Carlos Chastre

The degradation mechanisms of bonded joints between CFRP laminates and steel substrates under severe environmental conditions require more durability data and studies to increase the database and better understand their causes. Studies on bond properties of double-strap CFRP-to-steel bonded joints with two different composite materials as well as adhesive coupons subjected to freeze-thaw cycles for 10,000 h were conducted to reduce that gap. In addition, the equivalent to the number of thermal cycles and their slips induced in the CFRP laminates was replicated by an equivalent (mechanical) loading-unloading history condition imposed by a static tensile machine. The mechanical properties of the adhesive coupons and the strength capacity of the bonded joints were only slightly changed by the artificial aging. It was confirmed that the interfacial bond strength between CFRP and adhesive is critically related to the maximum shear stress and failure mode. The interfacial bond strength between adhesive and steel degraded with the aging. However, the equivalent thermal cyclic bond stress caused no detectable damage on the bond because only the interfacial elastic regime was actually mobilized, which confirmed that pure thermal cycles aging, per se, at the level imposed, have a low impact on the degradation of CFRP-to-steel bonded joints.

Pseudo-cyclic and cyclic loading were applied to CFRP-to-steel bonded joints built with two different CFRP laminates. In this paper, the strength capacity and bond-slip curves are presented and compared. The modes of failure are also described and associated with the types of material used, and the observed performances are correlated. The analysis of the results showed a threshold value for loading and amplitude level, below which the cyclic loading caused no detectable damage. For cycles above that limit, the region of the joints around the loaded end presented degradation reflected on the bond-slip stiffness and on the increase of residual deformation. It was found that the normalized dissipated energies either obtained from the bond-slip relationship or from the load-slip response had the same trend. The experimental data allowed also to establish a relationship between the damage developed within the interface and the normalized slip. A preliminary estimate of fatigue limit based on those data is suggested.

Deterioration of adhesively bonded CFRP/steel systems in salt fog environment, i.e., deicing salts and ocean environments, has to be taken into account in the design of steel strengthened structures. In the present work, monotonic and quasi-static cyclic loading were applied to CFRP-to-steel double strap joints for two kinds of CFRP laminates after being aged for a period of 5000 h to evaluate the bond behavior. The bonded joints exposed to salt fog had a different failure mode than that observed in the control specimens (0 h of exposure). The severe reduction of the maximum bond stress resulted from damage initiation that occurred in the corrosion region of the steel substrate, associated with final partial rupture on the corroded steel substrate around the edge of the bonded area: it was also correlated with reduced load carrying capacity. Results of pseudo-cyclic tests showed that the relationship between a local damage parameter (D) and normalized local dissipated energy (Wd/Gf) and the normalized slip increment (ΔS/ΔSult) exhibited almost the same trend in the un-aged and aged bonded joints. The normalized slip increment can be seen as a direct indicator for the local and global damage for the un-aged and aged bonded joints. However, monotonic and quasi-static cyclic tests results revealed that the stress concentration due to local corrosion of steel substrate could lead to brittle rupture or accelerated cumulative damage once the aged bonded interface had become weaker. The bonded joints have exhibited also a smaller relative deformation capacity between CFRP and steel.

Carbon Fiber Reinforced Polymer (CFRP) composites have a large potential for strengthening and retrofitting steel parts but due to their premature debonding from steel, further data and research are still required for wider application in such situations. In the present paper, the bond characteristics of CFRP-to-steel joints in pull-pull loaded conditions were studied. Monotonic loading of the double strap joints with different bond lengths was applied and the failure modes and interfacial bond-slip curves were obtained. A tri-linear bondslip model is proposed and it was derived from the experimental data. A closed-form solution approach is also proposed based on the tri-linear bond-slip model. The strength of the CFRP-to-steel interface, the distribution of the relative displacements between bonded materials, the strains developed in the CFRP laminate and the bond stresses along the interface are reported and the closed-form solution is compared with the experimental results. Two cases are selected for presentation: (i) one with the bond length greater than the effective bond length; and, inversely, (ii) one with bond length which is shorter than the effective bond length. The results predicted by the closed-form solutions are shown to be accurate enough when compared to the experiments.

This document has a broad scope and is not focussed on design issues. Precast construction under seismic conditions is treated as a whole. The main principles of seismic design of different structural systems, their behavior and their construction techniques are presented through rules, construction steps and sequences, procedures, and details that should lead to precast structures built in seismic areas complying with the fundamental performance requirements of collapse prevention and life safety in major earthquakes and limited damage in more frequent earthquakes.The content of this document is largely limited to conventional precast construction and, although some information is provided on the well-known “PRESSS technology” (jointed ductile dry connections), this latter solution is not treated in detail in this document.The general overview, contained in this document, of alternative structural systems and connection solutions available to achieve desired performance levels, intends to provide engineers, architects, clients, and end-users (in general) with a better appreciation of the wide range of applications that modern precast concrete technology can have in various types of construction from industrial to commercial as well as residential. Lastly, the emphasis on practical aspects, from conceptual design to connection detailing, aims to help engineers to move away from the habit of blindly following prescriptive codes in their design, but instead go back to basic principles, in order to achieve a more robust understanding, and thus control, of the seismic behaviour of the structural system as a whole, as well as of its components and individual connections.

