Evaluation for the Damaged Structures of Notre-Dame de Paris: A way for a correct Reconstruction

An impressive fire devastated the cathedral of Notre Dame in Paris, one of the symbols of European architecture. The flames started from the scaffolding embracing the base of the spire on the cathedral roof. The fire blazed up in the church during the religious celebration on April 15th at 6:45 p.m. The fire enveloped abruptly the roof and the spire erected by Viollet-le-Duc in 1860. The collapse took place about 80 minutes around 8 p.m [1-3]. Today, the clamor is all around, the silence is in the heart. At the time of the present report, the causes of the catastrophe are still wrapped in a dense smoke, like the one generated by the burning “forest” as the roof structure was called. This is the figure of the disaster. The Cathedral’s inferno devastated a world treasure, prompting an outpouring of collective sorrow and soulsearching over whether to recreate the destroyed oak-framed roofing and spire or adapt the cathedral to the 21st century. In the present paper, an original evaluation of the residual strength taking into account the fire effect and the water saturation in the limestone after the extinguishing is considered. The residual strength ratio (RSR) and the compressive strength evolution (CS) are carefully evaluated for the injured structures. An estimation of the effective strength ratio of the Cathedral walls is estimated. At the same time, the proposed approach is based on the solution of an extreme adaptive structure (grid shell) able to offer a strong temporary shelter in a short time and allowing a careful work of documentation and restoration of the roof cathedral by an approach like “how it was and where it was

Application of a Machine Learning Algorithm for the Structural Optimization of Circular Arches with Different Cross-Sections

Arches are employed for bridges. This particular type of structures, characterized by a very old use tradition, is nowadays, widely exploited because of its strength, resilience, cost-effectiveness and charm. In recent years, a more conscious design approach that focuses on a more proper use of the building materials combined with the increasing of the computational capability of the modern computers, has led the research in the civil engineering field to the study of optimization algorithms applications aimed at the definition of the best design parameters. In this paper, a differential formulation and a MATLAB code for the calculation of the internal stresses in the arch structure are proposed. Then, the application of a machine learning algorithm, the genetic algorithm, for the calculation of the geometrical parameters, that allows to minimize the quantity of material that constitute the arch structures, is implemented. In this phase, the method used to calculate the stresses has been considered as a constraint function to reduce the range of the solutions to the only ones able to bear the design loads with the smallest volume. In particular, some case studies with different cross-sections are reported to prove the validity of the method and to compare the obtained results in terms of optimization effectiveness

AE propagation velocity calculation for stiffness estimation in Pier Luigi Nervi’s concrete structures

Abstract In the present paper, the acoustic emission (AE) device is used with an innovative approach, based on the calculation of P-wave propagation velocity (vp ), to detect the stiffness characteristics and the diffused damage of in-service old concrete structures. The paper presents the result of a recent testing campaign carried out on the slant pillars composing the vertical bearing structures designed by Pier Luigi Nervi in one of his most iconic buildings: the Hall B of Torino Esposizioni. In order to investigate the properties of these inclined pillars, localizations of artificial sources (hammer impacts), by the triangulation procedure, were performed on three different inclined elements characterized by stiffness discrepancies due to different causes: the casting procedures, executed in different stages, and the enlargement of the hall happened a few years later the beginning of the construction. In the present work, the relationship between the velocity of AE signals and the elastic characteristics (principally elastic modulus, E) is evaluated in order to discriminate the stiffness level of the slanted pillars. The procedure presented made it possible to develop an innovative investigation method able to estimate, by means of AE, the state of conservation and the elastic properties and the damage level of the monitored concrete and reinforced concrete structures

Design of a modular exhibition structure with additive manufacturing of eco-sustainable materials

In this paper the mechanical characteristics of an innovative bioplastic material, the HBP - HempBioPlastic filament, is investigated. HBP was recently patented by an Italian company Kanésis that focused its activity on nature-derived materials. The filaments are the upshot of an original process allowing to reuse the surplus of the agricultural supply chains and transform it into new sustainable materials. At first, the 3D printed HBP samples were tested in tensile tests according to the ASTM- D638 standard and monitored in term of deformations by the Digital Image Correlation techniques (DIC) in order to evaluate the stress-strain behavior of different HBP textures under loading. In addition, using the HBP and the results coming from the experimental campaign, the design of an exhibition pavilion was proposed. The pavilion was modelled starting from the geometric construction of the fullerene. The supporting modular structure is combined by HBP modular elements, that can be produced by 3D printing or moulding. Finally, in order to demonstrate the feasibility of the proposed pavilion, a linear finite element analysis is presented on the base of the experimentally determined mechanical properties of HBP elements, under the effects of wind and seismic environmental actions

