Evaluación probabilista de la amenaza sísmica de Colombia con fines de actualización de la Norma Colombiana de Diseño de Puentes CCP-14

ResumenLa Asociación Colombiana de Ingeniería Sísmica (AIS) ha realizado una actualización del Código Colombiano de Diseño Sismorresistente para Puentes (CCP-14). Entre las diferentes tareas realizadas, ha establecido el valor de los coeficientes de diseño sismorresistente compatibles con la forma funcional del espectro elástico de diseño seleccionado. Para ello, se ha actualizado la evaluación probabilista de la amenaza sísmica a escala nacional y, a partir de ella, se han calculado dichos coeficientes para todo el territorio nacional. Con respecto al último estudio general de amenaza sísmica de Colombia, se dispone de cinco años más de registros de sismicidad y, por consiguiente, de un mejor entendimiento del entorno sísmico colombiano, lo cual ha permitido realizar actualizaciones relacionadas con los parámetros de sismicidad de las fuentes sismogénicas y utilizar relaciones de atenuación de movimiento fuerte calibradas a partir de registros locales. Se presentan los mapas de zonificación sísmica para los tres coeficientes de diseño incluidos en el CCP-14 así como la herramienta gratuita de visualización en línea de los resultados.AbstractA recent update of the Colombian earthquake resistant building code for bridges (CCP-14) was developed by the Colombian Association for Earthquake Engineering (AIS). Among the different tasks developed, the values for the seismic design coefficients, compatible with the functional form of the selected elastic design spectra were established. For that reason an update of the probabilistic seismic hazard assessment was performed from which the seismic design coefficients have been estimated for Colombia. With respect to the latest national seismic hazard assessment, 5 more years of earthquake records and the consequent better understanding of the Colombian seismic environment are included in the analysis by updating the seismicity parameters of the seismogenetic sources and using ground motion prediction equations calibrated with local strong ground motion records. The seismic zonation maps for the three seismic design coefficients included in the CCP-14 are presented as well as the free online results visualization too

Modelización probabilista de efectos de sitio en ciudades y su aplicación en Bogotá

A methodology for assessing site effects in cities is presented, which is based on the geometry of the prevailing geological formations and their relation to soft soil deposits. Based on a geological interpretation for the area of the city, the elevation (above sea level) of geological contacts is defined, and a three-dimensional geometric model of the subsoil of the city is obtained. The geotechnical information available is used to map soil types to the geometric model. The static and dynamic characteristics of the soil are defined as random variables and their probability moments are calculated using statistics on the geotechnical data available. A computational rectangular grid must be defined over the city and for each node synthetic stratigraphies are constructed with geotechnical parameters obtained following their probability distributions. The dynamic response is calculated for each node of the grid, by a 1D nonlinear analysis (linear equivalent) using a set of Fourier amplitude spectra generated at bedrock level using a source spectrum model, for different combinations of moment magnitude and rupture distance. Site-specific attenuation functions are generated and used to calculate seismic hazard at surface level. Uniform hazard spectra for 475 years return period are obtained. From these spectra harmonized design spectra to the NSR 10 are generated by random search of Fa and Fv parameters to ensure optimum fit. Following this methodology a site effects model for the city of Bogotá, Colombia, is constructed. This is used to exemplify trhee main direct application: i) obtaining transfer functions of the response spectrum for risk assessment, ii) generating Shake- Maps for emergency response purposes, and iii) the seismic microzonation of the city and obtaining elastic seismic-resistant design spectra

Numerical method for the holistic evaluation of the seismic risk based on the fuzzy sets theory

