Abstract

Los sistemas de aislamiento sísmico de base desacoplan parcialmente una estructura de los movimientos del terreno por medio de dispositivos colocados entre la estructura y su cimentación. De los diversos tipos de dispositivos desarrollados, los más utilizados son lo de elastómero laminado que están constituidos por capas alternadas de elastómero y acero. Este artículo es una contribución al tratamiento numérico conjunto de las estructuras con sus dispositivos de aislamiento de base de elastómeros laminados.

Abstract

La estimacion del daño producido por la accion sísmica en puentes existentes ha cobrado interes en los ultimos años, no solo para tratar de disminuir el numero de víctimas sino tambien para reducir los drasticos costos generados en diversos sectores economicos. En la caracterizacion y evaluacion del daño se han priorizado los metodos de aplicacion simple y confiable, ya que son una herramienta util en casos de analisis multiples relacionados con la simulacion por Monte Carlo. Optando por este camino, en este artículo se presenta una propuesta de analisis simplificado del daño ocasionado por terremotos en puentes de autopista de hormigon armado. Se muestra la formulacion basica del modelo dinamico propuesto y el procedimiento de evaluacion del daño estructural, basado en el calculo de la inercia dañada de los pilares del puente para la estimacion de su degradacion. Se dan ejemplos de calculo que muestran la fiabilidad y eficacia del modelo propuesto.

Abstract

En la actualidad existen muchos puentes, construidos hace veinte o treinta años, que han sido proyectados aplicando normativas que luego han sido actualizadas, tanto en lo referente a la peligrosidad como a los métodos de cálculo. Para estas estructuras son necesarias herramientas de evaluación confiables que permitan evaluar su futuro comportamiento sísmico. En busca de ese objetivo, en un trabajo previo los autores han propuesto un método de análisis basado en la determinación de la degradación máxima de las pilas del puente. En este artículo se aplica la metodología para la evaluación de la vulnerabilidad sísmica del Puente Warth, Austria, construido hace 30 años bajo requisitos de diseño ahora obsoletos. Para esta estructura se realizaron varias simulaciones porMonte Carlo, considerando las incertidumbres asociadas a los parámetros de definición de la peligrosidad sísmica y a las características estructurales. A través de los resultados obtenidos se define el comportamiento futuro de la estructura para un posible escenario sísmico y se comprueba la bondad y confiabilidad del modelo simplificado propuesto.

Abstract

The numerical simulation of composite materials is a field under continuous development. Its application to structural design has shown important improvements, leading to a better simulation of strengthened structures. This paper uses the serial/parallel mixing theory to predict the mechanical behavior of composites. This theory uses the constitutive equations of the component materials to obtain the composite performance. The advantages provided by this formulation to simulate concrete structures reinforced or retrofitted with Fiber Reinforced Polymers (FRP) will be shown from the analysis of several finite element models, consisting of a set of concrete frames with different strengthening configurations. The results obtained will show that the use of this theory to simulate FRP reinforced structures improves their analysis and design.

Abstract

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).

Abstract

In this paper, a new methodology is described to evaluate the effect of open air explosions on equivalent structures to the facades of buildings. The structural damage is defined by vulnerability surfaces that are a function of the explosion magnitude, the distance to the structure and the detonation damage index developed in this article. The proposed index considers the structural load capacity degradation, the fracturing and the loss material due to the explosion. The structure is modeled by means of discrete elements (DEM) which allows describing the multifracturing state. The load capacity of the structure is quantified by a virtual compression test on the damaged structure. The forces on the structure caused by the explosion are modeled by a semi-empirical methodology, which avoids the fluid-dynamic analysis and reduces the computation time.

Abstract

The strengthening of concrete structures with laminates of carbon fibers CFRP (Carbon Fibers Reinforced Polymer) began in the 1980s. Nowdays, this technology is one of the most promising one because of the good mechanical properties of laminates and their easy hand-work. Laminates are bonded to the concrete structure by means of epoxy resins. The load-carrying capacity of the strengthening depends directly on the proper behavior of the interface laminate-concrete. While the concrete is capable of transferring stresses to the laminate, this one becomes in charge and collaborates to the strength mechanism of the structure. The safety factor of the reinforcement can be guaranteed if we can predict the behavior at the interface between both materials. In this work we present a pure shear test and a simulation three-dimensional to characterize the behavior of the interface between the laminate and the concrete.

Abstract

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.

Abstract

Currently, many structures existing in seismic areas are highly vulnerable because they have been built without the use of seismic design codes or by using outdated codes. Often, methods for assessing the vulnerability of the structures do not take into account that their seismic behavior is dynamic and highly nonlinear and, moreover, that the structural characteristics and action have large uncertainties. This article aims to assess the vulnerability of structures taking into account that the mechanical properties of materials and the seismic action are random variables, by using advanced techniques based on the Monte Carlo method and on the nonlinear stochastic dynamics. The results obtained with these techniques are compared with those corresponding to a standard vulnerability assessment, based on deterministic models, in order to highlight the differences between both approaches. The main conclusion of this work is the need to address the vulnerability assessment problem from a probabilistic perspective which, combined with advanced nonlinear static and dynamic structural analysis techniques, provides a powerful tool giving information impossible to be captured by means of deterministic models. Finally, detailed results obtained for a building with waffle slabs, which is a structural typology widely used in Spain, are included and discussed.

Abstract

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.