Comparative study of the different models for the calculation of BLEVEs overpressure effects

The BLEVE, acronym for Boiling Liquid Expanding Vapour Explosion, is one of the most dangerous accidents that can occur in pressure vessels. It can be defined as an explosion resulting from the failure of a vessel containing a pressure liquefied gas stored at a temperature significantly above its boiling point at atmospheric pressure. This phenomenon frequently appears when a vessel is engulfed by a fire: the heat causes the internal pressure to raise and the mechanical proprieties of the wall to decrease, with the consequent rupture of the tank and the instantaneous release of its whole content. After the breakage, the vapour outflows and expands and the liquid phase starts boiling due to the pressure drop. The formation and propagation of a distructive schock wave may occur, together with the ejection of fragments, the generation of a fireball if the stored fluid is flammable and immediately ignited or the atmospheric dispersion of a toxic cloud if the fluid contained inside the vessel is toxic. Despite the presence of many studies on the BLEVE mechanism, the exact causes and conditions of its occurrence are still elusive. In order to better understand this phenomenon, in the present study first of all the concept and definition of BLEVE are investigated. A historical analysis of the major events that have occurred over the past 60 years is described. A research of the principal causes of this event, including the analysis of the substances most frequently involved, is presented too. Afterwards a description of the main effects of BLEVEs is reported, focusing especially on the overpressure. Though the major aim of the present thesis is to contribute, with a comparative analysis, to the validation of the main models present in the literature for the calculation and prediction of the overpressure caused by BLEVEs. In line with this purpose, after a short overview of the available approaches, their ability to reproduce the trend of the overpressure is investigated. The overpressure calculated with the different models is compared with values deriving from events happened in the past and ad-hoc experiments, focusing the attention especially on medium and large scale phenomena. The ability of the models to consider different filling levels of the reservoir and different substances is analyzed too. The results of these calculations are extensively discussed. Finally some conclusive remarks are reported.

Experimental analysis of fiber reinforced cementitious matrix (FRCM) confined masonry columns

The increasing use of Fiber Reinforced methods for strengthening existing brick masonry walls and columns, especially for the rehabilitation of historical buildings, has generated considerable research interest in understanding the failure mechanism in such systems. This dissertation is aimed to provide a basic understanding of the behavior of solid brick masonry walls unwrapped and wrapped with Fiber Reinforced Cementitious Matrix Composites. This is a new type of composite material, commonly known as FRCM, featuring a cementitious inorganic matrix (binder) instead of the more common epoxy one. The influence of the FRCM-reinforcement on the load-carrying capacity and strain distribution during compression test will be investigated using a full-field optical technique known as Digital Image Correlation. Compression test were carried on 6 clay bricks columns and on 7 clay brick walls in three different configuration, casted using bricks scaled respect the first one with a ratio 1:2, in order to determinate the effects of FRCM reinforcement. The goal of the experimental program is to understand how the behavior of brick masonry will be improved by the FRCM-wrapping. The results indicate that there is an arching action zone represented in the form of a parabola with a varying shape according to the used configuration. The area under the parabolas is considered as ineffectively confined. The effectively confined area is assumed to occur within the region where the arching action had been fully developed.

Assessing the effectiveness of ISO 3382 for evaluating the acoustical quality of italian historical theatres: the case study of the Bonci Theatre

The present study concerns the acoustical characterisation of Italian historical theatres. It moved from the ISO 3382 which provides the guidelines for the measurement of a well established set of room acoustic parameters inside performance spaces. Nevertheless, the peculiarity of Italian historical theatres needs a more specific approach. The Charter of Ferrara goes in this direction, aiming at qualifying the sound field in this kind of halls and the present work pursues the way forward. Trying to understand how the acoustical qualification should be done, the Bonci Theatre in Cesena has been taken as a case study. In September 2012 acoustical measurements were carried out in the theatre, recording monaural e binaural impulse responses at each seat in the hall. The values of the time criteria, energy criteria and psycho-acoustical and spatial criteria have been extracted according to ISO 3382. Statistics were performed and a 3D model of the theatre was realised and tuned. Statistical investigations were carried out on the whole set of measurement positions and on carefully chosen reduced subsets; it turned out that these subsets are representative only of the “average” acoustics of the hall. Normality tests were carried out to verify whether EDT, T30 and C80 could be described with some degree of reliability with a theoretical distribution. Different results, according to the varying assumptions underlying each test, were found. Finally, an attempt was made to correlate the numerical results emerged from the statistical analysis to the perceptual sphere. Looking for “acoustical equivalent areas”, relative difference limens were considered as threshold values. No rule of thumb emerged. Finally, the significance of the usual representation through mean values and standard deviation, which may be meaningful for normal distributed data, was investigated.

