Towards Resilient Offshore Wind Farms

This paper proposes using a performance-based engineering (PBE) approach to quantify the reliability of offshore wind turbines (OWT), for use in a larger assessment of wind farm resilience. The concept of resilience provides a useful framework for considering an OWT as a system that is comprised of both structural and mechanical components and to extrapolate these risks across a farm. An implementation based on the financial consequence of failure is used here, this allows failure states to be defined that combine analytical structural failure scenarios with empirical mechanical equipment failure rates within a unified calculation of material losses. The loss associated with the failure of each component is used to estimate the total annual loss for a case study farm. Results are presented in the form of a case study and indicate that failure of the structure may have an impact on the overall failure profile of the farm. This method provides a simple estimate of robustness for the farm, which is a component of any resilience assessment. It also provides a foundation from which a more detailed assessment of resilience, including adaptability and recovery, will be developed

MAPEAMENTO DA FRAGILIDADE AMBIENTAL DA BACIA DO RIBEIRÃO DO ESCALVADO – MG

Fatores genéticos do ambiente físico-natural podem apresentar características frágeis, suscetíveis a ocorrência de processos de degradação. Tal fato, associado à ocupação humana desordenada, agrava a fragilidade desses ambientes naturais. A partir dessas premissas, esta pesquisa objetiva classificar, mapear e analisar a fragilidade ambiental da bacia do ribeirão do Escalvado (MG) a partir da proposta metodológica de Ross (2012). Para tanto, foram realizados mapeamentos de variáveis relacionadas à declividade, drenagem, solos, geologia, dissecação do relevo e uso da terra. Estes parâmetros foram sobrepostos por meio de análise ponderada associada ao método de processo hierárquico analítico (AHP). Os resultados da sobreposição entre as variáveis naturais resultaram na distinção de classes de fragilidade potencial média (86,49%), forte (11,38%) e baixa (2,13%). Com relação à fragilidade emergente, a partir do cruzamento com as classes de uso da terra, obteve-se resultados que evidenciaram predomínio de classe de fragilidade emergente forte (64,85%), fraca (21,47%), muito forte (8,11%), média (4,69%) e muito fraca (0,88%). Concluiu-se que os ambientes frágeis da bacia se apresentaram condizentes tanto com sua historicidade relacionada à ocupação da sociedade, quanto à evolução geocronológica do sistema natural. PALAVRAS-CHAVE: Sobreposição ponderada; Fragilidade potencial; Fragilidade emergente; Bacia hidrográfica; Mapeamento

Clasificación de Puentes en Argentina para la Evaluación de su Vulnerabilidad Sísmica

Recientes progresos en los métodos de evaluación del riesgo sísmico han llevado al desarrollo de funciones de fragilidad para clases específicas de puentes. Como primera etapa, para la construcción de dichas Curvas de fragilidad para puentes en Argentina, ubicados en zonas de elevada y muy elevada peligrosidad sísmica, se procedió a la clasificación de los puentes de la red vial nacional correspondientes a las regiones de Cuyo y NOA en grupos característicos, conforme a los rasgos estructurales que tienen influencia preponderante en la respuesta sísmica de estas estructuras. Para ello, se analizaron estadísticamente los datos de inventario provistos por Vialidad Nacional, a través de su Sistema de Gestión de Puentes, para los distritos de Mendoza, San Juan, La Rioja, Salta y Jujuy. Esta tarea, además de servir para la clasificación ya indicada, permitió identificar aquellos puentes representativos de cada clase, los cuales servirán de ejemplares para posteriores análisis estructurales

Commentary: Evaluating the role of seagrass in Cenozoic CO2 variations

[No abstract available

Preliminary investigation of multi-hazard resilience analysis for urban transportation networks and data availability for hazard models and vulnerability of physical objects

