Rosalba Ferrari

Earthquake structural modal estimates of multi-storey frames by a refined Frequency Domain Decomposition algorithm

This paper targets the frequency domain identification of current structural modal properties under earthquake excitation. A new refined Frequency Domain Decomposition (rFDD) algorithm is implemented towards the output-only modal dynamic identification of heavy-damped frame structures, which are subjected to a wide set of strong ground motions. In fact, both seismic excitation and/or high damping values shall not fulfil traditional FDD assumptions. Despite that, with the present rFDD implementation quite limited errors in the modal parameter estimates have been achieved, including for the modal damping ratios (ranging from 1% to 10%). At first, the identification technique is formulated and explored analytically, by proving its potential effectiveness with seismic response input. Then, all strong motion modal parameters are consistently identified. As a fundamental necessary condition, synthetic response signals are adopted. These have been generated prior to dynamic identification from computed numerical seismic responses of a set of shear-type frames. The efficiency of the present original implementation is highlighted, by proving that consistent rFDD modal dynamic identification of structures at seismic input and simultaneous heavy damping looks feasible. Thus, the paper delivers a robust method for inspecting current structural modal properties of frame buildings under earthquake excitation and for observing their possible variation along experienced seismic histories.

Fusion of wireless and non-contact technologies for the dynamic testing of a historic RC bridge

In this paper, a dynamic testing and corresponding signal processing methodology is presented for condition assessment of bridge structures, via use of a diverse and potentially dense grid of low-cost and easily deployable monitoring technologies. In particular, wireless and non-contact sensors are simultaneously deployed on a historic reinforced concrete bridge in order to record acceleration and dynamic displacement response, under operational loading conditions. An innovative monitoring approach is proposed on both the hardware (sensors) and software (algorithmic) front, in which an effective data fusion procedure is adopted for fusing these alternative technologies for vibration-based monitoring in terms of both acceleration and displacement information. The demonstrated efficacy of the fusion procedure on the case-study of an actual operating system, the historic Brivio bridge, reveals the potential of this approach within the context of structural monitoring, where acquisition of heterogeneous information certainly proves advantageous.

Structural analysis of the Paderno d’Adda Bridge (Italy, 1889)

The Paderno d’Adda Bridge is a marvellous riveted iron viaduct with a doubly-built-in parabolic arch that crosses the river Adda near Milano, between Paderno d’Adda (Lecco province) and Calusco d’Adda (Bergamo province), in Lombardia, northern Italy. It was completed in 1889 by the “Società Nazionale delle Officine di Savigliano” (SNOS). In this work, following a previous contribution to the last SAHC08 Conference (Ferrari and Rizzi 2008), a complete FEM model of the bridge is presented, in the attempt of querying the performance of the structure at design stage. Several static loading conditions have been carried-out in the elastic range and results have been compared to those available in the original SNOS Report (1889), with remarkable correspondence.

Structural modelling of the piers of the Paderno d’Adda Bridge (1889, Italy)

This note focuses on a specific aspect of the structural modelling of the Paderno d’Adda Bridge, a marvellous Italian historic wrought iron bridge with riveted connections that was completed in 1889 and opened to both railway and road traffics [1-2]. Within the current attempt of building a full 3D FEM model of the structure [3-7], the metallic piers of the bridge are considered [5-6], specifically the pier on the arch. The morphology of the piers has been reconstructed from the inspection of the original design drawings and implemented into a FEM model. Then, a structural analysis has been performed in the elastic range, by considering loading distributions that were conceived at design stage and also conditions that are nearer to present-state railway standards.

Heterogeneous sensor fusion for reducing uncertainty in Structural Health Monitoring

This work attempts a comprehensive processing of response signals acquired from an experimental campaign on a local historical bridge using four different types of sensory systems. A general analysis setup is developed, allowing for consistent modal dynamic identification via individual signal processing as well as via data fusion through dedicated Multi-Rate Kalman filtering approach. The investigation reveals the potential and limitations in terms of utilization of novel instrumentation systems to be adopted for Structural Health Monitoring (SHM) purposes.