La teoría de conjuntos difusos ofrece un puente entre el procesamiento simbólico y el numérico que permite el uso de conceptos cualitativos útiles en el proceso de toma de decisiones relacionadas con la gestión del riesgo sísmico y, en general, con la gestión del riesgo de desastres. Su utilización en la evaluación del riesgo sísmico es necesaria en el caso en que los datos para aplicar un método de evaluación convencional del riesgo no estén disponibles o sean insuficientes. Una posible solución, considerada en este artículo, consiste en sustituir la información que falta por la opinión de expertos y en procesar las variables cualitativas y las calificaciones lingüísticas que se obtengan de dichas opiniones en lugar de valores numéricos. El procesamiento se realiza utilizando la teoría de conjuntos difusos. Para lograr una gestión eficaz, el riesgo se debe definir como las posibles consecuencias físicas, económicas, sociales y ambientales que pueden ocurrir en un período de tiempo determinado debido a fenómenos peligrosos. Desde esta perspectiva holística, y utilizando la teoría de conjuntos difusos, el método numérico propuesto calcula un nivel de riesgo físico y un nivel de agravamiento relacionado con las condiciones de fragilidad social y falta de resiliencia, para determinar un nivel de riesgo total. En el artículo se incluyen 2 ejemplos de aplicación del método propuesto y los resultados obtenidos se comparan con los correspondientes a un método convencional de evaluación holística.The fuzzy set theory offers a bridge between the symbolic and numerical processing, allowing managing qualitative concepts useful in the decision-making process related to the seismic risk management and, in general, to the disaster risk management. Its use in the seismic risk evaluation is necessary in the cases where the data required to apply a conventional method of assessing risk are not available or are insufficient. One possible solution, considered in this article, is to replace the missing information by expert opinions and to process the resulting qualitative variables and linguistic qualifications instead of numerical values. This process is based on the fuzzy set theory. In order to achieve an effective management, the risk must be defined as the potential physical, economic, social and environmental consequences which occur due to hazards in a given period of time. From this holistic perspective and using the fuzzy set theory, the proposed numerical method calculates a level of the physical risk and level of the aggravating conditions related to social fragility and to the lack of resilience, to determine a total risk level. In the article are included two examples of application of the proposed method and the obtained results are compared with those corresponding to a conventional method of holistic evaluation.Peer Reviewe

Probabilistic assessment of seismic risk of Barcelona, Spain, using the CAPRA platform

The Comprehensive Approach for Probabilistic Risk Assessment (CAPRA), is a robust methodology for modeling risk which allows identifying the most important aspects of catastrophes. CAPRA performs the evaluation of losses of the exposed elements using probabilistic metrics, such as the loss exceedance curve, the expected annual loss and the probable maximum loss, which are useful for multi-hazard risk analysis. The outcomes obtained with such a technical-scientific methodology are oriented to facilitate decision-making. They allow designing risk transfer instruments, evaluating the cost–benefit ratio, developing risk mitigation strategies and loss scenarios for emergency response, etc. The CAPRA platform is described in this paper by using as a testbed the city of Barcelona, Spain. Nevertheless, the results included for this urban area have not only a high scientific interest but also a practical one, because they are useful in taking risk reduction decision by the Municipalit

Estado del arte sobre aplicación de métodos numéricos y la simulación de escenarios de riesgo y al cálculo de la seguridad estructural

En este informe se estudian los métodos numéricos orientados hacia el cálculo de la seguridad de las estructuras, a la evaluación de su vulnerabilidad y riesgo, así como al desarrollo de escenarios de riesgo. Partiendo de una amplia revisión bibliográfica, se realiza una descripción del marco conceptual del riesgo, insistiéndose en las formulaciones que se han dado a los conceptos de amenaza, vulnerabilidad, fragilidad y daño involucrados en la definición del riesgo. A pesar de que los conceptos analizados son válidos para cualquier tipo de elemento en riesgo, para responder al principal objetivo de este estudio se pone énfasis en las estructuras de edificación y en las zonas urbanas. Dicho objetivo es el de estudiar los métodos de última generación orientados a la evaluación del daño esperado tanto en edificios individuales (lo que implica examinar su seguridad y vulnerabilidad) como en zonas urbanas (para las que se describirán procedimientos de simulación de escenarios de riesgo.) Después de incluir los principios relacionados con la evaluación de diferentes amenazas naturales (terremotos, tsunamis, erupciones volcánicas, huracanes, inundaciones, deslizamientos, avalanchas, etc.) para las que se introduce el concepto de escenario de amenaza, el presente estudio se centra más en la amenaza sísmica, al tener esta una mayor influencia en la seguridad de las estructuras que se hallan en zonas urbanas. Se describe, primeramente, del método del índice de vulnerabilidad, desarrollado en el ámbito del riesgo sísmico, que permite caracterizar la vulnerabilidad de las estructuras. Unas funciones de vulnerabilidad semiempíricas permite estimar el daño estructural para diferentes intensidades de la acción y para diferentes índices de vulnerabilidad estructural. En el segundo lugar, se examina el método del espectro de capacidad que se fundamenta en modelos de análisis no lineal de las estructuras y de curvas de fragilidad estructural. La acción se define mediante el espectro de demanda. El método proporciona las probabilidades de ocurrencia para diferentes estados mencionados, utilizándose como ejemplo la ciudad de Barcelona para la se han desarrollado escenario de riesgo para la amenaza sísmica