HUB-Istanbul work package (WP) 2.6 aims to develop tools to analyse the multi-hazard resilience of urban transportation network in complex and evolving metropolitan environment, and propose a demonstrative application to a case study area: Fikirtepe in Istanbul, Turkey. Research outcomes will be conveyed by five deliverables. This document is the first deliverable, summarising the overall framework of analysis and required data for assessing physical vulnerability. Based on the framework, the second deliverable will deal specifically with another type of data required to evaluate traffic functionality of roadways and network performance. Based on the framework and datasets identified in the first two deliverables, the third deliverable will develop a probabilistic model to incorporate multi-layered analysis and data, which will be demonstrated by pilot examples. The fourth deliverable will present a thorough analysis of real-world transportation networks in the case study area, including mapping, network analysis and network performance evaluation. The evaluation results should be used to support decisions through mathematically formulated decision tasks, which will be illustrated in the fifth deliverable. This first deliverable summarises and proposes the research objectives, the framework of multi-hazard disaster resilience analysis of urban transportation networks and data requirement for assessing physical vulnerability, which are accompanied with thorough literature review. Based on the development, major hazard threats and distributions of bridges are identified for the case study area, Fikirtepe in Istanbul, Turkey

PROBABLISTIC ASSESSMENT OF ROOF UPLIFT CAPACITIES IN LOW-RISE RESIDENTIAL CONSTRUCTION

Post hurricane damage investigations of light frame wood residential structures reveal that roof envelope failure induces considerable damage to the structure and its contents. Roof - to - wall (RTW) connection failures though not as common as roof sheathing failure also cause significant structural and material damage. Considerable changes have been made in the ASCE structural loads standard and International Building code (IBC) after hurricane Andrew in order to prevent RTW connection and sheathing failures. That includes not only a substantial increase in the design wind load in the past two decades but also a strict enforcement of tighter nailing schedules and stronger RTW connections (metal straps and hurricane ties). However a significant number of older buildings constructed with toenailed RTW connections exist and their safety and reliability needs to be investigated. Hence there is an apparent need to statistically understand the behavior of toenailed RTWconnections in existing buildings. Fragility analysis of roofs of older buildings will provide an insight on the prevailing level of safety and help to identify the shortcomings and the associated ramifications. Experimental statistics and analytical models of the toenail behavior and sheathing fasteners will help to formulate accurate roof fragility estimations. Estimation of the effect of wind load spatial correlation on the fragility estimation and the sensitivity of fragility curves to various modeling assumptions will further enhance the credibility of roof system fragility analysis methodologies. Since hurricane ties have replaced toenailed RTW connections in modern residential construction and are used as a retrofit measure to complement existing toenail connection capacities, understanding their behavior under high loads is essential. Experimental tests on hurricane ties subjected to uplift and combined (uplift and lateral) loads will not only provide an insight on the advantage of their usage in hurricane prone areas but also help in identifying the available design space when subjected to multi-axial loads. This information is crucial while developing statistical and analytical models for hurricane ties. This research study evaluated the in-situ capacity of roof-to-wall connections and sheathing to rafter fasteners in light-framed wood construction. The outcome of this study was an analytical model designed to approximate the uplift behavior of toenail connections and to facilitate modeling of roof systems. In addition, the study experimentally examined three very common hurricane ties under uni-axial, bi-axial and tri-axial loads. After testing over 350 connections and performing detailed analyses, the currently used design equation for combined loads was found to be inefficient (least usable design space) and overly conservative. A new design space taking a 25% reduction on all allowable loads for hurricane ties when subjected to multi-axis load is proposed. A finite element model of a light frame gable roof system was created using the developed analytical model of the RTW toenail connections and sheathing fasteners. Assessment of the overall impact of RTW and sheathing connector behavior on the wind-uplift fragility curves for the roof system was achieved using a Latin-hypercube based simulation strategy. It was found that the treatment of post ultimate connection behavior had a significant influence on the fragility assessment of the roof system. However assigning variable and uniform stiffness for roof-to-wall connectors and sheathing fasteners had little to no effect on the distribution pattern of wind uplift load among connectors. Additionally, the effects of gable end supports, sheathing thickness, nailing schedule and wind pressure spatial correlation on the fragility estimation were explored. The results indicated that the fragility estimations of both roof to wall connections and sheathing panel systems are not sensitive to the spatial correlation of wind pressure for wind perpendicular to the ridge

