Schools, Seismicity and Retrofitting. PERSISTAH Project (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva)

PERSISTAH Project (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva) Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING SUMARY BOOK REVIEW SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SUMARY SCHOOLS, SEISMICITY AND RETROFITTING SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) Antonio Morales Esteban, Emilio Romero Sánchez, Beatriz Zapico Blanco, María Victoria Requena García de la Cruz, Jaime de Miguel Rodríguez and João Estêvão Sevilla 2021 PERSISTAH Project (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) © Editorial Universidad de Sevilla 2021 c/ Porvenir, 27 - 41013 Sevilla Tlf. 954 487 447; 954 487 451 - Fax 954 487 443 Correo electrónico: [email protected] Web: <https://editorial.us.es> © Beatriz Zapico Blanco (coord.) 2021 © Antonio Morales Esteban (Universidad de Sevilla), Emilio Romero Sánchez (Universidad de Sevilla), Beatriz Zapico Blanco (Universidad de Sevilla), María Victoria Requena García de la Cruz (Universidad de Sevilla), Jaime de Miguel Rodríguez (Universidad de Sevilla) and João Estêvão (Universidade do Algarve) 2021 ISBN-e: 978-84-472-3122-5 DOI: http://dx.doi.org/10.12795/9788447231225 Layout and digital edition: Dosgraphic, S.L. ([email protected]) Collection Ediciones especiales Cover design: Emilio Romero Sánchez All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher (Editorial Universidad de Sevilla). Editorial Committee Araceli López Serena (Editorial Universidad de Sevilla Director) Elena Leal Abad (Deputy Director) Concepción Barrero Rodríguez Rafael Fernández Chacón María Gracia García Martín Ana Ilundáin Larrañeta María del Pópulo Pablo-Romero Gil-Delgado Manuel Padilla Cruz Marta Palenque Sánchez María Eugenia Petit-Breuilh Sepúlveda José-Leonardo Ruiz Sánchez Antonio Tejedor Cabrera This work has been developed within the framework of the PERSISTAH project, Projetos de Escolas Resilientes aos Seismos no Território do Algarve e de Huelva (0313_PERSISTAH_5_P), developed jointly by the universities of the Algarve and Seville and funded by the European Commission through the call EP – INTERREG VA Spain Portugal (POCTEP). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 7 Summary Symbols ...................................................................................... 11 Abbreviations ............................................................................... 13 Chapter 1. Introduction ............................................................... 15 1.1. Project objective and justification ................................................... 17 1.2. Main outcomes of the project ......................................................... 18 1.3. Document structure ....................................................................... 20 Chapter 2. Seismic hazard in the Algarve-Huelva Region .............. 21 2.1. The Algarve-Huelva Region .......................................................... 21 2.2. The impact of soil type on seismic hazard ....................................... 24 2.3. Seismic hazard in Spain .................................................................. 24 2.3.1. Chronological evolution of seismic building codes in Spain .. 25 2.3.2. Mandatory code in Spain ...................................................... 26 2.3.2.1. The Seismic Building Code (NCSE02) .................... 26 2.3.2.2. Update of the seismic hazard maps ........................... 32 2.3.3. Recommended code: Eurocode 8 ......................................... 34 2.3.3.1. Determining the response spectrum ......................... 35 2.3.3.2. Spanish National Annex ........................................... 37 2.4. Seismic hazard in Portugal .............................................................. 38 2.4.1. Historical seismic codes: Decree law no. 235/83 .................... 38 2.4.1.1. Probabilistic seismic hazard analysis .......................... 38 2.4.1.2. Determination of seismic action .............................. 39 2.4.2. Mandatory code: Eurocode 8 ................................................ 39 2.4.2.1. Construction of the response spectrum .................... 40 2.4.2.2. Portuguese National Annex ..................................... 40 2.5. Comparison of seismic hazard in the Algarve-Huelva region ........... 42 Chapter 3. Characterisation of schools .......................................... 47 3.1. Sources of information ................................................................... 47 3.1.1. Creation of the database ....................................................... 48 3.1.2. Creation of building specification sheets ............................... 48 3.1.3. Questionnaires sent to schools .............................................. 51 SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 8 SUMARY 3.2. School buildings characterisation process ........................................ 53 3.2.1. Classification according to structural system and year of construction ..................................................................... 53 3.2.2. Classification according to geometry and volumetry ............. 54 3.2.2.1. Compact type buildings ........................................... 55 3.2.2.2. Linear type buildings ............................................... 58 3.2.2.3. Intersection buildings .............................................. 60 3.2.2.4. Prism buildings ........................................................ 64 3.2.2.5. Juxtaposed buildings ................................................ 64 3.2.3. Sports facilites ...................................................................... 65 3.3. Characterisation of masonry buildings ............................................ 65 3.4. Characterisation of reinforced concrete frame buildings .................. 71 3.4.1. Date of construction and regulations ..................................... 71 3.4.2. Area and height .................................................................... 73 3.4.3. Slabs ..................................................................................... 73 3.4.4. Column and beams .............................................................. 74 3.4.5. Infill walls ............................................................................. 75 3.4.6. Irregularities ......................................................................... 76 3.4.7. Subtypes ............................................................................... 76 3.4.7.1. Square footprint ...................................................... 76 3.4.7.2. Rectangular footprint .............................................. 77 3.4.7.3. Intersection ............................................................. 79 3.4.7.4. Irregular .................................................................. 80 Chapter 4. Structural safety analysis ............................................. 81 4.1. Method .......................................................................................... 81 4.2. Capacity analysis ............................................................................. 82 4.3. Performance point .......................................................................... 84 4.3.1. N2 Method .......................................................................... 84 4.3.1.1. Implementation in the PERSISTAH software .......... 85 4.3.2. Capacity-demand spectrum method ..................................... 91 4.3.2.1. Implementation in the PERSISTAH software .......... 93 4.4. Structural damage analysis .............................................................. 93 Chapter 5. PERSISTAH Software ................................................ 99 5.1. Schools module .............................................................................. 100 5.1.1. Menu: School ....................................................................... 100 5.1.2. Menu: School buildings ........................................................ 103 5.1.3. Importing capacity curves ..................................................... 104 SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 9 SUMARY 5.2. Seismic action module .................................................................... 104 5.3. Damage module ............................................................................. 106 5.3.1. Operation ............................................................................ 106 5.3.2. Obtaining the School-score .................................................. 108 Chapter 6. Sismic retrofitting strategies ........................................ 109 6.1. International context ...................................................................... 110 6.1.1. ATC-40 ............................................................................... 110 6.1.2. FEMA 356 ........................................................................... 113 6.1.3. EC8 ..................................................................................... 115 6.1.3.1. Masonry buildings ................................................... 116 6.1.3.2. Reinforced concrete buildings ................................. 119 6.1.3.3. Other buildings ....................................................... 120 6.2. Masonry buildings .......................................................................... 125 6.2.1. State of the Art ..................................................................... 126 6.2.1.1. Wire mesh ............................................................... 128 6.2.1.2. Steel sheet bands ...................................................... 129 6.2.1.3. Injections ................................................................ 131 6.2.1.4. Reinforced concrete elements .................................. 132 6.2.1.5. Carbon fibre reinforced polymers (CFRP) ............... 133 6.2.1.6. Rebaring ................................................................. 134 6.2.2. Retrofitting schemes considered ........................................... 136 6.3. Reinforced concrete buildings ........................................................ 138 6.3.1. State of the art ...................................................................... 139 6.3.1.1. Bracings .................................................................. 139 6.3.1.2. Energy dissipation systems ....................................... 140 6.3.1.3. Shear walls ............................................................... 140 6.3.1.4. Confinement jackets ................................................ 142 6.3.2. Retrofitting schemes considered ........................................... 143 6.4. Seismic Reinforcement Index ......................................................... 145 Chapter 7. Example of seismic retrofitting .................................... 147 References .................................................................................. 153 List of tables ................................................................................ 159 List of figures .............................................................................. 161 SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 16 SUMARY (Mw = 8.7 – 9.0) and the 1969 earthquake (Mw = 8). The first is also the largest documented seismic event to have affected Europe, killing 100 000 people. The maximum seismic intensity of this region, based on past earthquakes, is high in the Algarve (IX-X) and Huelva (VII-VIII) (Teves-Costa et al., 2019). Although there is significant seismic risk, few seismic studies of the area have been carried out, as most seismic studies of the Iberian Peninsula focus on the east and south-east. The seismic vulnerability of the region’s buildings was evaluated using estimation methods such as SIRCO (Seismic Risk Simulator) (Fazendeiro Sá et al., 2016) or ERSTA (Algarve Seismic Risk and Tsunami Study) (Autoridade Nacional de Protecção Civi [ANPC], 2010). They conclude that it is possible to reduce seismic risk by improving prevention and emergency plans. In this sense, rigorous vulnerability analyses of existing buildings and the implementation of appropriate retrofitting solutions can contribute to the reduction of the levels of physical damage, human losses and the economic impact of future seismic events. The seismic behaviour of buildings plays a key role in the destructive potential of an earthquake. The vulnerability of existing buildings has been the focus of European interest in recent years. This is due to the damage caused by recent earthquakes, such as the L’Aquila earthquake in 2019 (Italy), the Lorca earthquake in 2011 (Spain) and the Amatrice earthquake in 2016 (Italy) (Ruiz-Pinilla et al., 2016; Del Gaudio et al., 2017; Fiorentino et al., 2018). A large part of the buildings of these cities were severely damaged during these earthquakes. Therefore, enhancing the seismic performance of buildings has become a major concern (Mazzoni et al., 2018) , which can be achieved through the implementation of seismic retrofitting techniques. The school buildings in the PERSISTAH project have been chosen as the object of study because of their relevance in case of an earthquake. On the one hand, their community present a high vulnerability, due to their low adult/child ratio and high occupation, making the evacuation of the building during an emergency complicated. Moreover, in the event of an earthquake, not only physical damage and injuries are expected: children would also be emotionally affected in a significant way. In this regard, several studies have shown that serious psychological problems can arise on children who have suffered the effects of an earthquake and the benefits of preparedness (UNICEF, 2011). On the other hand, school building structures also present high seismic vulnerability. Their typically simple and repetitive layouts were designed and calculated based on old regulations that did not take into account the seismic action. Approximately 50% of the buildings were designed with reinforced concrete and have two or three floors, and they have seismically weak elements such as short columns. This type of buildings were significantly damaged during the 2011 Lorca SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 17 SUMARY earthquake (Ruiz-Pinilla et al., 2016). Furthermore, the area is characterised by the presence of superficail soft soil layers, which can amplify the effects of earthquakes. In addition to this, due to their public nature, schools can also be used as shelters after a disaster. All this makes it essential to assess and guarantee their structural stability in the event of an earthquake. It is important to note that in the event of an earthquake, both regions (Algarve and Huelva) would be equally affected. One of the objectives of the project is to improve the knowledge related to the current situation of each country, particularly on seismic standards and construction practices. In this sense, the seismic regulations, construction techniques, civil protection policies and seismic risk reduction strategies of both countries have been compared. In addition, a database has been developed with information sheets from each primary school (142 in Algarve and 138 in Huelva), taking into account the specifications of each region. The main types of primary schools have been identified in this project. Subsequently, an inventory of the constructive and structural characteristics of each building has been created. With this information, the vulnerability of each school has been analysed through a non-linear static (pushover) analysis for obtaining the capacity curve. Finally, the ranking of the seismic behaviour of each school has been made through the School-Score system (a system of prioritisation of the seismic risk of school buildings). Seismic behaviour has been evaluated according to the hazard, vulnerability and exposure of each building. 1.1. PROJECT OBJECTIVE AND JUSTIFICATION The PERSISTAH project was conceived based on a number of key points regarding the seismic resilience of the Algarve and Huelva regions: — A significant part of the known seismic sources around the Algarve and Huelva areas would have a transboundary impact. — Knowledge of existing hazards and the seismic vulnerability of buildings is essential for effective emergency response. — It is important to study the application of mitigation measures in schools in the face of a possible seismic event. — The development of educational material and the communication of seismic risk to students and teachers would reduce the vulnerability of the community. — Making recommendations for rehabilitation aimed at technicians involved in construction will have a positive effect on the risk reduction. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 18 SUMARY — The creation of cooperative links in risk mitigation efforts between these two neighbouring regions will enhance the regions seismic resilience. Based on these points, the main objective of the European project PERSISTAH is the assessment of the seismic vulnerability of primary schools in the Algarve (Portugal) and Huelva (Spain) regions cooperatively. To this end, the objectives established by the National Platforms for Disaster Risk Reduction (PNRRC) of the National Civil Protection Commissions of Portugal and Spain have been considered. This objective can be subdivided into the following goals: — the classification of the school buildings of the area, — the assessment of their vulnerability, — the definition of a vulnerability index that allows to compare them, — the definition of rehabilitation measures for those buildings which may need them, — the application of those measures to one Portuguese and one Spanish school pilot building, — the creation of educational guides to create awareness of the seismic risks in the school community, and — the dissemination of the project results, where the present document is to be found. 