Hybrid simulation techniques in the structural analysis and testing of architectural heritage

L'abstract è presente nell'allegato / the abstract is in the attachmen

Recent Advances on Pseudodynamic Hybrid Simulation of Masonry Structures

Hybrid Simulation has been introduced to simulate the seismic response of civil structures. The hybrid model of the emulated system combines numerical and physical subdomains and its dynamic response to a realistic excitation is simulated using a numerical time-stepping response history analysis. In the current practice, lumped parameters structural topologies such as shear type frames or inverted pendulum characterize the physical subdomain and the design of the testing setup is straightforward. Although hybrid simulation has been extensively exploited for testing concrete and steel structures, in the authors' knowledge, there is still a paucity of scientific publications devoted to masonry applications. This is in contrast to the inherent uncertainty carried by masonry failure mechanisms, which hinders any attempt of implementing predictive numerical models. From this perspective, this paper summarizes our recent research achievements aimed at extending hybrid simulation to distributed parameter specimens, such as masonry walls, using the minimum number of actuators. The great potential of reduction bases in driving the substructuring process has been shown in a previous work and here is enhanced to floating physical subdomains

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

Bayesian Calibration of Hysteretic Parameters with Consideration of the Model Discrepancy for Use in Seismic Structural Health Monitoring

Bayesian model calibration techniques are commonly employed in the characterization of nonlinear dynamic systems, as they provide a conceptual and effective framework to deal with model uncertainties, experimental errors and procedure assumptions. This understanding has resulted in the need to introduce a model discrepancy term to account for the differences between model-based predictions and real observations. Indeed, the goal of this work is to investigate model-driven seismic structural health monitoring procedures based on a Bayesian uncertainty quantification framework, and thus make relevant considerations for its use in the seismic structural health monitoring, focusing on masonry structures. Specifically, the Bayesian inference has been applied to the calibration of nonlinear hysteretic systems to both provide: (i) most probable values (MPV) of the parameters following the calibration; and (ii) estimates of the model discrepancy posterior distribution. The effect of the model discrepancy in the calibration is first illustrated recurring to a single degree of freedom using a Bouc–Wen type oscillator as a numerical benchmark. The model discrepancy is then introduced for calibrating a reference nonlinear Bouc–Wen model derived from real data acquired on a monitored masonry building. The main novelty of this study is the application of the framework of uncertainty quantification on models representing data measured directly on masonry structures during seismic events

Effect of noise in the time-frequency estimate of the peridynamic bond elastic constant parameter

The Peridynamic (PD) theory is a modern nonlocal (nonlinear, elastic /inelastic, with-out/with memory) theory able to deal with long-range forces and discontinuity in materials. For this reason the theory is suitable for the monitoring of masonry structures. Starting from a special case of PD formulation, named Bond-Based Peridynamic (BBPD), a feature ob-tained by the idealization of real systems with BBPD is used for SHM purposes: the bond elastic constant parameter. To characterize the damage (i.e. permanent deterioration of ma-terial and/or geometric properties of the systems) occurring in systems idealized with PD models, a joint time-frequency direct estimate of the parameter values is performed using a Short Time Fourier Transform (STFF) of the systems response and the input acceleration at the base of the systems. The method is applied numerically and the effect of noise in the time-frequency evaluation of the parameter values is analyzed. The study concludes that PD can provides simply and strong information on the health of simulated systems, allowing at the same time an easy and scalable parametrization of civil, especially masonry, structures, while the bond elastic constant parameter can be used for the damage characterization, i.e. to detect, quantify and localize the damage in a generic system

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

Hybrid simulation with dynamic substructuring of masonry structures: A numerical study

Hybrid simulation is used to compute the time history response of an emulated system subject to a dynamic excitation by combining a physical and a numerical substructure. The former is tested in the laboratory by means of servo-controlled actuators whist a real-time computer simulates the latter and solves the coupled equation of motion. Hybrid simulation has been extensively applied for seismic response history analysis of steel and concrete frame structures. For these systems, subdomain partitioning follows storey levels and nodal joints among beam/column-like elements. In the case of planar masonry structures, distributed interfaces characterize system subdomains and, in principle, several actuators should be used to impose the correct boundary conditions to the tested specimen. This paper presents a new substructuring method for planar masonry substructures, which aims to reduce the number of actuators necessary to achieve a predetermined coupling accuracy between physical and numerical subdomains. The numerical validation of this procedure is illustrated for a masonry building facade system

Synergistic and combinatorial optimization of finite element models for monitored buildings

n/

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

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