Kinetic, thermodynamic, and structural transitions in order-disorder alloys and bulk metallic glass-forming alloys

The temperature dependence of equilibrium viscosity or relaxation time reflects an intrinsic property of glass-forming liquids known as fragility. The change in viscosity or relaxation time with temperature exhibiting an Arrhenius-like dependence is classified as being "strong"; whereas a non-Arrhenius temperature dependence of viscosity or relaxation time is classified as "fragile". The origin of large differences in fragility of different substances has not been well understood. This work addresses the following questions about the origin of fragility: how differ strong liquids from fragile liquids, why the fragility of a substance changes under some circumstances, and how the fragility change is related to the changes in thermodynamic properties and structures. First, the glass transitions of the crystalline order-disorder Fe50Co50 and (FeCo)100-xAlx systems are studied. It is found that the thermodynamic and kinetic behaviors of the order-disorder systems mimic an ideal strong liquid with a critical point. With the support from the simulation results for liquid systems, a unified picture of an underlying lambda transition is proposed for understanding strong and fragile classifications. The second approach to understanding fragility is to directly investigate a strong-fragile transition in a strong bulk metallic glass-forming liquid. Electrostatic levitation and the synchrotron X-ray scattering techniques enable the in-situ studies of the structural changes of the metallic liquid over a wide temperature range in the supercooled liquid region. These experimental findings show that the dynamic strong-fragile crossover is associated with sudden structural changes and thermodynamic anomalies, suggesting a weak first-order liquid-liquid transition in the system.Die Temperaturabhängigkeit der Gleichgewichts-Viskosität bzw. der Relaxationszeit während des strukturellen Einfrierens ist dabei eine intrinsische Eigenschaft, die sogenannte Fragilität, der glas-bildenden Flüssigkeit. Folgt die Änderung der Viskosität bzw. Relaxationszeit als Funktion der Zeit einer Arrhenius-Gleichung wird das glas-bildende System als "stark" klassifiziert, andernfalls als "fragil". Die Ursache der beobachteten, großen Fragilitätsunterschiede verschiedener Systeme ist bisher jedoch nicht vollständig verstanden. Diese Arbeit soll dem Ursprung der Fragilität von Materialien sowie den damit verbundenen kinetischen und thermodynamischen Änderungen nachgehen. Insbesondere sollen hierbei die folgenden Fragen beantwortet werden: Wie unterscheiden sich starke von fragilen Flüssigkeiten? Warum ändert sich die Fragilität einer Substanz unter gewissen Umständen? Wie ist diese Fragilitätsänderung mit Änderungen in den thermodynamischen Eigenschaften und der Struktur verbunden? Dabei wurden zunächst Glasübergänge von Ordnungs-Unordnungs-Übergängen in kristallinen Fe50Co50 und (FeCo)100-xAlx Systemen untersucht. Hierbei wurde festgestellt, dass das thermische und kinetische Verhalten der Ordnungs-Unordnungs-Übergänge dem einer ideal starken Flüssigkeit mit einem kritische Punkt entspricht. Unter Einbeziehung von Simulationsergebnissen an flüssigen Systemen wird als einheitliches Bild für das Verständnis des starken und fragilen Charakters verschiedener Flüssigkeiten ein zugrunde liegender Lambda-Übergang vorgeschlagen. Zusätzlich erfolgte im Rahmen dieser Arbeit eine direkte Untersuchung des Stark-Fragil-Übergangs innerhalb einer starken, Massivglas-bildenden Flüssigkeit. Durch Kombination von Elektrostatischer Levitation und Synchroton-Röntgenbeugungsexperimenten gelang eine in-situ Untersuchung struktureller Änderung der metallischen Flüssigkeit über einen weiten Temperaturbereich. Hierbei konnte gezeigt werden, dass der dynamische Stark-Fragil-Übergang mit abrupten strukturellen Änderungen und thermodynamischen Anomalien einhergeht. Dies deutet auf einen zugrunde liegenden schwachen Phasenübergangs erster Ordnung hin