Seismic vulnerability of historical structures with the discrete element method

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.Includes bibliographical references (p. 333-345).It is widely recognized that historical structures represent a cultural heritage which should be preserved and transmitted to future generations. In several countries, and particularly, in the Mediterranean area, where a large number of important monuments are exposed to seismic hazard, there is a growing interest for the problem of strengthening such structures in order to reduce their seismic vulnerability, while preserving their original architectural integrity. However the seismic vulnerability assessment of historical block structures is still a challenging task. In this work, after having explored the potentials and limitations of the Discrete Element Method for this type of problem, a new joint model for the quasistatic analysis of block structures is proposed. It accounts for (a) the non coplanarity of the contact surfaces, and (b) friction softening. The new model allowed a more accurate prediction of the inplane failure load and corresponding failure mechanism of opus quadratum walls (walls made of regular squared blocks without mortar). In particular it predicts the development of progressive internal displacements, and the formation of localized sliding band as observed in the experimental models. Such results confirm that even apparently negligible joint imperfections should not be ignored since they may cause significant modifications in the response of a block structure subjected to gravity and lateral loading.by Tommaso Pagnoni.Ph.D

Modeling Early Phases of COVID-19 Pandemic in Northern Italy and Its Implication for Outbreak Diffusion

The COVID-19 pandemic has sparked an intense debate about the hidden factors underlying the dynamics of the outbreak. Several computational models have been proposed to inform effective social and healthcare strategies. Crucially, the predictive validity of these models often depends upon incorporating behavioral and social responses to infection. Among these tools, the analytic framework known as “dynamic causal modeling” (DCM) has been applied to the COVID-19 pandemic, shedding new light on the factors underlying the dynamics of the outbreak. We have applied DCM to data from northern Italian regions, the first areas in Europe to contend with the outbreak, and analyzed the predictive validity of the model and also its suitability in highlighting the hidden factors governing the pandemic diffusion. By taking into account data from the beginning of the pandemic, the model could faithfully predict the dynamics of outbreak diffusion varying from region to region. The DCM appears to be a reliable tool to investigate the mechanisms governing the spread of the SARS-CoV-2 to identify the containment and control strategies that could efficiently be used to counteract further waves of infection

A GENERAL MODEL OF RESISTANCE PARTIAL FACTORS FOR SEISMIC ASSESSMENT AND RETROFIT

This paper presents a general model for computing partial factors on the resistance or capacity-side, to be used in codified limit-state design, accounting for epistemic uncertainty in the resistance model, aleatoric uncertainty on variables input to the model, statistical uncertainty on these variables stemming from limited available data, and target safety. The choice of resistance-side factors cannot be made independently of the demand-side ones, if a target safety is aimed at. The issue is only briefly discussed herein and derivations are carried out independently for the sake of illustration. The partial factor values can be obtained to replicate pre-existing (implicit, uncontrolled) safety from a former code, or to obtain a new consistent safety level, as desired. The format has been proposed in the framework of the ongoing Eurocodes’ revision work and the discussion makes reference to Part 3 of Eurocode 8, which deals with seismic assessment and retrofit of existing structures

Reliability of components and complex subsystems, Assessing the

"Progress report for: Rockwell International Corporation."Includes bibliographical referencesProgress repor

Determination of metals in species of commercial interest from marine wetlands, coastal and offshore areas influenced by Po River outflows

The impact of heavy metal pollution on estuaries and coastal environments is a matter of major concern worldwide because of their persistency and tendency to bioaccumulate in the aquatic ecosystems, in addition to their toxicity [1]. These elements can derive from natural sources, influenced by bedrock geology of the drainage catchment and by weathering. However, along the Italian Northern Adriatic coast, anthropogenic pressure, in particular agriculture, industrial and municipal discharges, significantly increased the naturally occurring amounts of metals in the aquatic environment [2]. At the same time, Po delta and neighboring areas are traditionally exploited for fishery and mollusks farming, providing many species commonly used in Italian diet. In this context, the aim of this study is to evaluate the concentration of several metals (Hg, As, Cd, V, Cr, Mn, Fe, Ni, Cu, Zn, Ba, Pb) in five marine species of commercial interest collected in different environments influenced by Po River outflow. Farmed mollusks come from both wetland (Tapes philippinarum) and coastal areas (Chamelea gallina), while native mussels (Mytilus galloprovincialis) and fish species (Solea solea and Squalus acanthias) were caught offshore. All species were sampled twice between 2018 and 2019. Furthermore, the metal content was measured also in surface sediments, to assess the environmental contamination of farming and capture areas. The analytical determination was carried out by different atomic spectroscopy techniques, which were selected based on their analytical figure of merit. In detail, graphite furnace atomic absorption, cold vapor atomic absorption spectrometry (mercury analyzer), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectrometry (ICP-MS) were employed. Certified Reference Materials (CRMs) were employed for quality control purposes. The results highlighted a correlation between the environmental state of the sites and metals content in the selected samples. The metals distribution in sediments were compared with the lithogenic composition, to attempt to discriminate between natural and anthropic input sources. In addition, the concentrations found in the selected marine species were correlated with those in surface sediments, thus confirming the tendency to bioaccumulate of heavy metals. Finally, contamination levels of hazardous metals in sediments and biota were compared with Environmental Quality Standard (EQS) and threshold levels (TL) for human health

Genome-Wide DNA Methylation Analysis of a Cohort of 41 Patients Affected by Oculo-Auriculo-Vertebral Spectrum (OAVS)

Oculo-auriculo-vertebral-spectrum (OAVS; OMIM 164210) is a rare disorder originating from abnormal development of the first and second branchial arch. The clinical phenotype is extremely heterogeneous with ear anomalies, hemifacial microsomia, ocular defects, and vertebral malformations being the main features. MYT1, AMIGO2, and ZYG11B gene variants were reported in a few OAVS patients, but the etiology remains largely unknown. A multifactorial origin has been proposed, including the involvement of environmental and epigenetic mechanisms. To identify the epigenetic mechanisms contributing to OAVS, we evaluated the DNA-methylation profiles of 41 OAVS unrelated affected individuals by using a genome-wide microarray-based methylation approach. The analysis was first carried out comparing OAVS patients with controls at the group level. It revealed a moderate epigenetic variation in a large number of genes implicated in basic chromatin dynamics such as DNA packaging and protein-DNA organization. The alternative analysis in individual profiles based on the searching for Stochastic Epigenetic Variants (SEV) identified an increased number of SEVs in OAVS patients compared to controls. Although no recurrent deregulated enriched regions were found, isolated patients harboring suggestive epigenetic deregulations were identified. The recognition of a different DNA methylation pattern in the OAVS cohort and the identification of isolated patients with suggestive epigenetic variations provide consistent evidence for the contribution of epigenetic mechanisms to the etiology of this complex and heterogeneous disorder