Exploring Problems and Prospective of Satellite Interferometric Data for the Seismic Structural Health Monitoring of Existing Buildings and Architectural Heritage

Satellite interferometric data represent a promising source of information for the Structural Health Monitoring (SHM) of the existing built environment. This is especially true because they show differential temporal-spatial displacements of remotely monitored points, which can be easily interpreted with a visual inspection of their time-histories for different locations defined a priori. However, the interferometric information is commonly referred to extended territories (at the scale of city or region), thus several problems arise in the implementation of automatic SHM techniques for the damage detection, localization, and assessment of the built environment at a point level (scale of the building or lower). Despite a long list of challenges, interferometric data have also the potential to become a useful source to assess the health of a structure, especially for helping in define structural early warning methodologies. For this reason, in the paper, the authors summarize the main challenges in the use of satellite interferometric data for civil SHM, and rather than proposing remedial actions, try to critically analyze the challenges and perspectives for future applications

Synergistic and combinatorial optimization of finite element models for monitored buildings

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Condition Assessment of an Early Thin Reinforced Concrete Vaulted System

For the analysis and conservation of architectural heritage a multi-disciplinary approach is required. In the specific case of early concrete buildings, survey and experimental investigations constitute a fundamental source of information for verifying the actual structural behavior and the residual safety levels. This paper reports the direct experience acquired from an extensive experimental campaign conducted on the Paraboloide in Casale Monferrato. The study aims to be an example of how condition assessment of the structural heritage of the early 1900s, with an apparently simple geometric shape and composition, can actually contribute in understanding hidden structural complexity. Moreover, this work may provide useful information to researchers and practitioners who are approaching this specific structural typology (e.g., the industrial heritage represented by parabolic concrete silos). In more details, results are presented regarding the in-situ investigations, and the laboratory tests carried out to analyze the mechanical performance inherent to both (i) local aspects of the structure, such as the quality of the materials and connections, and (ii) global aspects, such as the modal response of the structure. Furthermore, considerations are made on the results of the experimental campaign, also through the corroboration of numerical models

ANALYSIS OF THE DAMAGE STATE OF A MONUMENTAL BUILDING BY CONSIDERING THE VARIATIONS IN SOIL CONDITIONS

This paper investigates whether it is possible to identify the influence of soil conditions on the modal parameters of the structure for damage detection and overall structural health monitoring. To do so, the data gathered on a large monumental building damaged by differ-ential settlements are analyzed. In particular the dynamic response of the case study, a large monumental masonry building, was experimentally investigated within an operational modal analysis (OMA) campaign. Mechanical data obtained from the geophysical tests were in turn employed to build and characterize a numerical model of the soil underlying and sur-rounding the building. The resulting model was then used to study the sensitivity of the mod-al charasteristics of the building with respect to variations of external environmental factors (e.g., the water table level) which affect the underlying soil. The results obtained from this numerical study is deemed to represent a starting point for future experimental tests and investigations, whose final aim is relating ambient vibration measurement to the occurrence of differential settlements or subsidence, in order to detect progressive, and possibly pathological, behaviors

Towards the Seismic Monitoring of a Monumental Structure in Mixed Masonry-RC

The monumental historical heritage is recognized and appreciated worldwide. It is the result of the succession of different cultures that have inevitably influenced and characterized history; therefore, it represents an inestimable value to be preserved for future generations in order to transmit culture and art. In addition, there is a growing engineering interest in the protection of cultural heritage since it is strongly vulnerable. In the present work, the authors present the first attempt of geometric and mechanical modeling (Finite Element Model) and the subsequent sensitivity analysis of the Upper Basilica of the Sanctuary of Oropa (Chiesa Nuova), characterized by a mixed structure in masonry and reinforced concrete. The analysis conducted is placed at the beginning of a path of knowledge which, in subsequent steps, allows the understanding of the static and dynamic behavior of the analyzed structure. The goal of this work is to discriminate and validate which of the elastic parameters characterizing the individual components of the structure have a significant effect on the dynamic response of the structure, to facilitate the subsequent analysis aimed at defining the dynamic monitoring sensing system to be installed on the structure, and to support vulnerability analyses

