Marco Bovo

Dynamic identification of an ancient masonry bell tower using a MEMS-based acquisition system

In this paper results of dynamic tests performed on a bell tower located in Ficarolo (Italy) are reported. After the Emilia earthquake that occurred in 2012, the bell tower reported a serious damage pattern and, as a consequence, retrofitting interventions were carried out. Dynamic tests before and after the strengthening were performed to investigate the modal properties of the bell tower and to evaluate possible changes in dynamic behavior due to the intervention. Accelerations during ambient vibrations were recorded by means of an advanced MEMS-based system, whose main features are the transmission of the data in digital form and the possibility of performing some system analyses directly on-board of the sensors. Accelerations were acquired using 11 biaxial MEMS units. First 8 modes are clearly identified, with natural frequencies in the range 0.5-9.0 Hz. Finally, a comparison between the performances of the installed MEMS-based system and a traditional analog (piezoelectric) system is carried out and results are critically compared.

Effectiveness of FRCM Reinforcement Applied to Masonry Walls Subject to Axial Force and Out-Of-Plane Loads Evaluated by Experimental and Numerical Studies

ABSTRACT An experimental campaign and a numerical analysis devoted to the investigation of the out-of-plane behavior of masonry walls reinforced with Fiber Reinforced Cementitious Matrix (FRCM) are presented here. The main goal of this study is to analyze and evaluate the effectiveness of the strengthening system, by discussing failure modes and capacity of strengthened masonry walls, in order to assess their behavior under out-of-plane horizontal actions, such as, for example, seismic actions. A purposely designed experimental set-up, able to separately and independently apply an axial force and out-of-plane horizontal actions on masonry walls, was used. Experimental results are discussed and compared with the outcomes of nonlinear analyses performed on simplified finite element models of the walls. A proper evaluation of the flexural capacity of FRCM strengthened walls is the first step of the ongoing process of drawing reliable code guidelines leading to a safe design of strengthened masonry structures.

Structural Characterization of an Historical Building by Means of Experimental Tests on Full-Scale Elements

In order to properly design strengthening intervention of existing buildings, careful assessment of the structural behavior is certainly required. This is particularly important when dealing with historical constructions made of heterogeneous materials like masonry or stonework. In this context, this paper presents the results of knowledge process on a large monumental nineteenth century building located in Trieste. The traditional investigation approach considering a wide number of destructive tests for characterization of materials and evaluation of the structural details were not admissible due to the valuable cultural and historical importance of the building. Therefore, an alternative and not conventional investigation approach has been considered. After a wide historical research and a detailed structural survey, it has been possible to identify the main structural systems of the building. Then, to characterize the structural response, a limited number of nondestructive tests but on full-scale typological systems have been preferred to a larger number of destructive tests on specimens of the different materials. The selected experimental load tests have been conducted in order to assess the actual structural response of the main systems that constitute the building, thus allowing for a fine tuning of both the rehabilitation interventions and the numerical finite element models.

Seismic vulnerability assessment of a historical masonry building: Pandone Castle

The knowledge of a historical masonry building is a prerequisite both for the purposes of a reliable evaluation of the actual seismic safety and for the choice of an effective intervention for the preservation of the monumental building. It is therefore a need to refine the investigations and techniques of analysis by different degree of reliability, as well as in relation to their impact. Knowledge can be achieved with different levels of detail, depending on the accuracy of geometric survey operations, historical research, and experimental investigations. The aim of the study is the analysis of the seismic vulnerability of the historical building “Pandone Castle”. The knowledge procedure has led to the assessment of security level against seismic actions.

Model Updating and Damage Assessment of a RC Structure Using an Iterative Eigenvalue Problem

This study discusses the model updating performed on a two-story reinforced-concrete masonry-infilled building using the dynamic response obtained during ambient vibration measurements. Five infills were demolished at four stages creating four damage states. The numerical model of the building is developed based on the obtained material properties and geometry. The model updating process minimizes a target function defined as the least-square optimization of an inverse eigenvalue problem. The reference model is then updated using the experimental results in each stage of damage to assess the damage. The dynamic properties obtained from the updated model match well their experimentally-estimated counterparts. Also, the model can reliably locate the damage introduced to the structure.