Este trabalho apresenta o desenvolvimento de um software para análise de torres treliçadas em concreto armado, pós-tensionada por tirantes externos, com a finalidade de suporte para turbinas eólicas de eixo horizontal, em ambiente offshore. A torre está sujeita às ações gravitacionais, aerodinâmicas, hidrodinâmicas. Desenvolveu-se um código computacional, em linguagem MATLAB, específico para este tipo de torre. As dificuldades de uma análise tridimensional mais complexa foram reduzidas propondo-se um modelo simplificado bi-dimensional utilizando-se elementos de pórtico plano. As cargas de vento são variadas segundo o espectro de von Karman. Para as ondas marítimas e correntes são implementados o espectro de Pierson-Moskowitz e o de JONSWAP. As cargas hidrodinâmicas são avaliadas pela equação de Morison. Estas cargas são integradas ao longo dos elementos estruturais e transformadas em cargas nodais equivalentes, de acordo com o proposto por Souza. A análise é realizada no domínio do tempo com algoritmo de Newmark. Este software, por ser específico para este tipo de torre, possui facilidades na introdução de dados e na modelagem da estrutura. Com estas estratégias o modelo apresentou bons resultados para a avaliação de cargas, cálculo de freqüências naturais, resposta de deslocamentos, esforços e reações.

The wind energy production is a growing industry and the energy produced is renewable and environmentally cleaner than most of the other systems. The towers to support the wind energy generators may be built with precast concrete elements that are competitive in comparison to other structural systems. The evolution of the technology for wind energy production shows a clear need for larger wind turbines and longer blades and, consequently, taller towers, where precast concrete solutions are competitive. Truss precast concrete towers is a solution that complies with the demands of the present and future wind energy production. The research on the execution and structural behaviour of the connections between the tower elements is an important issue. This communication presents the experimental analysis of column to column connections for precast concrete towers. The tests included connections with commercial threaded bars welded to the rebars and connections with grouted corrugated steel sleeves. Thick joints (50 mm) filled with fibre reinforced grout and thin joints (3 mm) filled with epoxy resin were tested and analysed.

A demanda de energia, faz com que o homem esteja sempre a procura de novas soluções para a sua produção. Uma opção é a energia eólica, por se tratar de uma energia limpa, renovável e inesgotável. Para se evitar a ocupação das terras férteis, é natural a busca de soluções no mar. Portanto, neste trabalho é estudado o comportamento estrutural dinâmico de uma torre treliçada em concreto armado pós-tensionado por tirantes externos idealizada para uso offshore com a finalidade de suporte para turbinas eólicas de eixo horizontal. A torre está sujeita às ações gravitacionais, aerodinâmicas e hidrodinâmicas. Para considerar estas ações desenvolveu-se um código computacional específico usando a linguagem MATLAB. É proposto um modelo simplificado para análise bi-dimensional, utilizando-se elementos de pórtico plano com a finalidade de contornar as dificuldades de uma análise tridimensional. Embora específico para este tipo de torre, o codigo permite variar geometrias, carregamentos e alterações do nível do mar. Nas cargas aerodinâmicas élevado em conta o espectro de Von Karman. As cargas hidrodinâmicas são avaliadas pela equação de Morison. As cargas nodais equivalentes são determinadas por integração ao longo do elemento estrutural de acordo com o proposto por Souza. Os tirantes pós-tensionados são monitorados para não sofrerem esforços de compressão. A análise é realizada no domínio do tempo utilizando-se o algoritmo de integração de Newmark.. Através dos procedimentos adotados foi possível obter resultados para as freqüências, deslocamentose esforços, que se mostraram coerentes com os obtidos por modelos tri dimensionais mais complexos. O código desenvolvido permitiu a análise de forma simples, eficiente e confiável de torres treliçadas de concreto armado.

Reinforced concrete (RC) beams externally strengthened with glass fiber-reinforced polymer (GFRP) strips bonded to the soffit may see their load-carrying capacity reduced due to environmental conditions—especially due to the deterioration of bond between the adhesively bonded laminates and concrete, causing premature failure.
More research has been published on the detachment of the laminate progressing from the anchorage zone than on failure induced by the formation of flexural or shear-flexural cracks in the midspan followed by fiber-reinforced polymer (FRP) separation and failure designated as intermediate crack (IC) debonding. An experimental program to study degradation of the GFRP laminate beam specimens after accelerated temperature cycles, namely: 1) freezing-and-thawing type; and 2) cycles of the same amplitude (40°C [104°F]) and an upper limit approximately 70% of the glass vitreous transition temperature of the resin, Tg, is described.
Effects on the bond stress and ultimate capacity are reported. Substantial differences between shear and bending-induced failure and a decrease of bond stresses and engagement of the laminates on the structural response are analyzed.

Structural design relies essentially on tests made on cylinders of small size to estimate the probability of failure of prototype members, since full-scale testing of structures to determine their strength is not feasible. The confidence that such scale modeling deserves in terms of representation of actual behavior needs careful examination, due to such factors as material nonlinearities, difficulties of scale representation of particulate materials, and sometimes the impossibility of simultaneously satisfying independent dimensionless parameters. Some failures explained by linear fracture mechanics are associable with strong size effects, as opposed to the cases where small cracks are a material property. Besides research centered on these problems, a number of studies of scale effects have been associated with the increased probability of finding a flaw in larger objects. In fact, geometric similitude may coexist with microscopic randomness of flaws that cause size effects to appear. The type of material of the object under study may also be a decisive factor. For example, scatter of the mechanical properties in unidirectional fiber-reinforced polymers (FRPs) is much larger than in metals due to a larger density of flaws. Thus the strength of FRP laminates may depend on the volume of material involved. Strengthening reinforced concrete columns with FRP wraps leads to new constitutive laws for the overall response of the columns and requires small-scale testing followed by extrapolation for design use. The present paper focuses on the difficulties of this step, based on the experimental data obtained. The questions mentioned above are addressed, and the relevance of the adequate representation of the lateral stiffness of the FRP jacket in the scaled cylinders is emphasized. The paper also addresses the problem of testing confined cylinders with a given slenderness ratio H/D=height/diameter, within the range usually characteristic of short columns, and extrapolating the results for columns of different H/D. The importance of the parameter (thickness of jacket/diameter of column, representative of stiffness of jacket/stiffness of concrete core) is also examined. The influence of the parameter is shown to be relatively minor, whereas the nonscaling of the relative stiffness of the core and jacket would be a major cause of error. The experimental data, in terms of strain and strength, are also compared with numerical models proposed in the literature, and the quality of the approximations is analyzed.

