Horizon 2020 Marie Skłodowska-Curie Innovative Training Network

António Barrias

MSc
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António Barrias 2017-09-29T18:53:04+00:00

Research Interests:

Structural engineering; Bridge design; Bridge monitoring; Structural health monitoring; Structural numerical modelling

Biography:

Mr. Barrias completed his graduation in 2013 at FEUP (Faculty of Engineering of the University of Porto) in Civil Engineering – Structures specialization, with a final grade of 15 (out of 20), corresponding to grade A on the European grading scale. During his graduation he enrolled in the Erasmus programme at the Czech Technical University of Prague. His master thesis consisted on the study and design of a new road bridge between the cities of Porto and Vila Nova de Gaia.

After his graduation he made an IASTE internship at Technischen Universität Kaiserslautern, Germany for two months where he worked in the Department of Geotechnics.

From February of 2014 until August of 2015, he was a full researcher at LABEST (Laboratory of Concrete Technology and Structural Behavior) at FEUP where he was involved in the research programme entitled “GNSS and accelerometers data fusion in large structures monitoring”. He joined TRUSS ITN in September 2015.

Research Outputs:

  • Barrias, A., Pestana, A., Félix, C. and Figueiras, J. (2014), “Monitorização de deslocamentos em estruturas com recurso ao GNSS”, in Proceedings of 5ªs Jornadas Portuguesas de Engenharia de Estruturas, Lisboa.
Publications in TRUSS

The application of structural health monitoring (SHM) systems to civil engineering structures has been a developing studied and practiced topic, that has allowed for a better understanding of structures’ conditions and increasingly lead to a more cost-effective management of those infrastructures. In this field, the use of fiber optic sensors has been studied, discussed and practiced with encouraging results. The possibility of understanding and monitor the distributed behavior of extensive stretches of critical structures it’s an enormous advantage that distributed fiber optic sensing provides to SHM systems. In the past decade, several R & D studies have been performed with the goal of improving the knowledge and developing new techniques associated with the application of distributed optical fiber sensors (DOFS) in order to widen the range of applications of these sensors and also to obtain more correct and reliable data. This paper presents, after a brief introduction to the theoretical background of DOFS, the latest developments related with the improvement of these products by presenting a wide range of laboratory experiments as well as an extended review of their diverse applications in civil engineering structures. [DOI]

This paper reports on recent contributions by the Marie Skłodowska-Curie Innovative Training Network titled TRUSS (Training in Reducing Uncertainty of Structural Safety) to the field of structural safety in rail and road bridges (http://trussitn.eu). In TRUSS, uncertainty in bridge safety is addressed via cost efficient structural performance monitoring and fault diagnostics methods including: (1) the use of the rotation response due to the traffic traversing a bridge and weigh-in-motion concepts as damage indicator, (2) the combination of design parameters in probabilistic context for geometrical and material properties, traffic data and assumption on level of deterioration to evaluate bridge safety (via Bayesian updating and a damage indicator based on real time measurement), (3) the application of a fuzzy classification technique via feature selection extracted using empirical mode decomposition to detect failure, and (4) the testing of alternative vibration based damage sensitive features other than modal parameters. Progress has also been made in improving modern technologies based on optical fiber distributed sensing, and sensors mounted on instrumented terrestrial and on aerial vehicles, in order to gather more accurate and efficient info about the structure. More specifically, the following aspects have been covered: (a) the spatial resolution and strain accuracy obtained with optical distributed fiber when applied to concrete elements as well as the ideal adhesive, and the potential for detecting crack or abnormal deflections without failure or debonding, (b) the possibility of using the high-resolution measurement capabilities of the Traffic Speed Deflectometer for bridge monitoring purposes and, (c) the acquisition of bridge details and defects via unmanned aerial vehicles.

In the past decade, several works and studies have been performed with the goal of improving the knowledge and developing new techniques associated with the application of Distributed Optical Fiber Sensors (DOFS) in order to widen the range of applications of these sensors and also to obtain more correct and reliable data. In this document, after a very brief introduction to the fundamentals of this technology, the most representative work being developed at UPC—BarcelonaTech with the use of these sensors is going to be described. These applications range from laboratory experiments to real world structures monitoring scenarios where different challenges and particular issues had to be overthrown in each one of them. Furthermore, the most recent laboratory experiment performed by this group where DOFS were deployed is going to be described in greater detail. [DOI] -> Link to full text in repository

In the present paper, a novel technique is used to monitor and evaluate shear crack patterns in Partially Prestressed Concrete (PPC) beams. The proposed technique is based on experimental data obtained in two PPC beams tested in laboratory and instrument-ed by Distributed Optical Fiber Sensors (DOFS). The DOFS conform optical fiber grids bonded in the surfaces of the beams. The DOFS experimental data were obtained using an OBR (Optical Backscattered Reflectometer) system that provides continuous strain data with high spatial resolution and cracks can be characterized. The continuous (in space) monitoring of the strain along the DOFS, including the crossing of a crack provides additional information without requiring prior knowledge of the cracked zone.

Several experiences have demonstrated the feasi-bility of using OFDR theory and SWI technique in the structural monitoring of concrete structures (Villalba and Casas 2013, Rodriguez et al 2015). In the specific case of detection, location and control of cracking in concrete structures, OBR system is an attractive monitoring tool. In the evaluation of shear crack pattern, the inclination of the cracking pattern is an additional unknown property. Two PPC beams named I1 and I2, were tested using DOFS grids as measuring alternative to check the proposed structural monitoring method.