1.2. MAIN OUTCOMES OF THE PROJECT The PERSISTAH research project was conceived for having an impact on the Portuguese and Spanish society. This impact is maximised by the singularities of the seismicity of this geographical area, the international cooperation for risk reduction, and the relevance of the buildings under study. Accordingly, the PERSISTAH research project has contributed to shaping a society that is more resilient to earthquakes. The first contribution is the analysis of the seismic vulnerability of school buildings, which are very vulnerable to earthquakes. They play a fundamental role in the lives of children, who are the most vulnerable people in this type of event. After a disaster, the children should feel safe when returning to school, which means a return to normality. Moreover, because of their design and their public nature, they can be adapted as shelters after a disaster. The analysis of the schools seismic vulnerability has been carried out through an integrated assessment methodology. This methodology is based on SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 19 SUMARY a vulnerability analysis through the building capacity curve, used to obtain the structural performance point of the building. With this information, the damage probability of the school building is calculated. This methodology has been implemented in a new software (Estêvão, 2019; Estêvão, 2020), where was implemented the adaptation of a set of computer programming routines previously developed in the applications EC8spec (Estêvão, 2016) and SIMULSIS (Estêvão and Oliveira, 2012). The purpose of this software is to obtain the School-score, which is based on the damage probability and other parameters, such as the vulnerability of non-structural elements, number of students, aspects affecting evacuation, etc. These are essential elements to take into account when studying the seismic vulnerability of a school building. Obtaining a high value for this parameter indicates that the school is more vulnerable to earthquakes. In this context, a new school database was created with the collaboration of all team members. A list with the classification of the schools has been drawn up based on their School-score, and it will be taken into consideration for future seismic retrofitting interventions in the buildings. Furthermore, a series of training activities for technicians on the aspects of the methodology applied and the particularities of the seismic retrofitting design have been carried out, in order to reduce the structural and non-structural risk of the buildings. Another fundamental factor in this project is the significance of and need for international cooperation between countries when it comes to the reduction of seismic risk, since both regions, which present very similar geographical conditions, would be affected equally in the event of an earthquake. Finally, another key point of the project is the creation of seismic risk awareness among the educational community and their training in this subject. Children are the future of our society and play a vital role in it. They learn at school, and bring their knowledge home to their families, which makes of the schools a powerful motor for change. A seismic event causes a great psychological impact on them, and therefore, education and communication of existing risks is essential. A series of trainings have been carried out through a number of activities and seminars in schools for both teachers and students. These dealt with issues related to identifying risks both inside and outside the school building. In addition, earthquake drills were carried out. This action is key to increasing awareness of seismic risk and learning how to act in the event of an earthquake. A number of pedagogical resources for teachers have also been developed. These materials include practical activities for children to learn about these subjects in a fun way, together with easy self-protection actions to be carried out before and after a seismic event1. 1. Why does the ground shake? (https://dx.doi.org/10.12795/9788447230471). Practical guide for Earthquake resilient schools (https://dx.doi.org/10.12795/9788447230532). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 20 SUMARY 1.3. DOCUMENT STRUCTURE In the present document, the methodology and seismic regulations applied in the vulnerability analysis and subsequent seismic retrofitting of school buildings will be presented. This methodology responds to the objectives and main ideas of the project. Later on, the seismic hazard of the Algarve and Huelva area is discussed, as well as the seismic action used in each region for seismic analysis. In addition, the characterisation and typological classification of school buildings carried out for their subsequent seismic analysis is shown. Finally, several seismic retrofitting techniques proposed by the different regulations are outlined, as well as the different techniques studied in the project. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 21 SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) In this chapter, the seismic hazard of the Algarve-Huelva region is shown. In 2.1, the configuration of the region is analysed; in section 2.2, the influence of soil on seismic hazard is shown by analysing the geotechnical characteristics of both areas; in sections 2.3 and 2.4, the requirements set out in the applicable and recommended seismic building codes in Spain and Portugal, respectively, are outlined; lastly, in section 2.5, a comparison of the seismic action determined according to each seismic regulation is carried out, underscoring the fact that in the case of an earthquake, both areas would be equally affected. 2.1. THE ALGARVE-HUELVA REGION The Iberian Peninsula is characterised by having a moderate level of seismic activity in comparison with other areas of the world (Carre and Zornoza, 2011). However, in the south of the peninsula, there is a significant level of seismic activity. This is due to the convergence of the Eurasian and African tectonic plates, which extend throughout the Mediterranean region and the Strait of Gibraltar, reaching the Azores islands (figure 1). Figure 1. Convergence of the Eurasian and African tectonic plates. Chapter 2. Seismic hazard in the Algarve-Huelva Region SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 22 SUMARY Because of this convergence, the Iberian Peninsula has experienced numerous high-magnitude earthquakes that had disastrous consequences (table 1). Among these, the 1356 (Cape St. Vincent. Intensity VIII), 1722 (Gulf of Cadiz. Mw = 6.5), 1755 (Mw = 8.5 – 9.0) and the 1969 (Mw = 8) earthquakes stand out (Sá et al., 2018). The 1755 earthquake is known as the famous earthquake and tsunami of Lisbon, considered to be one of the most devastating historical seismic events in the world. At European level, it is the most catastrophic natural disaster ever documented. Table 1. Historical earthquakes felt in the Iberian Peninsula (Silva and Rodriguez Pascua, 2014). Year Place Mag. Consequences 1356 Cape St. Vincent I. VIII Serious damage in Western Andalusia and the South of Portugal. Serious damage in Lisbon. 1522 Alboran Sea 6.5 Total destruction of Almería and towns in Granada. 1531 Lisbon 7.0 Around 30 000 deaths in the city of Lisbon. 1680 Alahaurín el Grande (Málaga) 6.8 Various towns affected causing minor damage. 1722 Gulf of Cadiz 6.5 Serious human and material damage from Cape St. Vincent to Castro Marim. It caused a local tsunami in Tavira. 1755 SW of Cape St. Vincent 8.5 Destruction of most of Lisbon. Tsunami of almost 15 m in height. Between 10 000 and 90 000 deaths caused by both disasters. 1804 Alboran Sea 6.7 Serious damage in Motril (Spain). 1829 Torrevieja (Alicante) 6.6 Destruction of a large number of houses in various towns in the district. Around 400 deaths. 1884 Arenas del Rey (Granada) 6.7 Almost one thousand deaths. 1969 Cape St. Vincent 8.0 Several deaths and minor damage. 2007 SW of Cape St. Vincent 6.1 Minor damage. 2009 Isla Cristina (Huelva) 6.3 Minor damage. Cracks in buildings. Factory walls collapsed. 2011 Lorca (Murcia) 5.1 Significant damage and victims. Collapses of highly important buildings. 2016 Alboran Sea 6.3 Detachment of façades, cracks and minor injuries. Small tsunami in the Balearic Islands (Spain). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 23 SUMARY The region with the greatest seismic hazard on the peninsula is located in the southeast and comprises the Alboran Sea and Murcia. This region is characterised by frequent occurrence of moderateand low-magnitude earthquakes. For this reason, the majority of studies and analyses of seismic hazard and vulnerability are focused on this area. The most devastating seismic event that was most recently felt on the Peninsula was the 2011 Lorca earthquake (Murcia). Despite its moderate magnitude, its hypocentre was located at very little depth, at approximately 1 km from the surface and accelerations of 0.36 g were recorded. This resulted in devastating effects, causing more than 300 injuries, several casualties, and the relocation of more than 10 000 people (Salgado-Gálvez et al., 2016). However, the Algarve-Huelva region, in the southwest of the peninsula, is characterised by high-magnitude earthquakes (Mw ≥ 6) and long return periods (Morales-Esteban et al., 2014). This is due to the convergence of the tectonic plates and its closeness to the Azores–Gibraltar fault zone. Recent studies (Gràcia et al., 2010) have also identified fault zones in the southwest region of the Algarve, such as the Marqués de Pombal fault (figure 2) or the San Vicente fault. These faults caused some of the most damaging earthquakes in the Iberian Peninsula. Furthermore, the properties of the region’s soil increase the seismic hazard values. However, due to the long return periods of these events, the population inhabiting the region is not aware of the seismic hazard of the area. Figure 2. Map of active quaternary faults in the Iberian Peninsula with the magnitude of the earthquakes (created by the author). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 24 SUMARY 2.2. THE IMPACT OF SOIL TYPE ON SEISMIC HAZARD The territory of the Algarve and Huelva is characterised by having a similar geological profile, although with certain nuances, as can be observed in the geological map of Spain and Portugal by the Geological and Mining Institute of Spain (IGM) and Portugal’s National Laboratory of Energy and Geology (LNEG) (<http://info.igme.es/cartografiadigital/portada/>). Huelva is located above tertiary and quaternary materials of the Guadalquivir basin, with evident maritime influences and significant tidal floodplains which make up, in some provincial areas, extensive marshland areas (Meijninger, 2006). The main geological materials that can be found, from the shallowest to the deepest, are fluvial deposits, fluvial terraces, basal sandstones and sandy marlstones, to a greater or lesser degree. The bay of the Algarve is also essentially made of tertiary materials, particularly calcareous materials, clays and sands with some magmatic material (Terrinha et al., 2013). The presence of soft soil has an amplifying effect on seismic action. This is due to the fact that during a seismic event, soft ground does not have the capacity to dissipate seismic waves. Rocky ground, on the other hand, due to its inertia, has the capacity to absorb the energy that is released (Udías and Mézcua, 1986). In the Algarve, soft soils are to be found on the coast (where the majority of the population lives and where school buildings are located), in some valleys and near some rivers. In the province of Huelva, soft soils are very much abundant, particularly in the South, in estuaries, marshland and near to the coast. In comparison, the south-eastern area of Andalusia, with a geological profile mainly made of rock, is not affected by this amplification. The effects of the soil type are taken into account in seismic codes through a soil behaviour factor. This factor is tabulated for each type of soil, varying from rock to very soft soils such as slurries or sludge. 2.3. SEISMIC HAZARD IN SPAIN In this section, the temporal evolution of seismic codes in Spain, the requirements of seismic codes that are currently in place and the updates proposed in the document drawn up by the Spanish National Geographic Institute (IGN) on seismic hazard values will be analysed. Then, the requirements set out in the European code, of recommended application, related to the determination of seismic actions, will be described. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 25 SUMARY 2.3.1. Chronological evolution of seismic building codes in Spain The first Spanish seismic building code (PGS-1) was passed in 1969 (Ministerio de Planificación del Desarrollo, 1968). This code classified buildings according to their degree of importance. Schools were included in group I, “ordinary buildings”. Groups II and III encompassed buildings of high importance such as hydraulic constructions or energy plants. For buildings in group I, the application of this code was optional. In any case, the document proposed different seismic areas, values of seismic action and a design method. The following seismic building code was the PDS-1 which was passed in 1974 (Ministerio de Planificación del Desarrollo, 1974). This code established an initial classification of buildings according to their structural type to estimate damage, several seismic zones and a similar design method for the buildings to the one set out in the previous code. In 1994 a new seismic building code was passed called the Norma de Construcción Sismorresistente (Seismic Building Code) (NCSE94) (Ministerio de Obras Públicas Transportes y Medio Ambiente, 1994). This document set out new seismic hazard maps and introduced more complex design methods and more restrictive requirements. The seismic building code that is currently in force in Spain is the Normativa de Construcción Sismorresistente Española de 2002 (Spanish Seismic Building Code of 2002) (NCSE02) (Ministerio de Fomento, 2002). In this code, the criteria related to the seismic action to be considered in any building project, reform or retrofitting in Spain are established. Besides, since 2007 the NCSP-07, the eponymous applicable document for the seismic design and analysis of bridges, has been in force. In 2012, an Update of the seismic hazard maps in Spain was published, drawn up by the IGN and of recommended use (Ministerio de Fomento de España, 2012). Lastly, Eurocode 8 (EC8) (AENOR, 1998) is a European code drawn up by the European Committee for Standardization (CEN), the use of which is recommended within Spanish territory. The aim of this document is to standardise criteria related to the seismic design of buildings. The code is complemented by a National Annex drawn up by each country, in which the specific national parameters that should be considered when applying the code in each country are included. Below, the different criteria established by the NCSE02 code, the update of the seismic hazard maps and the EC8 for the case of Spain, as well as the considerations set out in its National Annex, are analysed. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 32 SUMARY 2.3.2.2. Update of the seismic hazard maps In 2012, an update of the seismic hazard maps drawn up by the IGN was published. The study included the most up-to-date knowledge of the seismicity of the peninsula and advances in techniques for creating new seismic hazard maps, together with the information contributed by recent studies on fault activity. Likewise, the study was adapted to European codes, and a standardisation process was carried out with neighbouring countries. 2.3.2.2.a. Probabilistic seismic hazard analysis For the proposition of new updated seismic hazard maps, a probabilistic seismic hazard analysis (PSHA) was carried out, using a Poissonian probabilistic model. This model determines the probability of occurrence of an event within a given time frame, using a mean value distribution. To prepare the database, the seismic catalogue was taken from the IGN, expanding the period considered to 2011 and eliminating earthquakes with a greater depth than 65 km. Given that the information available on many past earthquakes is not expressed in the parameters that are currently used to measure the severity of an earthquake, a standardisation of the catalogue was carried out according to the moment magnitude scale (Mw), using intensity correlations. Moreover, attenuation laws that have been tested and proved valid were used, and a new establishment of seismic zones was undertaken. In total, the catalogue accounted for 6 999 seismic events. 