A degradação da ligação entre compósitos de matriz polimérica reforçada por fibras (FRP) e o betão é uma das principais causas de possível rotura das vigas e lajes de betão armado reforçadas
externamente por compósitos de FRP. Desde há mais de 10 anos que se estuda, por isso, na UNL o
comportamento dessa ligação, integrado em programa mais alargado de estudo da durabilidade deste tipo de reforço, especialmente quando sujeito a condições ambientais severas que se simulam por processos artificialmente acelerados no laboratório. Em particular a degradação da aderência e o possível descolamento precoce do reforço têm sido modelados física e computacionalmente com principal incidência no uso de fibras de vidro (GFRP) e resina epoxídica. Nesta comunicação mostram-se resultados obtidos em termos de capacidade de carga, força transmitida ao reforço e tensões de aderência após envelhecimentos de pequenas vigas de betão armado (BA) por ciclos de nevoeiro salino, ciclos seco/molhado em solução salina, ciclos de temperatura entre +7,5ºC e +47,5ºC e gelo-degelo de -10ºC a +30ºC. Faz-se recomendação quanto à extensão máxima para diferentes envelhecimentos. Apresenta-se comparação entre resultados de modelação numérica e experimental.

Compressive stresses created by lateral external pressure on laminates are an important factor on success of the use of mechanical anchorage of externally bonded reinforcement (EBR). A program of double shear tests with imposed normal stresses on GFRP plates bonded to a concrete surface and a bond-slip model are described. Results generated numerically are summarized and used as reference values against those obtained after accelerated aging by freeze-thaw cycles, and temperature cycles of the same amplitude but range closer to the glass vitreous temperature. Numerical modelling showed that the bonded length is fully stressed prior to failure. Increasing lateral pressure led to a larger maximum bond stress and strength at the interface. Cohesion, fracture energy and internal friction angle changes are calculated and used to analyze the effects of the aforementioned cycles on the expected behaviour of the GFRP-concrete joints, namely at the interface.

Polymeric mortars or concrete are special building materials which can be used to repair or strengthen localized areas of structural elements. Following research on the behaviour of retrofitting reinforced concrete circular columns with FRP composite materials and bearing in mind the high strength of polymer concretes, it was decided to develop a solution to seismic retrofit of reinforced concrete columns with polymer concrete. The mechanical characteristics of different polymer concretes and especially their performance when subjected to cyclic axial compression, several bending tests, and monotonic and cyclic axial compression tests were studied, namely the compressive strength, the tensile strength on bending and the Young's modulus. Columns were also tested under axial compression and cyclic horizontal loads. The results of these tests are shown and interpreted. It is concluded that the improved behaviour in monotonic compression of polymer concrete is essentially associated with better strength characteristics of resin, whereas its superior behaviour under cyclic loading is linked to a smoother aggregate grading curve.

A ligação pilar-fundação tem um papel fundamental no comportamento das estruturas pré-fabricadas,
em particular, na presença de acções horizontais, como a acção dos sismos e do vento. Um dos sistemas de ligação pilar-fundação usados em estruturas pré-fabricadas consiste em deixar na extremidade inferior dos pilares armaduras salientes que são introduzidas em negativos executados nas fundações, sejam elas sapatas ou maciços de encabeçamento de estacas. Estes negativos são posteriormente injectados com “grout” para garantir a ligação. Foram estudados diferentes soluções de negativos para ligação das armaduras do pilar na fundação. Foram realizados ensaios monotónicos e cíclicos, para analisar não só o comportamento às acções estáticas mas também para a acção sísmica. No presente trabalho apresentam-se os resultados obtidos com a análise experimental efectuada. O estudo realizado permite apresentar recomendações para projecto e quais os tipos de ligações com melhor desempenho.

A ligação pilar-fundação tem um papel fundamental no comportamento das estruturas pré-fabricadas, em particular, na presença de acções horizontais, como a acção dos sismos e do vento, que introduzem esforços elevados na base dos pilares. Um dos sistemas de ligação pilar-fundação usados em estruturas pré-fabricadas consiste em deixar na extremidade inferior dos pilares armaduras salientes que são introduzidas em negativos executados nas fundações. Estes negativos são posteriormente injectados com grout para garantir a ligação. No presente trabalho foram estudadas diferentes soluções de negativos para ligação das armaduras do pilar à fundação, tendo sido realizados ensaios monotónicos para analisar o seu comportamento. Nesta comunicação apresentam-se e discutem-se os resultados obtidos da análise experimental efectuada.

