Structural Analysis of Steel Structures under Fire Loading

This paper focuses on the structural analysis of a steel structure under fire loading. In this framework, the objective is to highlight the importance of the right choice of analyses to develop, and of the finite element codes able to model the resistance and stiffness reduction due to the temperature increase. In addition, the evaluation of the structural collapse under fire load of a real building is considered, paying attention to the global behavior of the structure itself.

Improving the safety of steel bridges through more accurate and affordable modeling of connections

This thesis develops an improved and affordable method to model the connections of steel truss bridges with a view of improving their design, analysis and safety. The issue came to the fore when the I35-W Bridge in Minnesota collapsed on August1, 2007 [NTSB, 2008]. After many Finite Element Analyses, the National Transportation Safety Board (NTSB) found the buckling of an under-designed gusset plate to be the main cause of the disaster. After this tragedy, the Federal Highway Administration (FHWA) focused its attention on all the 465 steel deck truss bridges present in the National Bridge Inventory [NTSB, 2008], and provided guidelines to bridge owners to verify the safety of these kind of bridges. The present work focuses on the means to assess the structural safety for these particular types of steel truss bridges, and proposes a method for the correct and efficient modeling of the connections. It starts with the basic question: “how safe is it to consider all the connections in these types of bridges as rigid joints?” The work is organized in three parts: • the first gives an overview of the problem of the structural safety of complex structure such as bridges, and proposes the use of the sub-structuring method, [Przemieniecki, 1968], [Bontempi and Arangio, 2008]; • the second part reviews the relevant literature, standards and codes. Both the Eurocodes and the American codes are missing a way to assess the stiffness and strength of gusset plate connections. This work aims at filling the gap between advanced computing methods that can be brought to bear on a failure investigation, and the rigid connections, linear beam analysis typical of routine design, [AASHTO, 1994], [Astaneh, 2010], [Ballio and Mazzolani, 2005], [Crosti and Duthinh, 2010], [Chambers and Ernst, 2005], [EN 1993-1-8, 2003]; • in the third part, the proposed method is applied to the I-35W Bridge. The I-35W is classified as a Fracture Critical Truss Bridge, meaning that the failure of one major element would cause the collapse of the whole structure. The method makes use of the detailed finite element models of the NTSB and FHWA to find the strength and stiffness of the joint in question and replace it with five spring elements. The method provides accuracy and substantial computational savings for repeated load cases, particularly if many joints in the structure are similar, [NTSB, 2008], [FHWA, 2009]. The goal of the thesis then is to develop accurate but computationally affordable connection models to improve global analysis and thus allow bridge owners to predict the effects of joint deterioration, design deficiencies and to guide the requirements for structural monitoring.

We lack evidence to call Jatropha invasive

FLWNAinfo:eu-repo/semantics/publishe

L'investigazione antincendio sugli aspetti strutturali: una proposta di codifica

Lo scopo di questo articolo è quello di esporre una metodologia codificata di Structural Fire Investigation (Investigazione sugli aspetti strutturali in caso di incendio) atta ad individuare le cause scatenanti, pregresse e latenti, che hanno determinato l’evento accidentale. L’iter investigativo, associato a determinate operazioni strutturali e forensi che partono dalla raccolta delle informazioni iniziali al repertamento e controllo documentale per poi completarsi con le verifiche computazionali, sicuramente aiuta a determinare, in maniera rigorosa, le cause e l’origine di un incendio. La modellazione degli incendi con il software del NIST, Fire Dynamics Simulator (FDS) e l’analisi strutturale con vari codici di calcolo, permettono di verificare determinate ipotesi maturate durante il repertamento e di avvalorare scientificamente l’analisi semiotica rilevata sulla scena, fornendo dati forensi utili in fase dibattimentale. Quindi un’attività investigativa pianificata, permette a qualsiasi utente, (VV.F., personale delle Forze dell’Ordine, Consulente, Perito, CTU o Libero Professionista), di svolgere indagini in maniera appropriata secondo una linea guida che permette di non tralasciare controlli a volte rilevanti per la stesura della documentazione complessiva in forma di report finale

syphilitic chancres of the mouth three cases

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Modification of the 6-Hydroxydopamine Technique for the Correct Determination of Superoxide Dismutase

Heikkila & Cabbat (Anal. Biochem. 75, 356-362 (1976)) have proposed the autoxidation of the 6-hydroxydopamine as a method to test Superoxide dismutase activity in biological samples. This method has several advantages but in some instances leads to incorrect determinations. We present here a necessary modification of the method to avoid bias.Peer Reviewe