2.3.2.2.b. Results obtained and relation to the NCSE02 code The results obtained from the updated seismic maps of 2012 are not directly comparable to those used in the NCSE02. In this code, the seismic hazard map defines the seismic hazard of the territory, for a return period of 500 years, using the base ground acceleration value, ab, and the contribution factor, K. This base ground acceleration was defined for a type II soil and, based on this, the design ground acceleration is calculated ac, by multiplying ab by the importance factor, r, and the soil factor, S. The new seismic hazard map is, in reality, a collection of maps with different parameters, peak ground accelerations (PGA) and spectral accelerations calculated for various probabilities of exceedance or return periods. The results obtained in PGA for a return period of 475 years cannot be compared with the ab obtained in 2002. Furthermore, the map obtained in PGA for a return period of 475 years has been determined for a type I soil in order to adapt it to European codes. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 33 SUMARY Therefore, to use the elastic response spectrum of the NCSE02, the ab has to be replaced with this new PGA and the soil factor S must be modified. The adjustments would consist of the following: For r · ar ≤ 0.1 g S = C For 0.7 g < r · ar < 0.4 SC a g r =+ ⋅− ⋅⋅−1333 10 4.( )( .) ρ For 0.4 g ≤ r · arS = 1.0 Being: C the soil factor, dependent on the geotechnical characteristics of the foundation soil (NCSE-02 art. 2.4). ar the new PGA acceleration reference (TR = 475). Table 5. PGA Values (TR = 475) of the municipalities of the province of Huelva. Municipality PGA Municipality PGA Alájar 0,06 Huelva 0,12 Aljaraque 0,12 Isla Cristina 0,13 El Almentro 0,09 Jabugo 0,06 Almonaster la Real 0,07 Lepe 0,12 Almonte 0,10 Linares de la Sierra 0,06 Alosno 0,08 Lucena del Puerto 0,10 Aracena 0,06 Manzanilla 0,09 Aroche 0,07 Los Marines 0,06 Arroyomolinos de León 0,06 Minas de Riotinto 0,07 Ayamonte 0,12 Moguer 0,11 Beas 0,09 La Nava 0,06 Berrocal 0,07 Nerva 0,07 Bollullos Par del Condado 0,10 Niebla 0,10 Bonares 0,10 La Palma del Condado 0,09 Cabezas Rubias 0,07 Palos de la Frontera 0,12 Cala 0,06 Paterna del Campo 0,09 Calañas 0,07 Paymogo 0,08 El Campillo 0,07 Puebla de Guzmán 0,08 Campofrío 0,07 Puerto Moral 0,06 SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 34 SUMARY Table 5. PGA Values (TR = 475) of the municipalities of the province of Huelva (cont.). Municipality PGA Municipality PGA Cañaveral de León 0,06 Punta Umbría 0,13 Cartaya 0,12 Rociana del Condado 0,10 Castaño de Robledo 0,06 Rosal de la Frontera 0,07 El Cerro de Andévalo 0,07 San Bartolomé de la Torre 0,09 Corteconcepción 0,06 San Juan del Puerto 0,10 Cortegana 0,07 Sanlúcar de Guadiana 0,09 Cortelazor 0,06 San Silvestre de Guzmán 0,10 Cumbres de Enmedio 0,06 Santa Ana la Real 0,07 Cumbre de San Bartolomé 0,06 Santa Bárbara de Casa 0,08 Cumbres Mayores 0,06 Santa Olalla del Cala 0,06 Chucena 0,09 Trigueros 0,10 Encinasola 0,06 Valdelarco 0,06 Escacena del Campo 0,09 Valverde del Camino 0,08 Fuenteheridos 0,06 Villablanca 0,11 Galaroza 0,06 Villalba del Alcor 0,09 Gibraleón 0,10 Villanueva de las Cruces 0,08 La Granada de Río-Tinto 0,07 Villanueva de los Castillejos 0,09 El Granado 0,09 Villarrasa 0,09 Hieguera de la Sierra 0,06 Zalamea la Real 0,07 Hinojales 0,06 Zufre 0,06 Hinojos 0,10 2.3.3. Recommended code: Eurocode 8 Eurocode 8 (1998) arose as a way of standardise criteria relating to the seismic design of structures throughout Europe. However, each country draws up their own National Annex, in which the criteria established in the EC8 are completed or adapted. It is divided into 6 parts, being part 1 (EC8-1) (AENOR, 2018a) and part 3 (EC8-3) (AENOR, 2018b) the most important ones for this project. In part 1, the general rules, seismic actions and construction rules are presented. Part 3 includes the seismic evaluation and adaptation procedure for existing buildings. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 35 SUMARY 2.3.3.1. Determining the response spectrum In part 1, the process of determining the elastic response spectrum is set out. Seismic hazard is expressed through the reference peak ground acceleration (agR) for soil type A and determined according to the National Annex. This is the result of multiplying the design ground acceleration (ag) by the importance factor (gI) according to equation (2). In this part 1, a different importance factor is determined according to the construction type, with a value of 0.8 for structures of moderate importance; 1.0 for structures of normal importance; 1.2 for structures of great importance; and 1.4 for structures of special importance. However, this requirement must be compared with what is set out in the National Annex of each country. agR = ag · gI Eq. (2) The horizontal elastic response spectrum [Se(T)] is defined in accordance with the following expressions: 0 ≤ T ≤ TB ST aS T T eg B () (. )=⋅⋅+ ⋅⋅ −       12 51 η TB ≤ T ≤ TC ST aS eg () .=⋅⋅⋅ η 25 TC ≤ T ≤ TD ST aS T T eg C () .=⋅⋅⋅       η 25 TD ≤ T ≤ 4s ST aS TT T eg CD () .=⋅⋅⋅       η 25 2 Where: Se(T) is the elastic response spectrum. T is the vibration period of a linear single-degree-of-freedom system. ag is the value of the design ground acceleration on type A soil. TB is the lower limit of the period of the constant spectral acceleration branch. TC is the upper limit of the period of the constant spectral acceleration branch. TD is the value defining the beginning of the constant displacement response range of the spectrum. S is the soil factor. h is the damping correction factor with reference value h = 1, for 5% viscous damping. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 36 SUMARY The values of parameters TB, TC and TD and the soil factor S depend on the soil type. In Table 6, the criteria for determining the soil type are outlined. In this case, the EC8-1 establishes 5 soil type compared to the 4 determined by the NCSE02 standard. Table 6. Classification of soil types. Soil type Description A Rock or another rock-like geological formation, including at most 5 m of weaker material at the surface B Deposits of very dense sand, gravel or very stiff clay, at least a few tens of metres in thickness, characterised by a gradual increase of mechanical properties with depth C Deep deposits of dense or medium-dense sand, gravel or stiff clay with thickness from several tens to many hundreds of metres D Deposits of loose-to-medium cohesionless soil (with or without some soft cohesive layers), or of predominantly soft-to-firm cohesive soil E A soil profile consisting of a surface alluvium layer with values of vs (shear wave velocity) of type C or D and a thickness varying between 5 m and 20 m, underlain by stiffer material with vs > 800 m/s S1Deposits consisting of, or containing a layer at least 10 m thick, of soft clays/silts with a high plasticity index (IP > 40) and a high water content S2Deposits of liquefiable soils, of sensitive clays or any other soil profile not included in types A – E or S1 Furthermore, the EC8-1 differs from the NCSE02 by proposing 2 types of elastic response spectra: 1 and 2 (figure 4). According to the EC8, the type 1 response spectrum is used when the earthquakes that contribute the most to the seismic hazard are far away and of a moderate to high magnitude (Mw < 5,5). The type 2 spectrum is used for nearby earthquakes with a surface-wave magnitude not greater than Mw < 5,5. The parameters and the soil factor vary depending on the type of spectrum according to table 7. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 37 SUMARY Table 7. Values of parameters TB, TC and TD and soil factor S according to the type of spectrum. Soil type Seismic Action Type 1 Seismic Action Type 2 Smax TB (s) TC (s) TD (s) Smax TB (s) TC (s) TD (s) A 1.00 0.15 0.40 2.00 1.00 0.05 0.25 1.20 B 1.20 0.15 0.50 2.00 1.35 0.05 0.25 1.20 C 1.15 0.20 0.60 2.00 1.50 0.10 0.25 1.20 D 1.35 0.20 0.80 2.00 1.80 0.10 0.30 1.20 E 1.40 0.20 0.50 2.00 1.60 0.05 0.25 1.20 (a) (b) Figure 4. Elastic response spectrum of type 1 (a) and 2 (b) for each type of soil. The EC8-1 also proposes the design of an elastic response spectrum to account for the effects of the vertical forces caused by seismic action. In the linear analyses, the elastic response spectrum is reduced by a factor called the behaviour factor (q) which considers the type of structural system and its ductility. The determination of this factor is specified in the EC8-1 only for the design of new buildings. However, this process cannot be applied to existing buildings, which is why other codes are used such as the American one. 2.3.3.2. Spanish National Annex For the use of the response spectrum in EC8-1, the National Annex establishes a series of criteria related to the ground acceleration value and the importance factor. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 38 SUMARY The agR of the EC8 is established for a type A soil and a Tr of 475 years. however, the base ground acceleration values of the NCSE02 are established for a type II soil and a Tr of 500 years. Thus, in order to use them, the ab values must be multiplied by a reduction factor of 0.8, according to the equation (3).When using the updated seismic hazard values of 2012, there is no need to make any changes to the PGA, given that it is already expressed for a type I ground and a return period of 475 years. agR = 0.8 · ab Eq. (3) The Spanish Annex proposes a modification of the importance factor established in the EC8-1: the highest importance factor is increased from 1.2 to 1.3. This change affects this project, as schools are included in this importance class. 2.4. SEISMIC HAZARD IN PORTUGAL In this section, the chronological evolution of seismic codes in Portugal and the requirements of the currently applied seismic codes are analysed. 2.4.1. Historical seismic codes: Decree law no. 235/83 The first seismic building code in Portugal was the Decree no. 41 658 (RSCCS, 1958) (Nacional, 1958). The second seismic code was the Decree 44 041 (RSEP, 1961) (Nacional, 1961), which changed the seismic action due to the earthquake that occurred in Agadir in 1960. The Decree Law 235/83, Reglamento de Segurança e Acçoes para Estructuras de Edifícios e Pontes (Safety regulation and actions for buildings structures and bridges) (RSAEEP) passed in 1983 (Imprensa Nacional-Casa da Moeda, 1983), was the first seismic code to include modern dynamic analysis principles in the design of structures. 2.4.1.1. Probabilistic seismic hazard analysis The map of the six seismic zones considered in the RSAEEP (figure 5) was influenced by a study on seismic hazard, which resorted to a Poisson model and a type-III extreme value distribution, for a return period of 1 000 years (Oliveira, 1977). In this study, three sources of information were used: 1) a historical catalogue from the 10th century; 2) the Portuguese instrumental catalogue from 1902 (the earthquakes in the Spanish catalogue were also used for border zones); and 3) the maximum intensities observed after the earthquakes of 1902 (Oliveira, 1977). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 39 SUMARY Figure 5. Seismic zonation of Portugal (Decree law no. 235/83). In terms of the ground type, 3 types were established: type I, rocks; type II, hard soils of a medium consistency; and type III, soft soils. 2.4.1.2. Determination of seismic action Seismic action was defined through the power spectral densities of acceleration, for two types of earthquakes: 1) a moderate-magnitude earthquake not far from the focus, and 2) an earthquake of a high magnitude at a greater distance from the focus. The response spectra were determined using power spectra, though this was a difficult process. The influence of seismicity is taken into account through factor a for each seismic action. 2.4.2. Mandatory code: Eurocode 8 Since December 2019, Eurocode 8 has been the seismic code in force in Portugal. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 40 SUMARY 2.4.2.1. Construction of the response spectrum Establishing the response spectrum is carried out in a similar way to that specified in the EC8-1. However, the National Annex specifies the values of parameters TB, TC and TD, of the soil factor S and the importance factor. 2.4.2.2. Portuguese National Annex The Portuguese National Annex specifies the requirements set out in the EC8-1 for earthquakes of two kinds, as is the RSAEEP, but in this case type 1 is the distant earthquake and type 2 is the nearby earthquake. It proposes new importance factor values according to the importance class and for each type of seismic action (table 8). In the case of schools, the importance class is III, therefore, in the context of a type I response spectrum, it corresponds to an importance factor of 1.45, a higher value than that established by the Spanish National Annex. Table 8. Importance factors (gI). Importance class Seismic Action Type 1 Seismic Action Type 2 Continent Azores I 0.65 0.75 0.85 II 1.00 1.00 1.00 III 1.45 1.25 1.15 IV 1.95 1.50 1.35 It also proposes an update of the values of parameters TB, TC and TD and of the soil factor S for each type of seismic action (table 9). For ag ≤ 1 m/s2S = Smax For 1 < ag < 4 m/s2 SS Sa max max g =− −⋅− 1 3 1 () For 4 m/s2 ≤ agS = 1.0 SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 41 SUMARY Table 9. Values of TB, TC and TD and S for each type of response spectrum. Soil type Seismic Action Type 1 Seismic Action Type 2 Smax TB(s) TC(s) TD(s) Smax TB(s) TC(s) TD(s) A 1.00 0.10 0.60 2.00 1.00 0.10 0.25 2.00 B 1.35 0.10 0.60 2.00 1.35 0.10 0.25 2.00 C 1.60 0.10 0.60 2.00 1.60 0.10 0.25 2.00 D 2.00 0.10 0.60 2.00 2.00 0.10 0.30 2.00 E 1.80 0.10 0.60 2.00 1.80 0.10 0.25 2.00 In (Campos Costa et al., 2008) a proposal to update the National Annex was made in 2008. In this study, new seismic zones were proposed (figure 6) and a new probabilistic seismic hazard analysis was carried out using a Cornells method. (a) (b) Figure 6. Seismic zonation annex type 1 (a) and type 2 (b). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 48 SUMARY The characterisation of school buildings is carried out using the information available from each school: aerial images, on-site visits, surveys and original and refurbishment projects (both including descriptive and graphic reports) obtained from different municipal archives of Huelva, the College of Architects of Huelva and the Ministry of Education of the Andalusian Government. The process followed for the analysis and processing of the information obtained from each source is described below. 3.1.1. Creation of the database Based on the information obtained, a database has been created and implemented in the software developed within the framework of the research project. This database is divided into the following sections: — School identification. — General characterisation of the school campus. — General characterisation. — Type of construction. — Elements for seismic evaluation. — Existence of damage and level of maintenance of the building. — Risks and internal characteristics. — Envelope and exterior risks of the building. The fields included in each section are expecified in table 12. 3.1.2. Creation of building specification sheets When detailed enough information of a building was available, a specification sheet was drafted. These sheets collect specific information on the structural and constructive characteristics needed for the calculation of the seismic behaviour of the buildings. Table 13 shows the sections included in a sample building sheet. In total, 36 building specification sheets have been completed. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 49 SUMARY Table 12. Sections included in the database. School identification Characterisation of the school campus Building number Total area of the school Building reference Number of buildings Land registry reference Land area Type of school Percentage of free land Name of the school Morphology of the school grounds Country Is there any possible landslide hazard? Province Is it near a cliff? Municipality Distance from the coastline Address Firefighter capacity UTM coordinates Distance from nearby fire station Contact: phone number and email Designation of school year level Services Institutional nature Number of students Aerial image of the school Image of the school’s façade General characterisation Type of construction Distance from the nearest hospital Main structural system Conditions of evacuation and access and conditions of evacuation for emergency services Average distance between vertical structural elements Designation Average dimension of the columns section Main use Average dimension of the shear wall section Total area Average dimension of the beam section Maximum building height Average thickness of the load-bearing wall Number of floors Horizontal structural system Maximum building length Stiffness of the horizontal structural system Maximum building width Middle edge of the slab Average distance between floors Structural type of roof Date of construction Level of deterioration Has the school been restructured? Type of plane irregularity SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 50 SUMARY Table 12. Sections included in the database (cont.). General characterisation Type of construction Date of last retrofit Is there any chance of different buildings colliding? Main type Stiffness of the floor system Subtype Elements for seismic evaluation Existence of damage and maintenance of the building Is the distance between floors uniform? Is there a maintenance plan? Is there a problem in the building? Time between maintenance works Is there an atrium (areas without walls inside the building)? Who is in charge of the maintenance work? Are there any stairs or lifts with shear walls? Is there a foundation problem? Is there mass eccentricity? Is there a problem of beam deformation? Is there a soft floor? Is there a problem of floor deformation? Are there short columns? Are there cracks in the walls? Average percentage of short columns Are there problems with window deformation? Stratigraphic soil profile Are there problems with door deformation? Classification of the foundation Is there a water infiltration problem? Risks and internal characteristics Envelope and exterior risks Main type of non-structural wall Façade gap ratio Wall gap ratio Characteristics of the roof layout Non-structural suspended ceiling Percentage of gaps in the roof Characteristics of the lighting system Non-structural materials roof surface Type of furniture Is there any ornamental element? Type of piping Are there any parapets? Is there an air conditioner in the suspended ceiling? Is there a chimney? Façade wall type Is there any danger of collision with a tall adjacent building? SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 51 SUMARY Table 13. Building specification sheet for the calculation of the structural model. reference S050 name XXX address xxx date 1988 1 number of buildings datebuilding ref. 1988 SIrefurbished area 1432 heights GF 3sanit. 