WIM-based live-load model for advanced analysis of simply supported short- and medium-span highway bridges

The accuracy of bridge system safety evaluations and reliability assessments obtained through refined structural analysis procedures depends on the proper modeling of traffic load effects. While the live-load models specified in AASHTO procedures were calibrated for use in combination with approximate analysis methods and load-distribution factors commonly used in the United States, these existing models may not produce accurate results when used in association with advanced finite-element analyses of bridge structures. This paper proposes a procedure for calibrating appropriate live-load models that can be used for advanced analyses of multigirder bridges. The calibration procedure is demonstrated using actual truck data collected at a representative set of weigh-in-motion (WIM) stations in New York State. Extreme value theory was used to project traffic-load effects to different service periods. The results are presented as live-load models developed for a 5-year typical rating interval and for a 75-year design life. The outcome of the calibration indicates that maximum traffic-load effects can be calculated using finite-element models with the help of a single truck for short to medium one-lane multigirder bridges and two side-by-side truck configurations for multilane bridges. The proposed analysis trucks have axle configurations of the standard AASHTO 3-S2 and Type 3 legal rating trucks with appropriate factors to amplify their nominal weights. The amplification factors reflected the presence of overweight trucks in the traffic stream and the probability of multiple presence. The proposed live-load models are readily implementable for deterministic refined analyses of highway bridges and for evaluating the reliability of bridges at ultimate limit states considering the system’s behavior.Peer ReviewedPostprint (author's final draft

Methodology for development of live load models for refined analysis of short and medium-span highway bridges

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Structure and Infrastructure Engineering on 2018, available online at: http://www.tandfonline.com/10.1080/15732479.2017.1406961The accuracy of bridge system safety evaluations and reliability assessments obtained through refined structural and finite element analyses depends not only on the accuracy of the structural model itself but also on the proper modelling of the maximum traffic loads. While current code-specified live load models were calibrated to properly reflect the safety levels of bridge structures analysed using the simplified methods adopted in bridge design and evaluation manuals, these load models may not lead to accurate results when implemented during refined structural analysis procedures. This paper describes a method to calibrate appropriate live load models that can be used for advanced analyses of bridges. The calibration procedure is demonstrated using actual traffic data collected at a representative weigh-in-motion station in New York State. The proposed calibration methodology is applicable for developing live load models for different bridge service periods, bridge types and design/assessment codes or standards. Live load models obtained using the proposed calibration procedure are readily implementable for deterministic refined analyses of highway bridges to produce similar results to those of complex traffic load simulations. Examples are presented that describe how results of such calibrated live load models would be used in engineering practice.Peer ReviewedPostprint (author's final draft

Microbial communities in dark oligotrophic volcanic ice cave ecosystems of Mt. Erebus, Antarctica.

The Earth's crust hosts a subsurface, dark, and oligotrophic biosphere that is poorly understood in terms of the energy supporting its biomass production and impact on food webs at the Earth's surface. Dark oligotrophic volcanic ecosystems (DOVEs) are good environments for investigations of life in the absence of sunlight as they are poor in organics, rich in chemical reactants and well known for chemical exchange with Earth's surface systems. Ice caves near the summit of Mt. Erebus (Antarctica) offer DOVEs in a polar alpine environment that is starved in organics and with oxygenated hydrothermal circulation in highly reducing host rock. We surveyed the microbial communities using PCR, cloning, sequencing and analysis of the small subunit (16S) ribosomal and Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (RubisCO) genes in sediment samples from three different caves, two that are completely dark and one that receives snow-filtered sunlight seasonally. The microbial communities in all three caves are composed primarily of Bacteria and fungi; Archaea were not detected. The bacterial communities from these ice caves display low phylogenetic diversity, but with a remarkable diversity of RubisCO genes including new deeply branching Form I clades, implicating the Calvin-Benson-Bassham (CBB) cycle as a pathway of CO2 fixation. The microbial communities in one of the dark caves, Warren Cave, which has a remarkably low phylogenetic diversity, were analyzed in more detail to gain a possible perspective on the energetic basis of the microbial ecosystem in the cave. Atmospheric carbon (CO2 and CO), including from volcanic emissions, likely supplies carbon and/or some of the energy requirements of chemoautotrophic microbial communities in Warren Cave and probably other Mt. Erebus ice caves. Our work casts a first glimpse at Mt. Erebus ice caves as natural laboratories for exploring carbon, energy and nutrient sources in the subsurface biosphere and the nutritional limits on life

FONTI INTERNAZIONALI E COMUNITARIE COME NORME INTERPOSTE?

