Energy efficiency of social housing existing buildings – a portuguese case study

The European energy performance building regulations, Directive 2002/91/EC - Energy Performance of Buildings Directive (EPBD) of the European Parliament and Council, require that new buildings present minimum standards of energy efficiency. Accordingly the Portuguese regulations require that new buildings comply with minimum requirements on the energy performance and must have an energy performance certification through witch an energy efficiency label is attributed to the housing. It also require that existing buildings must have an efficiency energy label when submitted to a commercial transaction or to a deep rehabilitation. To achieve this goal the study of energy performance of existing buildings must be done. As many essentials elements to determine the U-factor and other thermal parameters are unknown, Portugal developed a simplified methodology to achieve the thermal performance of existing buildings. The aim of this paper is to present the study of the energy performance of a set of social dwellings that were constructed during the decade of 80, constructed before the former building thermal comfort specifications came into force. During the study the referred methodology was applied and conclusions of the energy efficiency label obtained were put out as the encountered difficulties. The study also compares the results obtained by the simplified methodology and by the detailed methodology that is required by Portuguese building thermal comfort specifications

Does Curvature Enhance Forecasting?

In this paper, we analyze the importance of curvature term structure movements on forecasts of interest rate means. An extension of the exponential three-factor Diebold and Li (2006) model is proposed, where a fourth factor captures a second type of curvature. The new factor increases model ability to generate more volatile and non-linear yield curves, leading to a significant improvement of forecasting ability, in special for short-term maturities. A forecasting experiment adopting Brazilian term structure data on Interbank Deposits (IDs) generates statistically significant lower bias and Root Mean Square Errors (RMSE) for the double curvature model, for most examined maturities, under three different forecasting horizons. Consistent with recent empirical analysis of bond risk premium, when a second curvature is included, despite explaining only a small portion of interest rate variability, it changes the structure of model risk premium leading to better predictions of bond excess returns.

Evaluation of strengthening techniques of traditional masonry buildings: case study of a four-building aggregate

Increasing appraisal of the durability, conservation state, and changeable use and function of old buildings in urban centers relies a great deal on the structural safety evaluation of vertical load capacity and the ability to resist horizontal forces. The need to assess seismic vulnerability, particularly of traditional masonry buildings, is a key issue. Evaluation of the seismic vulnerability of old buildings is essential in the definition of strengthening needs and minimization of damage from seismic actions in the safeguarding of built heritage. A three-dimensional model was developed for an aggregate of four traditional masonry buildings located in the old city center of Coimbra, in Portugal. The finite element modeling of these buildings has aimed to identify structural fragility, understand the damages detected, and evaluate the global structural safety of these types of buildings. The primary results obtained in this case study helped to interpret the structural damage and stress distribution, and verified global stability and its consequences. Different strengthening techniques to improve the global behavior of these buildings were modeled and analyzed. A comparison of the efficiencies of strengthening strategies is also discussed. DOI: 10.1061/(ASCE)CF.1943-5509.0000164. (C) 2011 American Society of Civil Engineers

Seismic vulnerability assessment of existing reinforced concrete buildings in urban centers

Despite the recent advances in the analysis of the seismic performance of reinforced concrete structures, the assessment of large building inventories aimed at defining and prioritizing structural retrofitting strategies is still a technically challenging task. This paper aims to contribute to bridging this gap by presenting a simplified methodology for assessing the seismic vulnerability of reinforced concrete buildings, which is then applied to a group of 91 buildings affected by recent earthquakes with different macroseismic intensities. The presented methodology is based on the evaluation of eight parameters associated with different factors that affect the seismic response of the building, namely its structural features, foundation conditions, and position within the urban mesh. The formulation of each parameter and the relative weight attributed to each one of them were defined on the basis of post-earthquake damage observation and expert opinion. After defined, the proposed methodology is applied to Faro city center. Based on the results obtained, a cost benefit analysis is made considering a strengthening solution to the buildings with soft-story irregularity

Seismic vulnerability of building aggregates through hybrid and indirect assessment techniques

This work approaches the seismic vulnerability assessment of an old stone masonry building aggregate, located in San Pio delle Camere (Abruzzo, Italy), slightly affected by the 2009 April 6th earthquake occurred in L’Aquila and its districts. This building aggregate has been modelled by using the 3muri software for seismic analysis of masonry constructions. On one hand, static non-linear numerical analyses were performed to obtain capacity curves together with the prediction of damage distributions for the input seismic action (hybrid technique). On the other hand, indirect techniques, based on different vulnerability index formulations, were used for assessing the building aggregate’s behaviour under earthquake action. The activities carried out have provided a clear framework on the seismic vulnerability of building aggregates, as well as aid future retrofitting interventions

Empirical formulation for estimating the fundamental frequency of slender masonry structures

