Methodologies for model-free data interpretation of civil engineering structures

Structural health monitoring (SHM) has the potential to provide quantitative and reliable data on the real condition of structures, observe the evolution of their behaviour and detect degradation This paper presents two methodologies for model-free data interpretation to identify and localize anomalous behaviour in civil engineering structures Two statistical methods based on (i) moving principal component analysis and (ii) robust regression analysis are demonstrated to be useful for damage detection during continuous static monitoring of civil structures. The methodologies are tested on numerically simulated elements with sensors for a range of noise in measurements. A comparative study with other statistical analyses demonstrates superior performance of these methods for damage detection. Approaches for accommodating outliers and missing data, which are commonly encountered in structural health monitoring for civil structures, are also proposed. To ensure that the methodologies are scalable for complex structures with many sensors, a clustering algorithm groups sensors that have strong correlations between their measurements Methodologies are then validated on two full-scale structures: The results show the ability of the methodology to identify abrupt permanent changes in behavior. (C) 2010 Elsevier Ltd All rights reserved

Development of a Displacement Sensor for the CERN-LHC Superconducting Cryodipoles

One of the main challenges of the Large Hadron Collider (LHC), the particle accelerator under construction at CERN (the European Organization for Nuclear Research) in Geneva, resides in the design and production of the superconducting dipoles used to steer the particles around a 27 km underground tunnel. These so-called cryodipoles are composed of an evacuated cryostat and a cold mass, that contains the particle tubes and the superconducting dipole magnet and is cooled by super uid Helium at 1.9 K. The particle beam must be centred within the dipole magnetic field with a sub-millimetre accuracy, this requires in turn that the relative displacements between the cryostat and the cold mass must be monitored with accuracy. Because of the extreme environmental conditions (the displacement measurements must be made in vacuum and between two points at a temperature difference of about 300 degrees) no adequate existing monitoring system was found for this application. It was therefore decided to develop an optical sensor suitable for this application. This contribution describes the development of this novel sensor and the first measurements performed on the LHC cryodipoles

Measurement of dynamic deformations using a path unbalance Michelson interferometer based optical fiber sensing device

A novel demodulation technique for performing dynamic deformation measurements using a path-unbalanced Michelson interferometer is reported, The method is based on the rf amplitude modulation of a low-coherence source, and demodulation Is achieved by tracking in the frequency domain the position of the minimum of the detected intensity. This technique is particularly suitable for deformation measurements in civil engineering structures where deformations of the order of few millimeters over the sensor length are expected. The method features a measurement range of at least 10 mm, sensitivity better than 10 μm, and dynamic deformation measurements with a bandwidth up to 100 Hz

Estudio de los acantilados activos y del campo de dunas de Bahía Creek, Río Negro, Argentina, como base para la elaboración de un mapa de peligro geológico