The thesis deals with the role of supranational sources of law in the Italian legal order. The first part is dedicated to EU Law, whose incorporation has been justified by the Italian Constitutional Court on the basis of Article 11 of the Constitution. This provision gives a constitutional rank to the law containing the order of execution of the Treaty. Thus, EU law, in the matters of its competence, both prevails over ordinary legislation and derogates to detailed constitutional provisions, with the exception of the duty to respect fundamental principles. Conflicts between self-executing EU norms and municipal provisions which are raised incidentally must not be solved by the Constitutional Court but by the ordinary judge on the basis of the direct effect of EU law. This approach is due to the fact that national law that contrasts with Union law do not interfere with the law of execution of the Treaty, which the dualist doctrine considers as a part of another legal system. An analogous constitutional rank in the hierarchy of sources is recognized to international customs which are transformed into municipal law by Article 10(1) of the Constitution. On the contrary, until 2001 international treaties were deprived of a general constitutional covering and therefore they had the same rank of the ordinary law of execution. At present, after the entry into force of new Article 117(1) of the Constitution, international agreements are considered as interposed sources which prevail over ordinary legislation and succumb with respect to constitutional rules. However, some recent judgments of the Italian Constitutional Court seem to indicate the willingness to recognize in the future a constitutional rank also to treaties. La tesi tratta il tema del ruolo svolto nel nostro sistema giuridico dalle fonti di origine sovranazionale. La prima parte \ue8 dedicata al diritto comunitario, il cui ingresso nel nostro ordinamento \ue8 stato giustificato dalla Consulta sulla base dell\u2019articolo 11, che offre copertura costituzionale alla legge di esecuzione del Trattato. Il diritto comunitario, pertanto, nelle materie di propria competenza prevale sulla legislazione ordinaria e deroga anche alle disposizioni costituzionali di dettaglio, salvo l\u2019obbligo di rispettare i principi supremi. I conflitti tra norme comunitarie self executing e leggi ordinarie sorti in via incidentale devono peraltro essere risolti non mediante il giudizio di costituzionalit\ue0 ma dal giudice ordinario con la diretta applicazione della norma comunitaria, perch\ue9 la legge anticomunitaria normalmente non interferisce con la legge di esecuzione del Trattato, che secondo la tesi dualista fa parte di un diverso sistema giuridico. Analoga \ue8 la collocazione riconosciuta nella gerarchia delle fonti alle consuetudini internazionali, che sono recepite dall\u2019articolo 10 comma 1. I trattati internazionali, invece, fino al 2001 erano privi di copertura costituzionale generale, e pertanto parificati alla legge ordinaria di esecuzione. Dopo l\u2019entrata in vigore del nuovo articolo 117 comma 1, invece, sono considerati fonti interposte, che prevalgono sulla legislazione ordinaria e soccombono nei confronti delle disposizioni costituzionali. Da alcune recenti sentenze, tuttavia, pare emergere che la Corte Costituzionale potrebbe arrivare a riconoscere anche ai trattati una posizione di livello costituzionale

Redundancy of bridge systems under lateral loads

The design of bridges has been traditionally done on a member by member basis and little consideration is provided to the remaining capacity after the failure of one structural element. As a consequence of several tragic collapses that followed the failure of single elements, the evaluation of the structural robustness of bridges has become of primary importance. In this work, a methodology is proposed to for the evaluation of the redundancy and robustness of bridges under lateral loads. The basis of the study is the research conducted under the auspices of the U.S. National Cooperative Highway Research Program (NCHRP) which developed approaches for the redundancy analysis of bridge superstructures and substructures. Generally, engineers have treated these two structural sub-systems separately by uncoupling their response assuming that the connections are due to bearing supports. Recently, the design of integral bridges has become more common especially in seismic hazard zones. In these cases, the bridge has to be analyzed as one monolithic system and a global evaluation of the structural redundancy of the entire system must be performed. The proposed method of analysis, which is based on a static non-linear analysis (pushover) using a finite element 3D space frame model, is applicable for the redundancy analysis of sub-systems connected by bearing supports as well as the entire system with either bearings or integral connections. The proposed analysis accounts for material non-linearity using realistic models for the stress-strain relationships of the different material constituents based on plasticity models that take into consideration the interaction between the axial forces and bending moments when necessary. A lumped plasticity model is adopted. A push over analysis is adopted because it provides an adequate indictor of the post-elastic behavior of the entire system. Load-response curves are hence calculated for the intact structure and for the damaged system, and then compared to evaluate the loss of capacity and safety. The results can be used to analyze the redundancy of existing bridges, give guidelines for robust design, and evaluate the quality of different retrofitting schemes and selecting the best option. In this work the proposed approach is applied to structural systems with increasing levels of complexity. First, the analysis is performed for a simple column, followed by the analysis of a multi-column bent, a retrofitted bent, a scaled bridge model and a full scale bridge. Emphasis is placed on the analysis of the full scale bridge to evaluate the variation of the redundancy indicators in relation to variations of some critical structural and geotechnical parameters including foundation stiffness and deck piers connection assumptions