Numerical Interpretation of Structural Behavior of Stone Arches of Historical Storehouses Building

The paper presents the numerical analysis performed for interpreting structural behavior of an historical masonry storehouse in Trieste, Italy. The large complex subject of the study is dated back to XIX Century and it is nowadays disused and in an advanced state of deterioration. The monumental building, after a detailed survey defining geometry and characteristics, were extensively tested by means of a comprehensive experimental campaign conducted on its walls, foundations and arches. The main outcomes of the in-situ and laboratory tests allowed to defining the properties and the behavior of some structural elements. The collected experimental data allowed defining and calibrating of detailed finite element models (global and partial) of the building composed of walls, columns, arches and vaults. The main goals of the modelling were the calibration of global material parameters to obtain a correct interpretation of the experimental tests conducted and the study of behaviour and capacity of the building when subject to horizontal loadings, such those due to a seismic excitation. Furthermore, nonlinear analyses were performed to estimate the ductility of the stonework arches-vaults system, taking also into account, or excluding, the flexibility of the foundation system.

Numerical Simulation of Seismic-Induced Failure of a Precast Structure during the Emilia Earthquake

AbstractThe paper describes the failure scenario of a precast building that collapsed during the 2012 Emilia earthquake. By means of time-history analyses on a detailed finite-element model, the dy...

Structural Health Monitoring of a Historical Masonry Bell Tower Using Operational Modal Analysis

This paper addresses the modal and structural identification of the historical masonry bell tower of Ficarolo, in Italy. After the seismic sequence of May 2012, the tower reported a serious damage pattern. Retrofitting interventions were designed and they mainly consisted in the rebuilding of cracked zones and the strengthening of masonry walls with carbon bars embedded in the masonry with epoxy resin. Afterwards, a continuous dynamic monitoring system has been installed on the tower. From the recorded structural response under ambient excitation, the dynamic characteristics of the tower are identified using Operational Modal Analysis techniques. Results of the first months of continuous monitoring are presented in this paper. Moreover, in order to analyse the evolution of the structural behaviour, the effect of changing temperature on the identified natural frequencies is investigated. The experimental modal parameters are also used to identify the elastic modulus of the reinforced masonry through the calibration of a Finite Element (FE) model of the tower. In addition, the influence of the soil-foundation system on the structural behaviour is evaluated. The calibration procedure is performed adopting an improved surrogate-assisted evolutionary strategy. The calibrated FE model can be adopted to simulate the structural response to far-field earthquakes. Moreover, the monitoring system can give valuable information on the structural behaviour and the structural health in the case of seismic events.

EVALUATION OF SEISMIC RESPONSE OF BUILDINGS USING DYNAMIC ANALYSIS ON STICK MODELS

Abstract. A new methodology for the study and evaluation of the seismic response of buildings is presented in this paper. The method involves the use of nonlinear time-history analysis on equivalent multi-degrees of freedom stick models, defined according to the classification given in FEMA440 Report. The steps for implementing the method and obtaining the equivalent model are described in the article. For the validation of the method, the results obtained from the stick models were compared to that obtained by time-history analysis on detailed finite element models of the structures (using the definition of detailed model described in FEMA440). The engineering parameters considered in the comparison are top displacements, interstorey drifts, forces at the floor and base shear. The results of the conducted analyses on the equivalent stick models match satisfactorily, in an excellent way in certain cases, those of the analyses carried out on detailed models. The time-history analyses on the stick models, allowing a considerable saving in terms of both computational effort and time for numerical solution and post-processing of results, could make this kind of analysis more attractive and feasible for a daily design, and comparable in terms of costs with pushover procedures.

Structural Behaviour of Historical Stone Arches and Vaults: Experimental Tests and Numerical Analyses

Recent seismic events showed the dramatic need, especially in case of historical and existing buildings, of important strengthening activities to be carried out. In order to properly design them, a careful assessment of real structural behaviour and load-carrying capacity of these buildings is strongly required. This is particularly important when dealing with constructions made of heterogeneous materials like masonry or stonework, where often conventional analysis techniques do not behave satisfactorily. This paper presents the results of an extensive experimental and numerical investigation on historical stone arches and vaults. A series of in-situ tests were carried out on different types of stone arches belonging to a large building of the XIX century, with the purpose of investigating their mechanical response and obtaining the structural behaviour of stonework under different types of in-plane loads. The experimental results were compared with the numerical solutions obtained by a detailed finite element model of a portion of the structure. Numerical linear and non-linear FE analyses were conducted in order to reproduce the experimental tests and analyse the interaction between series of arches that are linked by cross vault or tunnel vault. Finally, non-linear analyses with vertical and horizontal loads were carried out with the scope of simulating the seismic effect and to verify the ductility of this type of vaulted structures.