Estudio del encapsulado de sensores de fibra óptica para la medida de muy altas temperaturas y de pautas para su aplicación en la monitorización de túneles sometidos a fuego

[EN] Disasters such as the fires in the Tauern tunnel (2000), St. Gotthard tunnel (2001) and Wuxi Lihu (2010) show the importance and the necessity of monitoring structures vulnerable to fire. Through this strategy, the assessment of fire damaged structures would be possible and if necessary, the demolition operation would be guided. In those cases is vital to detect the fire in an early stage and to have available the temperature profile history, which means the exposition time and maximum temperatures as a function of time, in order to be able to evaluate the structural damage and reduce the time that the tunnel is closed and the economic losses associated with this time. The success of a monitoring strategy depends mainly of two aspects. On one hand, it is vital to have sensors systems that are able to resist the harsh conditions that are presents in a fire and at the same time they should be reliable, easy to install and cheap. On the other hand, it is necessary to develop monitoring strategies to design sensors network, data management and to facilitate the decision making process. Within this general context, this PhD. Thesis: 1. Develop fiber optic sensors to measure high temperatures on structures vulnerable to fire. The behavior and properties of the sensors are evaluated through experimental test, using both electrical and fire test furnaces. 2. Establishment of monitoring guidelines for tunnel under fire loads to design a sensor network including the number, type and positions of sensors to install. The development of the sensors has a strong experimental component, in which the different packaging and the properties of the resulting sensors are studied. The behavior of the sensors under harsh environments and under high temperatures are tested on fire test where the sensors were subjected to direct flames and temperature increments of the order of 200oC/min, similar to those in a real fire. Instead, the development of the monitoring guidelines is based on the results obtained from computational fluid dynamics models in which the temperatures reached along the tunnel in several fire scenarios are calculated. Furthermore, the development of the monitoring guidelines makes use of statistics and comparison techniques to define the optimal solutions of multi objective sensor network design problem.[ES] Acontecimientos como los incendios en los túneles de Tauern (2000), San Gotardo (2001) y Wuxi Lihu (2010) ponen de manifiesto la gran importancia y necesidad de monitorizar las estructuras vulnerables al fuego para poder evaluar su seguridad estructural, el daño generado, las zonas afectadas y, llegado el caso, proceder a su demolición de forma segura. En estos casos es vital poder detectar el fuego en forma temprana y conocer la historia de temperaturas, es decir el tiempo de exposición y las temperaturas máximas alcanzadas en función del tiempo para poder evaluar el estado de la estructura y el daño alcanzado; con el fin de reducir los tiempos en los que la estructura este fuera de servicio y las pérdidas que esto suele contraer. El éxito de la monitorización de estructuras sometidas a fuego depende fundamentalmente de dos aspectos. Por un lado es fundamental contar con sistemas de sensores que sean capaces de resistir las condiciones severas que se generan en un incendio, que a su vez sean fiables, fáciles de instalar y económicos. Por otro lado, es necesario contar con pautas de monitorización de estructuras vulnerables a la acción del fuego, que guíen el diseño de la red de sensores, que indiquen los métodos más adecuados para el procesado de los datos medidos y que faciliten la toma de decisiones en caso de incendio. En este contexto general, esta Tesis Doctoral: 1) Desarrolla sensores de fibra óptica para la medida de temperaturas en estructuras sometidas a altas temperaturas. Las propiedades y el comportamiento de estos sensores son evaluados en ensayos experimentales, empleando hornos eléctricos de altas temperaturas y hornos de ensayos de fuego. 