This article investigates the possibility of applying weldable optic fiber sensors to the corrugated rebar in reinforced concrete structures to detect cracks and measure the deformation of the steel. Arrays have initially been designed comprised of two weldable optic fiber sensors, and one temperature sensor to compensate its effect in measuring deformations. A series of tests were performed on the structures to evaluate functioning of the sensors, and the results obtained from the deformation measures shown by the sensors have been stored using specific software. Two reinforced concrete beams simply resting on the support have been designed to perform the tests, and they have been monitored in the zones with maximum flexion moment. Different loading steps have been applied to the beams at the center of the span, using a loading cylinder, and the measurement of the load applied has been determined using a loading cell. The analysis of the deformation measurements of the corrugated rebar obtained by the optic fiber sensors has allowed us to determine the moment at which the concrete has cracked due to the effect of the loads applied and the deformation it has suffered by the effect of the different loading steps applied to the beams. This means that this method of measuring deformations in the corrugated rebar by weldable optic fiber sensors provides very precise results. Future lines of research will concentrate on determining an expression that indicates the real cracking moment of the concrete.

Resumen-Conocer el comportamiento real de una estructura de hormigón armado es difícil. debido a los múltiples factores que influyen en el mismo. La heterogeneidad del hormigón y la evolución de sus características mecánicas y físicas a lo largo de la vida útil del material, hace que podamos obtener valores aproximados de su comportamiento. El objetivo de este trabajo de investigación es evaluar de una manera más precisa este comportamiento, mediante la inclusión en las estructuras de sensores de fibra óptica. Estos sensores nos proporcionan valores precisos de deformación en tiempo real, durante toda la vida de la estructura. Para obtener estos resultados, se han embebido los sensores en una viga de hormigón armado y se ha analizado realmente lo que le ocurre cuando la solicitamos a diferentes escalones de carga. Los resultados obtenidos los hemos comparado con los teóricos obtenidos del cálculo de resistencia de materiales, llegando a la conclusión de que, en efecto, las estructuras de hormigón armado son elementos complejos, pero que, con este sistema de monitorización, podremos obtener resultados más precisos de su comportamiento. Palabras Clave-Red de Bragg; Sensores de fibra óptica embebidos; hormigón autocompactante; fibra neutra; fisuración.

Deseo iniciar este capítulo de agradecimientos a Belén, María y Rodrigo.Cuando me embarqué en esta singladura, no fui consciente de todo el tiempo que les iba a robar. Aun así, me apoyasteis en todo momento, me disteis fuerzas para continuar, y ahora que por fin termina, sois tan felices como puedo serlo yo.Me siento orgulloso de teneros en mi vida.A mis padres, que, aunque ya no están entre nosotros, se esforzaron tanto por enseñarme que sin esfuerzo y sacrificio no se consigue llegar a la meta.A mis directores de tesis, Nieves y Edelmiro, por la confianza que han depositado en mí, por su aliento y ayuda en este largo proceso.

This article investigates the measurement of the real instantaneous deflection using a displacement transducer, and with fiber optic sensors embedded and welded to the corrugated rebars in order to determine the real cracking moment of the concrete. Two reinforced concrete beams simply resting on the support with point loading in the center of the span have been tested, at which point the maximum deflection is reached. Both the sensors and the displacement transducer have been placed in the center of the span. Different loading steps have been applied to the beams, using a loading cylinder, and the measurement of the load applied has been determined using a loading cell. During the loading process of the beams, the real moment at which they cracked has been determined, and which determines the change from the gross inertia to the cracked inertia in the study of the deflections. Two expressions have been deduced that modify the formula of the instantaneous deflection and demonstrate that they are valid to determine in a much more precise way the instantaneous deflections on simply resting on the support concrete beams. Future lines of research will concentrate on studying the instantaneous deflections of more complex beams, and thus obtain expressions that more closely approximate their actual behaviour.