Optimal ductility enhancement of RC framed buildings considering different non-invasive retrofitting techniques

Existing RC framed buildings lack significant ductility, especially when they have been built with pre-code criteria. Improving their ductile capacity can help to prevent them from the brittle collapse mechanism and to reduce the seismic damage expected. This paper aims to investigate the enhancement of the ductile response behaviour of RC framed buildings considering different non-invasive retrofitting techniques. To do so, a pre-code RC framed school located in the Spanish province of Huelva has been selected as a case study. Five non-invasive retrofitting techniques have been tested: FRP wraps and steel jackets in columns, steel beams and plates under RC beams and single steel braces. They have been selected so that they can be easily implemented in the building. Some of them have been studied in detail in previous works and others have been included for further research in this paper. In order to compare the results obtained, the most typical technique in the seismic retrofitting of RC framed buildings, the addition of X-bracings in bays, has also been tested. Most previous studies on the seismic retrofitting of RC buildings are focused on validating a method based on artificial models. This paper compares the different techniques in terms of the capacity improvement and the damage reduction, performing analyses in detail and adding them in an existing RC building. A sensitivity analysis has been carried out to determine the influence of each technique in the building’s ductile capacity considering the finite element method. Nonlinear static analyses have been performed to obtain the capacity, the displacement ductility factor (μ) and the behaviour factor (q) of each model defined. The damage expected has been determined considering the ductile and fragile failure of the elements according to the Eurocode-8 (EC8) requirements. To analyse the suitability and the efficiency of each solution, a benefit/cost ratio has been obtained taking into account the ductility improvement and the damage reduction with regards to the retrofitting costs. The results have shown that the best benefit has been obtained with the addition of steel braces. However, the optimal solutions have been single braces and steel jackets due to their combination between benefit and cost. It has been observed that the solutions that increase the stiffness of the joints have had a higher improvement due to the key role that joints have in the resistant capacity of RC structurers. Also, it has been obtained that the values of the fundamental periods have been reduced, when adding the retrofitting elements and materials, up to 30% owing to the increase of the stiffness of the system. Finally, it must be highlighted that a detailed analysis of the behaviour of the whole building must be conducted in order to avoid additional rotation effects and shear forces that could worsen the building’s seismic behaviour

Assessment of specific structural and ground-improvement seismic retrofitting techniques for a case study RC building by means of a multi-criteria evaluation

Existing reinforced concrete (RC) structures might not comply with current seismic codes due to their aseismic design and construction date. By seismically retrofitting them, it is possible to improve their seismic performance to resist the expected seismic loads. However, selecting the best solution is challenging since social and economic issues can affect the choice. Multi-criteria decision making (MCDM) provides an opportunity to overcome the challenge but there are some drawbacks in the available MCDM techniques. This paper reports an improved MCDM-based seismic retrofit: Additional criteria have been included and weighted according to their importance (ductility improvement and damage reduction); Finite element modelling of the case study building has been carried out instead of following methods based on different simplifications; iii) Structural performances have been assessed by determining the damage in local elements instead of following global assessment procedures; Effects of soil-structure interaction (SSI) have been taken into account to ultimately compare different structural and ground-improvement techniques. Consistency and sensitivity analyses have proved the stability of the results and the robustness of the method. It is shown that SSI can increase the seismic damage up to 17%, and regarding the seismic safety verification, the building needs to be retrofitted. Adding fibre reinforcement polymers and steel bracings are the best solutions due to the minimum architectural impact and the outstanding structural improvement, respectively. Nevertheless, the solution preferred is the addition of single steel braces in beam- column joints despite its high maintenance costs. The sensitivity analysis indicates that the most sensitive criteria are the functional compatibility and the reduction of the collapse risk

Analysis of the soil structure-interaction effects on the seismic vulnerability of mid-rise RC buildings in Lisbon