2) Establece unas pautas de monitorización en túneles frente a la acción del fuego que guían sobre el tipo de sensores a emplear, cómo, dónde y en qué cantidad deben colocarse. El desarrollo de los sensores tiene una fuerte componente experimental, en la cual se evalúan distintos encapsulados y las propiedades resultantes de los sensores formados por los distintos encapsulados. El comportamiento de los sensores a ambientes adversos y altas temperaturas es evaluado en ensayos de fuego que exponen a los sensores a llama directa y a gradientes de temperaturas del orden de los 200°C/min similares a los de incendios reales. Por su parte el desarrollo de las pautas de monitorización está basado en los resultados que se obtienen con modelos de mecánicas de los fluidos computacional en los que se estudian las temperaturas alcanzadas a lo largo del túnel en diferentes condiciones de incendios. A su vez el desarrollo de las pautas de monitorización requiere el empleo de herramientas estadísticas y de comparación de soluciones que han sido empleadas para determinar las configuraciones óptimas de colocación de sensores para problemas multiobjetivo.[CA] Esdeveniments com els incendis als túnels de Tauern (2000), Sant Gotard (2001) IWuxi Lihu (2010) posen de manifest la gran importància I necessitate de monitoritzar les estructures vulnerables al foc per a poder avaluar la seua seguretat, el dany generat, les zones afectades i, arribat el cas, procedir a la seua demolició de forma segura. En aquestos casos és vital poder detectar el foc de forma primerenca i conéixer la historia de temperaturas, és a dir, el temps d'exposició i les temperaturas màximes aconseguides en funció del temps per a poder avaluar l'estat de l'estructura i el dany aconseguit; a fi de reduir els temps en què l'estructura estiga fora de servici i les pèrdues que açò sol contraure. L'èxit de la monitorització d'estructures sotmeses a foc depén fonamentalment de dos aspectos. Per un costat és fonamental comptar amb sistemes de sensors que siguen capaços de resistir les condicions severes que es generen en un incendi, i al mateix temps siguen fiables, fàcils d'instal lar i econòmics. D'altra banda, és necessari comptar amb pautes de monitorització d'estructures vulnerables a lácció del foc, que guien el disseny de la xarxa de sensors, que indiquen els mètodes més adequats per al processat de les dades i que faciliten la presa de decicions en cas d'incendi. En aquest context general, la present Tesi Doctoral: 1. Desenrotlla sensors de fibra òptica per a la mesura de temperaturas en estructures sotmeses a elevades temperaturas. Les propietats i el comportament d'estos sensors son avaluats en assajos experimentals, emprant forns elèctrics d'elevades temperaturas i forns d'assajos de foc. 2. Establix unes pautes de monitorització en túnels enfront de l'acció del foc que guien sobre els tipus de sensors a emprar, com, on i en quina quantitat han de col locar-se. El desenrotllament dels sensors té una forta component experimental, en la qual s'avaluen distints encapsulats i les propietats resultants dels sensors formats pels distints encapsulats. El comportament dels sensors davant ambient adversos i altres temperaturas es avaluat en assajos de foc que exposen als sensors a flama directa i a gradients de temperaturas de l'ordre dels 200oC/min semblants als díncendis reals. Per la seua banda, el desenrotllament de les pautes de monitorització està basat en els resultats que s'obtenen amb models de mecániques dels fluids computacional on s'estudies les temperaturas aconseguides al llarg del túnel en diferents condicions d'incendis. Al mateix temps, el desenrotllament de les pautes de monitorització requerix l'ocupació de ferramentes estadístiques i de comparació de solucions òptimes en problemes multiobjectius.Rinaudo, P. (2015). Estudio del encapsulado de sensores de fibra óptica para la medida de muy altas temperaturas y de pautas para su aplicación en la monitorización de túneles sometidos a fuego [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54124TESI