TThis chapter concerns the need to evaluate the reliability of structural elements produced with recycled aggregates concrete (RAC) in order to address some designers’ scepticism towards the use of this eco-friendly material. The current knowledge on RAC’s behaviour demonstrates its viability for structural purposes. However, of the investigations performed so far very few are related to a fundamental aspect towards RAC world-wide application as a structural material: structural codes have a probabilistic basis.After briefly presenting the state-of-the-art knowledge on the material properties and structural behaviour of RAC, the limitations of the current knowledge are debated. Afterwards, an introduction to structural codification is presented, as well as the fundamentals of reliability analysis. Examples of code verifications are contextualized with their underlying assumptions and the information necessary for code calibration is discussed. The role of reliability in the calibration of structural codes is shown, common techniques for reliability calculations are briefly explained, and relevant references in the area are cited for the readers’ perusal.Having established how structural codes are calibrated, the state-of-the-art on the probabilistic and statistical knowledge of RAC properties is reviewed. The implications of the very reduced number of studies on this area are discussed and the need to conduct further studies is emphasized.Afterwards, investigations that used reliability analysis to calibrate partial safety factors applicable to RAC are reviewed. The methodology of each investigation is presented, the experimental tests that led to the definition of the probabilistic information of the RAC’s parameters are described and the need to have a wide range of data coming from different RAC compositions and aggregate sources is debated.This chapter finishes by contextualizing the current knowledge on RAC properties with the necessary information for code calibration procedures. The relevance of a code proposal towards RAC affirmation as a structural material is highlighted, as well as the requirements of such code. Suggestions for future studies are made.

This paper evaluates and compares the statistics of compressive strength data from three Portuguese ready-mixed concrete plants. A hierarchical model showed that different groups of concrete strength records are not statistically equivalent, even if they were produced in the same plant and using the same concrete composition. This finding is related to autocorrelation. For the same specified strength class, compositions produced less often result in higher average compressive strength and variability. The statistics of one of the plants were quite different from those of the others, even though the concrete of this plant also complied with the specifications. It was found that the average compressive strength of a mix may be quite dependent on the plant that produced it, even if the compressive strength complies with quality control specifications. Conformity with the target slump and strength class was checked following the conformity criteria of EN 206-1 for continuous production. Nonconformity with slump is more frequent than failure to comply with the strength class. A bias factor for reliability analyses was proposed.

The bias factor of the Eurocode 2 [CEN (European Committee for Standardization) (2008). Eurocode 2: Design of ConcreteStructures–Part 1-1: General Rules and Rules for Buildings] and ACI 318 [ACI (American Concrete Institute) (2014). Building CodeRequirements for Structural Concrete and Commentary] flexural resistance models of reinforced concrete beams are compared withemphasis on the effect of the incorporation of coarse recycled aggregates sourced from concrete waste. The bias factor of the yielding momentcalculations according to both codes is also investigated, and the bias in the cracking moment when Eurocode 2 material clauses are used. Thedatabase was composed of 174 beams, and the criteria that led to its development are discussed. The effect of recycled aggregate incorporationon the statistical descriptors of the bias factor is evaluated and probabilistic modeling using lognormal distributions is argued for. Preliminarypartial safety factors for the bias factor of recycled aggregate concrete beams are proposed. No significant differences in the bias of theultimate moment were found between the two comparison vectors: Eurocode 2 versus ACI 318 specifications and recycled versus naturalcoarse aggregate. The bias of the cracking moment increased when coarse recycled aggregates were incorporated, most probably due to thehigher heterogeneity of recycled aggregates.

This paper investigates whether the model uncertainty of reinforced recycled aggregate concrete (RAC) beams subjected to bending differs from that of reinforced natural aggregate concrete (NAC) beams. An introductory remark concerning the importance of the codification of RAC structural design is made and notions concerning model uncertainties and their role on structural codification are given. Afterwards, the criteria used in the construction of a database of RAC and NAC beams are referred before presenting the key findings of an analysis on the model uncertainty of the cracking, yielding and ultimate moments of beams subjected to four-point bending tests. The analytical moments were calculated following Eurocode 2 provisions. Probabilistic models for model uncertainties are proposed. Negligible differences in the model uncertainty of NAC and RAC beams are reported.

A produção de betão com substituição de agregados naturais por agregados reciclados minimiza os impactes da indústria da construção. Contudo, o recurso a este tipo de agregado é limitado devido a dúvidas dos diferentes agentes da indústria da construção e à ausência de regulamentação específica para o projecto de betão com agregados reciclados. A percepção de betões com agregados reciclados como um material heterogéneo com comportamento imprevisível é o principal entrave, quer para a aceitação da indústria, quer para o desenvolvimento de regulamentação. Diferentes aspectos relacionados com o efeitos da variabilidade das propriedades de betão com agregados reciclados na regulamentação de estruturas são abordados conceptualmente: a heterogeneidade dos agregados reciclados, o efeito desta heterogeneidade nas propriedades mecânicas de betão e os efeitos da variabilidade das propriedades de betão na sua fiabilidade estrutural. Os primeiros resultados de uma campanha experimental desenvolvida especificamente para abordar o efeito de agregados grossos reciclados na fiabilidade são apresentados e as suas implicações no projecto de estruturas discutidas. São apresentadas sugestões de desenvolvimentos futuros que visam a calibração de coeficientes parciais de segurança que possibilitem o projecto de estruturas de betão armado dimensionadas segundo o formato do Eurocódigo 2 e mantendo os mesmos níveis de segurança de betão convencional.

