Fiber optic sensors based on the fiber Bragg grating (FBG) technology [1] is widely used to produce quasi-distributed monitoring systems to measure mechanical parameters for Structural Health Monitoring (SHM) of civil engineering structures [2]. FBG sensors are produced in the core of the optical fiber, as a short segment of fiber where a diffraction grating is produced (5-10 mm). The principle of operation of the FBGs is based on the diffraction occurring at the grating: if broadband light propagates, a quasi-monochromatic counter propagating light originates. The wavelength of the diffracted light depends on the value of the refraction index of the core along the grating which in turn is affected by both temperature and strain. Thus, by measuring the wavelength change of the counter propagating light, the change of strain and the temperature can be worked out. The PREFOS Project [3] aims to develop a novel procedure to apply the use of FBGs to monitor the prestressed strands of civil engineering prefabricated components. In this paper, we report results of an experimental campaign intended to measure the sensitivity of saddle-like sensors to induced vibration and mechanical strain. Measurements were done performing static and dynamic tests on a steel strand equipped with 3 sensors. The tests have been performed applying different tensioning to the steel strand. Static measurements were worked out applying a stepwise tensioning increase. Dynamic tests were worked out at each stepped tension level, inducing vibration by both sharp hammer impact and release of hanged weight. The paper is organized as follows, in section 1 a general description of the testbed structure used for the experiments will be provided. In section 2 the results of static analysis and dynamic tests will be presented with the dynamic behavior of the strand evaluated by performing a simple Fast Fourier Transform (FFT). Finally, the conclusions will be drawn.

Fibre optical sensors technology is widely employed for structural health monitoring of civil engineering structures, mainly existing structures, to guarantee a proper structural safety level. This research proposes an industrial solution which leads to the production of self-monitoring prestressed, precast RC beams through optical fibre technology, for quality prebuilt beam control and to monitor structures when the implementation in the construction site is done. As a first step, steel strands have been instrumented with Fiber Bragg Grating sensors. It was feasible through the embedding of FBGs into fibreglass manufactured saddles for easy positioning and the fixing of optical sensors on rebars during the pre-cast production site of beams. The following step consists of performing executing tensile tests for comparing and validating FBG monitoring results to traditional measurement systems (extensometers) and Digital Image Correlation measurement system (DIC). Throughout this article, the manufacturing saddles process and preliminary thermal tests are presented to display the first monitoring parameters' results.

This paper reports the design and the realization of the energetic renovation of a residential building owned by ALER and located in Cinisello Balsamo (MI), by mean of the installation on the existing facades of an innovative insulating prefabricated sandwich panel, for a total of about 520 m2 covered. The energetic renovation process has been organized in the following steps: Before and after the installation of the prefabricated insulating panels, a dedicated monitoring campaign was performed for the evaluation of the thermal performance of the building, whose main results are also provided in this paper. This energetic renovation project has been performed in the framework of the European research project EASEE (“Envelope Approach to improve Sustainability and Energy efficiency in Existing buildings”), funded by the European Union under the 7th Framework Programme for Research and Development. This project, along its four years of duration, was aimed at developing innovative solutions for the energy upgrading of multi-storey residential buildings built before 1975, in a historical period in which the focus on energy efficiency was not so pressing, thus being highly energy-consuming buildings.

Fibre reinforced concrete is attracting the interest of many precast industries, owing to improved technology which solves the problems related to concrete casting and good fibre distribution in the matrix. Nevertheless, the use of fibres in the industrial production of the major load-bearing concrete elements needs an efficient and reliable approach that allows to take into account their contribution in the structural design. In this context, a broad experimental programme has been recently promoted by an Italian company, providing a large database on both the structural behaviour of precast covering members (f c ≅ 100 MPa) and the mechanical response of the constituting material (compression, direct and indirect tension). The prestressed roof elements investigated in the present paper are characterised by a thin-webbed open section, with fibres aimed at the complete substitution of conventional transverse reinforcement and stirrups placed only in the support regions. Hence, transverse bending, without either steel welded mesh or stirrups, requires a careful experimental check and a validation of suitable theoretical models to predict the ultimate bearing load with an adequate safety level. With this aim, 5 covering members (span=10+12.5 m) were tested up to collapse, and both deformations and failure modes were carefully monitored. Moreover, the constitutive tensile behaviour of the material was identified by means of fixed-end uniaxial tension and third point bending tests. On the basis of test results, an elastoplastic model (suitable for a plane-section approach) is proposed, in order to predict the structural behaviour in longitudinal and transversal bending of the roof elements investigated. The model prove to be quite reliable in predicting the fibre contribution to both mechanisms and provides a promising tool for the design of steel fibre reinforced structures.