Investigation of a Faulty Historical Structure: Saint Barbara Church

Anglès: This thesis faces the study of the Saint Barbara Church, which is located in Kutná Hora. In the first part of the work, a research on the historical background was carried out including the development of the city and the construction steps of the church. To understand the current state of the church it was vital to revise the historical intervention as well as the current ones. The second part of the thesis focused on the structural behavior of the church. Basically, the aim of the study was to analyze the buttresses since the stability of Saint Barbara strongly depends on them. Due to the location of the church and its damage pattern, special attention was paid to the temperature effect in the structure, particularly in the flying arches. To study the buttresses two non linear models were prepared using finite elements. The first model consisted on the buttress in its original shape and the second one considered the strengthened system. In order to define the materials in the numerical model, compression and tensile test were carried out on the laboratory. The models were run under four different load combinations, each of them include selfweight and one temperature load case. In that way it was possible to evaluate the behavior of the structure under possible extreme temperature situations and to compare between the responses of the two models. Supported on the results of the models and the visual survey, it was concluded that at the present the structure has a good static situation. It is remarkable that the current restoration follow the modern conservation criteria, being completely respectful of the structure. Some possible further interventions aiming to maintain the achieved state of conservation are also suggested.Castellà: Esta tesis afronta al estudio de la Iglesia de Santa Bárbara que esta localizada en Kutná Hora. En la primera parte de este trabajo, se realizó una investigación sobre los antecedentes históricos incluyendo el desarrollo de la ciudad y las etapas constructivas de la iglesia. Para poder entender el estado actual de la iglesia fue necesario revisar tanto las intervenciones históricas como las actuales. La segunda parte de esta tesis se focaliza en el comportamiento estructural de la iglesia. Básicamente, el objetivo del estudio fue analizar los contrafuertes ya que la estabilidad de Santa Bárbara depende fuertemente de ellos. Debido a la ubicación de la iglesia y a su patrón de daños, se debió prestar especial atención al efecto de la temperatura en la estructura, particularmente en los arbotantes. Para estudiar los contrafuertes se prepararon dos modelos no lineares usando elementos finitos. El primer modelo consiste en los contrafuertes en su forma original y el segundo considera el sistema reforzado. Con el fin de definir los materiales en el modelo numérico se realizaron pruebas de compresión y tracción en el laboratorio. Los modelos fueron ejecutados bajo cuatro combinaciones de cargas diferentes, cada una de ellas incluye peso propio y un estado de carga de temperatura. De este modo fue posible evaluar el comportamiento de la estructura bajo situaciones de temperaturas extremas y a su vez comparar las respuestas de los modelos. Basándose en los resultados de los modelos y la inspección visual se pudo concluir que la estructura presenta actualmente una buena situación estática. Es destacable que la restauración actual sigue los criterios de conservación vigentes siendo totalmente respetuosa de la estructura. Se sugieren algunas intervenciones complementarias con el objetivo de mantener el estado de conservación alcanzado

Improving tunnel resilience against fires: A new methodology based on temperature monitoring

Monitoring temperatures during tunnel fires is of major importance for both the firefighters extinguishing the fire, and the engineers in charge of the subsequent repair work. However, current methods of assessing fire damage have limitations when applied to tunnels and only provide estimates of the maximum fire temperatures at specific locations of the tunnel. This is not a desirable situation, as the temperature time curves associated with the fire event should be available for use in assessing the residual strength of the tunnel structure. This is the key parameter in defining repair work and the length of time the tunnel will need to be closed and thus the socio-economic cost of the tunnel fire. In addition, real-time recording of the temperature time curves would provide valuable information to the firefighters engaged in extinguishing the fire. This paper presents a new general methodology for the optimal placement of sensors in a tunnel to obtain the temperature evolution at any point along its lining during a fire. The methodology was applied to the Virgolo Tunnel in Italy, in which 100 potential high-temperature sensor configurations were tested and a set of optimal sensor configurations was proposed. The results of the analysis show that: (a) the proper location of the sensors is crucial; (b) it is possible to define a set of sensor configurations that minimize the cost of the monitoring system and maximize the accuracy of the estimated temperatures; (c) it is important to place at least three high-temperature sensors in each monitored cross section (at the crown and symmetrically on the haunches/side walls). The proposed methodology improves tunnel resilience against fires, as it enables safer infrastructure and a faster and more economic recovery of the tunnel after a fire eventThis work has been possible thanks to the financial support of the Spanish Ministry of Science and Innovation (Research Project BIA 2011-27104). Funding for this research was provided to Paula Rinaudo by the European Commission (Project Erasmus Mundus Action 2 ARCOIRIS). The authors are also grateful to Eduardo Cassiraga from the Universitat Politecnica de Valencia and to Eduardo Loma Ossorio for all the support provided.Rinaudo, P.; Paya-Zaforteza, I.; Calderón García, PA. (2016). Improving tunnel resilience against fires: A new methodology based on temperature monitoring. Tunnelling and Underground Space Technology. 52:71-84. https://doi.org/10.1016/j.tust.2015.11.021S71845

