Search

The existing European motorway infrastructure network is prone to ageing and subject to natural events (e.g. climate change) and hazards (e.g. earthquakes), necessitating immediate actions for its maintenance and safety. Within this context, the structural health monitoring (SHM) framework allows a quantitative assessment of the structural integrity, serviceability and performance, facilitating better-informed decisions for the management of the existing infrastructure. The European Commission Joint Research Centre (JRC) established the exploratory research project MITICA (Monitoring Transport Infrastructures with Connected and Automated vehicles) to investigate the opportunity to use novel methods for infrastructure motoring, aiming at the efficient maintenance of the European aging road infrastructure. This report summarizes the discussion and the outcomes of a workshop held at the JRC in Ispra (Italy) on June 6-7 2022, as part of the MITICA project. Considering the EU priority “A Europe fit for the digital age”, the workshop was dedicated to SHM and its application to civil infrastructure, focusing on innovative indirect structural health monitoring (iSHM) approaches that rely on the vehicle-bridge interaction and the deployment of sensor-equipped vehicles for the monitoring of the existing bridge infrastructure. The report aims to become a reference document in the area of iSHM using passing vehicles, for both scholars and policy makers.

The safety verification of in-plane loaded masonry panels requires the evaluation of at least three different collapse conditions connected with overturning, shear sliding, and shear - compression failure at the panels' toe. In reinforced panels, the resisting models should even take into consideration the presence of localized or distributed reinforcement., In general, the masonry is considered a Mohr-Coulomb type material not resisting tension and plastic in compression, while reinforcement is a brittle elastic material resisting tensile forces only [1]., The ultimate limit state is however linked with a given subset of compressed material inside the panel area. The compressed sections are therefore varying inside the panel as a function of the applied load. The collapse occurs in shear or overturning when one peculiar compressed section reduces to its minimum [2]., By equating the capacity in shear and overturning it is possible to derive an explicit statement of the minimum length of the compressed section which will be activated by a simultaneous failure in shear and overturning. A simple inequality is detecting the real failure mode and this allows directly computing the failure load resultant., The procedure is very fast and can deal even with localized or distributed reinforcement layers such as fiber strips or mesh reinforced mortars., Some examples of panels discussed in the literature show the effectiveness of the proposed verification procedure.

Nitrous oxide (N2O) is a strong greenhouse gas (GHG) and ozone depleter, with a warming potential 300 times higher than carbon dioxide (CO2). 1.2% of the total antrophopogenic N2O emissions are believed to originate from the wastewater treatment (WWT) sector. Conventional biological nutrient removal processes relying on nitrification and denitrification are known to produce N2O. A one year long-term study of N2O production and emissions was performed at Lynetten, Denmark’s largest WWTP. Nitrification and denitrification takes place by alternating process conditions as well as influent and effluent flows in 20 pairs of interconnected and surface aerated reactors. The long-term data revealed that the N2O emissions contribute to as much as 30% of the total CO2 footprint from the WWTP. High ammonium concentrations and long aeration phases lead to high N2O production and emissions rates. Nitrification phases were identified to produce and emit most of the N2O. High production and emissions were also associated with the afternoon loading peaks at the WWTP. During denitrification phases N2O was produced initially but consumed consequently. An effective control strategy was implemented, whereby N2O emissions were reduced from 0.8% to 0.3% of the nitrogen load during the mitigation period.

