Giosuè Boscato

Global Sensitivity-Based Model Updating for Heritage Structures

Sensitivity-based approaches to model updat- Q2 ing have become widely used because of their capability to calibrate the model by taking into account the influence of updating parameters associated to different structural elements. Global sensitivity analysis (SA) allows model updating to be carried out even in the case of elevated un- certainty about the material characteristics. Architectural heritage structures deserve specific attention on account of their intrinsic geometrical complexity and heterogene- ity. In this article, the concept of global SA is applied for the first time to complex monumental structures, and a comparative view is offered on more classical local sen- sitivity approaches. Different finite element (FE) calibra- tion techniques—via global and local SA—were applied to the intriguing case of the church of S. Maria del Suf- fragio in LAquila (Italy), severely damaged by the 2009 earthquake. The FE updating was based on experimental data acquired by a dynamic monitoring system. Finally, calibration strategies were assessed through time history analyses by comparing the responses to the recorded seismic event.

Free vibrations of a pultruded GFRP frame with different rotational stiffnesses of bolted joints

Experimental and numerical results for the dynamic response of an all-FRP (fiber-reinforced polymer) twodimensional frame in free vibration are presented. The frame was assembled of pultruded glass-fiber-reinforced polymer (GFRP) profiles and bolted beam-to-column connections with GFRP angles. To give a variable rotational stiffness to the four beam-to-column major-axis joints, all bolts were tightened by a constant torque of 10, 25, or 40 N · m. Experimental measurements were performed on the three configurations to identify the natural frequencies of the first vibration mode in the plane of the frame and to determine the ability of each structure to dissipate the initial acceleration imposed on it through damping. The results obtained are compared with analytical and finite-element calculations.It was found that an increased bolt torque improved the dynamic response of the GFRP frame by reducing its vibration time and maximum displacements and by enhancing its dissipation capacity.

Anime Sante Church's Dome After 2009 L'Aquila Earthquake, Monitoring and Strengthening Approaches

This work shows the results of monitoring of Santa Maria del Suffragio (Anime Sante) church, L’Aquila, Italy. The historical building was stricken and damaged by mainshock of April 6, 2009; the dome is the structural element that has been seriously hit by seismic event. The ambient response analysis of global structure and dome element enable to improve the FE model by model updating methodology using modal data. The identification techniques furnish useful information concerning the structural and mechanical properties of dome’s structure, these parameters are needed to evaluate the appropriate design of rebuilding and structural rehabilitation of dome. The geometric configuration and the self-weight of lantern induce to an independent dynamic response of macro-element against the behaviour of dome generating the first mechanism of collapse and the failure of dome shape. Different retrofitting configurations for the dome have been proposed in this paper.

SHM of Historic Damaged Churches

The paper shows the results of monitoring activities to check the structural response and the level of damage of two historic monument of LAquila: San Pietro di Coppito and Santa Maria Paganica, that were damaged by the main earthquake of April 2009. The diagnostics operation was planned and carried out in situ and in laboratory to verify the integrity of the residual stiffness of the structures and to define the mechanical parameters of the material. The mechanical characterization of materials was carried out through destructive tests on samples, taken directly on site, and micro-destructive tests through single and double flat jacks. To give a first qualitative assessment of overall was used sonic test (non-destructive test) on the main macro-structure. The global structural health monitoring (SHM) was carried out through ambient vibrations to define the real dynamic behavior in serviceability state and to calculate - via a modal identification of output-only systems-the dynamic parameters (mode of vibration, frequencies, displacements and damping ratios). The aim of this research is to prove the reliability of different diagnostic methodologies, the real extent of global and local damage and the extent of the residual stiffness of the macro elements of the structures (façade, tower, walls of nave, transept) that are subjected to different mechanism of failure.

Dynamic investigation on the Mirandola bell tower in post-earthquake scenarios

After the seismic events of the 20th and 29th of May 2012 in Emilia (Italy), most of the monumental and historic buildings of the area were severely damaged. In a few structures, partial collapse mechanisms were observed (e.g. façade tilting, out-of-plane overturning of panels…). This paper presents the case-study of the bell tower of the Santa Maria Maggiore cathedral, located in Mirandola (Italy). The dynamic response of the structure was evaluated through operational modal analysis using ambient vibrations, a consolidated non-destructive procedure that estimates the dynamic parameters of the bell-tower. The dynamic tests were carried out in pre-intervention and post-intervention conditions in order to understand the sensitivity of dynamic measurements to safety interventions. Furthermore, a comparative study is made with similar cases of undamaged masonry towers up to the 6th mode. Finally, an investigation on the state of connections and of the building itself is carried out via FE model updating.