Valencia bridge fire tests: Experimental study of a composite bridge under fire

[EN] The consequences of bridge fires and the lack of guidelines on the evaluation of the fire resistance of bridges have triggered a lot of recent research. Most of these studies are based on numerical models and thus need validation by experimental studies. This paper aims to bridge this gap by describing a battery of open air fire tests carried out under an experimental bridge at the Universitet Politecnica de Valencia in Valencia, Spain. The bridge, with a 6 m span and a composite deck with two steel I-girders supporting an RC slab, was submitted to four different fire scenarios similar to those of real bridge fires, although smaller in magnitude. Results show that: (a) maximum gas temperatures are reached in the region between the I-girders, (b) as gas and steel temperatures vary significantly along the longitudinal axis of the bridge, it is unrealistic to assume a longitudinally uniform gas or girder temperature (c) temperatures in the bottom flange and the web of the I-girders are very similar and significantly higher than top web temperatures, and (d) the magnitude of the fire load and its position are key factors in the bridge response. This study is of major importance as it enables the validation of the numerical models used in bridge fire engineering and is a crucial step towards the development of a performance-based approach for the design of bridges against fires. The information given will also be useful to those interested in carrying out open air experiinental bridge fire tests. (C) 2017 Elsevier Ltd. All rights reserved.Funding for this research was provided by the Spanish Ministry of Science and Innovation (Research Project BIA 2011-27104). The authors are grateful to the Infrastructure and Safety departments of the Universitat Politecnica de Valencia and the City of Valencia Fire Department (Cuerpo de Bomberos de Valencia), which provided crucial support in conducting the tests. Finally, the authors would like to thank Dr. Luke Bisby from the University of Edinburgh, and Dr. Juan Hidalgo and Dr. Cristian Maluk from the University of Queensland for their advice and support during the early stages of planning the fire tests.Alós-Moya, J.; Paya-Zaforteza, I.; Hospitaler Pérez, A.; Rinaudo, P. (2017). Valencia bridge fire tests: Experimental study of a composite bridge under fire. Journal of Constructional Steel Research. 138:538-554. https://doi.org/10.1016/j.jcsr.2017.08.008S53855413

Evaluation of new regenerated fiber Bragg grating high-temperature sensors in an ISO 834 fire test