Molecular phylogeny and historical zoogeography of four genera of Eastern Atlantic skates (Rajiformes, Rajidae)

The aim of this study was to reconstruct a solid phylogeny of four genera of the Rajidae family (Chondrichthyans: Batoidea) using a concatenated alignment of mtDNA genes. Then use the resultant tree to estimate divergence time between taxa based on molecular clock and fossil calibration and conduct biogeographic analysis. The intent was to prove that the actual distribution of species of Eastern Atlantic and Mediterranean skates is due to a series of vicariant events. The species considered belongs to two different tribe: Rajini (Raja and Dipturus) and Amblyrajini (Leucoraja and Rajella). The choice of this genera is due to their high presence in the area of interest and to the richness of endemic species. The results show that despite the ancient origin of Rajidae (97 MYA), the Eastern Atlantic and Mediterranean faunas originated more recently, during Middle Miocene-Late Pliocene, after the closure of connection between these areas and the Indo-Pacific ocean (15 MYA). The endemic species of the Mediterranean (Raja asterias, R. radula, R. polystigma and Leucoraja melitensis) originated after the Messinian salinity crisis (7-5 MYA), when the recolonization of the basin occurred, and are still maintained in allopatric distribution by the presence of biogeographic barriers. Moreover from 4 to 2.6 MYA we can observe the formation of sister species for Raja, Leucoraja and Rajella, one of which has a Northern distribution, and the other has a Southern distribution (R. clavata vs R. straeleni, L. wallacei vs L. naevus, R. fyllae vs R. caudaspinosa and R. kukujevi vs R. leopardus + R. barnardi). The Quaternary and present oceanographic discontinuities that occur along the western African continental shelf (e.g., Cape Blanc and the Angola–Benguela Front) might contribute to the maintenance of low or null levels of gene flow between these closely related siblings species. Also sympatric speciation must be invoked to explain the evolution of skates, for example for the division between R. leopardus and R. barnardi. The speciation processes followed a south-to-north pathways for Dipturus and a north-to-south pathways for Raja, Leucoraja and Rajella underling that the evolution of the genera occurred independently. In the end, it is conceivable that the evolutionary pathways of the tribes followed the costal line during the gondwana fragmentation. The results demonstrate that the evolution of this family is characterized by a series of parallel and independent speciation events, strictly correlated to the tectonic movement of continental masses and paleogeographic and paleoclimatic events and so can be explained by a panbiogeographical (vicariance) model.

Climatological analysis of temperature and salinity fields in the Mediterranean sea

A climatological field is a mean gridded field that represents the monthly or seasonal trend of an ocean parameter. This instrument allows to understand the physical conditions and physical processes of the ocean water and their impact on the world climate. To construct a climatological field, it is necessary to perform a climatological analysis on an historical dataset. In this dissertation, we have constructed the temperature and salinity fields on the Mediterranean Sea using the SeaDataNet 2 dataset. The dataset contains about 140000 CTD, bottles, XBT and MBT profiles, covering the period from 1900 to 2013. The temperature and salinity climatological fields are produced by the DIVA software using a Variational Inverse Method and a Finite Element numerical technique to interpolate data on a regular grid. Our results are also compared with a previous version of climatological fields and the goodness of our climatologies is assessed, according to the goodness criteria suggested by Murphy (1993). Finally the temperature and salinity seasonal cycle for the Mediterranean Sea is described.

Shyam Selvadurai's Funny Boy: a critical analysis

In this work, I will try to provide an insightful and accessible analysis of Funny Boy, a coming-of-age novel by Sri Lankan Canadian author Shyam Selvadurai. I will provide a brief biography of the author and a concise outline of the historical context. Subsequently, after discussing the novel's structure and its main characteristics, I will proceed to analyze the significance of the novel's title and the role played by ethnicity and sexuality as equivalent sources of alienation, both individually and through their combined agency. To that end, I will focus on what I consider to be the most salient episodes of the novel that, in my opinion, best exemplify the sense of alienation that any individual belonging to a minority group experiences at some point in their lives in mainstream society.

The influence of infill walls on seismic behavior of a historical building in Shanghai

Seismic assessment and seismic strengthening are the key issues need to be figured out during the process of protection and reusing of historical buildings. In this thesis the seismic behaviors of the hinged steel structure, a typical structure of historical buildings, i.e. hinged steel frames in Shanghai, China, were studied based on experimental investigations and theoretic analysis. How the non-structural members worked with the steel frames was analyzed thoroughly. Firstly, two 1/4 scale hinged steel frames were constructed based on the structural system of Bund 18, a historical building in Shanghai: M1 model without infill walls, M2 model with infill walls, and tested under the horizontal cyclic loads to investigate their seismic behavior. The Shaking Table Test and its results indicated that the seismic behavior of the hinged steel frames could be improved significantly with the help of non-structural members, i.e., surrounding elements outside the hinged steel frames and infilled walls. To specify, the columns are covered with bricks, they consist of I shape formed steel sections and steel plates, which are clenched together. The steel beams are connected to the steel column by steel angle, thus the structure should be considered as a hinged frame. And the infilled wall acted as a compression diagonal strut to withstand the horizontal load, therefore, the seismic capacity and stiffness of the hinged steel frames with infilled walls could be estimated by using the equivalent compression diagonal strut model. A SAP model has been constructed with the objective to perform a dynamic nonlinear analysis. The obtained results were compared with the results obtained from Shaking Table Test. The Test Results have validated that the influence of infill walls on seismic behavior can be estimated by using the equivalent diagonal strut model.