This paper analyses the studies made so far on the variability and reliability of recycled aggregate concrete. Since recycled aggregate concrete is seen by different agents of the construction industry as a variable material and no structural code has specifically been calibrated to its use, its role as a structural material is limited. Such calibration is hindered since specific research on the statistical and probabilistic data of recycled aggregate concrete properties is lacking.Investigations on the probabilistic knowledge of recycled aggregates and recycled aggregate concrete properties are discussed, and the studies made so far on the reliability of recycled aggregate concrete elements are summarised. Final remarks regarding the future prospects towards the consensual acceptance of recycled aggregate concrete structures are provided.

An investigation on the scatter of code-type constitutive models that relate compressive strength (fc) with tensile strength (fct) and Young’s modulus (Ec) of standard concrete specimens is presented. The influence of the mix design on the accuracy of the fc vs. fct and fc vs. Ecrelationships is discussed, with emphasis on the lithological type and morphology of the coarse aggregates. The uncertainty of the constitutive models is analysed in probabilistic terms and random variables that model the uncertainty of the fc vs. fct and fc vs. Ec relationships are proposed for reliability analyses of serviceability limit states. The suitability of the models proposed is assessed through preliminary conservative estimates of their design values.

Research on the variability of the properties of recycled aggregate concrete is lacking and is necessary for the development of reliability analyses and code calibration procedures. This paper presents an experimental programme on the within-batch variability of the compressive strength, Young’s modulus, and splitting tensile strength of several recycled and natural aggregate concrete mixes. The influence of the recycled concrete aggregates on the mechanical properties and variability of concrete is analysed and discussed and benchmarks with standard predictions for the variability of natural aggregate concrete are made. It was found that full recycled aggregate concrete incorporation did not increase the variability of any of the properties tested, but intermediate ratios of recycled aggregate incorporation did. The properties of high-strength concrete mixes were more variable than that of all other mixes, irrespective of recycled aggregate incorporation. All properties of all compositions were suitably modelled by normal distributions. The coarse recycled aggregates were sourced from concrete waste.

An analysis on the effect of the incorporation of coarse recycled concrete aggregates on the bond strength between concrete and embedded steel reinforcement is presented. The model’s uncertainty of the Level I provision of the anchorage length of fib Bulletin 72 on ribbed steel/recycled aggregate concrete bond is quantified. Afterwards, reliability analyses on the bond strength are made and a partial safety factor for the anchorage length of recycled concrete elements is proposed. The model’s uncertainty is evaluated through data from pullout tests, the only type of bond test that has been so far performed extensively on recycled aggregate concrete specimens. The limitations of this test in reproducing the bond of actual structural elements is discussed, and the model’s uncertainty is converted to that of lap splice tests. The bond strength of recycled aggregate concrete design was found to be less reliable than that of natural aggregate concrete, especially in the absence of confining reinforcement. For concrete with full recycled aggregate incorporation, a 25% increase in the anchorage length is proposed. Additional testing on the bond strength of lapped splices or beam-end specimens is recommended.

This paper investigates the effect of recycled coarse aggregate incorporation on the relationship between 150 mm cubic and Փ 150 mm cylindrical compressive strength (the reference strength of standards) by comparing data from recycled and natural aggregate concrete compositions in which both cubes and cylinders were tested. A conversion factor from cubic to cylindrical strength is proposed in two versions: A deterministic and a probabilistic one. Such factor has not been studied before and researchers have been converting cubic data as if natural aggregate concrete were tested. The probabilistic factor is intended for reliability analyses on the structural behaviour of recycled aggregate concrete using data from laboratory cube tests. It was found that the incorporation of recycled coarse aggregates sourced from concrete waste significantly decreases the expected value of the factor but the factor’s scatter is relatively unaffected.

Este artigo avalia se, para especificações de betão correntes, a resistência à compressão de betão pronto é significativamente dependente da central que o produziu, bem como se a variabilidade entre amassaduras de uma determinada composição é dependente da classe de resistência especificada. É apresentado um parâmetro probabilístico que converte a resistência à compressão característica especificada para a resistência à compressão expectável em provetes de betão cúbicos em condições padronizadas.É feita uma análise estatística e probabilística dos resultados de ensaios de resistência à compressão aos 28 dias de betão pronto produzido em três centrais de betão portuguesas durante o ano de 2017. Após a avaliação da representatividade da base de dados analisada, é feito um estudo comparativo dos parâmetros estatísticos dos dados de produção das diferentes centrais e é avaliada a influência da classe de resistência à compressão do betão nestes parâmetros. Define-se e analisa-se um parâmetro probabilístico que converte a resistência à compressão especificada para a resistência potencial de betão, para cubos de 150 mm. Este parâmetro contribui para uma futura proposta de um modelo probabilístico, a ser utilizado em análises de fiabilidade, que converte a resistência à compressão especificada para a resistência à compressão de elementos de betão em obra.Quer a análise estatística dos ensaios de resistência à compressão, quer o parâmetro de conversão são comparados com os resultados de investigações internacionais na área, aferindo-se se a qualidade da produção de betão pronto nacional é semelhante à de outras regiões.

