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.

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

Floating macro litter in European rivers - top items

The JRC exploratory project RIMMEL provides information about litter, mainly plastic waste, entering the European Seas through river systems. RIMMEL has collected data on riverine floating macro litter inputs to the sea. Data acquisition was based on the Riverine Litter Observation Network (RiLON) activities, which collected data from rivers in the European marine basins over a period of one year (September 2016 – September 2017). Data was collected by visual observations and documented with the JRC Floating Litter Monitoring Application for mobile devices, allowing a harmonized reporting, compatible with the MSFD Master List of Categories for Litter Items. This report includes the Top Items lists of riverine floating macro litter, based on the total amount of litter items identified during RiLON activities and ranked by abundance. Top Items lists have been elaborated considering the whole database for the European Seas and further detailed for each individual European regional sea: Baltic Sea, Black Sea, Mediterranean Sea and North-East Atlantic. The North-East Atlantic and the Mediterranean Sea regions showed similar litter categories in their Top 20 Items. These two regions provided most of the available data, influencing the general Top Items list. In the Black Sea and Baltic Sea regions, where data availability was limited, the Top Items lists showed more differences among the different regions. Overall, the general Top Items list for the European Seas showed a predominance of plastic item categories (artificial polymer materials). As a whole, plastic items made up to 80.8% of all objects, with plastic and polystyrene fragments comprising 45% of the identified items in the database. Additionally, Single Use Plastics such as bottles, cover/packaging and bags were also ranked among the most frequently found floating litter. The similarities in the Top 10 and Top 20 items for the different regions, and the appearance of Single Use Plastics scoring high in the ranking, support the need for common actions against plastic pollution at EU level.JRC.D.2-Water and Marine Resource

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.

Fire investigation del tunnel di Monte Bianco

L’incendio nel tunnel del Monte Bianco, ove persero la vita 39 persone, è stato il più grave nella storia dei tunnel transalpini. Tale evento disastroso ha spinto, negli anni successivi, a compiere migliorie nel settore della sicurezza antincendio nelle gallerie, ponendo molta attenzione agli aspetti di prevenzione, definendo criteri di progettazione innovativi e metodologie gestionali più efficaci. Lo scopo di questo articolo è quello di esporre delle fasi metodologiche di Fire Investigation atte ad individuare le cause scatenanti, pregresse e latenti, che hanno determinato tale evento accidentale. L’illustrazione di questa attività investigativa rappresenta un caso applicativo di quanto esposto nell’articolo Structural Fire Investigation e ingegneria forense. L’iter investigativo associato a determinate operazioni, in parte codificate, svolte anche attraverso l’ausilio di indagini computazionali (computational investigation), può aiutare a determinare nel dettaglio le cause e migliorare il livello di sicurezza antincendio di tali strutture.Le indagini svolte hanno messo in evidenza i difetti meccanici dell’automezzo e le carenze nella gestione dell’emergenza. Non si tratta dunque di uno scenario imprevedibile (black swans) ma di uno scenario probabile.The Mont Blanc tunnel fire was the most severe in the history of the trans-Alpine tunnels, where 39 people lost their lives. This disastrous event, which took two days of action, prompted, in subsequent years, to make improvements in the field of fire safety in tunnels, paying attention to the aspects of prevention and leading to the definition of design criteria and more effective innovative management methods. The purpose of this article is to expose the various methodological steps of Fire Investigation aimed at identifying all the causes, past and latent, which determined that accidental event. The illustration of this investigative activity in a case of application of the above article Structural Fire Investigation and forensic engineering. The investigative process associated with certain transactions, codified in part, carried out through the use of computational investigations, can help determine in detail the causes and improve the level of fire safety of such structures. The investigations have shown mechanical defects of the vehicle and deficiencies in emergency management. An unpredictable scenario (black swans) is out of question, as it is a very possible scenario

Collapse Analysis of a Metal Structure

Engineered trusses, made from a variety of materials, have a wide range of applications in civil engineering. A large part of them is used to realize entertainment structures; their structural safety gains therefore much more importance due to the people that can be involved in the collapse, (Giuliani, 2012). The latest collapses of those particular structures in USA and in Europe brought the attention of the society on the study of their safety. In this paper a metal truss structure is taken under consideration in order to identify the causes that could lead the structure through a collapse. In this specific case the errors in the structural design and the human errors during the erection of the structure are taken under consideration. By means of nonlinear analyses on a Finite Element Model (FEM) the failure sequence of this particular structure will be shown

Fire safety assessment of long tunnels

IN PRES

Il ruolo delle strutture nella protezione passiva contro l’incendio

“Antincendio - rivista italiana della prevenzione incendi e della protezione civile” Rivista tecnica, EPC Periodici