Fil: Toffani, Mauricio. Universidad Nacional de Río Negro. Río Negro, Argentina.Fil: Caselli, Alberto Tomás Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Laboratorio de Estudio y Seguimiento de Volcanes Activos. Río Negro, Argentina.Fil: Lothari Inaudi, Lucas D. Universidad Nacional de Río Negro. Río Negro, Argentina.Fil: Caselli, Alberto Tomás Consejo Nacional de Investigaciones Científicas y Técnicas. Río Negro, Argentina.Study of the active cliffs and the dune field from Bahía Creek, Río Negro, Argentina as base for the elaboration of a geological hazard map. In this paper, a physical characterization was carried out together with the study of some socioeconomic aspects of the coastal region of Bahía Creek; so, the active cliff and the dune field of Bahía Creek were analyzed as well as the development of the local popula-tion. The recorded characteristics permitted to develop a risk assessment of the active cliff erosion, calculated as a unique numerical measure through the risk index. It was studied in three sectors, resulting medium in two sectors and low in the remaining. In addition, based on satellite images, aerial photographs and wind data, the annual migration rate for the closest dunes to the town of Bahía Creek was calculated. According to the rate of migration of the dunes, estimated at 5.71 m/year, its future location was projected in the next 10, 25, 50 and 100 years. Knowing the risk index values of the cliff and the probable location of the dunes in the future, it was possible to draw up a geological hazard map for the Bahía Creek area, which was subdivided into high, medium and low hazard. The high hazard zone considers the areas where the active cliff and active dunes are currently located and where their retreat or advance, respectively, may occur in short – medium term, i.e., months or until the next 25 years. The medium hazard zone presents marked irregular terrain and is located next to the high hazard zone and may be affected within the next 50 years by the retreat of the cliff and the dune migration. On the low hazard zone, it is inferred that it will not be modified in a lapse of at least 100 years, consequently it is advisable to build there in the future. The area of the current population settlement is almost entirely within the high hazard zone. Therefore, likely management measures to be implemented in relation to it are discussedEn el presente trabajo se realizó una caracterización física junto al estudio de aspectos socioeconómicos de la región costera de Bahía Creek. Se analizaron así el acantilado activo y el campo de dunas de Bahía Creek y el desarrollo de la población local. Las características relevadas permitieron evaluar el riesgo de erosión del acantilado activo, calculado como una medida numérica única a través del índice de riesgo. Estas características fueron estudiadas en tres sectores, resultando el índice de riesgo medio en dos sectores y bajo en el restante. En base a imágenes satelitales, fotografías aéreas y datos de viento, se calculó la tasa de avance anual para las dunas ubicadas más próximas a la población de Bahía Creek. A partir de la tasa de avance de las dunas, estimada en 5.71 m/ año, se proyectó su futura ubicación en los próximos 10, 25, 50 y 100 años. Conociendo los valores del índice de riesgo del acantilado y la probable ubicación de las dunas en el futuro, se elaboró un mapa de peligro geológico para la zona de Bahía Creek, el cual considera sectores de peligro alto, medio y bajo. El sector de alto peligro considera las zonas donde actualmente se ubica el acantilado activo y las dunas activas y donde su retroceso o avance, respectivamente, pueda ocurrir en el corto - mediano plazo, es decir, meses o hasta los próximos 25 años. La zona de peligro medio presenta marcadas irregularidades del terreno, se ubica a continuación de la zona de alto peligro y podría verse afectada dentro de los próximos 50 años por el retroceso del acantilado y el avance de las dunas. En la zona de bajo peligro, se estima que el terreno no sufrirá modificaciones en al menos 100 años, en consecuencia se recomienda como área para realizar futuras edificaciones. La zona del actual asentamiento poblacional se encuentra casi en su totalidad dentro de la zona de alto peligro, por lo tanto se discuten posibles medidas de manejo a implementar en relación con el mismo

Review: optical fiber sensors for civil engineering applications

Optical fiber sensor (OFS) technologies have developed rapidly over the last few decades, and various types of OFS have found practical applications in the field of civil engineering. In this paper, which is resulting from the work of the RILEM technical committee “Optical fiber sensors for civil engineering applications”, different kinds of sensing techniques, including change of light intensity, interferometry, fiber Bragg grating, adsorption measurement and distributed sensing, are briefly reviewed to introduce the basic sensing principles. Then, the applications of OFS in highway structures, building structures, geotechnical structures, pipelines as well as cables monitoring are described, with focus on sensor design, installation technique and sensor performance. It is believed that the State-of-the-Art review is helpful to engineers considering the use of OFS in their projects, and can facilitate the wider application of OFS technologies in construction industry

Análisis de facies y petrografía de los depósitos del cretácico superior en el norte de la cuenca Neuquina: implicancias para el inicio de la etapa de foreland

