Desarrollo de sensores de alta temperatura para su uso en la monitorización de estructuras ante la acción del fuego

Abstract

Recent events such as the fires on the Channel tunnel (1996), St. Gotthard (2001), the Twin Towers in New York (2001), The Windsor Building in Madrid (2005) and the collapse of the MacArthur Maze in Oakland (2007) show the importance and the necessity of a monitoring strategy for fire vulnerable structures. Through this strategy, the assessment of fire damaged structures would be possible and if necessary, the demolition operation would be guided. To monitor structures subjected to fire it is essential to have high temperature sensors that enable to measure the temperature in critical points. The requirements of these sensors depend on singular factors as the estimated maximum temperature, the materials and the structural system of the structure. A structure provided of monitoring high temperatures system offers real time information to the emergency services and a better evacuation will be possible, reducing the consequences of the fire. Moreover, the temperature history of the structure provided of a system for high temperature monitoring is valuable information for the diagnosis process. Nowadays, the measurements of temperatures during fires are done mainly by high temperature thermocouples. However, fiber optic sensors have several advantages compared to electric sensors. For example, they are immune to electromagnetic interference; they have high precision and reliability on the measurements, they have good temporal stability, outstanding resistance to adverse environments and they can be multiplexed. In spite of the outstanding advantages of fiber optic sensors, its availability on the structural monitoring market of structures under fire is null or limited. In this work, three types of punctual and multiplexed fiber optic sensors developed at the Universitat Politècnica de València by the authors to measure high temperature are presented. The operation principle of the sensors and the steps in their development are exposed. The accurate performance of the sensors is evaluated through different tests performed on the laboratory and also validated using finite element models when possible. Especial emphasis is placed on the packaging of the sensors since it is essentially responsible of the singular capabilities of each sensor. Then, the different parts of monitoring systems, a comparison of the sensors and theirs possible applications are shown.