A utilização de Polímeros Reforçados com Fibras (FRP) no reforço de estruturas de Betão Armado (BA) tem tido cada vez mais aceitação devido à sua elevada resistência e rigidez, baixo peso específico e excelente resistência aos efeitos dos agentes ambientais. No entanto, actualmente, é comum utilizarem-se técnicas de reforço que dificilmente permitem tirar partido da resistência total destes materiais. Com o objectivo de explorar a capacidade total de Polímeros Reforçados com Fibras de Carbono (CFRP), foram estudadas e desenvolvidas duas novas técnicas de reforço de vigas à flexão designadas por Continuous Reinforcement Embedded at Ends (CREatE) e Horizontal Near Surface Mounted Reinforcement (HNSMR). Posteriormente realizou-se um estudo comparativo entre o desempenho destes sistemas de reforço e o de duas outras técnicas já estudadas e usuais, nomeadamente os sistemas Externally Bonded Reinforcement (EBR) e Near Surface Mounted Reinforcement (NSMR). A técnica CREatE provou ser a mais eficaz de todas as alternativas testadas mobilizando a totalidade do compósito de CFRP e dotando as vigas de BA com uma maior capacidade resistente e com uma ductilidade mais elevada.Como complemento deste trabalho experimental, desenvolveu-se também um programa de cálculo em MATLAB, capaz de simular o problema em estudo através de um modelo numérico de análise não linear através do equilíbrio de secções. A representatividade dos dados obtidos foi verificada através de uma análise comparativa entre os valores numéricos e os obtidos experimentalmente.The use of Fiber Reinforced Polymers (FRP) in order to strengthen Reinforced Concrete (RC) structures has been increasingly accepted due to their strength and stiffness, low weight and excellent resistance to the effects of environmental aggressive agents. However, the bonding techniques available and described in the literature can not allow the full use of the mechanical properties of these materials and premature failures are often observed and described by several researchers. In order to explore the full capacity of CFRP composites, two new bonding strengthening techniques of RC beams when subjected to 4-point bending tests were studied and developed. For these new techniques, the designation of Continuous Reinforcement Embedded at Ends (CREatE) and Horizontal Near Surface Mounted Reinforcement (HNSMR) has been assigned. Posteriorly, a comparative study has been carried out between those strengthening systems performance and two traditional techniques, namely, the Externally Bonded Reinforcement (EBR) and Near Surface Mounted Reinforcement (NSMR). The CREatE technique has proved to be the most effective of all alternatives tested, with the full utilization of the CFRP composite and the highest strength, combined with the highest ductility. A code using MATLAB software was developed as a complement of this experimental work, which is able to simulate the problem under study through a nonlinear numerical model based on the equilibrium of sections. The representativeness of the numerical data has been verified afterwards through a comparative analysis between those and the experimental results.

Com o crescente consumo de energia elétrica são cada vez mais os países que procuram fontes de energia renovável e limpa, entre elas a eólica. A quantidade de energia produzida é influenciada pela altura das torres, dimensões das pás e potência dos aerogeradores. Quanto maior for a elevação da turbina maiores são a velocidade e estabilidade dos ventos alcançados. A solução de torre treliçada em concreto armado pré-moldado idealizada por Lúcio e Chastre [2] permite a construção de torres altas e é competitiva em relação aos outros sistemas estruturais.As ligações têm uma importância fundamental no comportamento global das estruturas pré-moldadas. A viabilidade da ligação (fácil execução, baixo custo, comportamento/capacidade resistente) é preponderante na viabilização da construção destas torres.Até à data foram estudadas quatro ligações (S1, S2, S3 e S4), sendo neste artigo abordadas apenas as ligações do modelo S3 com junta de 3mm (barras salientes/bainhas corrugadas/selagem com grout) e do modelo S4 com junta de 50 mm (ligações aparafusadas produzidas comercialmente).Através dos resultados experimentais pode-se concluir que o mecanismo de rutura foi o mesmo nos dois modelos e que as soluções estudadas preenchem os requisitos para a sua utilização em estruturas pré-moldadas de concreto armado para suporte de aerogeradores.

The use of FRP composites for the confinement of concrete has become an important aspect to consider on strengthening of concrete columns. It is important therefore that accurate modelling tools are available for the design of this system considering, not only the peak values of load and strain, but also the complete stress–strain behaviour. A wide group of authors have proposed several models specific for FRP-confined concrete based either on theoretical assumptions (analysis-oriented-models – AOMs) or on mathematical calibration from testing results (design-oriented-models – DOMs). This article carries out the implementation and analysis of nine existing models for circular concrete columns in view of axially tested reinforced concrete columns confined with CFRP with three different diameters: 150; 250 and 400 mm. The global shape of curves, peak compressive load, stress–strain relation, axial-to-lateral relation and dilation response were studied to conclude which models’ curves were closer to tests. Quantification of errors in face of the testing results was carried out for the most important parameters – ultimate load, strain and lateral stress – as well as for other curve parameters. Some models are accurate in predicting the peak load, though only few can accurately predict the load–strain and dilation behaviour.

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The presented work aims at studying the modelling of long term performance of concrete compositions with different proportions of clinker as regards the diffusion of CO2 in concrete – carbonation. The replacing constituents of clinker that will be part of the binder in each concrete composition are limestone filler and low calcium fly ash (FA). The used percentage of FA by weight of binder was of 50%. Concrete compositions were made following standard prescribed requirements to attain service lives of 50 and 100 years as regards concrete performance against reinforcing steel corrosion. Test results of compressive strength and carbonation depth are reported at different curing ages of 28, 90, 180 and 365 days. Carbonation results were used for the implementation of modelling equations in order to estimate the design service life regarding reinforcing steel corrosion. Two performance-based methods were used: safety factor method and probabilistic method, and their results compared with the traditional prescriptive approach. At the age of 28 days the composition with OPC is the only one that reaches the target periods of 50 or 100 years. For the probabilistic method, different curing age results were analysed. For the tested results at 90, 180 and 365 days of age the reliability of some of the compositions with blended cements is within the minimum required, although still far from the higher performance of concrete with OPC.