Fil: Lothari Inaudi, Lucas D. Universidad Nacional de Río Negro. Río Negro, Argentina.Fil: Gómez, Ricardo. Universidad Nacional de Río Negro, Instituto de Investigaciones en Paleobiología y Geología, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Argentina.Fil: Tunik, Maisa A. Universidad Nacional de Río Negro. Instituto de Investigaciones en Paleobiología y Geología. Río Negro, Argentina.Fil: Casadio, Silvio A. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina.Fil: Tunik, Maisa A. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Buenos Aires, ArgentinaFil: Casadio, Silvio A. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Buenos Aires, ArgentinaFil: Gómez, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Buenos Aires, ArgentinaLa cuenca Neuquina es una de las principales cuencas generadoras de hidrocarburos de la Argentina. Esto, sumado al amplio registro sedimentario que posee, la han convertido en objeto de numerosos estudios geológicos. La mayoría de estos estudios fueron realizados en el centro de la cuenca, siendo muy escasos los antecedentes en la zona de la alta cordillera de Mendoza, donde se desarrolla el presente trabajo. Las rocas estudiadas pertenecen al Grupo Bajada del Agrio, compuesto por las formaciones Huitrín y Rayoso, y a la Formación Diamante, esta última equivalente al Grupo Neuquén. Estas unidades corresponden a la transición entre la etapa de back-arc y foreland (Cretácico Inferior-Cretácico Superior). El análisis sedimentológico de la sucesión expuesta en Vega de los Patos permitió determinar que la sección analizada presenta una transición entre depósitos de ambiente marino marginal restringido y abanicos fluviales (fluvial fan). Para el análisis petrográfico se tomaron ocho muestras de areniscas medias, dos de pelitas, dos de evaporitas y una carbonática, ésta última presenta una dolomitización intensa. Las areniscas fueron clasificadas como litoarenitas feldespáticas y litoarenitas, afectadas principalmente por la precipitación de cementos carbonáticos, ceolíticos y en menor medida por cementos ferruginosos. El análisis petrográfico también demostró que la fuente sedimentaria de la sucesión analizada es mixta, entre arco disectado y orógeno reciclado

Influence of mechanical and geometrical properties of embedded long-gauge strain sensors on the accuracy of strain measurement

