Lifetime extensions of nuclear fission reactors in the UK are required to satisfy growing demands for electrical power. Many of these reactors are nearing the end of their original design life, so the continued structural integrity, particularly of the reactors' prestressed concrete pressure vessels and containments is of prime concern. Currently, a lift-off inspection of a 1 % random sample of prestressing tendons is performed at 18 month to 5 year intervals to ensure adequate prestress is present in these structures, but the extended life times are making higher resolution, more frequent and in-depth monitoring techniques more desirable. In this thesis, a method of instrumenting prestressing strands with optical fibre Bragg grating strain sensors is outlined. An all-metal encapsulation and bonding technique is developed to ensure sensor reliability under the radioactive and high-stress environments of fission reactors. This 'smart strand' is complemented by a specially developed interrogation scheme capable of continuously and automatically monitoring static and dynamic nanoscale changes in Bragg grating strain. High-resolution interrogation was achieved by extending an interferrometric demodulation technique into the static measurement regime. By modulating the strain sensitivity using a fast optical switch, strain signals could be recovered independently of noise sources using various signal processing algorithms. The application of this technology could augment the continued monitoring of concrete vessel integrity, reducing both the risks and costs associated with performing lift-off measurements in the current and next generation of nuclear reactors.

This book is a printed edition of the Special Issue "Structural Health Monitoring (SHM) of Civil Structures" that was published in Applied Sciences

The use of sensors based on fibre optic technology allows a broad range of applications in the fields of structural and geotechnical monitoring, which can effectively improve the maintenance of infrastructures and the safety of communities. Thanks to its valuable features, such as distributed monitoring, the easiness and endurance of cabling, long term stability, reliable responses in both static and dynamic regimes and fibre optic technology, innovative and efficient solutions to quite difficult monitoring problems have already been provided. The increasing worldwide attention to infrastructures and communities with resilience capabilities against natural disasters has opened up new and challenging perspectives of applications to the use of fibre optic technology for structural and geotechnical monitoring. This book collects contributions in the development and application of monitoring solutions, based on fibre optic technology for structural and geotechnical engineering works and issues. In the book preface, the content of the contributions is reviewed, pointing out the relevance of the work, with respect to the advance and spreading of fibre optic technology for monitoring applications. All contributions provide a comprehensive discussion and report a rich bibliography on the current trends and issues relative to the theme of the work presented.

In this doctoral thesis it is proposed to research and assess the performance of the use of distributed optical fiber sensors (DOFS), more specifically the case of the optical backscattered reflectometry (OBR) based system, to the structural health monitoring (SHM) of bridges and large scale structures. This is a relatively recent technology that has demonstrated great promise for monitoring applications in a wide range of fields but due to its novelty, still presents several uncertainties which prevent its use in a more systematic and efficient way in civil engineering infrastructures. This is even more evident and relevant in the case of the application of this sensing technique to concrete structures. In this way, this thesis pretends to continue and further analyse this topic following the initial applications using the OBR system as a possible alternative/complementary monitoring tool in concrete structures. Therefore, in the present thesis, after an initial and thorough literature review on the use of DOFS in civil engineering applications, a set of experiments and analysis is planned and carried out. Firstly, different laboratory experimental campaigns are devised where multiple aspects of the instrumentation of DOFS technology in civil engineering applications are assessed and scrutinized. Consequently, the study of new implementation methods, comparison and performance analysis of different bonding adhesives and spatial resolution is performed through the conduction of load tests in reinforced concrete beam elements instrumented with OBR DOFS technology. Moreover, the long-term reliability of this sensing typology is also assessed through the conduction of a fatigue load test on two additional reinforced concrete beams. Afterwards, the use of the OBR system technology is assessed for the application in two real world structures in Barcelona, Spain. The first application corresponds to a previous monitoring work conducted in a historical masonry building and UNESCO World Heritage Site, which was subjected to rehabilitation works and where the collected data was analysed and interpreted in this thesis. The second real world structure application is an urban prestressed concrete viaduct that was exposed to major renovation actions, which included the widening of its deck and the introduction of new steel elements on the improved pedestrian sidewalks. This second application was conducted through a relatively extended period of time, which spanned from early summer to deep winter and therefore causing subsequent important thermal variations effects implications on the performance of the instrumented OBR system leading to the necessity of its compensation. Finally, taking into account the previous points, several conclusions are obtained related with the proficiency and limitations on the use of this particular type of optical sensing system in concrete structures. The advantages and disadvantages on the use of different types of bonding adhesives, implementation methodologies and spatial resolutions are described. Additionally, the performance of this technology in real world conditions is studied and characterized.

This book focuses on optical fiber sensing and structural health monitoring technologies. It provides detailed information on the basic theory of F-P optical fiber sensors, fiber Bragg grating sensors, fiber laser grating sensors and fully distributed optical fiber sensors. Drawing on the authors’ research achievements and many years of practical experience in the field of engineering structure health monitoring, the book elaborates on the structural principle, design and manufacture of optical fiber sensors and monitoring technologies, and briefly describes advances made with regard to multiple engineering structures.

This book provides a State of the Art Report (STAR) produced by RILEM Technical Committee 254-CMS ‘Thermal Cracking of Mas-sive Concrete Structures’. Several recent developments related to the old problem of understanding/predicting stresses originated from the evolution of the hydration of concrete are at the origin of the creation this technical committee. Having identified a lack in the organization of up-to-date scientific and technological knowledge about cracking induced by hydration heat effects, this STAR aims to provide both practitioners and scientists with a deep integrated overview of consolidated knowledge, together with recent developments on this subject.

The EURO-C conference series (Split 1984, Zell am See 1990, Innsbruck 1994, Badgastein 1998, St. Johann im Pongau 2003, Mayrhofen 2006, Schladming 2010, St. Anton am Arlberg 2014, and Bad Hofgastein 2018) brings together researchers and practising engineers concerned with theoretical, algorithmic and validation aspects associated with computational simulations of concrete and concrete structures. Computational Modelling of Concrete Structures reviews and discusses research advancements and the applicability and robustness of methods and models for reliable analysis of complex concrete, reinforced concrete and pre-stressed concrete structures in engineering practice. The contributions cover both computational mechanics and computational modelling aspects of the analysis and design of concrete and concrete structures: Multi-scale cement and concrete research: experiments and modelling Aging concrete: from very early ages to decades-long durability Advances in material modelling of plain concrete Analysis of reinforced concrete structures Steel-concrete interaction, fibre-reinforced concrete, and masonry Dynamic behaviour: from seismic retrofit to impact simulation Computational Modelling of Concrete Structures is of special interest to academics and researchers in computational concrete mechanics, as well as industry experts in complex nonlinear simulations of concrete structures.