Strain localization and quasi-brittle failure in frictional-cohesive materials is still an open and challenging problem in computational mechanics. Owing to its complexity and the significant implications on numerous engineering problems, a considerable effort has been devoted to the development of theories and techniques capable of dealing with this topic. The introduction of numerical methods in the 70's provided a way to compute solutions, even if approximated. The Finite Element Method is able to describe a large number of geometries, engineering problems and various boundary conditions and, for this reason, the displacement-based formulation represents the preferred choice in the mechanical analysis of solids. Moreover, assuming the displacement jump created by a crack to be smeared across an element band, the calculation of the onset and the evolution of a fracture can be performed. However, standard finite elements are well-known to behave poorly in the case of strain localization of softening materials. Indeed, the irreducible formulation is mesh-biased and the resulting fracture direction is frequently incorrect. Plasticity constitutive models are largely affected by this issue, being directional by their very nature. In addition, when dealing with isochoric conditions, locking of the stresses provokes spurious pressure oscillations, that spoil the numerical solution. Both problems can be shown not to be related to the mathematical statement of the continuous problem but to its discrete (FEM) counterpart. In this work, a novel mixed e-u strain-displacement finite element method for strain localization and failure in plasticity is presented. Thanks to the independent interpolation of the strain and displacement fields, it is characterized by enhanced kinematic properties which result in an improvement in the accuracy of stresses and deformations. Moreover, it is proved that the numerical quandaries typical of the irreducible formulation are alleviated with the introduction of this FE technology. The e-u FEM is applied to 2D and 3D problems aimed at benchmarking its numerical capabilities as well as proving high-fidelity predictions and simulations of experimental results. Firstly, failure under Mode I (opening) loading is considered, using a Rankine failure criterion to describe the mechanical behavior of materials, such as concrete, which exhibit cracking under tensile load. Secondly, failure under Mode II (shearing) loading is studied, employing the J2 von Mises and the Drucker-Prager failure criteria for incompressible and compressible plasticity cases. Thirdly, failure under Mode III (tearing) and Mixed Mode loading is discussed. To study the complex stress state arising in torsional and skew-symmetrical bending cases, Rankine and Drucker-Prager failure criteria are developed in both plasticity and isotropic continuum damage models. Finally, the formulation is applied to crack propagation in weak snowpack layers, which is the main cause for the initiation of snow avalanches. From the results, three main conclusions emerge: (i) the mixed e-u finite element method proposed is capable of overcoming many of the challenges posed by strain localization in solids, providing reliable and accurate solutions; (ii) the smeared crack approach is able to describe effectively the creation and propagation of fracture surfaces in Mode I, Mode II, Mode III and Mixed Mode loading; (iii) the improvement of the kinematic description, with continuity of displacements and strains, is considered a key factor to empower the numerical solution. The e-u finite elements share numerous aspects with the standard displacement-based ones, in terms of implementation of constitutive laws, initial set of data and geometrical discretization. However, the proposed mixed formulation is superior in predicting peak loads, strain localization patterns and failure mechanisms, demonstrating its generality and its possibilities in the engineering practice., La resolución de problemas de localización de deformaciones y fallos cuasi-frágiles en materiales friccional-cohesivos sigue siendo un tema abierto a discusión. Debido a su complejidad y a las implicaciones en numerosos problemas de ingeniería, se ha dedicado un considerable esfuerzo al desarrollo de teorías y técnicas capaces de manejar el comportamiento inelástico de los sólidos. La introducción de los métodos numéricos en los años '70 proporcionó técnicas rápidas de cálculo que permitían obtener una solución, aunque aproximada, del problema a tratar. El Método de Elementos Finitos (FEM) es capaz de describir de manera eficiente un gran número de geometrías, problemas de ingeniería y condiciones de contorno, por lo que hace de la formulación irreducible la opción mayoritariamente escogida en el análisis de cuerpos sólidos. Asimismo, considerando la regularización del salto por el desplazamiento producido por una grieta a través de una banda de elementos, es posible calcular la aparición y evolución de una fractura. Sin embargo, los elementos finitos estándar se comportan de manera inadecuada en cálculos de localización de deformaciones en materiales con ablandamiento. La formulación irreducible está altamente influenciada por la malla empleada, y frecuentemente la dirección de fractura resultante es incorrecta. Este fenómeno aparece de manera significativa en plasticidad, siendo ortotrópica. De igual manera, con modelos isocóricos, el bloqueo de las deformaciones provoca oscilaciones de presión espurias, que hacen inutilizable la solución numérica obtenida. Es posible demostrar que ambos problemas no están relacionados por la definición continua del problema, sino con su formulación discreta. En este trabajo se presenta una nueva formulación mixta e-u de elementos finitos en desplazamientos y deformaciones para la localización de deformaciones y fallo en plasticidad. Solucionando independientemente deformaciones y desplazamientos, la formulación se caracteriza por la mejora de las capacidades cinemáticas, que da como resultado una mejora crucial en la precisión del cálculo de tensiones y deformaciones. Además, se demuestra que los problemas numéricos de la formulación irreducible se ven mitigados con el uso de la técnica de los elementos finitos mixtos. En los ejemplos, se considera el fallo con carga de Modo I (apertura) a través de un criterio de fallo de Rankine para describir el comportamiento mecánico de materiales, como el hormigón, que fallan por carga de tracción. Luego, se estudia el fallo con carga en Modo II (cizallamiento), empleando los criterios de fallo de J2 von Mises y de Drucker-Prager para la plasticidad incompresible y compresible. Por fin, se discute el fallo en Modo III (rasgado) y en Modo Mixto. Se implementan los criterios de Rankine y Drucker-Prager, tanto en plasticidad como en daño continuo para estudiar el estado de tensión en casos de flexión desviada y de torsión. Entonces, surgen tres conclusiones principales: (i) el método de elementos finitos mixto e-u es capaz de superar los desafíos planteados por la localización de la deformación en sólidos, con soluciones confiables y precisas; (ii) el modelo de fisura distribuida describe la creación y propagación de superficies de fractura por carga en Modo I, Modo II, Modo III y Modo Mixto; (iii) la mejora de la descripción cinemática, con continuidad de desplazamientos y deformaciones, se considera un factor clave para mejorar la solución numérica. El e-u FEM comparte muchos detalles de implementación de leyes constitutivas, conjunto inicial de datos y discretización geométrica con el método estándar. Sin embargo, la formulación mixta propuesta es superior en la predicción de las cargas máximas, patrones de localización de deformación y mecanismos de fallo. Además, demuestra su generalidad y sus posibilidades para un uso favorable en la práctica de la ingeniería