AE monitoring and structural modelization of the Asinelli Tower in Bologna

The Acoustic Emission (AE) technique was used to assess the structural stability of the Asinelli Tower, the tallest building in the city of Bologna, which, together with the nearby tower, named Garisenda, is the renowned symbol of the city. AE is a passive, non-destructive structural evaluation technique based on the spontaneous emission of pressure waves by evolving fracture processes. The monitoring program was carried out with the aid of a USAM tool, which is part of the equipment used at the Fracture Mechanics Laboratory of the Department of Structural Engineering at the Politecnico di Torino. This tool makes it possible to conduct a complete analysis of AE signals, acquire a huge quantity of data from on site monitoring, and identify the microcracks triggering the damage processes in a structure. In the second part of the paper, the results from a preliminary linear analysis are presented, in order to assess the structural behavior of the tower. The cracking and crushing strengths of the masonry have both been compared with the calculated stresses. The numerical analysis gives a valuable picture of the modal response of the tower, providing useful hints for the prosecution of structural monitorin

Acoustic Emission Monitoring of the Turin Cathedral Bell Tower: Foreshock and Aftershock Discrimination

Historical churches, tall ancient masonry buildings, and bell towers are structures subjected to high risks due to their age, elevation, and small base-area-to-height ratio. In this paper, the results of an innovative monitoring technique for structural integrity assessment applied to a historical bell tower are reported. The emblematic case study of the monitoring of the Turin Cathedral bell tower (northwest Italy) is herein presented. First of all, the damage evolution in a portion of the structure localized in the lower levels of the tall masonry building is described by the evaluation of the cumulative number of acoustic emissions (AEs) and by different parameters able to predict the time dependence of the damage development, in addition to the 3D localization of the AE sources. The b-value analysis shows a decreasing trend down to values compatible with the growth of localized micro and macro-cracks in the portion of the structure close to the base of the tower. These results seem to be in good agreement with the static and dynamic analysis performed numerically by an accurate FEM (finite element model). Similar results were also obtained during the application of the AE monitoring to the wooden frame sustaining the bells in the tower cell. Finally, a statistical analysis based on the average values of the b-value are carried out at the scale of the monument and at the seismic regional scale. In particular, according to recent studies, a comparison between the b-value obtained by AE signal analysis and the regional activity is proposed in order to correlate the AE detected on the structure to the seismic activity, discriminating foreshock, and aftershock intervals in the analyzed time series

Acoustic emission wireless monitoring of structures and infrastructure

The damage assessment of buildings is currently made visually. The few non-visual methodologies make use of wired devices, which are expensive, vulnerable, and time consuming to install. Systems based on wireless transmission should be cost efficient, easy to install, and adaptive to different types of structures and infrastructures. The Acoustic Emission (AE) technique is an innovative monitoring method useful to investigate the damage in large structures. It has the potential to detect damage, as well as to evaluate the evolution and the position of cracks. This paper shows the capability of a new data processing system based on a wireless AE equipment, very useful to long term monitoring of concrete and masonry structures. To this purpose, computer-based procedures, including an improved AE source location based on the Akaike algorithm, are implemented. These procedures are performed by automatic AE data processing and are used to evaluate the AE results in notched concrete beams subjected to three point bending loading conditions up to the final failure. In this case, the final output of the code returns a complete description of damage pattern and evolution of the monitored structure. In the most critical cases, or in some cases requiring long in situ observation periods, the AE monitoring method is fine tuned for a telematic procedure of processing AE data clouds to increase the safety of structures and infrastructural networks. Finally, the proposed AE monitoring system could be used to determine the seismic risk of civil constructions and monuments subjected to earthquakes

Shell and spatial structures: Between new developments and historical aspects

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