Asymptotic Analysis of Complex LASSO via Complex Approximate Message Passing (CAMP)

Recovering a sparse signal from an undersampled set of random linear measurements is the main problem of interest in compressed sensing. In this paper, we consider the case where both the signal and the measurements are complex. We study the popular reconstruction method of $\ell_1$-regularized least squares or LASSO. While several studies have shown that the LASSO algorithm offers desirable solutions under certain conditions, the precise asymptotic performance of this algorithm in the complex setting is not yet known. In this paper, we extend the approximate message passing (AMP) algorithm to the complex signals and measurements and obtain the complex approximate message passing algorithm (CAMP). We then generalize the state evolution framework recently introduced for the analysis of AMP, to the complex setting. Using the state evolution, we derive accurate formulas for the phase transition and noise sensitivity of both LASSO and CAMP

Determinazione di aree economiche per la valutazione dell’impatto sul sistema produttivo italiano delle misure di contrasto all’epidemia da Covid-19

The paper proposes a new geography of nested economic areas that shape the Italian economy. These economic areas, named economic regions and economic macro-regions, are an upper tier integration of Local Labour Systems (LLS) obtained using a Community Detection algorithm called INFOMAP. This approachdetermines the optimal number of regions and the assignment of LLS to them, minimizing a function known as MAP Equation. In the paper, these economic areas are the unit of analysis for impact assessment on the Italian economy of control measures implemented by the government to counteract the epidemic from Covid-19. Moreover, if the purpose is to contain new epidemic hotbeds of Covid-19, these areas are the most suitable tool for doing so, because of their extremely high self-containment, much higher than that of LLSs. Finally, the paper suggests their utility for both epidemiological and socio-economic monitoring