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The façades of St. Leonard’s church and the castle in Atouguia da Baleia village in western region of Portugal are monuments built in Middle Ages. Significant stone degradation patterns are visible, being the alveolization an outstanding case study.The more porous type of sandstones similar to the variety found in the vernacular architecture of Atouguia da Baleia was treated with ethyl silicates. In order to allow the study of the durability of these conservation treatments, accelerated artificial ageing salt crystallization tests were carried out and an automatic ageing chamber was developed.Physical and mechanical behaviour was assessed on consolidated specimens before and after accelerated artificial ageing salt crystallization tests. The authors propose a prediction of the durability of these consolidation treatments by means of the salt crystallization ageing results.

Experimental research was carried out about into ethyl silicate applications on sandstone samples. Consolidation was assessed by drilling strength, impregnation depth and also monotonic and cyclic uniaxial compressive tests in order to evaluate the compressive mechanical behaviour of treated sandstone. The stress–strain compression diagrams showed a significant increase in the values of mechanical parameters after consolidation treatments. The difference in compressive strength values between monotonic and cyclic compression disappears after the consolidation treatments. An equation of consolidation effect was obtained from an analytical model by means of compressive behaviour assessed by stress–strain diagrams. These sandstone samples have values of porosity similar to the more weathered variety of sandstone found in facades of monuments in the village of Atouguia da Baleia, in the western region of Portugal. The most important degradation pattern found on sandstone building stones is alveolization caused by salt crystallization since the Middle Ages.

Building stones, particularly sandstone and granite, are very important in the building elements of Portugal’s historical and cultural heritage. Experimental research, based on uniaxial compressive tests, was carried out on selected representative samples of lithotypes of rocks used in historic built heritage, with a view to evaluating the compressive mechanical behaviour of different building stones. The results showed that porosity plays a central role in the compressive behaviour of granites and sandstones. As porosity can be evaluated in field conditions with non-destructive tests it was decided to derive an analytical model to predict compressive behaviour based on the knowledge of porosity of the building stones. A cubic polynomial function was adopted to describe the pre-peak regime under compression to implement the model. Furthermore, a statistical correlation between mechanical and porosity data had to be defined. Good agreement between experimental and analytical compressive stress–strain diagrams, from which the mechanical properties like compressive strength and modulus of elasticity can be derived, was achieved.

Sandstones are very important in the building elements of world’s historical and cultural heritage. The façades of St. Leonard’s church in Atouguia da Baleia village in western region of Portugal are an outstanding example of the effect of alveolization on going for several centuries. In Middle ages there was an harbour and a sodium chloride rich environment near this church was responsible for this significant stone degradation pattern.
A new approach of consolidating products application on stone walls façades based on Karsten pipe using total head to allow full absorption of stone was followed.
Experimental research, based on physical and mechanical tests, was carried out on selected representative samples of a variety of sandstones on monuments treated with ethyl silicates in order to assess the effectiveness and harmfulness of these treatments.
The comparison of results between traditional immersion applications and Karsten pipe’s based procedure on stone monument indicate the potential viability of this new approach when difficult conditions of consolidating products’ absorption occurs on stone monuments.

Abstract Sandstones are widely used in the building elements of the world’s stone monuments. Alveolization due to salt crystallization-dissolution is the most important degradation pattern found on the Middle Ages’ sandstone façades of St. Leonardo’s Church in Portugal. An outstanding case of widespread distribution of deep and large alveolization patterns found mainly on portals and vaults of its sandstone façades appeared as a result of the past and present proximity of the seashore. On stonewall façades, a new approach of consolidating products’ treatments using the total head was followed in order to allow full absorption of stone. Physical and mechanical tests were carried out on selected representative specimens of varieties of sandstones on the monument. Treatments with ethyl silicates were assessed by means of its effectiveness, harmfulness, and durability. The comparison of results between the application of this new procedure on this stone monument and the traditional intervention treatments highlighted the potential viability of the former to overcome difficult conditions of absorption of consolidating products.

Sandstone building stones are important in the building elements of Portuguese monuments, particularly in the western and southern regions. Alveolization due to salt crystallization was the most important degradation pattern found in the old sandstone façades of buildings in the village of Atouguia da Baleia. Because weathering progressively increases porosity in stones, experimental research was conducted on the most porous variety of sandstone, which is similar to the type of stones found in the façades of ancient buildings in that village. An automatic salt crystallization accelerated ageing chamber was developed. Monotonic and cyclic uniaxial compressive tests were carried out on samples after sodium chloride crystallization ageing tests had been performed, in order to assess the compressive mechanical behavior of sandstone during accelerated ageing. The results of stress–strain compression diagrams showed a clear decreasing trend in the values of mechanical parameters during the salt crystallization ageing progress. The difference in compressive strength values between monotonic and cyclic compression also decreases with as salt crystallization ageing progresses. A predictive equation that correlates the compressive strength of sandstones with salt crystallization ageing cycles is proposed.

No património edificado português as rochas granulares assumem importância relevante nos elementos construtivos presentes no património histórico e cultural, nomeadamente as pedras graníticas e areníticas. Tendo por objectivo a avaliação do comportamento mecânico de rochas granulares presentes no património edificado histórico foi realizado um estudo de investigação experimental sobre amostras dos litótipos seleccionados e que são representativos de rochas presentes no próprio edificado, em termos de propriedades petrográficas, físicas e mecânicas. Neste artigo apresenta-se um modelo analítico definido com base em ensaios experimentais que permite efectuar a simulação do comportamento das rochas em compressão uniaxial (diagramas de tensão-deformação), função de propriedades físicas e mecânicas obtidas através de ensaios não destrutivos e quasi não destrutivos. Este modelo permite desta forma a avaliação do comportamento mecânico de rochas granulares sem afectar a integridade do património histórico.

