The OSS (acronym of the Italian name “Osservatorio Sismico delle Strutture”) is a network of permanent seismic monitoring systems installed in public buildings, and also in some bridges and a dam. Each system consists of a number of sensors sufficient to completely describe the dynamic behaviour of the structure. Structural typologies have been selected according to their representativeness of the public building stock and to their importance for the emergency management. Some relevant aspects are addressed, including: (i) a brief description of the network, (ii) a résumé of data usually collected and organized for each structure (structural survey and in situ tests on materials, experimental modal analysis, FEM models and structural identification) and (iii) a description of data management tools and procedures (network operation performance, post-earthquake automatic analysis, public access to data). At the end, on-going and future use of OSS data is briefly discussed, with reference to statistical analysis of relevant parameters of the available records, real-time post-earthquake damage assessment and an in-field reconnaissance visit after a recent earthquake. © 2015, Springer Science+Business Media Dordrecht

This paper presents an overview of the research activities developed in the framework of the ReLUIS project founded by Department of Civil Protection (DPC) in 2017 and 2018 and focused to analyze some experimental accelerations made available by the Osservatorio Sismico delle Strutture (OSS), an Italian network of permanent seismic monitoring systems belonging to DPC. In particular, the recordings acquired by OSS on three selected masonry structures hit by the 2016/2017 Central Italy were acquired, analyzed and re-elaborated by a team of researchers from the

A new technique for the identification of nonlinearity in multi-degree of freedom systems is presented. The technique is based on the joint application of the Gabor and the Hilbert transforms to the transient response of a system. The Gabor transform is used first to identify a time-variant matrix representing the spatial behaviour of the system. This matrix is then used to decouple the transient response into a set of uncoupled quasi-harmonic components. Finally the Hilbert transform is applied to identify the dissipative and restoring forces associated with each component which is equivalent to a single degree of freedom system. Numerical examples are supplied to help clarify the main advantages and the possible limitations of the method in the presence of strong nonlinearities and closely spaced frequencies.

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