An acoustic emission approach to the structural health monitoring of historical metallic tie-rods

The application of Non-Destructive Testing and Structural Health Monitoring systems in historical buildings is of great interest due to the need to guarantee safety and conservation. The present memory focuses on the case study of the historical wrought iron tie-rods of Duomo di Milano, Italy. In recent years, two of these elements presented critical failures. Consequently, a monitoring methodology based on acoustic emission was defined. First, the fracture toughness of wrought iron was characterized by employing standard small-scale specimens taken from one of the failed tie-rods. Meanwhile, acoustic emission was acquired to define a methodology for detecting and localizing the damage events, separating those due to background noise by applying suitable pattern recognition algorithms. Subsequently, a tensile test was performed on a full-scale section of the same tie-rod. Before and after the test, phased-array ultrasonic testing and magnetic particle inspections were carried out to identify and map defects and their possible development due to load application. Finally, it was possible to conclude that magnetic inspections allow identifying the presence of surface defects effectively, phased-array testing estimates the geometry of the defect accurately, and acoustic emission is a promising technique for monitoring the structural integrity of historical metallic tie-rods

Correction to: Fire spalling sensitivity of high-performance concrete in heated slabs under biaxial compressive loading

The article ''Fire spalling sensitivity of high-performance concrete in heated slabs under biaxial compressive loading'', written by "Francesco Lo Monte, Roberto Felicetti, Chiara Rossino", was originally published electronically on the publisher's Internet portal (currently SpringerLink) on 25 January 2019 without open access

A Cloud-Native Web Application for Assisted Metadata Generation and Retrieval: THESPIAN-NER

Within the context of the Competence Centre for the Conservation of Cultural Heritage (4CH) project, the design and deployment of a platform-as-a-service cloud infrastructure for the first European competence centre of cultural heritage (CH) has begun, and some web services have been integrated into the platform. The first integrated service is the INFN-CHNet web application for FAIR storage of scientific analysis on CH: THESPIAN-Mask. It is based on CIDOC-CRM-compatible ontology and CRMhs, describing the scientific metadata. To ease the process of metadata generation and data injection, another web service has been developed: THESPIAN-NER. It is a tool based on a deep neural network for named entity recognition (NER), enabling users to upload their Italian-written report files and obtain labelled entities. Those entities are used as keywords either to serve as (semi)automatically custom queries for the database, or to fill (part of) the metadata form as a descriptor for the file to be uploaded. The services have been made freely available in the 4CH PaaS cloud platform

Experimental Study on the Explosive Spalling in High-Performance Concrete: Role of Aggregate and Fiber Types

A complete description of the mechanical behavior of High-Performance Concrete in fire still requires further efforts to fully understand the tricky phenomenon of spalling, whose complexity comes from the interaction among different phenomena, namely: the microstructural changes occurring in concrete at high temperature, the pressure rising in the pores, and the stress induced by both thermal gradients and external loads. To what extent these different aspects influence each other is still not completely clear, and within this context a comprehensive experimental campaign has been launched at the Politecnico di Milano, focusing on the role played by concrete grade, aggregate type, and fiber type and content. Eleven concrete mixes are investigated considering three grades (fc ≥ 40, 60 and 90 MPa), three aggregate types (silico-calcareous, basalt and calcareous aggregates) and different fiber types and contents (steel and monofilament or fibrillated polypropylene fibers)

Cortical facilitation of tactile afferents during the preparation of a body weight transfer when standing on a biomimetic surface

Self-generated movement shapes tactile perception, but few studies have investigated the brain mechanisms involved in the processing of the mechanical signals related to the static and transient skin deformations generated by forces and pressures exerted between the foot skin and the standing surface. We recently found that standing on a biomimetic surface (i.e., inspired by the characteristics of mechanoreceptors and skin dermatoglyphics), that magnified skin–surface interaction, increased the sensory flow to the somatosensory cortex and improved balance control compared to standing on control (e.g., smooth) surfaces. In this study, we tested whether the well-known sensory suppression that occurs during movements is alleviated when the tactile afferent signal becomes relevant with the use of a biomimetic surface. Eyes-closed participants (n = 25) self-stimulated their foot cutaneous receptors by shifting their body weight toward one of their legs while standing on either a biomimetic or a control (smooth) surface. In a control task, similar forces were exerted on the surfaces (i.e., similar skin–surface interaction) by passive translations of the surfaces. Sensory gating was assessed by measuring the amplitude of the somatosensory-evoked potential over the vertex (SEP, recorded by EEG). Significantly larger and shorter SEPs were found when participants stood on the biomimetic surface. This was observed whether the forces exerted on the surface were self-generated or passively generated. Contrary to our prediction, we found that the sensory attenuation related to the self-generated movement did not significantly differ between the biomimetic and control surfaces. However, we observed an increase in gamma activity (30–50 Hz) over centroparietal regions during the preparation phase of the weight shift only when participants stood on the biomimetic surface. This result might suggest that gamma-band oscillations play an important functional role in processing behaviorally relevant stimuli during the early stages of body weight transfer

Sailing with solar and planetary radiation pressure

Literature on solar sailing has thus far mostly considered solar radiation pressure (SRP) as the only contribution to sail force. However, considering a sail in a planetary mission scenario, a new contribution can be added. Since the planet itself emits radiation, this generates a radial planetary radiation pressure (PRP) that is also exerted on the sail. Hence, this work studies the combined effects of both SRP and PRP on a sail for two case studies, i.e. Earth and Venus. In proximity of the Earth, the effect of PRP can be significant under specific conditions. Around Venus, instead, PRP is by far the dominating contribution. These combined effects have been studied for single- and double-sided reflective coating and including eclipse. Results show potential increase in the net acceleration and a change in the optimal attitude to maximise the acceleration in a given direction. Moreover, an increasing semi-major axis manoeuvre is shown with and without PRP, to quantify the difference on a real-case scenario

Sailing with solar and planetary radiation pressure

Literature on solar sailing has thus far mostly considered solar radiation pressure (SRP) as the only contribution to sail force. However, considering a sail in a planetary mission scenario, a new contribution can be added. Since the planet itself emits radiation, this generates a radial planetary radiation pressure (PRP) that is also exerted on the sail. Hence, this work studies the combined effects of both SRP and PRP on a sail for two case studies, i.e. Earth and Venus. In proximity of the Earth, the effect of PRP can be significant under specific conditions. Around Venus, instead, PRP is by far the dominating contribution. These combined effects have been studied for single- and double-sided reflective coating and including eclipse. Results show potential increase in the net acceleration and a change in the optimal attitude to maximise the acceleration in a given direction. Moreover, an increasing semi-major axis manoeuvre is shown with and without PRP, to quantify the difference on a real-case scenario