Throughout the last decades, the increasing development of the urban metropolis and the need to establish fundamental infrastructure networks, promoted the development of important projects worldwide and several Multi-Span Large Bridges have been erected. Certainly, many more will be erected in the next decades. This international context undoubtedly justifies the first International Conference on Multi-Span Large Bridges. The Multi-Span Large Bridges book contains the keynote lectures and the extended abstracts of selected papers presented at the Multi-Span Large Bridges International Conference (MSLB2015), organized by the Faculty of Engineering of the University of Porto, in cooperation with IST (Lisbon), University of Minho and LNEC, held in Porto, Portugal, from 1st to 3rd July, 2015. The most relevant themes covered in the book are: Landmark Projects, Conceptual Design, Innovative Construction Methods, Special Foundations and Geotechnical Site Investigations, Life Cycle, Monitoring, Maintenance & Management, Incidents and Accidents, New Materials and Special Devices, Extreme Loads, Rehabilitation, Safety and Serviceability, and Structural Analysis. The Multi-Span Large Bridges book shares the knowledge of several world experts, contains the description of relevant experiences and reports state-of-art achievements which, definitely, will be invaluable to bridge engineers, structural engineers and scientists.

This book presents the study and development of sensing systems for the remote detection of gases with the use of microstructured optical fibres of the hollow-core type (HC-PCF) and the use of signal processing techniques usually associated with absorption spectroscopy. Photonic Crystal Fibres (PCF) arose as an exceptionally interesting player in the field of gas sensing since they promote the creation of short and direct interaction paths between light and gas and can be tuned to address any specific gas. Thus, their principle of operation and main optical properties were studied and described. The diffusion time of gases inside of microstructured fibres is a subject of special importance. As a consequence of its theoretical study and experimental analysis, fruitful results for the planning of a new configuration for a sensing head were achieved. Light coupling between standard optical fibres and hollow-core photonic crystal fibres is a practical issue that was also evaluated in the aim of the work here presented. Wavelength Modulation Spectroscopy is also presented and described in this book as it is a powerful and sensitive technique suitable for gas detection.