Abstract

Over the past few decades, the conservation and seismic assessment of historical buildings has gained great importance. In particular, the prediction of the dynamic response of masonry constructions plays a central role in retrofitting and conservation interventions. Finite element modelling has become the most common and accessible approach to study the behavior of complex masonry structures, however, the gap between numerical and experimental analysis may lead to erroneous results. This work describes the model updating procedure applied to the finite element model of San Giovanni’s church in Macerata, condemned in October 2016 after the Central Italy Earthquake. The laboratory of Proof and Research on Structures and Materials of Roma Tre University carried out an extensive in-situ testing campaign including geometric survey, video endoscopy, flat-jack test, sonic tomography and ambient vibrations test in order to investigate the state of the building. The work involved both numerical and experimental analysis: the results of the testing campaign were interpreted and correlated with an accurate finite element model developed with the software Midas Gen. Operational modal analysis was performed in order to extract the modal parameters of the building (modal frequencies, shape vectors and modal damping). Material characteristics and boundary conditions were updated according to the Douglas-Reid method. In the end, the final model was compared to the initial model to evaluate and discuss the process.

Abstract

Dynamic monitoring is a well-established technique used to gain information on the global health of constructions. In particular, ambient vibration tests have achieved important results in the dynamic characterization of modal parameters. Several techniques and instrumentations are currently available, however the accuracy of these results is often unquestioned. The mutual validation between different modal analysis techniques is an important procedure to assess the reliability of the results. In the present paper the ambient vibration tests performed on the so-called ‘Temple of Minerva Medica’ in Rome considering different techniques and instrumentations will be described and compared. While it is referred to as the Temple of Minerva Medica, the structure is actually a ruined decagonal nymphaeum in opus latericium that dates to the 4th century AD. Today, the construction is located between the main central train station (Roma Termini) and the local tram way. Ambient vibration data were acquired during different campaigns [1] to characterize the effects of the vibrations and the modal parameters of the structure. This work deals with the data collected on the 11th of July 2019 within the project “Tecnologie per il miglioramento della Sicurezza e la ricostruzione dei centri Storici in area sismica” coordinated by DTC Lazio (Distretto Tecnologico beni e attività culturali). The instrumentation comprised of several seismographs equipped with triaxial velocimeters and piezoelectric accelerometers. A variety of techniques were applied to process the acquired vibration data in order to extract the modal parameters of the studied structure including PolyMAX, FDD, EFDD, CC-SSI, HVSR and FRF. Comparison of the modal parameters obtained by each different technique was considered to provide indications on the reliability of the instruments.

Abstract

This paper describes the design, test and validation processes of a dynamicidentification algorithm aimed at the time-dependent assessment of modern structures and heritage buildings for civil and seismic engineering purposes. Full validation of the algorithm is performed through analysis of numerically simulated data from an idealized masonry tower. Making use of output-only vibration measurements, the non-parametric algorithm can generate dynamic features results as time-dependent functions for the complete observation period. The algorithm can work in the presence of different dynamic loads and non-linear structural behaviours, close spectral frequency components and noisecontaminated data. Time-dependent structural dynamic parameters that can be computed are modal frequencies, modal displacements, modal curvatures, and higher derivatives of mode shapes. The proposed algorithm aims to be used as the core estimator of timedependent identification methods devoted to the health monitoring of structures and infrastructures, being suitable for a multitude of tasks ranging from the simple operational modal analysis (in pre and post-event condition) to the complex online assessment of the structural response during seismic events for rapid damage identification.

Abstract

Selected results from the investigation program of a historic R.C. bridge are presented in the paper. The bridge, crossing the Adda river between the Municipalities of Brivio and Cisano Bergamasco, consists of three tied arch spans, about 44.0 m length each, and represents a crucial node for the vehicular traffic of the region. After a maintenance intervention performed on one pier, the local Authorities committed to Politecnico di Milano an extensive investigation including: (i) documentary research and review of the bridge history; (ii) visual inspection and geometric survey of each span; (iii) full-scale load tests and ambient vibration tests; (iv) FE modelling of each span and validation of the numerical models (through comparison with the available experimental results) and (v) structural assessment of the bridge in its present condition. After a concise review of the bridge history, the paper summarizes the complete results of the experimental tests performed on one span (visual inspection, geometric survey, full-scale load tests and dynamic tests) as well as the development of numerical models.