Application of FMEA method for assessment of reliability of structures

In the last years several methods have been proposed, aimed to explore the theme of degradation and reliability of building components, with the main purpose of preventing performance deficits in general, and especially from sudden and unforeseen faults. This topic is an element of strong competitiveness in the world of professionals and business, and fits with the trend clearly demonstrated by the regulatory framework, particularly in the field of structures. One of the methods that can be used to assess the suitability of a component to its performance specifications, and which belongs to the field of Risk Management, is FMEA, (Failure Modes and Effects Analysis). This methodology analyzes a project from the point of view of its reliability before it is carried out and realized.To allow this verification the components are firstly verified in the form of drawings, technical specifications, flow-charts, information, standards, etc. that are all the elements that make up the documentation of the work to be performed and the knowledge that is available on the subject. There have been many applications of FMEA on building components, and it is of particular interest - considering the recrudescence of seismic events of the last decade, but also the emergence of structural defects, even of a certain gravity – for the use in the field of structures. This is of a considerable relevance in a period when there are issues about the possibility of adaptation of the real estate to earthquakes, but it also raises the argument of the modalities and the criteria leading the inevitable reconstruction of what no longer exists. In this article an example of application to a reinforced concrete structure is shown, from which it is possible to notice the most critical items and the modalities for preventing negative events

Performance characterization of the concrete subjected to fire in terms of sustainability

The research, in a context of a sustainability of the building process, that should consider adequately the problem of building waste disposal, has the objective of determining the performance characteristics of concrete under the effect of fire, in order to evaluate the possibility of reutilization, and in positive case, what could the best uses be, considering the current regulations. The experimentation, carried out on cubic samples with a side of 15 cm (according to UNI EN 12390, using aggregates with Dmax= 30 mm), with Portland cement of mixture 42,5 in two types (one with Pozzolana CEM II/B-P 42.5 and one with limestone CEM II/A-LL 42.5), with class of resistance C25/30, is based on the following parameters: increase of temperature, nature of fire, heating speed, time of exposition. The tests that have been carried out were both destructive (sclerometric, ultrasounds, Sonreb) and non-destructive (crushing and thermogravimetric), and the experimental results obtained also show that: - the concretes present a remaining mechanical resistance that is lower than 50% of the initial one, after they have been subjected to the full cycle of temperature increase; - between 200°C and 600°C, there is a significant decomposition of the binding component (hydrated cement), while that of limestone is predictable for temperatures higher than 700°C; - the phenomenon of the “explosive spalling” – verified on two samples – has far more devastating consequences than the simple decay of the mechanical characteristics as, considered in a structural element, it causes a reduction of the resisting section, with a consequential increase of tensions in the remaining part, and direct exposition of the reinforcement without protection, situations which can cause the structural collapse of the element. Some uses in the field of transport have been hypothesized, also basing on the indications of the current regulations and on the detected statistics of the current uses

Safety assessment of scenarios triggered by accidental seawater immersion of lithium batteries in innovative naval applications

The request of lithium-ion batteries in naval applications features an increasing trend due to the need of high performance energy storage devices. Beside the hazard of runaway when the battery is crushed or overcharged, the naval environment poses additional safety issues due to the possible immersion with seawater of the battery room following accidental flooding. In such a case, seawater electrolysis may generate hydrogen and chlorine, thus giving rise to an explosive and toxic mixture in a confined environment. In this study, a quantitative safety assessment of the possible accidental scenarios induced by seawater electrolysis in battery rooms is performed. The analysis is based on i) the deterministic evaluation of the hazardous gases development according to a three-dimensional physically-based electrochemical model and ii) the discussion of possible prevention and mitigation measures. The dynamics of gas release and the time required to produce an explosive atmosphere are evaluated as a function of the level of seawater for a reference case study. The outcomes of the study support the safety assessment of accidental scenarios induced by seawater electrolysis in naval applications and provide indications on the effectiveness of hazard reduction measures. More specifically, the study reveals that a proper electric insulation of the surface of battery terminals represents a sensible mitigation strategy to reduce the severity of explosions in addition to the ventilation of the battery room

MULTICRITERIA ANALYSIS FOR CHOOSING MAINTENANCE STRATEGIES

The life cycle of building components can be managed according to different maintenance strategies, which mainly differ in performance and economic terms. What is the most convenient among the possible scenarios? It has been shown in the past that the typology of maintenance interventions and the consequent periodicity are closely related to performance decay, and can lead to choices that, however, generally concern the purely economic sphere. In this sense, it seems interesting to know the modalities of the performance decay, which may allow – even though for many components the "measurement" of its values is problematic - the construction of performance / time curves. This result was possible, in other experiments conducted in the past, for one of the components to be considered most critical for the whole building (the plaster), thanks to a study that sampled 53 buildings with homogeneous characteristics (both from the technological point of view and from the era of realization), observed within 20 years. This paper highlights that the only economic evaluation is not enough to identify the ideal solution, because – inter alia - there is a more suitable solution depending on the context framework in which the decision maker is operating. Commitment, budget, component typology, time span to consider, are the main factors influencing the choice, not ignoring design issues. A Topsis multicriteria analysis is proposed, the results of which are an interesting starting point for define maintenance plans characterized by greater reliability, not only technical but also economical