Assessing escapes from short rotation plantations of the invasive tree species Robinia pseudoacacia L. in Mediterranean ecosystems: a study in central Italy

Black locust (Robinia pseudoacacia L.) is a fast growing tree species native to temperate North America, and widely diffused and naturalized in Europe. It is one of the candidate species for establishing bioenergy plantations on mar- ginal lands in temperate and sub-Mediterranean regions. This potential is in contrast to its well-known invasive habit, leading to a potential damage to plant biodiversity in many European countries. Advise against black locust plantation in regions where it is already invasive has been issued by several international reports, as well as the adoption of mitigation measures (e.g., “containment” buffer zones) to prevent the spread of the species into natural and semi-natural habitats. In the Mediterranean basin, however, no studies have been carried out aimed at quantifying the escape rate of black locust saplings from plantation stands and its recruitment into natural habitats, together with the effectiveness of a buffer zone in reducing the spread. In this study we investigated the spread of black locust along 35 transects surround- ing three 20-year- old plantations and including three different land cover types: abandoned arable land, semi-natural woodland and a buffer zone (orchards) with a low degree of farming input. In addition, the effect of soil disturbance on seed propagation was investigated. Our results demonstrate that the density of black locust regeneration is strongly affected by the land cover, abandoned agricultural land being the most prone to black locust colo- nization. Contrastingly, the spread was minimal in the buffer zone and negligi- ble in semi-natural woodland. During the investigated year, seed generative propagation was also negligible. The semi-natural woodland seems to resist well to black locust invasion, though further observations are needed to assess the consequences of stand harvesting disturbance as well, according to local standard forest management. Buffer zones seem to be very effective in con- trolling black locust invasion. Best management practices, with active farming inputs, are also discussed

Il pioderma gangrenoso: nuovi aspetti clinici e patogenetici

Il pioderma gangrenoso (PG) \ue8 una rara dermatosi neutrofilica ad evoluzione cronica. Esordisce tipicamente con una o pi\uf9 pustole sterili che, nella presentazione classica della malattia, evolvono rapidamente in ulcere dolenti, di ampiezza e profondit\ue0 variabile, caratterizzate da bordi netti e rilevati di colorito eritemato-violaceo. Varianti di PG meno comuni sono la vegetante e la bollosa. Il PG \ue8 frequentemente associato a patologie sistemiche, in particolare malattie infiammatorie croniche intestinali, affezioni reumatologiche ed ematologiche e neoplasie, ma pu\uf2 presentarsi anche in forma idiopatica. La diagnosi di PG si basa sull\u2019aspetto clinico delle lesioni e sul quadro istopatologico, il quale, seppure non tipico, \ue8 suggestivo. Le terapie pi\uf9 accreditate per il trattamento del PG sono rappresentate dai corticosteroidi sistemici e dalla ciclosporina; tuttavia non sono al momento disponibili linee guida clinico-terapeutiche basate su studi controllati. Negli ultimi quattro anni abbiamo valutato in modo prospettico 20 pazienti (10 donne e 10 uomini) portatori di diverse varianti di PG, con l\u2019obiettivo di proporre una classificazione che metta in relazione il numero delle lesioni cutanee e la percentuale di superficie corporea coinvolta (BSA) con l\u2019approccio terapeutico. Sono stati individuati tre sottogruppi di PG: localizzato (numero di lesioni \uf0b3 1, \uf0a3 3; BSA \uf0a3 5), multilesionale (numero di lesioni > 3, \uf0a3 10; BSA > 5) e disseminato (numero di lesioni > 10; BSA > 25). La ciclosporina sistemica, in monoterapia o in associazione ai corticosteroidi sistemici, si \ue8 dimostrata la terapia pi\uf9 efficace sia nel PG multilesionale che in quello disseminato, mentre il tacrolimus ha dato ottimi risultati nelle forme localizzate. Gli antagonisti del TNF-\u3b1 vanno considerati in casi selezionati di PG resistente alla terapia immunosoppressiva convenzionale. Riteniamo pertanto che tale algoritmo terapeutico possa rivelarsi utile nella pratica clinica, anche se studi controllati dovranno confermarne la validit\ue0. Valutando i risultati di uno studio immunoistochimico da noi condotto, presentiamo infine alcuni aspetti nuovi nella patogenesi del PG