Soil-structure interaction (SSI) effects are usually omitted in the seismic vulnerability analyses of buildings. However, it has been proved that they might notably affect their seismic performance. In fact, European seismic codes establish that they should be included in the analyses of certain structures: with considerable second order (p-Δ) effects or mid/high-rise buildings. These characteristics are shared by reinforced concrete (RC) buildings in Portugal, which represent a considerable amount of its building stock. Moreover, a significant percentage (50%) have been constructed prior to restrictive seismic codes, i.e., without adequate seismic design. To obtain reliable results when including the SSI effects, the state-of-the-art reveals that a proper modelling of soil and foundations should be carried out. Nevertheless, most of the related studies are based on ideal structural and soil configu- rations. In addition, it has been found that there is a lack of studies and guidance, even in codes, on the quantification of the SSI effects. Therefore, this paper focuses on quantifying the SSI effects in RC buildings seismic vulnerability analyses by means of two approaches: the Beam on Nonlinear Winker method (BNWM) and the direct modelling of soil. The aim is to propose a method to practically include the SSI effects and to thor- oughly characterise the soil behaviour. The method has been applied to a case study RC mid-rise building of Lisbon. A clay-type soil commonly found in Lisbon has been characterised, carrying the analyses out under undrained conditions. 3D finite elements procedures have been proposed to reproduce the complex soil nonlinear constitutive law to represent the behaviour of the entire system (soil + foundation + structure) as realistically as possible. The results have been compared in terms of the seismic safety verification and the fragility assessment. The results have shown that the modal behaviour and the deformed shape of the building are the same with and without the SSI. Nonetheless, it has been demonstrated that increasing the soil flexibility leads to higher periods and higher seismic damage. For this case study, the maximum capacity of the models can be reduced by up to 15% if the SSI effects are considere

Comparative analysis between the Spanish and Portuguese seismic codes. Application to a border RC primary school

The Iberian Peninsula is close to the Eurasia-Africa plate boundary resulting in a considerable seismic hazard. In fact, the southwestern Iberian Peninsula is affected by far away earthquakes of long-return period with large-very large magnitude. A project named PERSISTAH (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva, in Portuguese) aims to cooperatively assess the seismic vulnerability of primary schools located in the Algarve (Portugal) and Huelva (Spain). Primary schools have been selected due to the considerable amount of similar buildings and their seismic vulnerability. In Portugal, the Decreto Lei 235/83 (RSAEEP) is mandatory while in Spain, the mandatory code is the Seismic Building Code (NCSE-02). In both countries, the Eurocode-8 (EC-8) is recommended. Despite the fact that both regions would be equally affected by an earthquake, both seismic codes are significantly different. This research compares the seismic action of Ayamonte (Huelva) and Vila Real de Santo António (Portugal). Both towns are very close and located at both sides of the border. Moreover, they share the same geology. This analysis has been applied considering a RC primary school building located in Huelva. To do so, the performance-based method has been used. The seismic action and the damage levels are compared and analysed. The results have shown considerable differences in the seismic actions designation, in the performance point values and in the damage levels. The values considered in the Portuguese code are significantly more unfavourable. An agreement between codes should be made for border regions.This work has been supported by the INTERREG-POCTEP Spain-Portugal programme and the European Regional Development Fund through the 0313_PERSISTAH_5_P project and the VI-PPI of the University of Seville by the granting of a scholarship. The grant provided by the Instituto Universitario de Arquitectura y Ciencias de la Construcción is acknowledged.info:eu-repo/semantics/publishedVersio

Assessment of integrated solutions for the combined energy efficiency improvement and seismic strengthening of existing URM buildings

The European building stock is an aging infrastructure, mainly built prior to building codes. Furthermore, 65% of these buildings are located in seismic regions, which need to be both energetic and seismically retrofitted to comply with performance targets. Given this, this manuscript presents integrated constructive solutions that combine both energy efficiency improvement and seismic strengthening. The goal and novelty is to design and to evaluate one-shot, compatible, noninvasive, and complementary solutions applied to the façades of buildings with a minimum cost. To do so, different constraints have been borne in mind: the urban environment, achievable seismic and energy performance targets, and reduced construction costs. The method was applied to an old Spanish neighbourhood constructed in the 1960s. Different retrofitting packages were proposed for an unreinforced masonry case study building. A sensitivity analysis was performed to assess the effects of each configuration. A benefit/cost ratio was proposed to comparatively assess and to rank the solutions. The results of the seismoenergetic performance assessment showed that improving the behaviour of walls leads to higher benefit ratios than improving the openings. However, this latter strategy generates much lower construction costs. Integrating seismic into energetic retrofitting solutions supposes negligible additional costs but can improve the seismic behaviour of buildings by up to 240%. The optimal solution was the addition of higher ratios of steel grids and intermediate profiles in openings while adding thermal insulation in walls and renovating the window frames with PVC and standard 4/6/4 double glazing

Fast seismic assessment of built urban areas with the accuracy of mechanical methods using a feedforward neural network