Modal Identification of Structures with Interacting Diaphragms

System identification proves in general to be very efficient in the extraction of modal parameters of a structure under ambient vibrations. However, great difficulties can arise in the case of structures composed of many connected bodies, whose mutual interaction may lead to a multitude of coupled modes. In the present work, a methodology to approach the identification of interconnected diaphragmatic structures, exploiting a simplified analytical model, is proposed. Specifically, a parametric analysis has been carried out on a numerical basis on the simplified model, i.e., a multiple spring–mass model. The results were then exploited to aid the identification of a significant case study, represented by the Pavilion V, designed by Riccardo Morandi as a hypogeum hall of the Turin Exhibition Center. The structure is indeed composed of three blocks separated by expansion joints, whose characteristics are unknown. As the main result, light was shed on the contribution of the stiffness of the joints to the global dynamic behavior of structures composed of interacting diaphragms, and, in particular, on the effectiveness of the joints of Pavilion V

Combining satellite geophysical data with continuous on-site measurements for monitoring the dynamic parameters of civil structures

One key issue in the Structural Health Monitoring (SHM) of buildings is the influence of the soil on the dynamics of the system. The lack of accurate information on soil-structure interaction represents a source of significant uncertainty and generates difficulties in assessing the state of structural health. In this respect, satellite data could represent a valuable tool for soil knowledge. This paper presents the first study of satellite data coming from the environmental Copernicus program of the European Space Agency (ESA) for the alternative application in the field of SHM. In particular, Land Surface Temperature (LST) and Soil Water Index (SWI) data are elected to study surface temperature and moisture condition of the soil. Once examined and processed, these records have been statistically analyzed, crossed with on-site experimental quantities (natural frequencies and environmental variations), and given as input to a Finite Element (FE) model. The final goal is to understand the actual structural behavior, but also to monitor the evolution of the dynamic parameters for the purposes of structural and seismic monitoring. The largest oval masonry dome in the world was chosen as a prominent case study to demonstrate this novel approach to SHM

Damage detection and localisation in buried pipelines using entropy in information theory

In recent years, entropy measures, and more specifically, spectral entropy have emerged as an efficient method for the damage assessment of both mechanical systems and civil structures. In the present work, entropy measures are applied as a damage-sensitive feature for the real-time structural health monitoring of buried pipelines. The management of these underground Fluids Distribution Systems (FDSs) is critical for supplying clean water, oil, gas, and other goods. However, the health state of these systems tends to deteriorate over time so that they become more vulnerable to leaks or catastrophic failure events. Maintenance surveys and visual inspections are expensive and labour-intensive, due to the difficulties in accessing buried pipelines. Thus, Vibration-Based Inspection (VBI) techniques and continuous monitoring would be perfectly suited for the task. The approach is validated numerically on the soil-structure models of a typical pipeline structure (i.e. Steel Pipes - SPs)

Detection and Localization of Multiple Damages through Entropy in Information Theory

According to recent works, entropy measures, and more specifically, spectral entropies, are emerging as an efficient method for the damage assessment of both mechanical systems and civil structures. Specifically, the occurrence of structural system alterations (intended in this work as stiffness reduction) can be detected as a localized change in the signal entropy. Here, the Wiener Entropy (also known as the Spectral Flatness) of strain measurements is proved as a viable tool for single and multiple damage assessment including damage detection, localization, and severity assessment. A case study from oil & gas engineering, i.e., a finite element model of a buried steel pipeline, is utilized for this aim

Satellite interferometric data for seismic damage assessment

Radar satellites allow the collection of data on large areas without direct access to structures. Thereby, they appear very attractive for Structural Health Monitoring (SHM) purposes. Data collected by satellites can be processed to obtain temporal histories of displacements through which the health state of a monitored system can be potentially identified. However, anomalies in the time histories of displacements are not necessarily due to damage. Environmental phenomena, such as variations in atmospheric temperature, and rain, can modify the behavior of structures without compromising their safety. The impact of these phenomena on the structural response can hinder the identification of anomalies or lead to false alarms if such alterations are misinterpreted as damage. Furthermore, if the monitored system is a historical structure, uncertainties on the structural behavior are inevitably increased during aging. The purpose of this article is to discuss the possibility of identifying damage due to seismic actions considering the impact of variations of environmental factors on the time histories of the displacements retrieved by satellite data. The structural health condition of a historical structure located in the city of Rome (Italy) hit by the October 2016 Central Italy earthquakes is investigated based on interferometric satellite data. The satellite data are acquired by COSMO-SkyMed (CSM) of the Italian Space Agency between 2010 and 2019 and are processed by CNR IREA