0,75 1F 3 2F total URM XRC frame Steel frame SlabWaffle slab beams RC XSteel Wood materials RC HA-175 WoodSteel AEH-400 Safety NORMAL separation min 2,75 rebar sanit. 4φ12 av GF 4φ12 1Fmax 7,85 4φ12 2F section sanit. 30x30 stirrups sanit. GF φ6 to 15cm 30x30 GF 1F φ6 to 15cm 30x30 1F 2F φ6 to 15cm 2F NObracingload bearing wall panelsdimensionrebar 22+3floor thickness pesoluz span section40x50 rebar sup 6φ20 inf 6φ20 span stirrups φ8 to 15cm section30x40 rebar sup 2φ14 inf 2φ14 stirrups φ6 to 20cm 26+4floor thickness weight span span section60x30 rebar infsup 3φ12 4φ20+2φ16 span stirrups φ8 to 10cm section30x30 rebar sup 2φ10 inf 2φ12 footing stirrup φ8 to 10cm dim. thicknessdepth rebar slab thickness pile type yes 2nº/pile caps φ40diameter -depth pile cap 13x70x60 stirrups strut sup.4φ12/inf.4φ20 dimensionrebar stirrups safe load ballast coeff. nogeotechnical e concrete type roof steel type type gable thickness20-30 cm -weight typeexternal wallsE+L+AT+HS+E thickness25-26cm -weight parapet type NO thicknessweight partition type E+HS+E thicknessweight type NOsusp. ceiling thicknessweight 6,75 HORIZ.: SANIT. load bearing beams type C1 tie beams type A1 HORIZ.GF AND F beams load bearing type C1 tie beams type A1 VERTICAL columns S050_1 CONSTRUCTIVE SYSTEM FOUNDATION STRUCTURAL SYSTEM SCHOOL CHARACTERISTICS 3.1.3. Questionnaires sent to schools In order to complete and verify the gathered data, an online questionnaire was sent to each of the schools, requesting information on the current state of the buildings. The information from the surveys makes it possible to include data on maintenance, possible damage to the building, possible reforms and SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 52 SUMARY extensions, as well as to corroborate existing technical data. The content of the questionnaire is available in table 14. Information has been obtained from 47 schools, 33% of the total number. Table 14. Questionnaire sent to school management. School’s identification data Name of the school Extra services Population Number of students Educational levels School’s general information Slope of the land Distance from the nearest hospital Is it near a cliff or ravine? Evacuation conditions Distance from the coastline Does the building have regular maintenance? Distance from the nearest fire station How often is maintenance performed? Manoeuvrability of the fire brigade Who is in charge of maintenance? Building 1: technical details Main use of the building Are there deformations in windows? Number of floors Are there deformations in doors? Date of construction of the building Are there any damp patches? Has the building had any structural alterations or extensions? Is there a suspended ceiling? Type of structure Type of light fixtures in classrooms Level of deterioration of the building Type of furniture in classrooms Are there structural joints? In what condition are the pipes in the facilities? Is there a covered patio? Is there an air conditioning installation on the ceiling? Are there shear walls in the staircase or lift? Type of roof Are there heavy elements on the roof? Are there any ornamental elements (such as cornices or shields) that can come loose easily? Are there open areas on the ground floor (without infills) and built on the first floor? Are there chimneys? Are there foundation problems? Are there any tall buildings adjacent to the building? Are there cracks and crevices? Is there a kitchen? SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 53 SUMARY 3.2. SCHOOL BUILDINGS CHARACTERISATION PROCESS The process of characterising school buildings was carried out based on the information obtained as explained in the previous sections. In this classification, as mentioned before, a sample of 269 buildings was considered. Firstly, the buildings have been grouped according to their structural system and date of construction. Secondly, a classification has been made according to geometry and volumetry. These two classifications are a first approach to the analysis of the large volume of data available. Results obtained from the first and second classification are shown in the following chapters. 3.2.1. Classification according to structural system and year of construction The way the analysis of the seismic vulnerability of a building is performed depends highly on its structural system. Moreover, retrofitting techniques and rehabilitation measures are specific to each structural system. This is the reason why a first classification of the buildings was made based on their structural type. Figure 10 shows the groups into which the buildings have been divided according to their structural system. Most of the buildings were built with reinforced concrete (RC) frames (82%), followed by unreinforced masonry (URM) load-bearing walls (13%). Steel buildings account for 4% of the total. It has not been possible to identify the structural system for only 1% of the buildings. 222 82% 35 13% 10 4% 2 1% RC frames Masonry Steel Unknown Figure 10. Classification of schools according to their structural system. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 54 SUMARY The sample was also analysed based on the date of construction of the buildings (figure 11). 31% of the buildings were constructed in the 1980s, 18% during the 1970s and 15% on the 1990s. It is important to highlight the relationship between the date of construction and the structural system. Most of the masonry buildings were constructed before 1970, while most of the buildings that were built during the ‘70s and ‘80s are reinforced concrete frame buildings. 03 12 47 76 37 26 15 6 1 13 63 84000001020430 0 10 20 30 40 50 60 70 80 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s Unknown Year Number of buildings RC frames Masonry Steel Figure 11. Classification of buildings according to date of construction and structural system (not considering buildings for which the structural system is unknown). 3.2.2. Classification according to geometry and volumetry The volumetry and footprint of the buildings under study were analysed from available aerial and exterior images. Six main geometrical types have been identified and are shown in figure 12: compact, linear, prism, intersection, juxtaposition and sport. These types are, in turn, divided into several subtypes that allow us to define typologies with expected similar seismic behaviour. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 55 SUMARY 98 36% 91 34% 50 19% 15 6% 9 3% 6 2% Compact Linear Intersection Prism Sport Yuxtaposition Figure 12. Classification of buildings according to their geometric and volumetric characteristics. 3.2.2.1. Compact type buildings Compact buildings are characterised by quite square footprints and are very regular in volume. The spans and openings, regardless of the structural type, are small (around 5 m maximum). Therefore, they are mostly buildings without structural joints (67%). Construction dates range from 1955 to 2015. 91% of the buildings consist of RC frames and the remaining 9% of URM walls. In addition, this type is subdivided into several subtypes, as listed below. 3.2.2.1.a. No courtyards Number of buildings: 59. Description: the dimensions and built area of these buildings are not very high. Their main feature is that they do not have any courtyards or gaps in the slabs (except for the stairwells). They are mostly composed of a single floor (72%) and have no structural joints. The largest dimension reaches 35 m, although the average is 23m. The smaller average dimension is 16m and the built area is about 517m2. In Figure 13. Volumetric classification. School S084. Building: 2. Type: Compact. Sub-type: no courtyards. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 56 SUMARY addition, they are very regular in floor plan and height, with only 16% of them having atriums or porches for access to the building. 84% have a sloping roof, with ceramic tiles (78%) or metal panels (22%). The rest are characterised by flat roofs with flooring or gravel. 3.2.2.1.b. H-shape Number of buildings: 15. Description: these are identical buildings, a prototype. The floor plan is rectangular with dimensions of around 48 × 25 m with setbacks of the edge of the slab at the ends. The structural system consists of RC frames with structural joints. They are three stories high and have entrance atriums to the building in the central bays. Construction dates range between 1970 and 1988. The sloping roof is finished with ceramic tiles. 3.2.2.1.c. Compact Number of buildings: 12. Description: these are buildings of larger dimensions in terms of floor plan and surface area when compared to the subtype “no courtyards”. 50% has one floor and the rest, two. Dimensions range from 30-50 m long to 20-30 m wide. Their average built area is 1,352 m2. 33% have atriums and most of them do not have setbacks in the slab. 60% have flat roofs finished with flooring or gravel, with the rest having a gable roof with ceramic tiles. All have reinforced concrete frames and most (60%) have no structural joints. Construction dates range from 1958 to 2015. Figure 14. Volumetric classification. School S006. Building: 1. Type: compact. Subtype: H-shape. Figure 15. Volumetric classification. School S050. Building: 1. Type: compact. Sub-type: compact. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 57 SUMARY 3.2.2.1.d. With courtyards Number of buildings: 59. Description: these buildings are the largest, as well as the most irregular and complex. The structural system consists of RC frames, with structural joints in most cases analysed (70%) and two floors (80%). Their length ranges between 25-60 m and the width between 20-30 m. The average value of the built area is 1 642m2. 60% has a sloping roof with ceramic tiles and the rest has a flat roof with gravel or flooring. Construction dates range from 1979 to 2010. 3.2.2.1.e. Symmetrical Number of buildings: 8. Description: these are identical buildings that represent a prototype. They are symmetrical in plan and volume, although the perimeter is very irregular with several protrusions and entrances. They have two courtyards in their central part and have atriums along the end bays. They have two floors and their dimensions are 60 × 35 m, with a built area of about 2 100 m2. The roof is sloped with metal panels. The structure is made of RC frames. Figure 16. Volumetric classification. School S026. Building: 1. Type: compact. Sub-type: with courtyards. Figure 17. Volumetric classification. School S076. Building: 1. Type: compact. Subtype: symmetrical. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 64 SUMARY 3.2.2.4. Prism buildings Number of buildings: 15. Description: they represent an identical prototype made of a rectangular block which in 46% of the cases has a small annexed building (and which belongs, in most cases, to the compact buildings group). The prototype is built with RC frames and has structural joints. Construction dates range between 1970 and 1989. The average built area is 1 477 m2 and their dimensions vary between 25 and 50 m long and 17 and 20 m wide. They are two storeys high and have irregularities such as atriums or setbacks of the slab. They have a sloping roof with ceramic tiles. 3.2.2.5. Juxtaposed buildings Number of buildings: 6. Description: they serve as a link between buildings belonging to other groups and which have been built recently: from 1990 to 2011. They have flat roofs with gravel or flooring as finishing materials and their dimensions are not very large: 400 m2 of average built area, 22 m long and 15 m wide. They have no irregularities and were built with reinforced concrete frames without structural joints. Figure 30. Volumetric classification. School S013. Building: 1. Type: prism. Figure 31. Volumetric classification. School S020. Type: juxtaposed. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 65 SUMARY 3.2.3. Sports facilites Number of buildings: 9. Description: these are buildings for sports use built mostly (66%) with a steel structure with trusses and finished with metal panels. The dates of construction are recent, from 2004 to 2012. They have one floor and their built area varies from 550 m2 to 1 200m2. 3.3. CHARACTERISATION OF MASONRY BUILDINGS In total, 35 URM buildings have been identified. These correspond to 13% of the total of those considered in the project. 45% of them are main school buildings (access or main use), while 37% are secondary buildings. 82% of them are classroom buildings, while the use of the remaining percentage could not be identified. From the questionnaires sent to the schools, information could be obtained regarding the level of deterioration of the buildings in 31% of the cases: low (8%), medium (5%) and high (17%). The year of construction of these buildings ranges from the 1940s to the 1990s. However, most of them were built during the 1950s (see figure 11). The technical information contained in the buildings project documentation found is generally very brief. However, it has been possible to identify a number of common building characteristics that have been summarised in table 15. Eighteen single-storey and sixteen double-storey buildings have been identified. The dimensions of the single-storey buildings range from 15 to 45 m long and 6 to 25 m wide. The construction area varies between 120 and 1 500m2, the average value being 430 m2. As for the two-storey buildings, dimensions vary between 22 to 85 m long and 15 to 35 m wide. The construction area of these buildings ranges from 450 to 2 900 m2, with an average value of 1 200 m2. Single-storey buildings account for 63% of all cases. 74% of the buildings have entrance atriums. This generates an irregularity in floor plan and volume. In the case of the two-storey buildings, no information could be obtained for 37% of them, so no indicative conclusions can be drawn. Figure 32. Volumetric classification. School S025. Type: sports facility. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 66 SUMARY Table 15. Common characteristics of URM buildings. Walls Type Unreinforced masonry, heavy-duty brick Material Perforated ceramic brick. 1 cm thick cement mortar bed and head joints Thickness Varies from 25 to 40 cm (figure 33) Bonding The walls are bonded together, so there are no problems in their connections Slabs Operation One-way Thickness Varies from 25 to 30 cm (figure 34) Materials Ceramic vaults and reinforced or prestressed beams with a compression layer Type Sanitary slab on the ground floor: prestressed beams and ceramic vaults. Slab type in the other floors: reinforced beams and ceramic vaults Other aspects Rigid diaphragm behaviour Flat crest beams 20 to 30 cm wide Roof Shape Mainly sloping roof Material Ceramic tile Geometry Spans Between 4 m and 7.2 m Number of floors One to two floors Height of the floors Height of the ground floor: between 0.55 m and 1 m, due to the presence of the sanitary floor slab. Typical floor height: between 3 m and 3.30 m Structural joints No, one single structural block Wall openings ratio Due to their function, they have large openings in their walls (a) (b) Figure 33. “Un pie” (a) and “un pie y medio” (b) masonry wall section. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 67 SUMARY As for the type of roof, 32 buildings were built with a sloping roof. 30 buildings are made of ceramic tiles and two are made of metal panels. In addition, three of the buildings were built with a flat roof. The finishing materials are gravel, in two cases, and flooring, in one case. Due to their teaching function, the classrooms are typically y accessed through a corridor that runs parallel to the main façade of the building. In these cases, it is also common for the wall separating the corridor from the classrooms to be load-bearing. Also, the partitions separating classrooms from each other, usually perpendicular to the longest direction of the building, are usually blind. Furthermore, because of their function, façades tends to have a high percentage of openings in the walls. This significantly affect the seismic response of the structure, causing a concentration of shear stresses and deformations. This effect has been shown to lessen in the presence of load-bearing internal walls. In these cases, the load path will involve these internal load-bearing walls and the role of the façade becomes less relevant. For this reason, it is vital to take these walls into account in seismic assessment, verifying whether they are indeed load-bearing walls or simply interior partitions. The first regulation concerning the construction of resistant brick masonry walls in Spain was the MV-201 (Ministerio de la Vivienda de España, 1972) published in 1972. These regulations were not very restrictive and, in most cases, were not considered by the designers during the design and construction of the buildings (Andrade, 1993). The minimum strengths established for the construction materials were 100 kg/cm2 for bricks and 5 kg/cm2 for mortar, M-5 according to the Spanish designation. A minimum type of cement to be used was also indicated: P-250 (Portland cement with a compressive strength of 250 kp/cm2). The dimensions of the bricks, as well as the area and position of the gaps, were also limited. In the case of perforated bricks, the dimensions were 24 × 11,5 × 5,3 with a gap area of less than 2,5 cm2. In addition, a 60 m separation between structural joints was established for oceanic climates. The characteristic factory-produced compressive strength was limited by the strength of the brick, the plasticity of the mortar and the thickness of the joints. For the calculation, a masonry resistance reduction coefficient of 2,5 was indicated. (a) (b) Figure 34. Sanitary one-way slab (a) and (b) typical section. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 68 SUMARY The next standard was NBE FL-90 (Ministerio de Obras Públicas Trasnportes y Medio Ambiente, 1990) published in 1990. This was more of a revision of the previous regulations, improving the quality control requirements, but it did not introduce new requirements (Andrade, 1993). In the present book, the mechanical properties of the brick masonry were obtained from the analysis of the applicable regulations, bibliography and available project documentation. The characteristic masonry compressive strength (fk) has been determined from the ratio set out in Eurocode 6 (EC6) (AENOR, 2013). fk = Kf · fba · fmb Eq. (4) The compressive strength of the brick (fb) has been determined from the regulations applicable in the year of construction. In the project documentation, a brick strength of 15 N/mm2 has been identified in all cases. However, the MV-201 standard establishes a minimum value of 10 N/mm2, which must be considered in the vulnerability analysis. The mortar strength (fm) established in the available documentation is 4 N/mm2. However, the minimum value is 5 N/mm2 according to MV-201. Kf is a constant that depends on the type of brick and mortar determined. In the EC6, values of 0,65 and 0,25 are established for a and b respectively. The masonry deformation modulus is another parameter involved in the analysis of the seismic behaviour of URM buildings. The ratio of the EC6 is used for recent buildings. However, the deformation modules obtained from this ratio are excessive for older buildings built during the 1970s and 1980s (Martínez et al., 2001). Therefore, the relationship recommended in the French UIC Code 778-3 has been used (Martín-Caro Álamo, 2001). This method is more conservative and realistic, and depends on the elastic modulus of the brick (Eb). E = 0.35 · Eb · fmb Eq. (5) In the French code, the Eb determined for a medium-hard brick is 10 000 MPa. Furthermore, this value is similar to the values set in the Italian reference code NTC 2008 (NTC 2008. Decreto Ministeriale 14/1/2008. Norme tecniche per le costruzioni. Ministry of Infrastructures and Transportations. G.U. S.O. n.30 on 4/2/2008; 2008 [in Italian]., n.d.). Therefore, the values determined in the masonry resistance calculation are those set out in table 16. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 69 SUMARY Table 16. Mechanical parameters of the brick masonry. Structural parameter Minimum value Maximum value Most likely value Brick compressive strength ( fb) 10 30 15 Mortar compressive strength ( fm) 5 16 4 Constant K0,40 0,55 0,45 Masonry compressive strength ( fk) 2,52 7,71 5 MPa Shear strength (t0) — — 0,24 MPa Deformation modulus (E)2 800 3 500 3 500 MPa Shear modulus (G) — — 875 MPa Density (W) — — 18 kN/m3 In table 17, buildings have been classified according to their characteristics. Parameters such as number of floors, dimensions, built area or presence of irregularities have been taken into account. Buildings in the same group or subtype present similar seismic behaviour, sharing the main deficiencies, so analogous interventiones may be carried out. The characteristics of each subtype are the following: — Small linear: one-storey buildings of rectangular proportions with a built area of less than 600 m2 and a maximum length of 37 m. They have a sloping roof with ceramic tiles. The vulnerability of these buildings is not expected to be among the highest in the group of URM buildings. The percentage of openings is low-medium in the major direction and very low-low in the minor direction. — Medium linear: buildings of rectangular proportion, but of greater dimensions, up to 85 m long, two storeys high and a maximum built area of 1 570 m2. The type of roofing is still mostly sloping with ceramic tiles. Generally, these buildings are more vulnerable than the previous group. The percentage of openings is medium-high and very low in the major and minor directions, respectively. — L-shaped linear: the irregularity in the plan of this type of building makes it more vulnerable to earthquakes due to torsional effects. Buildings are comparable to two medium or small linear buildings combined. However, since they do not have structural joints, they work together. The percentage of openings is very high and medium-high in the major and minor directions, respectively. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 70 SUMARY Table 17. Classification of the types of vulnerability for buildings with load-bearing walls. Type Linear Compact Intersection Subtype Small Medium L-shape No courtyards E-shape No. of floors 1 floor (1F) 9 1 1 5 2 2 floor (2F) 1 6 2 4 4 Dimensions Length (m) 20-37 25-85 44-76 16-26 (1F) 22-36 (2F) 34-43 (1F) 33-47 (2F) Width (m) 6-25 15-35 17-56 7-24 (1F) 13-26 (2F) 20-30 (1F) 21-27 (2F) Built area (m2) 125-610 500-1 570 795 (1F) 2 900 (2F) 120-624 (1F) 450-1 200 (2F) 400-900 (1F) 1 260-1 400 (2F) Date of construction 1950-1994 1955-1970 1955-1969 1955-1986 1955-1980 Atrium Yes, in the middle 3 1 1 1 2 No 1 2 1 4 1 No data 6 4 1 4 3 Type of roof Inclined 10 5 2 9 6 Flat — 2 1 — — Roof finish Ceramic tile 10 5 2 7 6 Metal panels — 1 — 2 — Gravel — — 1 — — Flooring — 1 — — — % openings (nº of buildings) In X Medium (4) Low (3) High (3) Medium (2) Low (1) Very high (3) High (2) Medium (1) Low (1) Very low (2) Medium (1) Low (2) In Y Medium (1) Low (2) Very low (5) Low (1) Very low (4) High (1) Medium (1) Low (1) Low (2) Very low (5) Medium (1) Low (3) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 71 SUMARY — Compact without courtyards: one floor buildings in this category can be compared with small linear ones, and those with two floors with medium linear buildings. However, their higher regularity and square shape makes them less vulnerable. Single-storey buildings have less than 625 m2 of floor space and are 26 m long. The two-storey buildings are up to 1 200 m2 in area and 36 m long. All have a sloping roof with ceramic tiles. The percentage of openings is low - very low in the minor direction, and variable in the major. — E-shaped intersection: these buildings have a comb-shaped floor plan with similar dimensions, both in length (up to 47 m) and width (up to 30 m), regardless of the number of floors. They all have a sloping roof with ceramic tiles. Their shape accentuates their vulnerability. The opening ratio is low-medium in both directions. 3.4. CHARACTERISATION OF REINFORCED CONCRETE FRAME BUILDINGS In total, 222 RC frame school buildings have been identified. The analysis of the configuration of the buildings leads to the following conclusions. 3.4.1. Date of construction and regulations The date of construction of these buildings varies between the 1950s and the present day, with the vast majority being built during the 70s and 80s. The structural and construction requirements of reinforced concrete buildings in Spain have evolved considerably over time. These changes have been reflected in table 18. Table 19 collects the values obtained from the mechanical properties of the RC identified in the documentation. It is important to note that no design information is available for several buildings in this group. Therefore, in the evaluation of its seismic response and vulnerability, the values necessary for the calculation established in the regulations have been considered according to its date of construction. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 72 SUMARY Table 18. Evolution of mechanical properties and construction criteria for reinforced concrete buildings according to regulations. Regulations EH-68 EH-73 EH-80 EH-88 EH-91 EH-98 EHE-08 Date 1968 1973 1980 1988 1991 1998 2008 Concrete fckmin (N/mm2)12 12,5 15 15 15 20 25 E (N/mm2)No No 1900 fck 1900 fck 1900 fck 31000 fcm 38500 fcm Steel fy (N/mm2)230 220 410 (CS-400) 410 (CS-400) 410 (CS-400) 400 (B400S) 400 (B400S) Diameter (Φmin) (mm) 5 6 4 No 4 6 6 Types bars Smooth Smooth and corrugated Smooth and corrugated Smooth and corrugated Smooth and corrugated Corrugated Corrugated Provision No No On hanger On hanger On hanger On hanger On hanger Others Actions No No Yes Yes Yes Ye s Ye s Coat. No No No Yes Yes Yes Ye s Coefficient security S: steel C: concrete No No S: 1,15 C: 1,5 S: 1,15 C: 1,5 S: 1,15 C: 1,5 S: 1,15 C: 1,5 S: 1,15 C: 1,5 Table 19. Mechanical properties of reinforced concrete buildings according to available design documentation. Parameter Units Concrete (RC-175) Steel (CS-400) Weight by volume (W/V) kN/m324,51 76,47 Strain modulus (Ec) kN/m2According to regulation 210 Poisson’s ratio (U) 0,2 0,3 Coef. Thermal expansion (A) 1/C 10E-05 1,2E-05 Concrete strength ( f’c)MPa 17,5 Elastic limit (Fy) kN/m2420 Minimum tensile strength (Fu) kN/m2Fy · 1,10 SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 73 SUMARY 3.4.2. Area and height The floor area of these buildings varies between 125 m2 and 4 700 m2. 56% (125) have two floors, and the rest (80) have only one. The latter are the buildings with the smallest built area. Only 20 buildings are three storeys high, with an area between 2 000 and 3 000 m2. Of these, 13 are H shaped and share common characteristics. A large number of the buildings have a sanitary slab. This rises above the ground, from 0,35 m to 0,8 m, resulting in short columns. This is one of the typical seismic vulnerabilities in RC frame buildings. The shear forces concentrate on these short columns, worsening the seismic behaviour of the building. The height of a standard storey ranges from 3 m to 3,45 m. 3.4.3. Slabs The slab of virtually all the buildings observed is one-way, with some (few) cases with a two-way or reticular slab. These are used to support higher spans. In both cases, and given the construction techniques used, these slabs can be considered as a rigid diaphragm for calculation purposes. The thickness of both types ranges from 0,25 to 0,3 m. The characteristics of the slabs are as follows (figure 35): Figure 35. Sanitary (a), one-way (b) and two-way (c) slab typical section. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 80 SUMARY 3.4.7.4. Irregular The last of the groups identified are the irregular buildings, formed from the aggregation of various volumes of different sizes. This makes the estimation of their seismic behaviour at a typology level more complex. Only 5 structural blocks have been included in this group. In table 24 their main characteristics are listed. Table 24. Properties of irregular RC buildings. Type Adjacency I I No. of floors 1 1 No. of buildings 2 3 Length (m) Min. 32 50 Max. 57 65 Mean 45 57 Width (m) Min. 24 51 Max. 29 60 Mean 27 45 Proportion 1,7 1,3 Date By decade 90 80 00 Atrium Yes 1 2 No 1 1 Unknown — — Setback of the slab Yes — — No 2 3 Unknown — — Type of roof Sloped 1 1 Flat 1 2 Roof finish Ceramic tile 1 1 Metal panels — — Gravel — 1 Flooring 1 1 Based on the data obtained, it can be concluded that the fundamental differences between these blocks are their dimensions and proportions. Other characteristics, such as date of construction, type of roof, irregularities and setbacks, are practically identical. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 81 SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) This section shows the structural safety analysis process, which will be applied in the software developed (Estêvão, 2019). 4.1. METHOD For the analysis of the seismic vulnerability of the primary education schools, the seismic behaviour of the different types of schools has been analysed through the capacity - demand spectrum method (Freeman, 2004) (performance-based method). Due to the scale of the school buildings, this analysis is the most appropriate for this study. The evaluation of the seismic safety of school buildings includes: 1. Obtaining and analysing the constructive and structural characteristics of the different school buildings. In addition, information is obtained on the various aspects that influence the building’s seismic vulnerability (distance from the nearest fire station, accessibility for emergency teams, evacuation, etc.). 2. Non-linear static calculation to obtain the capacity curves in both directions of the buildings. 3. Determining the elastic response spectrum according to seismic regulations or attenuation laws. 4. Obtaining the performance point of each building, in the two orthogonal directions. 5. Evaluating seismic safety according to different damage limit states. Chapter 4. Structural safety analysis SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 82 SUMARY 4.2. CAPACITY ANALYSIS The vulnerability assessment is based on the capacity curves (figure 37), which graphically represent the non-linear relationship between the base shear and the displacement of the control node, which is generally located at the centre of masses of the top level. It is obtained through a non-linear static or pushover analysis in both directions of the building (X and Y). It consists on the application of an incremental horizontal load until the collapse of the structure is reached, which allows to determine the capacity of the building to resist the seismic action, considering the non-linear behaviour of the structure. The analysis can be carried out with different commercial software depending on the structural system and applying different load patterns. These load patterns are obtained by two methods according to EC8: a uniform pattern providing the mass of each degree of freedom (mass of each floor of the building); and a modal type pattern, which is proportional to the displacement produced by the vibration mode with the highest mass participation. Figure 37. Capacity curve of a system equivalent to a system with multiple degrees of freedom. PERSISTAH Software. According to the EC8, in order to obtain the capacity curves, the two lateral load patterns must be applied in both X and Y directions, as well as in the positive and negative directions. Accidental eccentricity of the centre of mass (three centres of mass in each direction) should also be considered. Applying all these rules, it is necessary to consider at least 24 capacity curves (2 × 2 × 2 × 3 = 24). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 83 SUMARY The first thing to do in any non-linear static analysis method is to idealise a single degree of freedom (SDOF) system with a K* stiffness and a mass m* which is equivalent to the initial multi-degree of freedom (MDOF) system. The transformation of the initial system (MDOF) is done through the equivalent mass (m*) for SDOF and the transformation factor (G ), according to Annex B of EC8 part 1. mm ii i N ∗= = ∑ φ 1 Eq. (6) Γ= ∗ = ∑ m mii i N φ 2 1 Eq. (7) Where fi and mi are the displacement (configuration of the deformation adopted in the transformation process) and the standardised mass of each floor of the building, respectively (normally fi = 1 on the control node). The capacity curves of the MDOF system can be calculated through the use of any structural analysis software. This is done by applying a set of forces (Fi) Eq. (8) to the structure at each node of freedom (N). It is advisable that the sum of these forces be equal to the unit ∑N i = 1 Fi = 1. Fi m m ii = ∗ φ Eq. (8) The base shear V is given by the load parameter l that is normally calculated by the computer program where the non-linear static analysis is executed. VF i i N =⋅ = = ∑ λλ 1 Eq. (9) Once the capacity curves for the MDOF structural system are obtained, it is possible to compute them for an SDOF system. Displacement d* and the equivalent force F* in the equivalent SDOF system is given by the following functions, through the transformation factor (G) and where V is the base shear and d the displacement in the equivalent MDOF system. dd ∗= Γ Eq. (10) FV ∗= Γ Eq. (11) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 84 SUMARY 4.3. PERFORMANCE POINT The performance point (displacement vs. base shear), which represents the maximum response of the building, is obtained by the intersection of the capacity curve and the linear response spectrum, both in spectral coordinates. The structural behaviour of each school has been analysed according to the N2 Method (Peter Fajfar, 2000), according to the iterative process proposed by Annex B of EC8 part 1 (AENOR, 2018a). The capacity-demand spectrum method of the ATC-40 standard (Applied Technology Council [ATC], 1996) was also used when considering an actual earthquake scenario (Estêvão, 2019). These routines have been successfully applied previously to evaluate the structural behaviour of buildings in the Algarve (Estêvão, 2016) and in the Azores (Estêvão and Carvalho, 2015), which are two Portuguese earthquake-prone regions. 