LCC analysis for glued laminated timber components exposed in external

The aim of the experimentation is to characterize the performances of glued laminated timber components exposed to atmospheric agents, in the light of the concept of Life Cycle Cost, particularly emphasized in the Italian new legislation on public works. In fact, it could be seen that the design of the construction details and the initial characteristics of glue laminated timber components, require a particular attention to avoid errors that may undermine the possibility to perform the structural functions for which, above all, this material it is dedicated. The experimentation consisted of a series of tests aimed to identify the performance of glued laminated timber beams taken in site, after a work executed some years ago on a theatre built in Roman era, and to compare them with similarly manufactured new elements. The tests performed were thermography, ultrasound, Wood-Pecker penetrometer, mechanical characterization. The results will be used to begin setting limits and conditions for outdoor use of glue laminated timber, and assume a reliable life cycle, and consequently identify the most appropriate maintenance strategy for the LCC

Drying Techniques and Storage: Do They Affect the Nutritional Value of Bee-Collected Pollen?

In this study, the effect of different drying processes (freeze-drying (FD), microwave-assisted drying (MWD) and classic hot air drying (HAD)) on the polyphenols, flavonoids, and amino acids content was investigated on bee-collected chestnut, willow and ivy pollen for human consumption. Furthermore, the pollen chemical properties were monitored after three and six months of storage, and then analyzed using a multivariate approach. Chestnut pollen was the richest source of polyphenols, flavonoids, and rutin, while ivy pollen contained the highest amount of total and free amino acids, and total and free proline. Drying and storage affected pollen chemical composition with species-dependent effects. MWD allowed the best retention of flavonoids in chestnut pollen for up to six months of storage. All drying techniques led to a depletion of flavonoids in willow pollen; however, MWD ensured the highest flavonoids content after six months. FD and MWD did not lead to flavonoids depletion in ivy pollen during storage. Additionally, storage did not affect the rutin content, which was highest in FD willow samples after six months. Notably, both FD and MWD techniques are efficient in preserving amino acids-related quality of bee pollen up to six months of storage

Physically-based deconvolution of impedance spectra for LSCF-based SOFC

A physically-based model for the interpretation of the impedance spectra of an anode-supported LSCF/GDC/YSZ/Ni:YSZ solid oxide fuel cell is presented in this work. The model locally describes transport and reaction phenomena within the cell components through mass conservation equations. The microstructural properties of the electrodes are predicted through numerical three-dimensional reconstruction of the microstructure, with input parameters obtained from the analysis of SEM pictures of each layer. Simulations show that the model reproduces impedance spectra obtained in different operating conditions with the same set of fitting parameters, comprising material-specific kinetic constants and electrochemical capacitances, which fairly agree with independent literature data and a previous analysis of the spectra through DRT. The model allows for the deconvolution and quantification of the characteristic resistance and frequency of the different physical processes that build up the impedance of the cell. In particular, 7 processes are identified: charge-transfer reactions between LSCF/GDC, GDC/YSZ and Ni/YSZ interfaces appear in the high-frequency range, the medium-frequency feature is due the oxygen reduction reaction and the gas diffusion in the anode, while the low-frequency arc is mainly due to the gas conversion in the anodic channel. An additional low frequency contribution (< 1Hz), not considered in the model, is observed and tentatively attributed to the adsorption of oxygen onto the LSCF surface. Simulation results suggest that more efforts must be dedicated to characterize and improve the oxygen transfer at the LSCF/GDC and GDC/YSZ interfaces. The study shows that a quantitative interpretation of impedance spectra is possible with a reduced number of fitting parameters when a physically-based approach is adopted, making the model an attractive tool for diagnostic purposes

Honeybee-collected pollen for human consumption: impact of post-harvest conditioning on the microbiota

Bee pollen is gaining attention as functional food for human consumption. However, scanty information is available on the effects of post-harvest conditioning methods on microbial populations associated to bee pollen. Here, we assessed the microbiological quality and safety of bee-collected chestnut and willow pollen processed by different treatments, such as conventional, freeze- and microwave-assisted drying. Conventional drying of chestnut pollen significantly reduced the abundance of aerobic mesophilic bacteria and the contamination by enterobacteria and yeasts. No impact of freeze-drying and microwave-assisted conditioning was found on hygiene indicators. In chestnut pollen, microwave-assisted drying effectively reduced aerobic sporeforming bacteria, while all conditioning treatments strongly decreased coagulase-positive staphylococci. None of the conditioning methods allowed the reduction of moulds contamination and the abundance of sulphite-reducing clostridia. Our findings stress the importance of studying the microbiota of bee-collected pollen for human consumption, in order to process safe pollen with high microbiological quality

Impacto ambiental da cultura do arroz irrigado com uso de índice de qualidade de água (IQA).

O presente trabalho tem por objetivo avaliar o possível impacto da cultura do arroz irrigado sobre a qualidade das águas do Rio Camboriú (Camboriú/SC), através do estabelecimento de um índice de qualidade de água.bitstream/CNPMA/5829/1/comunicado_08.pd