Gianni Bartoli

Structural static testing by interferometric synthetic radar

In this paper, the authors propose a radar technique for building structural static testing or monitoring. The technique is based on interferometric step-frequency continuous-wave (SFCW) radar. It works synthesising microwave holographic images, and comparing pairs of holograms to obtain a deformation map. The application of the interferometric technique for structural static testing of a concrete pedestrian bridge is described. The radar-measured deformation profile has been compared with a finite element simulation of the bridge.

Wavelet Packet Methods for the Analysis of Variance of Time Series With Application to Crack Widths on the Brunelleschi Dome

In this article we extend the definition of wavelet variance to wavelet packets. We also adapt to wavelet packets an iterated cumulative sum of squares algorithm for the location of variance change points. Wavelet packets have greater decorrelation properties than standard wavelets in that they induce a finer partitioning of the frequency domain of the process generating the data. This allows our procedure to be applied to a wide class of processes. We show this on simulated data and on a benchmark time series. Our initial interest in wavelet variance change points location was motivated by an application to time series of crack widths on the Brunelleschi dome of the Santa Maria del Fiore cathedral in Florence. The structure of the dome includes an internal thick dome and an external thin one. In an effort to understand the dynamics of the crack widths we apply wavelet packet variance analysis to measurements from instruments located in the different parts of the outer and inner domes, highlighting different features and seasonal behavior. Our findings agree well with the structural functions of the different elements of the dome and also reveal some interesting aspects regarding the dynamics of crack evolution.

A numerical study on seismic risk assessment of historic masonry towers: a case study in San Gimignano

After a brief introduction on the research project RiSEM (Seismic Risk of Monumental Buildings), the paper discusses on the seismic assessment of historic masonry towers according to the Italian “Guidelines for the assessment and mitigation of the seismic risk of the cultural heritage” that identifies an analysis methodology based on three different levels of evaluation, according to an increased knowledge of the structure. The RiSEM project aimed at developing and testing innovative and expeditious methodologies (i.e. either without or with a minimal direct contact with the masonry building) to evaluate all the main structural features of the monumental buildings required for the assessment of their seismic safety. As a relevant case study the “Town of Fine Towers”, San Gimignano (Italy), listed under the UNESCO World Cultural Heritage Sites, was selected. The paper summarizes the analyses performed on one of the San Gimignano towers: the Coppi-Campatelli one. The seismic vulnerability of the tower was evaluated with reference to the above guidelines, and the paper reports and critically compares the results obtained for the three levels of evaluation there defined: LV1 (analysis at territorial level), LV2 (local analysis) and LV3 (global analysis).

Cappella dei Principi in Firenze, Italy: Experimental Analyses and Numerical Modeling for the Investigation of a Local Failure

AbstractThe paper reports the results of a research aimed at analyzing and interpreting the cracking pattern on the Cappella dei Principi (Prince’s Chapel, the Medici’s mausoleum) in the Basilica of San Lorenzo (Florence, Italy). The research was motivated by the sudden collapse of a keystone of an internal barrel vault sustaining one of the lateral apses. After a brief description of the geometry of the structure, the principal results obtained from in situ surveys (flat-jack tests and cored samples) are described; then the numerical analyses developed both to obtain the static identification of the monument and to assess the possible causes leading to the observed failure are illustrated. The numerical modeling operation has been performed step by step, from linear and quite simple models built with plane elements up to a nonlinear model with three-dimensional elements. The nonlinear FEM, which has been tuned by utilizing the results of the in situ measures, is allowed to both qualitatively and quantita...

The stochastic differential calculus for the determination of structural response under wind

Abstract In the present work, a method related to stochastic differential calculus is applied to study the behaviour of structures under wind action. The generality of the method allows to solve problems affected by a wide range of nonlinearities (mechanical, geometrical and due to wind-structure interaction). As an application example, the response of Tacoma Narrows Bridge sectional model under wind has been considered.

Incremental dynamic and nonlinear static analyses for seismic assessment of medieval masonry towers

AbstractDiscrete rigid blocks interacting through nonlinear elastic damageable interfaces are used to model the global behavior of a medieval masonry tower under seismic actions. The seismic vulner...

Nonlinear Dynamic Analysis of Cooling Towers under Stochastic Wind Loading

Abstract A numerical model for simulating the nonlinear dynamic response of natural draught cooling towers to wind loading is introduced. Geometrical and physical nonlinearities are considered in the F.E. modeling of the doubly-curved thin shell structure. An original simulation procedure of the artificial wind loading is used, generating directly the multi-correlated field of the (stochastic) time series of the external pressures. The effective correlation structure of the fluctuating pressure is imposed from the experimental data obtained by wind tunnel tests. Some preliminary analyses, carried out for checking the performance and reliability of the model, are finally reported.

Numerical Modeling of the Structural Behavior of Brunelleschi’s Dome of Santa Maria del Fiore

The study discusses some recent results regarding the identification of the static and dynamic behavior of the Brunelleschi’s Dome of Santa Maria del Fiore in Florence, which was declared part of the UNESCO World Heritage sites in 1982 together with the city center. First, a brief sketch of the main geometric characteristics and the relevant constructive aspects conceived by Brunelleschi are outlined with a description of the present crack pattern. Then a finite element model was built to assess the static and dynamic behavior of the monument and identified taking into account the results of an in situ investigation developed in the 1980s. The numerical model was used with an ad hoc nonlinear procedure to replicate the mechanical behavior of masonry. Obtained results allowed to assess and to discuss both the Dome’s internal stress and cracking pattern. The identified numerical model was subsequently employed to provide a first evaluation of the seismic behavior of the Dome. While showing how advanced numerical analyses can provide useful hints to evaluate the existing damage on monumental heritage, this study aims at contributing to the assessment of the safety and vulnerability of one of the most emblematic masonry domes all over the world.

Semiempirical Formulations for Estimating the Main Frequency of Slender Masonry Towers

AbstractThe paper focuses on the analysis of the outcomes of some experimental tests carried out in San Gimignano (Siena, Italy), aimed at measuring the natural frequencies of the medieval masonry ...

Epistemic Uncertainties in Structural Modeling: A Blind Benchmark for Seismic Assessment of Slender Masonry Towers

AbstractThe paper reports the results of a blind benchmark developed as a part of the preliminary activity of the research project RiSEM (Italian acronym for Seismic Risk on Monumental Buildings). ...