Risk-based highway bridge inspection intervals

Infrastructure maintenance programs establish schedules for routine inspections of highway bridges with little consideration of their current conditions. The time interval between two inspections is traditionally set based on experience and on engineering judgment. For example, in the US considerable expenditures are incurred to meet the required biennial routine inspection of all bridges many of which may be in good condition. It is therefore of great interest for the engineering community to develop an approach to control inspection schedules of individual bridges and minimize their associated costs using rational criteria that account for the lower risk of postponing the inspection of bridges that are subject to reduced deterioration mechanisms and low traffic loadings. The implementation of such a risk-based approach would go a long way in helping optimize the limited resources available for maintaining the vast highway infrastructure system. The object of this Ph.D. dissertation is to develop a rational approach for determining a risk-based optimum time interval between bridge inspections. The proposed theoretical approach subsequently serves for proposing a simple procedure that is implementable in routine practice by bridge engineers using easily available bridge-specific data. To illustrate the proposed procedure using actual bridge data, the work uses highway data from the state of New York (NYS) in the United States of America (USA) in the form of Weigh-in-Motion (WIM) truck traffic data and bridge records provided through the National Bridge Inventory (NBI) database. These data are used to develop a theoretical framework able to define the capacity of bridges probabilistically and the risk of bridge failure if a bridge’s inspection is deferred for a limited period of time. The calculations performed in this dissertation based on data collected in the state of New York are limited to simple span composite steel-concrete superstructures that constitute a large proportion of short to medium span bridges in North America. However, the same concepts can be extended to other types of superstructures and other regions of the world as appropriate data become available. The conclusions of this study include the demonstration of the inadequacy of utilizing a standard two-year inspection interval for all bridges. To overcome this problem a simplified procedure is proposed for an easy practical engineers’ application.Els programes de manteniment d'infraestructures estableixen plans periòdics d'inspecció bàsica en els quals l'estat actual dels ponts té relativament poca importància a l'hora de definir l'interval de temps. L'interval temporal entre dues inspeccions es basa normalment en la practica habitual i en la experiència passada. Per exemple, als Estats Units d'Amèrica una gran part del pressupost de despesa destinat al manteniment de la xarxa d'infraestructures es deriva al pla d'inspeccions biennal de ponts tot i que, aquests, en molts casos mostren bones condicions estructurals. Per això la comunitat enginyeril està interessada en el desenvolupament de protocols que controlin el pla d'inspecció de ponts i que minimitzin els costos associats a traves de criteris racionals. Aquets criteris han de ser capaços de reconèixer els ponts que presenten un risc alt degut a la elevada exposició a processos de deteriorament i a sobrecarrega de tràfic intens i minimitzar els costos d'inspecció associats. La implementació d'estratègies basades en el càlcul del risc permet optimitzar el pressupost total disponible per al manteniment de les xarxes de carreteres. L'objecte d'aquesta tesi doctoral es el desenvolupament d'un procediment racional basat en el càlcul del risc per a estimar l'interval òptim entre dues inspeccions bàsiques. L'estratègia teòrica proposada es fa servir posteriorment per a la aplicació pràctica d'aquests criteris utilitzant dades inicials fàcils d'obtenir per l'usuari final que estigui interessat en aplicar el mètode per a un pont en concret. La metodologia proposada en aquest treball utilitza dades de la xarxa de carreteres de l'estat de Nova York (NYS) als Estats Units d'Amèrica (USA), a partir de mesures de tràfic del tipus Weigh-in-Motion (WIM) i de informacions provinents de la base de dades del National Bridge Inventory (NBI). Aquestes dades es fan servir per a desenvolupar una eina metodològica capaç de calcular la capacitat estructural de superestructures des del punt de vista probabilista i quantificar l'increment de risc al que la societat està sotmesa en cas de decidir incrementar l'interval d'inspecció per damunt dels 2 anys. Per al càlcul dels intervals d'inspecció es fa servir el concepte de risc, que a la vegada es basa en models de càlcul probabilistes. L'interval d'inspecció òptim s'obté minimitzant el risc de fallada obtingut combinant la probabilitat de fallada amb el cost associat. El cost de fallada s'obté estimant els costos potencials relatius com víctimes, ferits, reconstrucció del pont, interrupció del tràfic vehicular, impacte ambiental i cost d'inspecció. Els càlculs duts a terme en aquesta tesi estan basats en dades de la regió del estat de Nova York i limitats a ponts simplement recolzats amb superestructura mixta acer-formigó que constitueix una important tipologia en l'àmbit nord americà. No obstant, els mateixos conceptes poden ser aplicats a altres regions del mon a mesura que la informació necessària estigui a disposició. L'estudi demostra la ineficiència d'utilitzar un interval d'inspecció de dos anys per a tots els ponts i proposa una metodologia simplificada per calcular l'interval d'inspecció recomanat per ser implementat en la pràctica engineril d'una manera senzilla.Los programas de mantenimiento de infraestructuras establecen planes periódicos de inspección básica en los cuales el posible estado de los puentes en el momento de la inspección tiene relativamente poca importancia. El intervalo temporal entre dos inspecciones se fija sobre la base de la práctica habitual y sobre experiencia pasada. Por ejemplo, en los Estados Unidos de América una gran parte del presupuesto de gasto destinado al mantenimiento de la red de infraestructuras se deriva al plan de inspecciones bienales de puentes aunque en muchos casos muestran buenas condiciones estructurales. Por esta razón, es de suma importancia para la comunidad el desarrollo de protocolos para controlar el plan de inspección de puentes y minimizar los costes asociados a través de criterios racionales, para poder destinar los recursos asignados a inspección allí donde más falta hacen. Dichos criterios tienen que ser capaces de reconocer aquellos puentes que presentan mayor riesgo debido a la exposición a procesos de deterioro y a sobrecarga de tráfico intenso y minimizar los costes de inspección asociados. La implementación de estrategias basadas en criterios de riesgo permite optimizar el presupuesto total disponible para el mantenimiento de las redes de carreteras El objeto de esta tesis doctoral es el desarrollo de un procedimiento racional basado en el cálculo del riesgo para determinar el intervalo óptimo entre dos inspecciones básicas. El enfoque teórico propuesto se emplea posteriormente para la aplicación en la práctica de dichos criterios utilizando datos de partida fáciles de obtener para el usuario final que esté interesado en aplicar el método para un puente en concreto. La metodología propuesta en este trabajo se materializa a través de los datos disponibles de la red de carreteras del estado de Nueva York (NYS) en Estados Unidos de América (USA), desde mediciones de tráfico del tipo Weigh-in-Motion (WIM) hasta informaciones en el marco de la base de datos del National Bridge Inventory (NBI). Esos datos se utilizan para desarrollar una base metodológica capaz de calcular la capacidad portante de superestructuras desde el punto de vista probabilista y cuantificar el incremento de riesgo que supone incrementar el intervalo de la inspección básica, actualmente fijado en dos años En la práctica actual, el cálculo de la capacidad portante de puentes sujetos a sobrecarga de tráfico (en estado límite de servicio y último) se lleva a cabo a partir de modelos típicamente elástico-lineales en los que se evalúan los esfuerzos para el elemento más crítico y sucesivamente se considera el cálculo no lineal para la verificación de dicho elemento. Este enfoque está aceptado y ha demostrado su validez y fiabilidad en numerosas aplicaciones. Sin embargo, a pesar de que estos modelos pueden tener en cuenta el deterioro detectado en las campañas de inspección, normalmente no consideran sobrecargas de tráfico realistas, el comportamiento estructural del conjunto del puentes y no sólo de sus elementos por separado, o la evolución posible del deterioro entre intervalos de inspección. En este estudio, se emplean datos de tráfico real obtenidos de sistemas WIM para estimar la sobrecarga de tráfico máxima esperada que puede ser bastante diferente de la que típicamente sugieren los códigos de diseño y evaluación estructural de puentes. De la misma manera, la respuesta conjunta de la estructura se tiene en cuenta en este trabajo utilizando modelos capaces de simular el comportamiento no-lineal de los materiales y la evolución de la redistribución de los esfuerzos cuando la estructura se encuentra en rangos de deformaciones próximos a rotura. Esto permite mejorar el cálculo de la capacidad estructural y detectar aquellos puentes cuya configuración tipológica y topológica resulta en un comportamiento redundante que no es posible tener en cuenta en los modelos de cálculo tradicionales. Además, se incluye en el modelo el deterioro de los materiales tras estudiar datos históricos sobre la pérdida de capacidad portante de una gran cantidad de puentes seleccionados del NBI. Para el cálculo de los intervalos de inspección se emplea el concepto de riesgo, que a su vez se basa en modelos de cálculo probabilistas. El intervalo de inspección óptimo se obtiene minimizando el riesgo de fallo obtenido combinando la probabilidad de fallo con el coste asociado. El coste del fallo se obtiene estimando los costes potenciales relativos como víctimas, heridos, reconstrucción del puente, interrupción del tráfico vehicular, impacto ambiental y coste de inspección. Los cálculos llevados a cabo en esta tesis están basados en datos de la región del estado de Nueva York y limitados a puentes simplemente apoyados con superestructura mixta acero-hormigón que constituye una importante tipología en el ámbito norteamericano. Sin embargo los mismos conceptos pueden ser aplicados a otras regiones del mundo a medida que la información necesaria se encuentre disponible. El estudio demuestra la ineficiencia de utilizar un intervalo de inspección de dos años para todos los puentes y propone una metodología simplificada para calcular el intervalo de inspección recomendado para ser implementada en la práctica ingenieril de una forma sencilla.Postprint (published version