Determinants of risk: Exposure and vulnerability

Many climate change adaptation efforts aim to address the implications of potential changes in the frequency, intensity, and duration of weather and climate events that affect the risk of extreme impacts on human society. That risk is determined not only by the climate and weather events (the hazards) but also by the exposure and vulnerability to these hazards. Therefore, effective adaptation and disaster risk management strategies and practices also depend on a rigorous understanding of the dimensions of exposure and vulnerability, as well as a proper assessment of changes in those dimensions. This chapter aims to provide that understanding and assessment, by further detailing the determinants of risk as presented in Chapter 1. The first sections of this chapter elucidate the concepts that are needed to define and understand risk, and show that risk originates from a combination of social processes and their interaction with the environment (Sections 2.2 and 2.3), and highlight the role of coping and adaptive capacities (Section 2.4). The following section (2.5) describes the different dimensions of vulnerability and exposure as well as trends therein. Given that exposure and vulnerability are highly context-specific, this section is by definition limited to a general overview (a more quantitative perspective on trends is provided in Chapter 4). A methodological discussion (Section 2.6) of approaches to identify and assess risk provides indications of how the dimensions of exposure and vulnerability can be explored in specific contexts, such as adaptation planning, and the central role of risk perception and risk communication. The chapter concludes with a cross-cutting discussion of risk accumulation and the nature of disasters

Evaluación holística del riesgo sísmico en zonas urbanas

Risk has been defined, for management purposes, as the potential economic, social and environmental consequences of hazardous events that may occur in a specified period of time. In the past, the concept of risk has been defined in many cases in a fragmentary way, according to each scientific discipline involved in its appraisal. A framework and a multidisciplinary risk evaluation model is proposed in this article that take into account not only the expected physical damage, the number and type of casualties or the economic losses, but also the conditions related to soial fragility and lack of resilience which favor second order effects (or indirect effects) when an earthquake strikes an urban centre. Thus, the mentioned evaluation is holistic, that is based on an integrated and comprehensive approach, made by using indicatos andoriented towards guiding decision-making. Th conceptual framework and the model proposed are also valid for their applicationto multihazard risk evaluation, although this article has been focused on the evaluation of the seismic riskk. The first step in obtaining the Urban Seismic Risk index (USRi) consists of calculating a Physical Risk index for each unit of analysis starting form existing physical risk scenarios. An impact factor, associated with a set of socio-economic and lack of resilience conditions of the community, is applied in a second step to the physical risk index in order to obtain the USRi. It has been demostrated that the proponed holistic evaluationmodel of the seismic risk in robust, provideing stable and reliable values of the USRi. Finally, numerical simulation results of the seismic risk obtained with the proposed model are given in the article for the cities of Bogota (Colombia), Barcelona (Spain) and Manila (The Phillipines)

Evaluation of the habitability of buildings affected by an earthquake using the fuzzy sets theory and the artificial neural networks