The development of practical tools for providing accurate ecological assessment of rivers and species conditions is necessary to preserve habitats and species, stop degradation and restore water quality. An understanding of the causal mechanisms and processes that affect the ecological water quality and shape macroinvertebrate communities at a local scale has important implications for conservation management and river restoration. This study used the integration of wastewater treatment, river water quality and ecological assessment models to study the effect of upgrading a wastewater treatment plant (WWTP) and their ecological effects for the receiving river. The WWTP and the water quality and quantity of the Drava river in Croatia were modelled in the software WEST. For the ecological modeling, the approach followed was to build habitat suitability and ecological assessment models based on classification trees. This technique allows predicting the biological water quality in terms of the occurrence of macroinvertebrates and the river status according to ecological water quality indices. The ecological models developed were satisfactory, and showed a good predictive performance and good discrimination capacity. Using the integrated ecological model for the Drava river, three scenarios were run and evaluated. The scenario assessment showed that it is necessary an integrated approach for the water management of the Drava river, which considers an upgrading of the WWTP with Nitrogen and Phosphorous removal and the treatment of other diffuse pollution and point sources (including the overflow of the WWTP). Additionally, if an increase in the minimum instream flow after the dams is considered, a higher dilution capacity and a higher self-cleaning capability could be obtained. The results proved that integrated models like the one presented here have an added value for decision support in water management. This kind of integrated approach is useful to get insight in aquatic ecosystems, for assessing investments in sanitation infrastructure of urban wastewater systems considering both, the fulfilling of legal physical chemical emission limits and the ecological state of the receiving waters.