Redundancy of bridge systems under lateral loads

The design of bridges has been traditionally done on a member by member basis and little consideration is provided to the remaining capacity after the failure of one structural element. As a consequence of several tragic collapses that followed the failure of single elements, the evaluation of the structural robustness of bridges has become of primary importance. In this work, a methodology is proposed to for the evaluation of the redundancy and robustness of bridges under lateral loads. The basis of the study is the research conducted under the auspices of the U.S. National Cooperative Highway Research Program (NCHRP) which developed approaches for the redundancy analysis of bridge superstructures and substructures. Generally, engineers have treated these two structural sub-systems separately by uncoupling their response assuming that the connections are due to bearing supports. Recently, the design of integral bridges has become more common especially in seismic hazard zones. In these cases, the bridge has to be analyzed as one monolithic system and a global evaluation of the structural redundancy of the entire system must be performed. The proposed method of analysis, which is based on a static non-linear analysis (pushover) using a finite element 3D space frame model, is applicable for the redundancy analysis of sub-systems connected by bearing supports as well as the entire system with either bearings or integral connections. The proposed analysis accounts for material non-linearity using realistic models for the stress-strain relationships of the different material constituents based on plasticity models that take into consideration the interaction between the axial forces and bending moments when necessary. A lumped plasticity model is adopted. A push over analysis is adopted because it provides an adequate indictor of the post-elastic behavior of the entire system. Load-response curves are hence calculated for the intact structure and for the damaged system, and then compared to evaluate the loss of capacity and safety. The results can be used to analyze the redundancy of existing bridges, give guidelines for robust design, and evaluate the quality of different retrofitting schemes and selecting the best option. In this work the proposed approach is applied to structural systems with increasing levels of complexity. First, the analysis is performed for a simple column, followed by the analysis of a multi-column bent, a retrofitted bent, a scaled bridge model and a full scale bridge. Emphasis is placed on the analysis of the full scale bridge to evaluate the variation of the redundancy indicators in relation to variations of some critical structural and geotechnical parameters including foundation stiffness and deck piers connection assumptions