4.3.1. N2 Method The N2 method is presented in Annex B of EC8-1 with two possible approaches: an iterative and a non-iterative approach. Both approaches have been used in the analysis method implemented in the software developed for the seismic evaluation of school buildings. The iterative approach of the N2 method has been implemented in the software through the algorithm developed in (Estêvão, 2019; Estêvão, 2020). To apply this method, the first thing to do is to obtain an elastic-perfectly plastic relationship between the forces (F*) and the displacements (d*) in the SDOF (figure 38) system. This ensures that the deformation energy of the equivalent system is the same as in the initial system. The force corresponding to the elastic limit (Fy*), which represents the ultimate strength of the equivalent SDOF system, is equal to the base shear in the formation of the plastic mechanism. Where the initial stiffness of the SDOF system has been determined by matching areas, so that the area covered by the MDOF and the bilinear (SDOF) capacity curve are equal. The other necessary parameter is the displacement corresponding to the elastic limit of the SDOF system, dy*, defined by the following function Eq. (12), where Em* is the deformation energy for the formation of the plastic mechanism (see Eq. [13]). This corresponds to the area under the capacity curve. dd E F ym m y ∗∗ ∗ ∗ =−         2 Eq. (12) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 85 SUMARY EF dd m dm ∗∗ ∗ =⋅ ∗ ∫ () 0 Eq. (13) Figure 38. Bilinear capacity curve. SDOF equivalent system. Annex B: EC8, part 1. The period of the structure for the SDOF system (T*) has been calculated according to Annex B of EC8 part 1, using the following function: Tmd F y y ∗ ∗∗ ∗ =2 π Eq. (14) 4.3.1.1. Implementation in the PERSISTAH software In the PERSISTAH software, the user can choose between the iterative and non-iterative approach. The iterative one (figure 39), is the most precise and, therefore, is the default method implemented in the software through the algorithm (figure 39) developed in (Estêvão, 2019; Estêvão, 2020). The different factors that define the bilinear curve, stiffness (km*), force (Fy*) and displacement (dy*), are determined through the following algorithm: SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 86 SUMARY Figure 39. Diagram of the algorithm developed for the N2 iterative method (Estêvão, 2019). Step 1: Determination of the area under the capacity curve Em* delimited by the limit point (dm*, Fm*), which in this case coincides with the maximum SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 87 SUMARY force of the capacity curve, and the stiffness (km*) of the elastic-perfectly plastic structural system, in this case the force Fy* is equal to Fm*, and dt* = dm* (figure40): kF dE F m m m m m ∗∗ ∗∗ ∗ = ⋅−      2 Eq. (15) dF k y m m ∗∗ ∗ = Eq. (16) Figure 40. Capacity curve of the elastic-perfectly plastic structural system where dt* = dm*. Step 2: Determination of the target displacement for the equivalent SDOF system. This displacement is calculated evaluating the elastic response spectrum at T* (period of the equivalent SDOF system). dSTT et e ∗∗ ∗ =     () 2 2 π Eq. (17) The target inelastic displacement (dt*) is then determined with different equations for short period range structures (T* < TC) and for structures where the period range is medium and long (T* ≥ TC). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 88 SUMARY Table 25. Equations for determining the target displacement. Annex B: EC8, part 1. Short period range (T* < TC)Medium and long period range (T* ≥ TC) If F m ST y e ∗ ∗ ∗ ≥ () elastic response dd tet ∗∗ = dd tet ∗∗ = If F m ST y e ∗ ∗ ∗ < () non-linear response dd qqT Td t et u u C et ∗ ∗ ∗ ∗ =+−     ≥11() qmST F u e y =⋅ ∗∗ ∗ () Eq. (18) The relationship between the different magnitudes is shown in two spectral acceleration/displacement graphs below (figure 41). The period T* is represented by the line linking the coordinates origin and the point of the elastic response spectrum with coordinates, det* (SDOF elastic displacement) and Se(T*). (a) (b) Figure 41. Determination of the target displacement for an equivalent SDOF system for short periods (a) and long periods (b). Annex B: EC8, part 1. Step 3: If the difference between the old performance point and the new one is greater than a given maximum error, then the Et* area under the capacity curve of the new target displacement dt* is calculated. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 89 SUMARY — If dt* < dm* (figure 42), then: dd E F yt t y ∗∗ ∗ ∗ =⋅ −         2 Eq. (19) kF d i y y ∗ ∗ ∗ = Eq. (20) Figure 42. Capacity curve of the elastic-perfectly plastic structural system where dti* < dm. — If dti* > dm* (figure 43), then: Fkdkd E k ymt mt t m ∗∗∗∗∗ ∗ ∗ =⋅ −⋅−⋅         () 22 Eq. (21) dF k y y m ∗ ∗ ∗ = Eq. (22) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 96 SUMARY The different percentages of spectral acceleration (%Se) (response spectrum of EC8), corresponding to the displacements d*t,D associated to a given damage limit state, are obtained from the following equations. %() SS ST e a e =⋅ ∗ ∗100 Eq. (31) — If T* ≥ TC (medium and long period range): SSdT aeatD ∗∗∗ ∗ == ⋅     , 22 π Eq. (32) — If T* < TC (short period range): ST d T FT T m a C tD yC ∗ ∗ ∗ ∗∗ ∗ =⋅+−         142 π , () Eq. (33) If Fy*/m* > Sa*, then Sa* = Sea*. With this, the efficiency curve is obtained (figure 48), which serves to obtain the most unfavourable capacity curve for a given damage limit state. Figure 48. Efficiency curve. PERSISTAH software. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 97 SUMARY Once the different damage limit states have been defined, the software develops the fragility curves (figure 49). These curves define the probability that the expected overall damage of a structure will reach or exceed a certain specific damage limit state (Barbat et al., 2008). These curves have been determined according to the lognormal RISK-EU probability distribution. Fragility curves can be calculated for each performance point (target displacement dt) (Eq. 34). A curve is defined for each damage state, which is defined by plotting P[Di|dt ] (Estêvão, 2019). PD dl nd d it Di t Di [|]=             Φ1 β Eq. (34) where Φ is the cumulative distribution function for the normal distribution, dDi the mean displacement for a given damage state and bDi the corresponding standard deviation of the logarithm of the displacement dDi. This value bDi can be defined by the user in the PERSISTAH software. The probability of obtaining a given damage limit state (Di), considering the different damage states defined above as OP = D1, DL = D2, SD = D3, NC = D4 and D5 = collapse is given by the following equations: rD5 = P[D4|dt] Eq. (35) rD4 = P[D3|dt] – P[D4|dt] Eq. (36) rD3 = P[D2|dt] – P[D3|dt] Eq. (37) rD2 = P[D1|dt] – P[D2|dt] Eq. (38) rD1 = 1 – P[D1|dt] Eq. (39) Fragility curves are defined by the relationship between a displacement and the probability of reaching a given limit state rDi. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 98 SUMARY Figure 49. Fragility curves. PERSISTAH software. Once the seismic evaluation of each school building has been carried out by applying the method developed (by obtaining of the performance point and with the evaluation of the damage limit states), the School-score is according to Eq. (40). This value will make it possible to classify school buildings according to their seismic risk (Estêvão, 2019). School -core Se =100 % Eq. (40) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 99 SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) The PERSISTAH software (Estêvão, 2019; Estêvão, 2020) follows the Eurocode 08 part 1 and 3, considering the national annexes of Spain and Portugal (NP EN 1998-1: 2010 and NP EN 1998-3: 2017). First, using any structural analysis software and according to EC3-3, a set of capacity curves is obtained for each building. Then, the curves are fed into the PERSISTAH software, where the seismic analysis methods described in the previous section are applied to obtain the seismic safety of each building (performance point, fragility curves, damage analysis and school-score) school building (Estêvão, 2019). This software can be used by the relevant authorities and civil protection bodies both in Spain and Portugal. It will be available on the research project website (<https://datalab.upo.es/persistah>) for public use and information. The software is easy and intuitive to use, and is available in three languages: Portuguese, Spanish and English. The collaboration between the various institutions, the University of the Algarve and the University of Seville, is essential for this software to be used in both countries. The software has been developed for the management of seismic safety in schools. It is divided into three main modules: the first one, aimed at generating a geo-referenced database of the schools; the second one, for the selection of the seismic action to be considered for the evaluation of each school; and the third one, to determine the degree of damage and the School-score of each school building. The IT strategy developed and applied in the program is relatively complex (Estêvão, 2020; Estêvão, 2019) and has been outlined in figure 50. It represents the diagram of the software operation, which consists of three different modules each with different routines. Chapter 5. PERSISTAH Software SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 100 SUMARY Figure 50. Diagram of the operation of the PERSISTAH software. Obtaining the School-Score. 5.1. SCHOOLS MODULE Schools, as described in Chapter 3, have been grouped into several types and subtypes. This module presents a school management menu, where it is possible to define the general characteristics of the school (figure 51), and to include its aerial image and georeference. 5.1.1. Menu: School Within the schools module, a school database is to be found, featuring fields as: schools, buildings and photos. In this section, it is possible to define the general characteristics of the schools (figure 51), such as: reference code, name, address, telephone, e-mail, level of education, ownership, no. of students, built area, no. of buildings, plot area, % of surface area, morphology of the land, distance from the coast, operational capacity of the fire brigade, distance from a fire station, distance from the nearest hospital and conditions of access and evacuation. As described in section3.1.1, this information was collected for each of the schools in the Algarve and Huelva provinces, and was fed into the PERSISTAH software. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 101 SUMARY Figure 51. Schools tab. PERSISTAH software. Figure 52. Menu for georeferencing schools. Aerial image. For each school, the data concerning the general characterisation (figure53) and the photographs (figure 52) can be modified or filled in. In fact, during the development of the PERSISTAH project, the database was completed or modified based on new data coming from the school inspections or the answers to the surveys. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 102 SUMARY Figure 53. General characterisation of the school. It is possible to filter the database by country, region and municipality, and to export the filtered results to Google Earth (figure 54) or to Excel. With this, detailed information from any school or group of schools can be easily obtained and effectively presented. Figure 54. Exporting the location of schools in Google Earth. PERSISTAH software. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 103 SUMARY 5.1.2. Menu: School buildings In the Buildings menu, information for each building or module that is structurally independent (between joints) is gathered. It is divided into different sections (structural data, irregularities and foundations, non-structural elements, building maintenance and location and photos) ( figure55). Figure 55. Buildings tab. PERSISTAH software. The structural characteristics (capacity curve [figure 56]) and photographs of each building (elevations, interiors, aerial, etc.) can be entered independently. The photo section is very intuitive and it is possible to visualise the images of the building in a simple way (figure 57). Figure 56. Capacity curve input module. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 104 SUMARY Figure 57. Photos tab. PERSISTAH software. 5.1.3. Importing capacity curves The PERSISTAH software is able to import capacity curves in text format (.txt) were shear (kN) and displacement (m) values are displayed in columns. In addition, the equivalent mass values (m*) for SDOF and the transformation factor (G ) must be calculated externally, calculated according to Annex B of EC8, part 1, and fed to the software. Once this data is entered, the program draws the capacity curve (figure 56). Several capacity curves can be incorporated in each direction, making it possible to compare different capacity curves for the same building. For example, this can be used to compare the capacity curves of the original building with the capacity curves of various retrofitting models. 5.2. SEISMIC ACTION MODULE In this module, the user can define the seismic action by means of two different methods. The first is based in the hazard stipulated by the codes (essentially for the verification of retrofitting needs). The second defines the seismic action through a seismic scenario (which is particularly important for civil protection). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 105 SUMARY In the code based definition (figure 58), the seismic actions of several seismic codes have been implemented: the Eurocode-08, the Spanish seismic standard NCSE-02, and the Portuguese NP EN 1998-1:2010. Figure 58. Seismic action module. Response spectrum. When the seismic action is defined through a seismic scenario with a certain magnitude and epicentre (figure 59). The response spectrum is obtained by applying attenuation laws. Figure 59. Seismic action corresponding to a seismic scenario. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 112 SUMARY or three storeys high, so seismic demand reduction systems —which are expensive and recommended for complex or higher buildings— are not applied. The buildings under study behave well on a global level, i.e. the floors have a satisfactory stiffness and the structural elements are correctly joined together, so the first group of strategies is excluded. For illustrative purposes, techniques relating to diaphragm stiffening are presented in figure 64. Figure 64. Horizontal diaphragm stiffening systems: a) Reinforced concrete slab on existing slab; b) Steel plate on existing slab; c) Thickness increase by means of plywood layer (Wooden slab); d) Bracing under existing slab. Furthermore, the retrofitting scheme selected must be in line with the building’s configuration, allowing the normal development of teaching activities, minimising inconveniences during its execution and reducing the architectural impact. This excludes a number of alternatives such as the use of moment resisting frames or buttresses. The latter are illustrated by way of example in figure 65. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 113 SUMARY (a) (b) Figure 65. Stiffening systems using buttresses: a) Reinforced concrete; b) Steel profiles. 6.1.2. FEMA 356 The American standard FEMA 356 (American Society of Civil Engineers [ASCE], 2000) proposes different intervention strategies depending on the deficiency to be corrected: local modification of components, elimination or reduction of irregularities, increase of global stiffness, global retrofit of the structure, reduction of mass, seismic isolation, and supplemental energy dissipation. These strategies are presented in table 27, together with the corresponding methods of intervention. In the table, the methods considered in this guide have been highlighted in grey according to various criteria (see 6.1.1). According to this standard, each retrofitting measure must be evaluated in conjunction with other measures on the existing structure, and with the structure itself, verifying its effects on the structure’s stiffness, strength and deformability. It is also necessary to check the compatibility of new and existing elements. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 114 SUMARY Table 27. Retrofitting Strategies in FEMA 356. Strategy Deficiencies System/Method Local modification of components – Resistance – Deformation capacity – Stiffness Steel cladding on beams and columns Addition of plywood in wooden slab Jacketing of RC columns Reduction of the cross section Elimination or reduction of irregularities – High demand for inelastic deformation – Irregular displacement Triangulated (braced) frames Shear walls Bending-resistant frames Partial demolition (> building impact) Removal of parts from the structure (towers or side flanges) Creation of structural joints (irregular building – various regular structures) Overall structure stiffness – Excessive lateral deformations – Structural elements without adequate ductility to resist deformation Triangulated (braced) frames Shear walls Global retrofit of the structure – Inelastic behaviour low levels of ground movement – Inadequate overall resistance Triangulated (braced) frames Shear walls Bending-resistant frames Mass reduction – Excessive mass in building – Global structure flexibility – Global structural weakness Demolition of upper floors Replacement of heavy cladding and interior partitions Removal of large storage and equipment loads Seismic isolation – Excessive seismic forces – Demand and excessive deformation – Protection of important building elements – Protection of non-structural elements Bearings between the structure and the foundation Energy-dissipating bearings (dampers) Supplemental energy dissipation – Excessive deformation due to the overall flexibility of the structure Viscous fluid dampers (hydraulic cylinders) Deformation expiration plates Friction pads SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 115 SUMARY In school buildings, structures are usually simple and have two or three floors, so the base isolation and supplemental energy dissipation systems, which are expensive and recommended for buildings of greater complexity or height, are not applied. Mass reduction strategies with high architectural impact are not applied either, as these buildings have a low storage load, lightweight cladding, and low height. Even so, the engineer criterion prevails, so an individual study must be carried out when selecting a strategy. Figure 66 shows two of the most commonly used seismic retrofitting systems: triangular or braced frames and shear walls. (a) (b) Figure 66. Stiffening systems: (a) Bracing systems; (b) Shear walls. 6.1.3. EC8 European regulation EC8, part 3, presents a series of general criteria for intervention in the structure and general information on the types of intervention possible. According to this standard, seismic enhancement strategies should increase the capacity of systems resistant to lateral forces and horizontal diaphragms, and/or reduce the demand imposed by seismic actions. The general classification of the different types of intervention (table 28), is very similar to those proposed by the American standard FEMA 356: stiffness and reinforcement of the structure and its foundation, improvement of ductility, reduction of mass, base isolation and additional damping. As in previous sections, the techniques considered in this study have been highlighted in grey in this table. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 116 SUMARY Table 28. Types of intervention. Eurocode 08 part 3. Local or global modification of the damaged or undamaged elements, considering the stiffness, resistance and/or ductility of these elements Repair Reinforcement Complete replacement Addition of new structural elements Bracing systems Shear walls RC, wood or steel straps (load-bearing walls) Modification of the structural system Elimination of some structural joints Widening of joints Elimination of vulnerable elements Modification to obtain more regular and/or more ductile arrangements Addition of a new structural system to resist all or part of the seismic action Transformation of existing non-structural elements into structural elements Introduction of passive protection devices Dissipative bracings Base isolation Restricting or changing the use of the building Partial demolition Unlike the American standards (ATC-40 and FEMA 356), where a series of specific interventions are presented within each general strategy, the European regulations present a series of strategies in a general way, as well as a series of criteria to be taken into account when intervening in a structure. In each annex according to the different structural systems (masonry buildings, RC structures and steel and mixed structures), a series of strategies and methods of intervention are presented specifically, which are set out, in a schematic way, below. 6.1.3.1. Masonry buildings The Eurocode 08, part 3, in its Annex C “Masonry buildings” presents different retrofitting strategies within which the different methods of repair and reinforcement of buildings with URM load-bearing walls are classified. These retrofitting techniques are presented schematically in table 29. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 117 SUMARY Table 29. Retrofitting strategies, Eurocode 08 part 3 Annex C Masonry buildings. Strategy Deficiencies System/Method Repairing cracks Small opening (<10 mm); thin wall Sealing with mortar Small opening (<10 mm); thick wall Injections with cement paste Epoxy-based concrete paste injections Wide opening (>10 mm) Mastering with bricks or elongated stones Crack connection (dovetail clips, metal plates or polymer grids) Sealing with cement mortar Vertical cracking (walls with levelled tendons) Small diameter wire in bed-joints Polymeric grid strips in bed-joints Large diagonal cracks Concrete ribs Polymeric grids (one or both sides) + mortar and plaster Repair and reinforcement of wall intersections Poor connection between concurrent walls Reinforced concrete strap Steel plates or mesh on guide line Insertion of inclined steel reinforcements in holes with fluid mortar Post-tensioning Reinforcement and stiffening of horizontal diaphragms Distortions in the plane Additional layer – wood panels (perpendicular or oblique) RC overlay + welded mesh (shear connections and wall anchorage) Mesh in two diagonal directions (anchored to beams and perimeter walls) Roof trusses Bracing and anchoring to support wall Horizontal diaphragm (bottom chord level) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 118 SUMARY It can be established that the school buildings under study analysed in the province of Huelva (Spain) generally present the following characteristics: — They have wall crest beams (tying beams) and a good connection between the competing walls, so there is no need to resort to strategies to reinforce the wall intersections or between walls and slabs. — They have rigid diaphragms, generally one-way span reinforced concrete slabs, so they do not need to be stiffened. — They have single-leaf ceramic brick walls of various thicknesses, so the techniques of reinforcing multi-leaf walls with rubble filling are not applied. — They do not have structural joints. In some cases the largest dimension reaches 70 m in length. Table 29. Retrofitting strategies, Eurocode 08 part 3 Annex C Masonry buildings (cont.). Strategy Deficiencies System/Method Tie beams Damaged tie beam Repair or reconstruction If there are none, add Reinforcement of buildings by means of steel braces Bad connection and overall behaviour (out-of-plane failure) Longitudinal or transverse braces to walls, external or in perforations Post-tensioning straps (improves tensile strength) Reinforcement of rubble-filled masonry walls (multileaf walls) Rubble filling Reinforcement by means of fluid mortar Mortar + steel reinforcement anchored to the outer leaves Reinforcement by means of reinforced concrete jackets or steel profiles Out-of-plane failure Shotcrete reinforced with wire mesh or steel bars (one or two sides with cross ties) Steel profiles (one or two sides) Reinforcement by polymer grid jackets Out-of-plane failure Polymeric grids (one or both sides) + ductile pastes (lime and cement with fibre-based reinforcement), should be anchored to the perpendicular walls SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 119 SUMARY According to the above, and based on its low architectural impact on the building, and its ease and speed of application (only the external part of the wall is involved, without interrupting teaching activities), the most relevant techniques proposed by this standard are: reinforcement by steel straps, reinforcement of walls by means of reinforced concrete jackets or steel profiles, and reinforcement by means of sheet metal jackets or polymer mesh (table 29). The study of retrofitting techniques for URM school buildings is discussed in more detail in section 6.2 of this guide. 6.1.3.2. Reinforced concrete buildings The Eurocode 8, part 3, in its Annex A “Reinforced concrete buildings” generally develops a series of techniques for the repair and reinforcement of buildings with a reinforced concrete structure. The three retrofitting techniques proposed in this annex are presented schematically in table 30. Table 30. Retrofitting strategies, Eurocode-08 part 3 Annex A Reinforced concrete buildings. System/Method Improvement/Enhancement Concrete jacketing Bearing capacity Bending and/or shear resistance Deformation capacity Poor splice resistance due to overlaps Steel jacketing Bearing capacity Poor splice resistance due to overlaps Ductility by confinement Plating and wrapping with fibre reinforced polymers (FRP) Shear strength of columns and walls Ductility by confinement at the ends of structural elements Prevention of poor overlap failure As we can see in this standard, three specific retrofitting methods are presented (table 30) unlike the American standards (ATC-40 and FEMA 356), which present a more exhaustive classification of these systems (table 26 and table 27). However, in Annex B “Steel and composite structures” it is specified that the local seismic retrofitting systems proposed for the structural elements and for the connection between elements (table 32), can be applied to any SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 120 SUMARY structural system. Therefore, most of them are compatible and can be applied to reinforced concrete structural elements. The study of retrofitting techniques for reinforced concrete school buildings is developed in detail in section 6.3 of this guide. 6.1.3.3. Other buildings The European seismic standard EC8, part 3, in its Annex B “Steel and composite structures” presents a series of seismic rehabilitation strategies for buildings with steel or mixed structures, which are a minority among schools in the province of Huelva. Unlike the systems proposed for reinforced concrete buildings, for buildings with steel or composite structures this annex presents a more complete classification with a series of strategies at the global (table 31) and local (table 32) level, within which the various specific retrofitting systems are classified. The retrofitting strategies proposed for these buildings are in fact applicable, according to this annex, to any structural system. The objective of the general seismic retrofitting strategies is to increase the overall capacity of the structure and the horizontal diaphragms to resist lateral forces, and to reduce the seismic demand, very similar to those mentioned in the American standards ATC 40 and FEMA 356 (table 26 and table 27, respectively) for reinforced concrete structures. Comprehensive seismic retrofitting interventions should include one or more strategies, as can be seen in table 31. Regarding the assessment and local seismic adaptation of structural elements, the standard indicates a number of general requirements that will not be discussed in detail in this document. The different types of local seismic retrofits proposed in this standard for structural elements are shown below schematically (table 32). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 121 SUMARY Table 31. Global Retrofitting Strategies Eurocode-08, Part 3, Annex B Steel and composite structures. Strategy Intervention Stiffness and reinforcement of the structure and its foundation system Bending-resistant frames Improved mixed action steel beams and RC slab (higher overall stiffness) Connectors Embedding beams and columns in RC Semi-rigid and/or partially resistant steel or composite joints Bracings (greater overall stiffness) Triangulated (braced) frames Off-centre bracing and tapering (brace connection in dissipative zone) better than concentric bracing Improves ductile response and prevents beamcolumn instability Steel, RC or composite walls Increased overall stiffness Bracings in moment-resisting frames Improved ductility of the structure The systems proposed in Table 21 for structural elements can be applied Reduction of mass Replacement of heavy plating with lighter systems Disposal of unused equipment and stored loads Replacement of masonry partitions with lightweight systems Removal of one or more floors Seismic isolation Base isolation Structures with fundamental periods >1.0 s Additional damping SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 128 SUMARY 6.2.1.1. Wire mesh The global retrofitting techniques by means of meshes (figure 67 and figure68), are techniques that have a good architectural integration, being inserted inside the wall. Furthermore, they are cheap and easy to apply that are normally used in rehabilitation works. They provide the wall with increased confinement and resistance to tensile forces, preventing the formation of cracks. In addition, they increase both the in-plane and out-of-plane resistance of the wall. Steel has been widely used to reinforce walls by placing meshes anchored to the masonry and covered with shotcrete or cement mortar. Depending on the type of mesh and the installation technique, various solutions can be found. In the case of ferro-cement (figure 67), the meshes are made of welded wire or other fibres and are covered with concrete micro-mortar (Fulop and Suppola, 2011). It is also possible to implement meshes with intermediate diameters (4-6mm) applied on one or both sides of the wall with the same construction solution, as in (Diz et al., 2015). Finally, there are retrofitting techniques through the use of shotcrete (figure 68). In this case, a larger diameter mesh (6-14 mm) is used, covered with shotcrete (Shabdin et al., 2018). Figure 67. Ferro-cement. Diagram and construction detail. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 129 SUMARY Figure 68. Steel rod mesh covered by shotcrete. Diagram and construction detail. 6.2.1.2. Steel sheet bands Steel can also be applied to the outside of the wall by means of cross bracing (figure 69) or forming a grid (figure 70) with steel sheet bands. These systems provide an improvement in the tensile behaviour of the wall, out-of-plane resistance and an increase in stiffness. Cross bracing presents a difficulty in achieving the necessary strength at the ends, where the bands are more concentrated. They are usually easy and fast to execute and low cost, both in terms of material and execution. They are usually used only on one side of the wall but can be placed on both sides. A variant of the techniques mentioned above is the three-dimensional tying system (figure 71). In this case, stainless steel strips (thickness 0,8 mm; width 20mm) are used instead of bands or meshes. These are placed on both sides of the wall and connected together to form a 3D wall tying system. A pre-stressing is applied to these strips, which gives a slight compression to the wall (Dolce et al., 2009). Studies on this solution have concluded that it is an effective reinforcement (Spinella, 2019), due to the considerable increase in the overall strength and ductility of the structure. It is a more invasive technique than the previous ones, which requires a series of perforations to be made through the wall. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 130 SUMARY Figure 69. External steel bands. Figure 70. Rectangular steel band mesh. Figure 71. Three-dimensional tying system. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 131 SUMARY 6.2.1.3. Injections Another type of global intervention are the injections of cement or epoxy resin grout into the wall (figure 72) or into cracks in the wall (figure 73). This type of intervention does not change the appearance of the wall, and also restores the continuity of the wall, covering the possible flaws and cracks. In multi-leaf walls, they seal the potential internal holes of the wall, providing a considerable increase in its stiffness and resistance. Figure 72. Injection of grout or epoxy resin. Figure 73. Injection of grout or epoxy resin in cracks. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 132 SUMARY 6.2.1.4. Reinforced concrete elements As for global actions using reinforced concrete elements, two techniques can be highlighted: rigid core and confinement by means of tie beams or columns (figure74). (a) (b) Figure 74. General action with reinforced concrete elements. (a) rigid core and (b) confinement with RC columns and beams. The rigid core system is executed by drilling holes in the centre of the wall along its entire height up to the foundation. The usual diameter of the hole is 50-125 mm, depending on the thickness of the structural element and the characteristics of the intervention. After placing the reinforcement in the hole, cement grout or polymer/epoxy sand is pumped in, until the hole is filled. This method increases the lateral resistance and the energy dissipation capacity of the wall. Furthermore, it has no architectural impact on the building. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 133 SUMARY When using a confinement system, reinforced concrete columns are introduced at each corner, at the ends and in the wall gaps. In the case of long walls, the columns are inserted at regular intervals. These columns are connected horizontally by means of tie beams on each floor or, in the case of a great height, at regular intervals. These elements are made of reinforced concrete with variable dimensions according to the characteristics of the reinforcement. This system improves the ductility, the energy dissipation capacity of the wall, and its out-of-plane behaviour. However, the execution of these two retrofitting techniques is complicated, compared to the ones, in which only the outside of the wall is involved. 