In many civil and geotechnical applications it is of interest to monitor the strain deep inside the structure; consequently, it is necessary to embed the sensors into the structure's material. Construction and geotechnical materials, such as concrete and soil, can be affected by local defects, e.g. cracks, air pockets and inclusions. To monitor these materials at a structural level it is necessary to use long-gauge sensors. As the sensor has to be embedded in the host material, its presence causes perturbation of the strain field and influences the accuracy of the strain measurement. The aim of this research was to identify the critical parameters that influence the accuracy of the strain measurement, to study how these parameters affect the accuracy, and to give recommendations for sensor users. The study was based on finite element analysis and all involved materials were assumed to have the MöhrCoulomb elastic, perfectly plastic behavior. A suitability of the numerical model for the analysis was verified using the experimental results of two cases reported in the literature and one on-site application. The study revealed that the most important parameters that influence the accuracy of the strain measurement are the goodness of interaction (strain transfer) between the host material and the anchor pieces of the sensor, the ratio between equivalent Young's modulus of the sensor and the Young's modulus of the host material, the radius of the anchor piece and the gauge length. The numerical model and parametric study are presented in detail along with practical recommendations. © 2012 IOP Publishing Ltd.The authors would like to thank the Spanish Ministry of Education, with support received under the National Program for Mobility of Researchers (O.M. EDU/1456/2010, ref. PR2010-0293) which enabled the joint work that made this study possible. The Streicker Bridge project was realized with help of Turner Construction Co., HNTB, AG Construction Corp., Vollers Excavating & Constr., SMARTEC SA, Micron Optics, Princeton Facilities, and staff and students of CEE department of Princeton University.Calderón García, PA.; Glisic, B. (2012). Influence of mechanical and geometrical properties of embedded long-gauge strain sensors on the accuracy of strain measurement. Measurement Science and Technology. (23):1-15. https://doi.org/10.1088/0957-0233/23/6/065604S11523Glišić, B., & Inaudi, D. (2007). Fibre Optic Methods for Structural Health Monitoring. doi:10.1002/9780470517819Ansari, F. (2007). Practical Implementation of Optical Fiber Sensors in Civil Structural Health Monitoring. Journal of Intelligent Material Systems and Structures, 18(8), 879-889. doi:10.1177/1045389x06075760Li, H.-N., Zhou, G.-D., Ren, L., & Li, D.-S. (2009). Strain Transfer Coefficient Analyses for Embedded Fiber Bragg Grating Sensors in Different Host Materials. Journal of Engineering Mechanics, 135(12), 1343-1353. doi:10.1061/(asce)0733-9399(2009)135:12(1343)Torres, B., Payá-Zaforteza, I., Calderón, P. A., & Adam, J. M. (2011). Analysis of the strain transfer in a new FBG sensor for Structural Health Monitoring. Engineering Structures, 33(2), 539-548. doi:10.1016/j.engstruct.2010.11.012Kesavan, K., Ravisankar, K., Parivallal, S., Sreeshylam, P., & Sridhar, S. (2010). Experimental studies on fiber optic sensors embedded in concrete. Measurement, 43(2), 157-163. doi:10.1016/j.measurement.2009.08.010Azenha, M., Faria, R., & Ferreira, D. (2009). Identification of early-age concrete temperatures and strains: Monitoring and numerical simulation. Cement and Concrete Composites, 31(6), 369-378. doi:10.1016/j.cemconcomp.2009.03.004Glisic, B. (2011). Influence of the gauge length on the accuracy of long-gauge sensors employed in monitoring of prismatic beams. Measurement Science and Technology, 22(3), 035206. doi:10.1088/0957-0233/22/3/035206Leng, J. S., Winter, D., Barnes, R. A., Mays, G. C., & Fernando, G. F. (2006). Structural health monitoring of concrete cylinders using protected fibre optic sensors. Smart Materials and Structures, 15(2), 302-308. doi:10.1088/0964-1726/15/2/009Calderón, P. A., Adam, J. M., Ivorra, S., Pallarés, F. J., & Giménez, E. (2009). Design strength of axially loaded RC columns strengthened by steel caging. Materials & Design, 30(10), 4069-4080. doi:10.1016/j.matdes.2009.05.014Adam, J. M., Ivorra, S., Pallarés, F. J., Giménez, E., & Calderón, P. A. (2009). Axially loaded RC columns strengthened by steel caging. Finite element modelling. Construction and Building Materials, 23(6), 2265-2276. doi:10.1016/j.conbuildmat.2008.11.014Adam, J. M., Ivorra, S., Pallares, F. J., Jiménez, E., & Calderón, P. A. (2008). Column–joint assembly in RC columns strengthened by steel caging. Proceedings of the Institution of Civil Engineers - Structures and Buildings, 161(6), 337-348. doi:10.1680/stbu.2008.161.6.337Adam, J. M., Ivorra, S., Pallares, F. J., Giménez, E., & Calderón, P. A. (2009). Axially loaded RC columns strengthened by steel cages. Proceedings of the Institution of Civil Engineers - Structures and Buildings, 162(3), 199-208. doi:10.1680/stbu.2009.162.3.199Johansson, M., & Gylltoft, K. (2001). Structural behavior of slender circular steel-concrete composite columns under various means of load application. Steel and Composite Structures, 1(4), 393-410. doi:10.12989/scs.2001.1.4.393Johansson, M., & Gylltoft, K. (2002). Mechanical Behavior of Circular Steel–Concrete Composite Stub Columns. Journal of Structural Engineering, 128(8), 1073-1081. doi:10.1061/(asce)0733-9445(2002)128:8(1073