According to the preliminary results obtained in this paper, the use of DOFS is a feasible methodology to obtain important information in the study of shear structural behavior in concrete structures. Continuous strain data at different loading levels were obtained with high spatial resolution by OBR system. Using this data, detection and location of flexural and shear cracks were obtained without requiring prior knowledge of the cracked zone.

Finally, in the evaluation of the shear crack pattern, not only crack initiation and location are of importance, but also crack width, shear crack angles and shear sliding displacements along the cracks have to be measured to evaluate the shear performance of a structural element. -> Link to full text in repository

References.-
Villalba S. and Casas J. 2013. Application of optical fiber distributed sensing to health monitoring of concrete structures. Mechanical Systems and Signal Processing, 441-451.
Rodríguez G., Casas J., and Villalba S. 2015. Cracking assessment in concrete structures by distributed optical fiber. Smart Materials and Structures, 24, 1-11.

It’s widely recognized that during its lifetime, civil engineering structures are subjected to adverse changes that affect their condition and structural safety. These changes are due to several factors such as damage and deterioration induced by environmental aggressions, design and/or construction errors, overloading, not expected events such as earthquakes or simply due to the normal degradation associated with the normal use of the structure through their working life. In this way, the application of Structural Health Monitoring (SHM) systems to these civil engineering structures has been a developing studied and practiced topic, that has allowed for a better understanding of structures’ conditions and increasingly lead to a more cost-effective management of those infrastructures.

In this field, the use of fiber optic sensors has been studied, discussed and practiced with encouraging results. These sensors present several advantages when compared with the more traditional and used electric sensors, such as their immunity to electromagnetic interferences and corrosion, their ability to withstand high temperatures and their small dimensions and light weight just to name a few. Furthermore, with distributed fiber optic technology it’s possible to measure virtually any point along a single fiber allowing for truly distributed sensing measurements with great spatial resolution. The possibility of understanding and monitor the distributed behaviour of extensive stretches of critical structures it’s an enormous advantage that distributed fiber optic sensing provides to SHM systems. These distributed fiber optic sensors (DOFS) when bonded or embedded in the structural material works as its nervous system and for all these reasons, it is acknowledged as the most promising fiber optic sensing technique.

In the past decade, several R&D works have been performed with the goal of improving the knowledge and developing new techniques associated with the application of DOFS in order to widen the range of applications of these sensors and also to obtain more correct and reliable data. This paper presents, after a brief introduction to DOFS, the latest developments related with the improvement of these products as long as a review of their diverse applications on structural health monitoring with special focus on engineering structures. -> External link to publisher’s version -> Link to full text in repository

Two different existing structures monitored with distributed optical fiber sensors, are described in this paper. The principal Structural Health Monitoring (SHM) results of a valuable hospital rehabilitation (Sant Pau Hospital) and the enlargement of a prestressed concrete bridge (Sarajevo bridge), are presented. The results are obtained using a novel Distributed Optical Fiber Sensor system (DOFSs) based on an Optical Backscattered Reflectometry (OBR) technique. The versatility and easy installation of DOFSs compared with traditional monitoring systems is an important characteristic to consider its application in monitoring real world structures. The DOFS used in this study provide continuous (in space) strain data along the optical fiber with high spatial resolution in order of centimeters. Also and because the structural surfaces generally are roughness, the procedure to attach the optical fiber to two monitored structures are described. This is an important aspect because the influence in strain transfer between the DOFS and the surface is one of the principal parameters that should be considered in the application of the OBR technique.

Numerous works presenting information regarding the study of the potential of these sensors have been published in the last decade (Rodríguez et al. 2015 a,b; Palmieri & Schenato 2013) but very few showcase their application to real world structures. One of the various advantages of this technology is the easy installation to real life structures and the variety of them that can be instrumented with it. In both studied instrumentations the used fiber is based on a type of fiber optic in which the wavelength is established and compatible with a commercial data acquisition system. Each section of optical fiber has a maximum length of 50 meters and the union between the fiber and structural element (concrete/masonry) was performed using a twocomponent type epoxy adhesive. A coating of a polymer (polyimide) was used to protect the fiber against scratches and environmental attack.

Due to their particularities, each one of these structures underwent changes in their structural behavior without, nevertheless, ceasing to serve their purpose, i.e. accommodating patients in the case of the Sant Pau Hospital and the passage of vehicles and pedestrians in the case of Sarajevo bridge thanks to the application of these sensors. With the results obtained in this work, the OBR theory associated with DOFS proved its reliability in SHM of civil engineering applications and continues to showcase the promising future of monitoring systems based on this technology. -> Link to full text in repository

References.-
Palmieri, L. & Schenato, L., 2013. Distributed optical fiber sensing based on Rayleigh scattering. The Open Optics Journal, 7(1).
Rodríguez, G., Casas, J.R. & Villaba, S., 2015. Cracking assessment in concrete structures by distributed optical fiber. Smart Materials and Structures, 24(3), p.35005.
Rodríguez, G., Casas, J.R.. & Villalba, S., 2015. SHM by DOFS in civil engineering : a review. Structural Health Monitoring and Maintenance, 2(4), pp.357–382.