[EN] Temperature, one of the most important parameters in building fires, is now mostly measured with high-temperature thermocouples, which have the typical drawbacks of electric sensors, such as their sensitivity to electrical and magnetic interference. Fiber optic sensors are an alternative to electric sensors and offer many advantages, although their use in fire engineering is somewhat limited at the present time. This paper presents a set of new fiber optic sensors for measuring high temperatures, based on Regenerated Fiber Bragg Gratings (RFBGs). The sensors were placed near the surface of two concrete specimens and then tested under ISO 834 fire curve conditions for one hour. We consider this an important step forward in the application of high-temperature fiber optic sensors in fire engineering, as the sensors were subjected to direct flames and temperature increments of the order of 200 degrees C/min, similar to those in a real fire. The RFBG sensors measured maximum gas temperatures of circa 970 degrees C, in good agreement with those provided by thermocouples in the same position. The gas temperature measurements of the FOSs were also compared with the adiabatic temperatures measured by plate thermometers and concrete specimens surface temperatures calculated with numerical heat transfer models. (C) 2014 Elsevier Ltd. All rights reserved.This work has been possible thanks to the financial support of the Spanish Ministry of Science and Innovation (Research Projects BIA 2011-27104 and TEC2011-29120-C05-05). Funding for this research was provided to Paula Rinaudo by the European Commission (Erasmus Mundus Project Action 2 ARCOIRIS).Rinaudo, P.; Torres Górriz, B.; Paya-Zaforteza, I.; Calderón García, PA.; Sales Maicas, S. (2015). Evaluation of new regenerated fiber Bragg grating high-temperature sensors in an ISO 834 fire test. Fire Safety Journal. 71:332-339. https://doi.org/10.1016/j.firesaf.2014.11.024S3323397

Experimental and analytical evaluation of the response time of high temperature fiber optic sensors

Gas temperature is a key variable in many high temperature applications. Sensors for measuring gas temperatures must be selected according to many different criteria, response time being one of the most important. Response time quantifies the time that the sensor needs to react to a sudden temperature variation. When rapid temperature fluctuations are expected, as in the case of fire tests, significant instantaneous errors can occur if the sensor response time is longer than the duration of the temperature fluctuation. Despite the importance of response time, there is no general agreement on how to quantify this value in high temperature fiber optic sensors. This paper proposes a methodology to estimate the response time of fiber optic temperature sensors based on an analytical model of the heat transfer between the sensor and its surroundings. The method is validated by an experimental study. In addition, the response times of three different high temperature fiber optic sensors developed by the authors are compared with each other and with the response time of some widely used thermocouples. The results show (i) that fiber optic sensors have a significantly shorter response time than thermocouples with similar packaging, (ii) that the response time is shorter during the heating phase than the cooling phase, and (iii) highlight the importance of considering this parameter in the sensor selection process. (C) 2016 Elsevier B.V. All rights reserved.This work has been possible thanks to the financial support of the Spanish Ministry of Science and Innovation (Research Project BIA 2011-27104). Funding for this research has been provided to Paula Rinaudo by the European Commission (Erasmus Mundus Action 2 ARCOIRIS).Rinaudo, P.; Paya-Zaforteza, I.; Calderón García, PA.; Sales Maicas, S. (2016). Experimental and analytical evaluation of the response time of high temperature fiber optic sensors. Sensors and Actuators A: Physical. 243:167-174. https://doi.org/10.1016/j.sna.2016.03.022S16717424

Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio

Search for charginos in e+e- interactions at sqrt(s) = 189 GeV

An update of the searches for charginos and gravitinos is presented, based on a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Promptly decaying lightest neutralinos and long-lived staus are searched for in the context of light gravitino scenarios. It is assumed that the stau is the next to lightest supersymmetric particle (NLSP) and that the lightest neutralino is the next to NLSP (NNLSP). Data collected with the Delphi detector at centre-of-mass energies from 161 to 183 \GeV are analysed. No evidence of the production of these particles is found. Hence, lower mass limits for both kinds of particles are set at 95% C.L.. The mass of gaugino-like neutralinos is found to be greater than 71.5 GeV/c^2. In the search for long-lived stau, masses less than 70.0 to 77.5 \GeVcc are excluded for gravitino masses from 10 to 150 \eVcc . Combining this search with the searches for stable heavy leptons and Minimal Supersymmetric Standard Model staus a lower limit of 68.5 \GeVcc may be set for the stau mas

Hadronization properties of b quarks compared to light quarks in e+e- -> q qbar from 183 to 200 GeV

The DELPHI detector at LEP has collected 54 pb^{-1} of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e+e- -> b bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself.Comment: 13 pages, 2 figure