6.2.1.5. Carbon fibre reinforced polymers (CFRP) Carbon fibre reinforced polymers (CFRP) (figure 75) is one of the most widely used materials in the seismic retrofitting of URM buildings. There are various configurations, which can be executed on one or both sides of the wall. However, they are usually placed on the outside of the wall to obtain greater ease and speed of execution. These reinforcements are usually covered with shotcrete or mortar and are completely integrated into the wall. The method considerably improves the strength, displacement capacity and energy dissipation capacity of walls. It has several advantages: low weight, high mechanical properties, lack of corrosion and high feasibility of installation (Proença et al., 2012). Most CFRP studies focus on the analysis of the strength of compression diagonals through the application of cyclic loads and analyse the behaviour of reinforced walls. In (Martinelli et al., 2016), the authors examined broad bands of fibre vertically, horizontally, and diagonally. In (Turco et al., 2006), the bands used were narrow and the reinforcement was embedded in channels. As concluded in (Papanicolaou et al., 2011; Faella et al., 2010; Capozucca, 2013), this technique has two main weaknesses: the lack of adhesion between the bands and the wall, and its high price. In (Fathalla and Salem, 2018), a four-storey residential building was reinforced with CFRP bands of different thicknesses and configurations. The analysis concluded that CFRP bands have a high capacity to prevent structural collapse with less local damage. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 134 SUMARY Figure 75. Reinforcement configurations using CFRP bands. 6.2.1.6. Rebaring An important aspect in this type of building is the presence of openings in the wall, which reduces its seismic capacity. In (Sanaz and Armen, 2012), the authors conclude that the openings significantly affect the seismic behaviour of the wall, causing a concentration of shear forces in some areas of it. Similar conclusions were obtained in the experimental analysis presented by (Reyes et al., 2018), in which the influence of window and door openings in loadbearing walls is analysed. In this study, openings are shown to be a key influencing factor in the shear strength of walls, and damage patterns are generally concentrated in the areas between them. This phenomenon has also been corroborated by inspections of school buildings following major earthquakes (Augenti et al., 2004). In the case of the earthquake in the Italian region of Molise in 2002, masonry walls with a greater number of openings were found to have deeper and more severe cracks. All these studies establish that the presence of a high opening ratio considerably increases the seismic vulnerability of URM buildings. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 135 SUMARY A recent experimental study analysed a new technique for reinforcing masonry walls (Proença et al., 2019), which consists of installing steel bars in the openings perimeter. A wall sample was tested cyclically until failure, first without reinforcement and then with a steel rebar. The results showed that the rebaring produced a significant increase in resistance and deformation capacity in plane, as well as in the energy dissipation accumulated until collapse. Although it is a very efficient and novel technique, studies and experimental data on it are currently limited. This system can be executed with a tubular profile embedded in the perimeter of the opening (figure 76) or, externally, by means of another type of steel profile, such as the one in (figure 77). If a surface reinforcement is carried out using steel rod mesh (see section 6.2.1.1 Wire mesh in this chapter), the opening can be reinforced by increasing the amount of reinforcement on the perimeter itself. Figure 76. Steel rebar in opening perimeter. Elevation and cross-section. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 136 SUMARY 6.2.2. Retrofitting schemes considered In accordance with the characteristics of the buildings studied, several of the solutions set out in the previous section have been selected as suitable: wire mesh on the outer surface of the wall, CFRP mesh, and metal rebars for openings (figure 77). These solutions have been studied in depth. All of them can be implemented working exclusively from the outside of the building, without affecting the rooms. They are cheap and easy to carry out and, furthermore, do not interfere with the configuration and use of the wall on which they are applied. The retrofitting is fully integrated into the building, without causing any visual impact. Furthermore, these solutions are reversible and do not change the configuration of the building. (a) (b) (c) Figure 77. Retrofitting systems analysed: steel mesh (a), CFRP mesh (b), and steel rebar (c). The first technique is based on the addition of a steel mesh on the outside of the load-bearing walls, as shown in figure 77 (a). For its execution, it is necessary to remove the existing paint and plaster and to apply a bonding layer of acrylic resin. Then, the meshes are placed by means of mechanical anchors, and finally they are plastered and painted. The technique requires the use of skilled labour. The work is carried out exclusively outside the wall and, therefore, does not involve interrupting the normal development of the teaching activity in the school. Another advantage of this technique is its low cost and easy implementation. The second technique consists of reinforcing the walls with carbon fibre reinforced polymer mesh (CFRP), figure 77 (b). The execution procedure is similar to that used in the previous technique, but in this case the bands are stuck on with epoxy resin. CFRP is a very efficient material that also allows to SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 137 SUMARY considerably improve the resistance conditions and capacity of the wall; however, it is expensive. As with wire mesh, the execution is carried out from the outside of the building, making it easier to implement, and the solution does not change in any way the aesthetics or functionality of the wall on which it is applied. With the third technique, metal rebaring (figure 77 [c]), the properties of the wall are improved by intervening in the openings, which are the weak points of this type of structures. To do this, the window sills must be removed and then metal profiles made of rolled steel must be placed in the outer corner of the openings. The profiles, which form a frame, are fixed to the wall by means of mechanical anchors. Finally, the existing sill is replaced. Like the two previous methods, rebaring has good architectural integration in the building, as well as an easy and fast execution that is carried out from the outside of the building. When the behaviour of a wall reinforced with this technique is compared with that of a solid wall (without openings), the results are similar, especially in terms of maximum resistance. In addition to this, this technique presents an outstanding cost-benefit ratio. In the studies carried out in this project, the relative effectiveness of the selected techniques was studied by carrying out non-linear static numerical analyses of as built and retrofitted models. The results obtained show that all the retrofitting techniques improve the seismic behaviour with respect to that of the original structure, greatly increasing its resistant capacity and notably reducing the target displacement at the performance point. In the model reinforced with rebaring, a decrease in the openings deformation has been observed, thus causing an increase in the stiffness of the structure. This retrofitting technique is the best in terms of cost-benefit ratio, since the retrofit is carried out locally, and not in the entire surface of the wall and with very cheap materials. The addition of a steel mesh with ø8 rods spaced 20 cm and L120.12 rebars has caused the greatest reduction in damage levels. Generally, most retrofitting systems have improved the level of damage, except for some configurations. In terms of cost, CFRP band reinforcement is the most expensive reinforcement technique. However, this solution has not reached maximum efficiency in terms of improving seismic behaviour. In general, the addition of L120.12 bars has been shown to have the best cost-benefit ratio. The addition of bars has reduced deformation, increasing thee stiffness of the structure. The addition of a steel mesh has caused the greatest increase in maximum strength. However, the addition of bars has led to the greatest reduction in displacement of the performance point. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 144 SUMARY On the other hand, on the upper floors, infills with horizontal openings can lead to the formation of short columns. These can be corrected by (figure 81): — reinforced concrete jackets, — steel jackets. Additionally, many of these buildings were built before seismic regulations came into force, which means that the details of the beam-column connections may not be enough to consider the frames as rigid, leaving the building with insufficient resistance to lateral loads. This situation can be improved by: — individual steel braces at column-beam joints, — reinforced concrete shear walls (figure 79). The effectiveness of each proposed solution has been studied exhaustively based on its cost-effectiveness, efficiency and architectural integration. To speed up the process, a reinforcement index where all these factors are applied has been developed. It can be seen in the following section (6.4 Seismic Reinforcement Index). Non-linear static analysis reveals that introducing elements in the most vulnerable direction of the building can lead to higher efficiency values than incorporating few elements in both directions. In this sense, shear walls lead to improvements in both directions. For this reason, it is very important to conduct a first analysis to detect the weak points and the seismic behaviour of the building, to identify which is the most vulnerable direction and the most effective zones to introduce the seismic reinforcement in. The steel bracing is the solution that produces the greatest improvement in the overall seismic behaviour of the building. This system increases resistance and stiffness, considerably improving the soft floor effect. However, the most effective areas should be carefully studied, as these solutions have the greatest architectural impact. This system is the most cost-effective according to the values obtained, after applying the reinforcement index method (see section 6.4) and after being compared with the other reinforcement solutions. Reinforcement by means of individual bracing has been shown to be an acceptable technique. However, we concluded that the number and position of the reinforcement elements is key for obtaining high efficiency of the retrofitting. In terms of cost, the most economical reinforcement techniques are the installation of steel jackets and individual bracing on the columns, with the latter being the most cost-effective (and least architecturally harmful). Steel and reinforced concrete jackets are the least profitable techniques due to their low efficiency values and high cost. Furthermore, it has been shown that it is not necessary to add reinforcement elements to all the columns or openings SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 145 SUMARY of a building. Selecting the most effective positions for the installation of the reinforcement must be done carefully to achieve cost-effective improvements. 6.4. SEISMIC RETROFITTING INDEX A tool has been developed to classify the various reinforcements within the scope of this project. The seismic retrofitting (SR) index proposed by (RequenaGarcía-Cruz et al., 2019) is based on efficiency, cost and architectural impact. It focuses on the most salient aspects affecting buildings. It is obtained through Eq. (41), and is based on the following parameters: the efficiency index (EI), the cost index (CI) and the architectural impact index (AI). RI = a1dEI + a2bCI + a3gAI Eq. (41) Coefficients d, b and g modify the main indexes according to the unique aspects of each situation. Coefficients a1, a2 and a3 are the important factors. This method can be applied to any seismic retrofitting scheme. The results obtained in the analysis carried out have shown that this method satisfactorily fulfils the proposed objective. Furthermore, it can be adapted to the reinforcements applied to URM buildings. In this case, the different parameters of efficiency and architectural impact should be modified according to the reinforcement methods applied to this type of building. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 146 SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 147 SUMARY The retrofitting techniques analysed within the research project have been applied in two of the schools that were more vulnerable to earthquakes. These schools present one of the most unfavourable School-score indexes and, therefore, they have greater need for seismic retrofitting compared to the other school buildings. A project for the seismic rehabilitation of a school building in the province of Huelva (Spain) and another in the Algarve region (Portugal) has been carried out. The project carried out at the school in Huelva is briefly described below. Figure 82. Ground floor. C.E.I.P. Los Llanos, Almonte (Huelva). Chapter 7. Example of seismic retrofitting SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 148 SUMARY The project for the seismic retrofitting of a URM school building in the province of Huelva has been carried out. The school was the C.E.I.P. “Los Llanos” located in Calle Los Llanos, no. 10, in the town of Almonte (Huelva). It should be noted that this URM building presented one of the most unfavourable School-score index. Furthermore, because of its size (figure 82 and figure 83), it adapts to the conditions and scale of intervention proposed in the project. In this project, the seismic retrofitting techniques analysed in the study on the seismic reinforcement of URM school buildings (Segovia-Verjel et al., 2019), carried out in the research project, have been applied. Figure 83. First floor. C.E.I.P. Los Llanos, Almonte (Huelva). In this case, two retrofitting methods have been applied: the installation of a steel mesh on the outer side of the wall; and the reinforcement of the façade openings by means of a rebar plus an increase in the density of the steel mesh. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 149 SUMARY Figure 84. North elevation. C.E.I.P. Los Llanos, Almonte (Huelva). Figure 85. South elevation. C.E.I.P. Los Llanos, Almonte (Huelva). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 150 SUMARY Figure 86. East elevation. C.E.I.P. Los Llanos, Almonte (Huelva). Figure 87. West elevation. C.E.I.P. Los Llanos, Almonte (Huelva). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 151 SUMARY The retrofitting consisted on the following steps: — Step 1: Preparation of the external wall surface by sandblasting aluminium silicate particles. — Step 2: Application of acrylic resin bonding agent on the exposed mortar. — Step 3: Placing of austenitic stainless-steel mesh of 20 × 20 cm Ø8 mm on the wall by means of mechanical anchoring with zinc-coated screws of Ø8 mm and 120 mm in length. — Step 4: Application of unrodded cement mortar on the mesh. — Step 5: Installation of fibreglass mesh covered with PVC. — Step 6: Application of a screeded and trowelled cement mortar. — Step 7: Surface finish with cement-based stone paint. This procedure was applied to the entire surface of the external face of the load-bearing walls, paying special attention to the door and window openings, where additional bars were placed on the perimeter. The perimeter of the openings was also reinforced with steel rods, can be seen in figure 80. This retrofitting scheme produces a similar effect to the rebaring method analysed in the study in section6.2. SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 152 SUMARY Figure 88. Construction details. Seismic retrofitting project by the C.E.I.P. School Los Llanos, Almonte (Huelva). SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) 153 SUMARY SCHOOLS, SEISMICITY AND RETROFITTING Beatriz Zapico Blanco (coord.) Abeling, S., Dizhur, D., Ingham, J. (2018). An evaluation of successfully seismically retrofitted URM buildings in New Zealand and their relevance to Australia. Aust. J. Struct. Eng. 19, 234-244. <https://doi.org/10.1080/13287982.2018.1491820>. AENOR (2018a). Eurocódigo 2: Proyecto de estructuras de hormigón. 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Performance of School Buildings during the 2002 Molise, Italy, Earthquake. Earthq. Spectra 20, S257-S270. <https://doi.org/10.1193/1.1769374>. Autoridade Nacional de Protecção Civi (ANPC) (2010). Estudo do risco sísmico e de isunamis do Algarve. Autoridade Nacional de Protecção Civil, Carnaxide, Portugal. Barbat, A.H., Pujades, L.G., Lantada, N. (2008). Seismic damage evaluation in urban areas using the capacity spectrum method: Application to Barcelona. Soil Dyn. Earthq. Eng. 28, 851-865. <https://doi.org/10.1016/j.soildyn.2007.10.006>. Battarra, M., Balcik, B., Xu, H. (2018). Disaster preparedness using risk-assessment methods from earthquake engineering. Eur. J. Oper. Res. 269, 423-435. <https://doi.org/ 10.1016/J.EJOR.2018.02.014>. Campos Costa, A., Sousa, M.L., Carvalho, A. (2008). Seismic Zonation for Portuguese National Annex of Eurocode 8, 8-15. Capozucca, R. (2013). Effects of mortar layers in the delamination of GFRP bonded to historic masonry. Compos. 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