Coupled reliability model of biodeterioration, chloride ingress and cracking for reinforced concrete structures

International audienceMaintaining and operating civil infrastructure systems has been recognized as a critical issue worldwide. Among all possible causes of safety reduction during the structural lifetime, deteriora- tion is particularly important. Structural deterioration is usually a slow time-dependent process controlled by safety and operation threshold specifications. This paper presents a model of RC deterioration by coupling biodeterioration (i.e., chemical, physical and mechanical action of live organisms), steel corrosion, and concrete cracking. The final purpose of the model is to compute the reduction of the concrete section and the area of steel reinforcement in order to assess the change of structural capacity with time. Given the uncertainties in both the parameters and the model, the probabilistic nature of loads, the material properties and the difussion process are taken into account to evaluate structural reliability. The model is illustrated with an example where the inelastic behavior of a pile subject to random loading is considered. The results of the analysis have shown that the effect of biodeterioration on the structural performance is significant and can cause an important reduction of its lifetime. On the whole, the paper states that modeling the effects of biodeterioration in RC structures should be included as part of infrastructure planning and design, especially, when they are located in aggressive environments

Quebrada Doña María : de amenaza a sujeto de derechos

13 páginasIn an era marked by climate change, disaster risk prevention and mitigation has been gaining strenght, especially since the last decade, which has resulted in increased attention from the scientific world, governments and citizenship. However, many people remain outside knowledge and awareness, regarding the risks posed by certain natural events, which increase their potential damage as urban growth occurs and there are more and more alterations on geographical scenarios, such as rivers and bodies of water. All this takes place in Doña María creek, in Itagüí, which has generated minor emergency situations, but which can become major disasters, if a thorough investigation and contingency work is not done in this regard. In this sense, the present work synthesizes the main policies on the subject, as well as some background, that allow us to understand the ravine as a subject of tights and the risks that the population located in the lower part of its basin experiences, all in order to formulate some recommendations that can contribute to planning instruments of isntances, as well as to more accurate decisions.En una época marcada por el cambio climático, la prevención y mitigación del riesgo de desastres ha ido cobrando mayor fuerza, en especial, a partir de la última década, lo que se ha traducido en una mayor atención del mundo científico, los gobiernos y la ciudadanía. No obstante, muchas personas siguen al margen del conocimiento y sensibilización, respecto a los riesgos que representan ciertos eventos naturales, que incrementan su potencial daño a medida que se da el crecimiento urbano y se producen cada vez más alteraciones sobre los escenarios geográficos, como ríos y cuerpos de agua. Todo esto tiene lugar en la quebrada Doña María, en Itagüí, la cual ha generado situaciones de emergencias menores, pero que pueden llegar a ser grandes desastres, si no se hace un trabajo minucioso de investigación y de contingencia al respecto. En este sentido, el presente trabajo sintetiza las principales políticas sobre el tema, así como algunos antecedentes, que permiten entender la quebrada como sujeto de derechos y los riesgos que experimenta la población ubicada en la parte baja de su cuenca, todo con el fin de formular algunas recomendaciones que puedan aportar a los instrumentos o instancias de planificación, así como a decisiones más acertadas.Magíster en Gobierno y Políticas PúblicasMaestrí

Pattern Recognition Techniques Implementation on Data from In-Line Inspection (ILI)

PresentationOnshore pipeline failure caused by corrosion represents about 16% of the overall number of incidents during the period from 2004 to 2011 according to databases such as CONCAWE and PHMSA. In-Line Inspection (ILI) is one of the available inspection techniques used to determine overall pipeline status, highlighted because it establishes a clear perspective of inner and outer condition of the pipe against the failure modes and wall thickness. Furthermore, it supports measures to prevent risk based on standards such as ASMEB31G or API579-1/ASME FFS-1. However, this approximation could represent a conservative assessment of the pipeline status, taking into account the uncertainty associated with ILI inspection tools such as MFL and UT. Several researches have been conducted to analyze available inspection techniques attempting to reduce noise generated by their inspection tools, and determine procedures in order to establish correct metal loss detection, excelling pattern recognition analysis and reliability concepts. Therefore this work seeks to transform a set of data obtained from two ILI runs, into useful information to support decision making in risk analysis based on pattern recognition techniques and reliability concepts, in order to obtain base failure frequencies for prior analysis from individual and grouped flaws. Moreover, growth corrosion and remaining life models supported on the standards mentioned above were evaluated using a pressure failure criteria. As a result it was obtained that the failure probability of the grouped flaws increases 10% in comparison with the corresponding flaws evaluated individually