The fundamental frequency of a structure enables better assessment of its seismic demand for anefficient design and planning of its maintenance and retrofit strategy. The frequency is independentof the type of external loads, however, depends on structural stiffness, mass, damping andboundary conditions. In the case of slender masonry structures such as towers, minarets chimneys,and pagoda temples, it is influenced by mass and stiffness distribution, connection to adjacentstructures, material properties, aspect ratio and slenderness ratio. In this present article, the datacollected from various literature reviews on the slender masonry structures regarding dynamic,geometrical, and mechanical characteristics have been correlated to identify the major parametersinfluencing the fundamental frequency of such structures. The database has been used for developing an empirical formulation for predicting the fundamental frequency of such structures. Thecomparison between the experimental fundamental frequencies and the estimated fundamentalfrequencies are carried out in order to define reliability and accuracy of these empirical formulae

Movimentos da Estrutura a Termo e Critérios de Minimização do Erro de Previsão em um Modelo Paramétrico Exponencial

In this paper, we study how different choices of loadings affect forecasting in the exponential term structure model proposed by Diebold and Li (2006). The loadings are defined through a specific parameter lambda which controls both the decaying speed of the slope as well as the maximum of the curvature factors. In particular, adopting a database including Brazilian fixed income future contracts (ID future), we analyze four different rules of choices depending on metrics that minimize forecasting errors, for different forecasting horizons. We conclude that the optimal rule changes for different regions of ID future maturities/different forecasting horizons, indicating that the choice of how movements will be parameterized in this exponential model should be done with care, tailored for each particular application of the model.

Impact of unoccupied flats on the thermal discomfort and energy demand: case of a multi-residential building

Energy consumption and indoor thermal comfort are two major issues that always come into play in any building retrofit. Furthermore, if the impact of user behaviour and their social activities in buildings must be taken into consideration when defining renovation strategies, the importance of occupancy can also be very important for the performance of the building. This subject is of special relevance in the context of social housing, where the number of unoccupied flats is sometimes quite expressive due to their temporary and intermittent use. A multi-residential social housing neighbourhood was used as a case study to assess the impact of occupancy of different flats on the overall energy savings and indoor thermal comfort of the building. The indoor environment (air temperature and relative humidity), the envelope airtightness (blower door test) of occupied and unoccupied flats and the tenants’ habits were assessed during 7 weeks. The exterior weather data was collected from a local weather station. This data was used to calibrate a numerical model created with EnergyPlus software. The model was used for a sensitivity analysis where the importance of occupancy was evaluated. The occupied and unoccupied flats position (under, over and adjacent) within the building was changed, to assess the impact on the indoor thermal comfort of the occupied flats (according to EN 15251). The results confirmed the importance of occupancy as a decrease of the thermal discomfort rate up to 34.3% for the winter period and an increase up to 85.3% in the summer period were found.publishe

Estratégias e metodologias para intervenções de reabilitação urbana : avaliação da vulnerabilidade e do risco sísmico do edificado da baixa de Coimbra