Knowledge of the Construction Technique of the Multiple Leaf Masonry Façades of Palazzo Ducale in Venice with ND and MD Tests

This paper presents a first program of non-destructive tests carried out on two medieval façades and inside the main rooms of Palazzo Ducale in Venice, i.e. the room of Maggior Consiglio and the room of Scrutinio. A probably multiple leaf load-bearing brick masonry and an external cladding of polychrome stones compose these façades under investigation. The aim of the tests concern the improvement of knowledge about the construction technique and the mechanical features of these important historical facades. The program was set up after a preliminary historic investigation. Non-destructive and minor-destructive investigations (i.e. pattern surveys, endoscopic tests and georadar test) on the inner sides of the two walls of the area under examination were carried out for the analytical determination of the construction technique and structural characteristics, not clearly inferable from the literature.Due to the complexity of the structure and the transformations undergone in seven hundred years of life, and to the very limited investigable areas of the internal surface, the results of investigations cannot be extended to the entire structure. Nevertheless, these tests provide valuable clues to give a correct interpretation of the construction technique and to contribute to identify the possible mechanical properties, which provide knowledge about the health state of the building.

Creep Effects in Pultruded FRP Beams

The paper presents results of two creep tests on pultruded open-section GFRP beams aimed to evaluate the long-term deformations, the residual deflection after unloading, and the influence of creep strains on the flexuraltorsional buckling phenomenon. Two beams were subjected to a constant load for about one year. Then one of the beams was unloaded to evaluate its residual deflection. For the other beam, the load was increased up to failure, and the residual buckling strength was compared with that of a similar beam tested up to failure. The parameters of the Findley power law are evaluated, and the experimental results are compared with those of numerical analyses and with available formulations for prediction of the time-dependent properties of composite beams. Results of the investigation testify, in particular, to a noninsignificant time-dependent increment in deflections of the beams and to a significant reduction in their buckling strength due to creep deformations.

Collapse Mechanisms due to Earthquake in the Structural Typologies of Historic Constructions: The Case of Mirandola

During the seismic event of May 2012 in the Emilia-Romagna Region (Italy), several cultural heritage structures collapsed or were severely damaged. This paper gives a description of the damage/collapse mechanisms observed on some of these buildings. The Church of Gesù, the City Hall and the tower of the Cathedral in Mirandola (MO) were analyzed. In particular, this article focuses on the behavior analysis of a church, a palace and a bell-tower, mainly masonry construction, that are the most widespread types of protected monuments proposed in the Italian code as simplified models for the verifications on the entire cultural heritage of a prior assessment of the seismic risk. The survey permitted to detect the most significant damage, mainly related to the cracks of the masonry and to understand the different collapse mechanisms.

Structural Behaviour and Comparison of CGF Panels

A CGF Panel (Concrete Glulam Framed Panel) is a concrete panel with a glued laminated timber frame. The experimentation on this new construction system at LabSCo (Laboratory of Strength of Materials) of IUAV University of Venice, inspired a wide research on buildings made of this construction system investigating in different aspect of building behaviour: particularly about mechanical property of the materials, mechanical of the system and building physics. This paper presents the results of quasi-static in-plane tests on single panel and configurations of some different panels. The tests in the laboratory are used for measuring the in-plane strength and stiffness of individual panels and wall sections consist of some panels in order to verify and measure the behavior of the connections between the various parts of the single panel and the connection between the panels. Thanks to the results obtained it was possible carry out the FE model to calibrate the characteristics in relation to experimental data. Finally, in order to compare this constructive system with the well known X-lam systems, on the basis of the calibration of the models we were able to set up a comparable FE model with those of the X-lam wall described in the publication: Quasi-Static and Pseudo-Dynamic Tests on XLAM Walls and Buildings inherent in the SOFIE project coordinated by the CNR-IVALSA (Italian National Research Council - Trees and Timber Institute)

Dynamic Parameters of Pultruded GFRP Structures for Seismic Protection of Historical Building Heritage

The seismic events in the last decades evidenced the vulnerability of the architectural heritage with respect to these phenomena. Therefore, timely provisional and permanent interventions are often required in post-seismic scenarios.In response to the call for more efficacious solutions, a great deal of interest has been given to glass fiber-reinforced polymers (GFRPs) composite. GFRP composites offer the advantage of high strength, low self-weight and durability.This research proposes some first evaluations on the dynamic behaviour of pultruded FRPs (Fiber Reinforced Polymers) strut and tie spatial structure for seismic protection of historical building heritage. The dynamic identification has been carried out using the ambient vibrations test to measure the mode of vibration, frequencies, displacements and damping ratios of the structures. The Operational Modal Analysis (OMA) has been carried out to identify the modal characteristics through poly-reference Least Square Complex Frequency-domain (pLSFC) estimator.Basing on the experimental results the dissipative capacity has been evaluated through the calculation of the behaviour factor q.The experimental dynamic parameters were used to calibrate a numerical finite element model employed under the hypothesis of kinematic equivalence to evaluate the q factor considering the elastic-brittle behaviour of FRP material. The dissipative capacity of structure was assigned to the global geometric configuration - frame with concentric diagonal bracings - through the strength hierarchy criteria locating the dissipative zones in the tensile diagonals. The analysis was carried out considering some typological variations to investigate the variability of the behaviour factor q.