Probabilistic lifetime assessment of RC structures under coupled corrosion-fatigue deterioration processes

International audienceStructural deterioration is becoming a major problem when considering long term performance of infrastructures. The existence of a corrosive environment, cyclic loading and concrete cracking cause structural strength degradation. The interaction of these conditions can only be taken into account when modeling the coupled action. In this paper, a new model to assess lifetime of RC structures subject to corrosion-fatigue deterioration processes, is proposed. Separately, corrosion leads to cross section reduction while fatigue induces the nucleation and the propagation of cracks in steel bars. When considered together, pitting corrosion nucleates the crack while environmental factors affect the kinematics of crack propagation. The model is applied to the reliability analysis of bridge girders located in different chloride-contaminated environments. Overall results show that the coupled effect of corrosion-fatigue on RC structures affects strongly its performance leading to large reduction in the expected lifetime

Probabilistic Evaluation of the Sustainability of Maintenance Strategies for RC Structures Exposed to Chloride Ingress

International audienceNowadays, multiple constraints imposed by economical, social and environmental considerations undergo maintenance planning optimization into a major challenge to designers, owners and users of infrastructure. This study presents a simplified methodology to evaluate the sustainability of maintenance strategies used in reinforced concrete structures exposed to chlorides. The proposed approach is illustrated throughout the paper with an application to large-scale maintenance of a real structure (Agri-foodstuffs terminal wharf). The repair strategy consists of demolition of the polluted concrete and rebuilding of cover by using three techniques (wet shotcrete, dry shotcrete and formed concrete). The repair times are estimated by taking the randomness of chloride ingress into account. Three criteria are used to evaluate the sustainability of the repair techniques: present value life-cost, waste production and CO2 emissions. Based on this multi-criteria comparison, a simplified decision-making scheme based on a multi-objective index is proposed

A Markov regime-switching framework to forecast El Niño Southern Oscillation patterns

International audienceThe El Niño-Southern Oscillation (ENSO) is an ocean-atmosphere phenomenon involving sustained sea surface temperature fluctuations in the Pacific Ocean, causing disruptions in the behavior of the ocean and atmosphere. We develop a Markov switching autoregressive model to describe the Southern Oscillation Index (SOI), a variable that explains ENSO, using two autoregressive processes to describe the time evolution of SOI, each of which associated with a specific phase of ENSO. The switching between these two models is governed by a discrete time Markov chain (DTMC), with time-varying transition probabilities. Then, we extend the model using sinusoidal functions to forecast future values of SOI. The results can be used as a decision-making tool in the process of risk mitigation against weather and climate related disasters

Influence of weather and global warming in chloride ingress into concrete: a stochastic approach

International audienceReinforced concrete (RC) structures are subject to environmental actions affecting their performance, serviceability and safety. Among these actions, chloride ingress leads to corrosion and has been recognized as a critical factor reducing the service life of RC structures. This paper presents a stochastic approach to study the influence of weather conditions and global warming on chloride ingress into concrete. The assessment of chloride ingress is carried out on the basis of a comprehensive model that couples the effects of convection, chloride binding, concrete aging, temperature and humidity. A simplified model of temperature and humidity including seasonal variations and global warming is also proposed in this work. Three scenarios of global warming are defined based on: gas emissions, global population growth, introduction of new and clean technologies and use of fossil sources of energy. The proposed approach is illustrated by a numerical example where it is found that the climate changes may yield to significant lifetime reductions. These results justify the implementation of countermeasures directed to (1) reduce and/or mitigate the action of global warming on weather and (2) minimize the impact of climate changes on RC structures