Capacity curves obtained from nonlinear static analyses are widely used to perform seismic assessments of structures as an alternative to dynamic analysis. This paper presents a novel ‘en masse’ method to assess the seismic vulnerability of urban areas swiftly and with the accuracy of mechanical methods. At the core of this methodology is the calculation of the capacity curves of low-rise reinforced concrete buildings using neural networks, where no modeling of the building is required. The curves are predicted with minimal error, needing only basic geometric and material parameters of the structures to be specified. As a first implementation, a typology of prismatic buildings is defined and a training set of more than 7000 structures generated. The capacity curves are calculated through push-over analysis using SAP2000. The results feature the prediction of 100-point curves in a single run of the network while maintaining a very low mean absolute error. This paper proposes a method that improves current seismic assessment tools by providing a fast and accurate calculation of the vulnerability of large sets of buildings in urban environments.info:eu-repo/semantics/publishedVersio

Design of an improvement cycle in classroom based on problems and collaborative learning. Application to the calculation of pile foundations

El presente Ciclo de Innovación y Mejora en el Aula (CIMA) se aplica a la asignatura “Mecánica del Suelo y Cimentaciones (MSC)”, impartida en el tercer curso del grado en Fundamentos de la Arquitectura (Plan 2012) de la Universidad de Sevilla. Según el Plan de Estudios, a esta asignatura se le asignan 6 créditos y se imparte durante el segundo cuatrimestre. En líneas generales, la asignatura se centra en las siguientes cuestiones: — Identificación de tipos de suelos, tipologías de cimentaciones, estructuras de contención, sistemas de mejora y recalce y excavaciones. — Diseño, cálculo, análisis y definición de estructuras de suelo, cimentaciones, estructuras de contención, patología y recalce. — Seguridad en las cimentaciones según normativa. — Estudio y análisis del comportamiento del suelo. El número total de alumnos en la clase es 32. El aula donde se imparte la materia cuenta con sillas y mesas no fijas para permitir y fomentar el trabajo en grupo. El objetivo final de la asignatura consiste en que los alumnos sean capaces de razonar lógicamente, buscar sus propios recursos, tengan autonomía en la toma de decisiones, trabajen en equipo y sean responsables

Rehabilitación sísmica estructural de colegios de educación primaria

El presente libro tiene como objetivo la presentación del trabajo desarro-llado en el proyecto europeo de investigación PERSISTAH (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva, en portugués), el cual se ha desarrollado de forma cooperativa por la Universidad de Sevilla (España) y la Universidad del Algarve (Portugal). Dicho proyecto de investigación se centra en el estudio y la valoración del riesgo sísmico de edificios de educación primaria en el territorio del Algarve (Portugal) y Huelva (España). Para ello se han tenido en cuenta los objetivos establecidos por las Plataformas Nacionales para la Reducción de Riesgo de Catástrofes (PNRRC) de las Comisiones Na-cionales de Protección Civil de Portugal y de España.Programa INTERREG-POCTEP España-Portugal e o Fundo Europeu de Desenvolvimento Regional (FEDER)info:eu-repo/semantics/publishedVersio

¿Por qué se mueve el suelo?

Está guía está concebida para apoyar la formación del personal educativo de enseñanza primaria, que quiera mejorar su conocimiento y desarrollar actividades sobre el riesgo sísmico y de tsunami. Los contenidos e información de este documento son fruto del trabajo realizado en el marco del proyecto PERSISTAH, y también como continuación de otros proyectos en los que algunos autores han participado.Programa INTERREG-POCTEP España-Portugal e o Fundo Europeu de Desenvolvimento Regional (FEDER); Projeto PERSISTAH (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva)info:eu-repo/semantics/publishedVersio

Guía práctica para un colegio resiliente a los sismos

Esta guía pretende ser un recurso, que no un manual, para aumentar la resiliencia de la comunidad educativa, mostrándole qué es lo que puede hacer por sí misma y cómo puede fortalecer sus capacidades frente al riesgo sísmico (por ejemplo, estando informada y familiarizada con las características que inciden en la vulnerabilidad de un espacio en caso de terremoto, y preparada para proteger a los estudiantes bajo su tutela antes de que la tierra tiemble).Programa INTERREG-POCTEP España-Portugal e o Fundo Europeu de Desenvolvimento Regional (FEDER); Projeto PERSISTAH (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva)info:eu-repo/semantics/publishedVersio