La teoría de conjuntos difusos y las redes neuronales son herramientas de inteligencia computacional que cada vez tienen un uso más extendido en la ingeniería sísmica. En este artículo se desarrolla un método y una herramienta computacional que hace uso de estas técnicas para apoyar la evaluación del daño y de la seguridad de los edificios después de sismos fuertes. Se utiliza una red neuronal artificial de tres capas y un algoritmo de aprendizaje tipo Kohonen, así como conjuntos difusos para manipular información subjetiva como las calificaciones de los niveles de daño presentes en los edificios evaluados. También se aplica una base de reglas difusas para contribuir al proceso de toma de decisiones. Se ha desarrollado un programa de ordenador que utiliza estas técnicas, cuyos datos de entrada del programa corresponden a la información subjetiva e incompleta del estado del edificio obtenida por profesionales posiblemente inexpertos en el campo de la evaluación del comportamiento sísmico de los edificios. El método propuesto ha sido implementado en una herramienta de especial utilidad durante la fase de respuesta a emergencias, que facilita las decisiones sobre habitabilidad y reparabilidad de los edificios. Para ilustrar su aplicación, se incluyen ejemplos de aplicación del programa para dos clases diferentes de edificios.The fuzzy sets theory and the artificial neural networks are computational intelligence tools which are nowadays widely used in earthquake engineering. This paper develops a method and a computer program which use these computational intelligence tools in order to support the damage and safety evaluation of buildings after strong earthquakes. The model uses an artificial neural network with three layers and a Kohonen learning algorithm; it also uses fuzzy sets in order to manage subjective information such as linguistic qualification of the damage levels in buildings and a fuzzy rule base to support the decision making process. All these techniques are incorporated in the developed computer program. The input data is the subjective and incomplete information about the building state obtained by possibly non experienced evaluators in the field of the seismic performance of buildings. The proposed method is implemented in a tool especially useful in the emergency response phase, when it supports the decision making regarding the building habitability and reparability. In order to show its effectiveness, two examples are included for two different types of buildings.Peer Reviewe

Ambivalence towards discourse of disaster resilience

This paper investigates empirically how the international aid community (IAC)—donors and practitioners—considers and implements disaster resilience in a specific country setting, Nepal, and throughout the rest of the world. A key finding is that there is ambivalence about a concept that has become a discourse. On a global level, the IAC utilises the discourse of resilience in a cautiously positive manner as a bridging concept. On a national level, it is being used to influence the Government of Nepal, as well as serving as an operational tool of donors. The mythical resilient urban community is fashioned in the IAC's imaginary; understanding how people create communities and what type of linkages with government urban residents desire to develop their resilience strategies is missing, though, from the discussion. Disaster resilience can be viewed as another grand plan to enhance the lives of people. Yet, regrettably, an explicit focus on individuals and their communities is lost in the process

Deep-sequencing reveals broad subtype-specific HCV resistance mutations associated with treatment failure

A percentage of hepatitis C virus (HCV)-infected patients fail direct acting antiviral (DAA)-based treatment regimens, often because of drug resistance-associated substitutions (RAS). The aim of this study was to characterize the resistance profile of a large cohort of patients failing DAA-based treatments, and investigate the relationship between HCV subtype and failure, as an aid to optimizing management of these patients. A new, standardized HCV-RAS testing protocol based on deep sequencing was designed and applied to 220 previously subtyped samples from patients failing DAA treatment, collected in 39 Spanish hospitals. The majority had received DAA-based interferon (IFN) a-free regimens; 79% had failed sofosbuvir-containing therapy. Genomic regions encoding the nonstructural protein (NS) 3, NS5A, and NS5B (DAA target regions) were analyzed using subtype-specific primers. Viral subtype distribution was as follows: genotype (G) 1, 62.7%; G3a, 21.4%; G4d, 12.3%; G2, 1.8%; and mixed infections 1.8%. Overall, 88.6% of patients carried at least 1 RAS, and 19% carried RAS at frequencies below 20% in the mutant spectrum. There were no differences in RAS selection between treatments with and without ribavirin. Regardless of the treatment received, each HCV subtype showed specific types of RAS. Of note, no RAS were detected in the target proteins of 18.6% of patients failing treatment, and 30.4% of patients had RAS in proteins that were not targets of the inhibitors they received. HCV patients failing DAA therapy showed a high diversity of RAS. Ribavirin use did not influence the type or number of RAS at failure. The subtype-specific pattern of RAS emergence underscores the importance of accurate HCV subtyping. The frequency of “extra-target” RAS suggests the need for RAS screening in all three DAA target regions