Nuevos conceptos para la evaluación cualitativa de la confiabilidad en el diseño estructural

La calidad de los modelos mecánicos que describen el comportamiento estructural es ampliamente reconocida. Sin embargo, existe la percepción generalizada de que las especificaciones de diseño contenidas en los códigos conducen a estructuras que no son óptimas en términos de seguridad y economía. Esto se debe principalmente a: (1) la necesidad de establecer requisitos suficientemente amplios para cubrir un gran número de casos; y (2) a la utilización de modelos determinísticos que manejan de manera superficial la incertidumbre de las variables y el proceso. Dentro de la comunidad científica, esta situación ha generado un debate sobre la necesidad de la transición de una forma de pensamiento determinística a una interpretación completamente probabilística. Recientemente, un número importante de publicaciones internacionales indican que los avances computacionales han abierto una ventana muy promisoria para la modelación cualitativa de la confiabilidad y para la elaboración de códigos y reglamentaciones de diseño más eficientes. Para que este cambio sea posible, es necesario el desarrollo de nuevas estrategias fáciles de aplicar en la actividad diaria del diseño. Este artículo llama la atención sobre la importancia del diseño probabilístico, presenta los conceptos básicos y propone la utilización de métodos de simulación (eg. Monte Carlo) en aspectos prácticos de la actividad diaria del diseño

Impacto Ambiental y Gestión del Riesgo de Ladrilleras en la vereda Los Gómez de Itagüí

El presente artículo busca reflexionar y contextualizar la situación actual de las ladrilleras y los tejares de la vereda Los Gómez en el municipio de Itagüí con respecto al impacto ambiental que ha ocasionado esta actividad desde hace varias décadas. Es un análisis acerca de una realidad que expone a sus habitantes en un escenario de riesgo latente. La dinámica de la industria ladrillera en la vereda Los Gómez incide en los aspectos sociales, económicos, ambientales, laborales, de salud pública y de seguridad en esta zona. La industria ladrillera en Los Gómez no cuenta con proyectos que puedan compensar la problemática por deterioro social y ambiental que ella genera. Por lo tanto es importante analizar los compromisos que deben cumplir por ley los productores, así como las acciones que corresponden a las autoridades con dos fines: proteger la vida y los recursos naturales.Palabras clave: Gestión del riesgo de desastres, impacto ambiental, ladrilleras, Plan de Ordenamiento Territorial, contaminación, recursos naturales, salud pública.Abstract This paper aims to reflect and put into context the current situation of brickworks and tile factories at Los Gómez rural district in the municipality of Itagüí concerning the environmental impact this activity has brought about for several decades. This analysis shows how inhabitants are put into a latent risk scenario. Brickworks industry dynamics at Los Gómez village impinges upon social, economic, labor, public health and safety aspects in this area. Brickworks industry at Los Gómez does not have any project seeking to offset the social and environmental damage issue it generates. Therefore, it is important to analyze duties producers are to abide by, as well as legal actions that correspond to the authorities with for two purposes: to safeguard both human life and natural resources.Keywords: Disaster risk management, environmental impact, Territorial Ordering Plan, pollution, natural resources, public health

REVISIÓN DE LOS CRITERIOS DE CONFIABILIDAD DEL CÓDIGO DE DISEÑO ESTRUCTURAL COMO ALTERNATIVA PARA LA COMPETITIVIDAD

Los códigos modernos de diseño de elementos y sistemas estructurales utilizan factores parciales de carga yresistencia para garantizar la confiabilidad de la estructura. La definición de criterios de aceptabilidad delriesgo y la variabilidad de la resistencia y solicitación son los aspectos principales para la determinación de esosfactores parciales. Este documento presenta un análisis del ahorro en costos que significa la modificación de losfactores parciales establecidos por la NSR-98 manteniendo el mismo nivel de seguridad. Aunque los ahorros sonsustanciales, es necesario considerar otros factores que participan en la optimización de costos de una construcciónantes de tomar una decisión sobre la modificación de la normas