José Luís Santos

Abstract
This article aims to present a procedure to take into account the variability of the time-dependent behavior of concrete on its structural effects, evaluated from the study of creep and shrinkage based on experimental data obtained on-site. For this purpose, the Sao Joao Bridge, a railway bridge built in Porto, Portugal in 1991, is presented as a case study. Sao Joao Bridge is a railway bridge crossing the river Douro. It is a prestressed concrete structure, with a total length of 1,028 m, including the main span of 250 m, two side spans of 125 m, six approaching spans on the left river bank, and three approaching spans on the right river bank (Porto). During bridge construction, a comprehensive structural health monitoring (SHM) system was set up, as well as an on-site study of time-dependent behavior of concrete. This study was based on creep 15 specimens and 15 shrinkage specimens, prepared simultaneously with some segments of the deck, using the same material, and it was kept running during almost 20 years. The results of this study were treated statistically and used as random variables in a probabilistic analysis of the time-dependent behavior of the bridge. After a brief description of the mentioned on-site study and the bridge SHM system, the paper presents the procedure followed on the bridge numerical probabilistic analysis. Finally, the values computed by the numerical model are presented and compared with the experimental values provided by the SHM.

Abstract
Bi-core optical fiber structures are studied for applications in sensing. In this paper, an analysis is performed on the spectral characteristics of light propagating in these fibers with central launching core illumination from a standard single mode fiber. Reflective and transmissive configurations are addressed. The characteristics of a reflective bi-core fiber structure for measurement of strain, temperature and absolute value of torsion are investigated and highlights for further research are presented.

Abstract
We present the design, fabrication and optical characterization of functional metamaterials for optical sensing of Hydrogen based on inexpensive self-assembly processes of metallic nanowires integrated in nanoporous alumina templates[37-42]. The optical properties of these materials strongly depend on the environmental concentration or partial pressure of hydrogen and can be used to develop fully optical sensors that reduce the danger of explosion. Optical metamaterials are artificial media, usually combining metallic and dielectric sub-wavelength structures, that exhibit optical properties that cannot be found in naturally occurring materials. Among these, functional metamaterials offer the added possibility of altering or controlling these properties externally after fabrication, in our case by contact with a hydrogen rich atmosphere. This dependency can be used to design[43-45]and develop optical sensors that respond to this gas or to chemical compounds that contain or release hydrogen. In this paper we present some designs for hydrogen functional metamaterials and discuss the main parameters relevant in the optimization of their response. © 2019 SPIE.

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