The Ponte delle Torri is a large medieval masonry bridge, one of the main architectural heritage of Spoleto, Italy. The location of the bridge is less than 50 km from the main epicenters of the recent Central Italy earthquakes (Mw > 5.0) that occurred between August 2016 and February 2017. In addition, some minor quakes of the sequence (Mw between 3.0 and 4.0) occurred within 10 km from the bridge, causing some damages and fear among the population around Spoleto. In this context, the present paper aims at contributing to understand the effects on the structural health of the bridge by analyzing the ambient vibration data acquired before, during and after the seismic sequence, as changes in the dynamic behavior of the structure might indicate the evolution of the state of damage of the monument. In particular, vibration data were processed by modal analysis techniques for mutual validation of the extracted modal parameters. Environmental and vibration data were simultaneously acquired to take into account the seasonal effects on the dynamic behavior. Through a preliminary finite-element model (FEM) the modal shapes were obtained to choose the positions where to locate the sensors for the vibration spot acquisition session of June 2015. The same positions were acquired in October 2016 and at the end of May 2017. Subsequently, a more detailed FEM was produced based on a 3D reconstruction by structure-from-motion stereo-photogrammetry technique with high-resolution photos from unmanned aerial vehicle of the bridge. The model was validated through comparison with the damage pattern experienced by the bridge and then used for assessing the seismic safety by means of both, nonlinear dynamic and static push-over analyses.

Health assessment and ambient vibration testing of the “Ponte delle Torri” of Spoleto during the 2016–2017 Central Italy seismic sequence

A signal processing framework for operational modal analysis in time and frequency domain

Diagnostic analysis and dynamic identification of a glass suspension footbridge via on-site vibration experiments and FE numerical modelling

Given a series of intrinsic features of structural glass systems (i.e., material properties, type of restraints, operational conditions, etc.), special care should be spent at the design stage, to ensure appropriate fail-safe requirements, but also in the service life of these innovative building components and assemblies. In this paper, the dynamic characterization of simple monolithic glass elements is presented, based on non-destructive laboratory experiments and Operational Modal Analysis (OMA) techniques, including Finite Element (FE) numerical simulations, classical analytical models, and video-tracking approaches. It is shown, in particular, how the actual restraint condition (i.e., flexibility of supports, with respect to ideal boundaries) can affect the vibration parameters of a given glass member (frequency and damping capacity). This turns out in possible variations of its overall structural performance, including stress-strain-related effects, hence suggesting the need for even further dedicated studies and methods for the reliable analysis and design of structural glass assemblies and complex systems under dynamic loads.

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Vibration Analysis and Dynamic Characterization of Structural Glass Elements with Different Restraints Based on Operational Modal Analysis

Comparison of experimental and operational modal analysis on a back to back planetary gear

Comparison of experimental and operational modal analysis on a laboratory test plate

Comparison of Experimental and Operational Modal Analysis on a Laboratory Test Plate

The modal parameters in Operational Modal Analysis (OMA) are often estimated based on non-parametric signatures of the structure’s dynamic response. For time domain OMA methods the non-parametric signatures are often correlation functions (CFs) and the pre-processing step for these methods is thus the estimation of CFs. The present paper demonstrates how measurement noise from sensors and measurement equipment affects the estimated CFs. Furthermore, the influence of the measurement noise on the modal parameter estimates is discussed. It is shown how effects of this noise can easily be avoided by ignoring the first part of the CFs when estimating the modal parameters. This is demonstrated by a theoretical review and on simulated and experimental data. The paper also addresses how to add noise to simulated data, so that it resembles a real-life scenario.

Influence of Noise in Correlation Function Estimates for Operational Modal Analysis

In this paper we compare two commonly used methods for estimation of correlation functions, the periodogram (or correlogram) method and the Welch’s method, and show that they are statistically equa ...

Influence of Correlation Estimation Methods on Damping Estimates

The dynamic characteristics of ship structures are becoming more important as the flexibility of modern ships increases, for example, to predict reliable design life. This requires an accurate dyna ...

Esben Orlowitz

Papers

Comparison of experimental and operational modal analysis on a laboratory test plate

Comparison of Experimental and Operational Modal Analysis on a Laboratory Test Plate

Influence of Noise in Correlation Function Estimates for Operational Modal Analysis

Influence of Correlation Estimation Methods on Damping Estimates

Operational Modal Analysis for Dynamic Characterization of a Ro-Lo Ship