenges.

When the time came to choose the specialization for my Masters, despite the fact that during my studies I discovered other areas that incited my interested, I knew all along that there was only one single correct option and that was structures. With my love for the superb examples of bridges present in Porto, when the opportunity appeared to propose the design of new road bridge between Vila Nova de Gaia and Porto as my master’s thesis I pleasantly took that challenge.

After concluding my master’s degree, in September 2013, I did a brief IAESTE (International Association for the Exchange of Students for Technical Experience) internship of two months in TU Kaiserslautern where I was aiding in the experiences being conducted in the Laboratory of Soil Structures and at the same time starting to develop a personal interest for laboratory work.

Hence, later, when the opportunity appeared, I became a researcher at the Laboratory of Concrete Technology and Structural Behaviour (LABEST) in FEUP where I was involved in the research programme “GNSS and accelerometers data fusion in large structures monitoring”. This project enabled me to combine my newfound interest in research with my passion with bridges and contributed greatly in my inclination of pursuing a research career in this area and, in this way, applying for TRUSS programme for the ESR 11 topic.

This is a very exciting and promising theme. Distributed fiber optic sensors, besides the advantages of discrete fiber optic sensors such as immunity to electromagnetic interferences, corrosion, long-term reliability, small size and weight, offers the possibility of continuous monitoring of strain and temperature along the whole length of the fiber. This is of great interest especially for concrete structures where the prediction of the exact location of cracks is impossible and in this way, it’s possible to cover bigger lengths of the structure that would otherwise require a large number of sensors in a more cost-effective and simple way. There are three different processes of scattering that can be explored in a DOFS system: Brillouin, Raman and Rayleigh scattering. Optical Backscatter Reflectometry (OBR) technique takes advantage of the later in order to obtain strain and temperature measurements with high spatial resolution.

Measuring process by OBR technique

The objectives of the project are to analyze the spatial resolution, strain accuracy obtained with these sensors without the failure and debonding from the concrete structures and their long-term reliability. It’s also intended to, at the end of this project, propose the criteria for the design and deployment of a permanent monitoring system based on these sensors.

DOFS real world application (active part)

DOFS real world application (passive part)

In the next post, after an introduction of TRUSS, I will talk about my developed work on this topic literature review, so please stay tuned.

Feel free to contact me at antonio.de.sousa.barrias@gmail.com or antonio.jose.de.sousa@upc.edu