Doutoramento em Engenharia CivilEsta dissertação aborda o tema da renovação e reabilitação urbana, para o qual o meio técnico e científico tem-se progressivamente consciencializado. O contributo deste trabalho começa pela reflexão e contextualização das actuais tendências das acções de reabilitação urbana pelo nosso País, no desenvolvimento de um modelo que permite a identificação de várias acções concorrentes. Uma vez identificados problemas, potencialidades, dificuldades e oportunidades, é possível a definição de uma estratégia com o objectivo de orientar as acções e processos de reabilitação de forma sustentável. No desenvolvimento de propostas e na definição de estratégias de reabilitação urbana, é fundamental a elaboração da inspecção e diagnóstico adequado à escala da área em análise. É proposto um modelo de procedimento, para o registo e diagnóstico do estado de conservação dos edifícios, testado e aplicado no processo de Renovação Urbana da Baixa de Coimbra, atendendo aos vários objectivos parciais. A acção de diagnóstico estruturado e credível para a caracterização construtiva dos edifícios de centros urbanos antigos, a análise das suas condições de degradação e principais anomalias, permitiu a criação de uma base de informação relevante sobre o edificado antigo desta área da cidade que disponibiliza, não apenas resultados directos de pesquisas simples sobre os edifícios, a arquitectura e outros aspectos socio-demográficos, mas permite também apoiar outros estudos, com recurso a modelos e análises mais sofisticados, nos quais resultarão indicadores e resultados mais profundos, como por exemplo, na avaliação da segurança estrutural e vulnerabilidade das construções. Apresentam-se os resultados de uma campanha de ensaios in-situ de caracterização das alvenarias, usando macacos planos para aprofundar o conhecimento do comportamento mecânico das alvenarias antigas, nomeadamente na caracterização do estado de tensão instalado nas paredes, e na caracterização do comportamento mecânico (resistência à compressão, módulo de elasticidade) informação fundamental quando se analisa as construções antigas. Nas últimas décadas a avaliação do risco sísmico, tal como outros fenómenos naturais, é de preocupação crescente, considerada essencial na actividade e definição de estratégias de planeamento e gestão urbana. A avaliação da vulnerabilidade sísmica dos edifícios existentes na perspectiva da mitigação do risco sísmico deve colocar-se não só em relação aos edifícios isolados de relevante importância histórica e cultural, mas também, em relação aos aglomerados de construções em centros urbanos. A análise do desempenho de edifícios em sismos recentemente ocorridos, tem permitido identificar os aspectos estruturais que mais influenciam na sua vulnerabilidade, e consequentemente na produção de mecanismos de danos. Serão apresentados os resultados de avaliação da vulnerabilidade segundo uma nova metodologia proposta, baseada num índice de vulnerabilidade que consequentemente permite a avaliação do dano e criação de cenários de perda (económicas e humanas). É discutida e avaliada a aplicação da metodologia proposta e a sua integração numa plataforma SIG. Foram desenvolvidos modelos mecânicos simplificados, que através de uma análise não-linear, avaliam a vulnerabilidade de edifícios isolados e agregados de edifícios (quarteirões), discutindo quer aspectos associados a incerteza na definição da capacidade das estruturas, quer na identificação do desempenho e resposta das estruturas. Confrontam-se os resultados produzidos com a metodologia baseada no índice de vulnerabilidade. Desenvolveram-se ainda modelos numéricos com dois objectivos: analisar diferentes estratégias de reforço e reparação, e confrontar os resultados produzidos com os da metodologia mecanicista. Desta forma discute-se com diferentes níveis de detalhe, as formas de avaliação da vulnerabilidade, apresentação e interpretação dos resultados, associadas inevitavelmente à sua escala de operacionalidade.This dissertation approaches the subject of renewal and urban rehabilitation, for which the technical and scientific sphere have been progressively alert and conscientious. The contribution of this work begins with the reflection and framework of the actual tendencies of urban rehabilitation actions in our Country, with the development of a model that allows the identification of several competitive actions within the process. Once identified problems, strengths, difficulties and opportunities, it is possible to define a strategy with the goal of guiding actions and processes on rehabilitation in a sustainable manner. In the development of proposals and definition of urban rehabilitation strategies is fundamental to carry out a thorough inspection and diagnosis, appropriate to the scale of the area under analysis. It is proposed a procedure, to register and diagnose the conservation state of the buildings, tested and applied in the process of Urban Renewal of the Historical City Centre of Coimbra, attending to several partial goals. The structured and reliable diagnosis task for the constructive characterization of the buildings of old urban centres, their degradation conditions and most significant defects, has allowed the creation of a database of relevant information on the old building stock of this area of the city, that provides, not just direct results from simple queries regarding the buildings, the architecture and other socio-demographic aspects. It also allows supporting other studies, with resource to models and more sophisticated analyses, for which will result indicators and insightful results, as for example, concerning the evaluation of structural safety and building vulnerability. It is also presented results of a in-situ testing campaign to collect further data on the mechanical characterization and behaviour of masonry using flat-jack testing techniques, specifically on the compressive stress state, and other mechanical properties (deformability, compressive strength and Young modulus) fundamental information when analyzing old buildings. In the last decades the evaluation of the seismic risk, just as other natural phenomenon’s, are of rising concern, considered essential in the activity and definition of strategy planning and urban management. The evaluation of the seismic vulnerability of the existent building stock in the perspective of the seismic risk mitigation should not be placed only in relation to the isolated buildings of relevant historical and cultural importance, but also, in relation to the agglomerate of buildings in urban centres. The analysis of building performance in recent earthquakes, has allowed identifying the structural aspects that mainly influences in their vulnerability, and consequently in the occurrence of damage mechanisms. The results of evaluation of the vulnerability will be presented in accordance to a new proposed methodology based on a vulnerability index that consequently allows the evaluation of damage and creation of loss scenarios (economical and human). It will be discussed and evaluated the application of the proposed methodology and its integration in an SIG platform. It was also developed simplified mechanical models, that through an non-linear analysis, evaluate the vulnerability of isolated buildings and building aggregates (group of buildings), discussing aspects associated to he uncertainty in the definition of the structure capacity, and in the identification of the structural performance and response of structures. The results produced are confronted with the methodology based on the vulnerability index. Two numerical models were also developed, with two aims: to analyze different retrofitting and repair strategies and to confront the results produced with the mechanical model. This way it is discussed with different levels of detail, the approaches for vulnerability evaluation, presentation and interpretation of the results, associated necessarily to its operative scale