The wind energy production is a growing industry and the energy produced is renewable and environmentally cleaner than most of the energy production systems. The supports of the wind energy generators may be built with precast concrete elements. The precast solutions for these structures are competitive in comparison to other structural systems. The evolution of the technology for wind energy production shows a clear need for larger wind turbines and longer blades and, consequently, taller towers. The experience also shows that precast concrete solutions increase their competitiveness as the tower height increases. Offshore wind farms have some advantages in relation to onshore ones, which explains recent investments in this area. Also in this case, the durability of concrete in the sea when compared to steel, gives advantages to precast concrete in relation to other structural solutions. This paper shows the evolution of the supports of the wind energy generators and the advantages of the use of precast concrete towers.

Os compósitos de FRP podem descolar prematuramente da superfíce de betão, isto é, antes de esgotada a sua resistência elástica. Esta situação é mais provável se não forem tidos em conta factores como o tipo de preparação da superfície, a exposição a acção ambiental severa, e a resistência do próprio betão. Com o objectivo de analisar a influência de parte destes factores no desempenho da ligação compósito de fibra de vidro (GFRP) e betão, empreendeu-se uma campanha experimental baseada em ensaios de corte duplo. Os resultados permitiram determinar e comparar as forças máximas transmitidas ao GFRP e tensões de aderência máxima para diferentes tratamentos de superfície e condições de envelhecimento. Foram também determinadas aproximações para curvas de tensão de aderência vs. deslizamento (bond-slip). Os resultados obtidos são contrastados com resultados obtidos por modelação numérica.

During the last years several projects and studies have improved the knowledge about Textile Reinforced Mortar (TRM) technology. TRM has already been used in strengthening masonry and reinforced concrete structural elements such as walls, arches, columns and beams. This material is presented as a real alternative to the use of fibre-reinforced polymers (FRP) in situations where these composites have presented some drawbacks or their use is banned. Textile Reinforced Mortar show a complex mechanical behaviour derived from the heterogeneity of the constituent materials. This paper aims to deepen the knowledge of this composite material in terms of tensile behaviour. Following this scope, this paper presents an experimental campaign focused on thirty one TRM specimens reinforced with four different reinforcing ratios. The results are analysed and contrasted with two distinct models. i) the Aveston-Cooper-Kelly theory (ACK) which is based on a tri-linear analytical approach; and ii) a nonlinear numerical simulation with a 3D Finite Element code. The Finite Element Analysis (FEA) of the TRM tensile tests also showed no significant dependence on the basalt-to-mortar interface, i.e., the choice of a bond-slip curve in order to reproduce the bond stresses and slippages along the interface is irrelevant and it can be simply considered as rigid interface.

The recent development of inorganic based composites as low-cost materials in reinforced concrete structural strengthening and precast thin-walled components, requires the creation of models that predict the mechanical behaviour of these materials. Textile Reinforced Mortar (TRM) shows complex stress–strain behaviour in tension derived from the heterogeneity of its constituent materials. This complexity is mainly caused by the formation of several cracks in the inorganic matrix. The multiple cracking leads to a decrease in structural stiffness. Due to the severe conditions of the serviceability limit state in structural elements, the prediction of the stress–strain curve is essential for design and calculation purposes. After checking other models, an empirical nonlinear approach, which is based on the crack control expression included in the Eurocode 2, is proposed in this paper. Following this scope, this paper presents an experimental campaign focused on 31 TRM specimens reinforced with four different reinforcing ratios. The results are analysed and satisfactorily contrasted with the presented non-linear approach.

Precast concrete sandwich panels started being used as cladding for buildings, together with the rise of industrial prefabrication, during the mid-20th century. Since then, society and industry have become increasingly aware of energy efficiency in all fields, for both affordability and sustainability consciousness. As such, buildings have been subject to increasingly stringent requirements with the technology of sandwich panels kept continually at the forefront.
Nowadays, sandwich panels have reached the highest standards of functional performance as structural efficiency, flexibility in use, the speed as well as of aesthetic appeal. These combine in building construction with the well-known advantages of prefabrication; such as construction, quality consciousness, durability and sustainability. Sandwich panels have gained more and more important in their field, thus representing quite a significant application within the industry of prefabrication and an important share of the market.
The Commission ‘Prefabrication’ is keen to promote the development of all precast structural concrete products and to transfer the knowledge to practical design and construction. Now filling a strategic gap, by issuing this Guide to Good Practice, which includes design considerations, structural analysis, building physics, use of materials, manufacturing methods, equipment, field performance, and provides a comprehensive overview of the information currently available worldwide. The Commission is particularly proud that this document is a result of close cooperation with PCI and that it will be published by both fib and PCI. This cooperation started six years ago, first with comparing the different approaches to several issues, then progressively integrating up to producing common documents, like this one, that wasn’t yet treated in a specific Guide by either body.

Weathering imposes vital effects on stony monuments. Mostly, the degree of weathering is determined by simple test results, ignoring simultaneous effects of various weathering factors. Hence, the main purpose of this study is to develop prediction models with fuzzy inference systems to determine the weathering degree of the Persepolis stone, using various accelerated ageing tests in laboratory condition and to extrapolate the results to the natural condition, considering climatic information. The results suggest reliable conformity between the prediction of the weathering degree of the stone and the weathering degree observed in the Persepolis complex in natural condition.

This paper presents a comparative evaluation of efficiencies of different accelerated ageing tests (freezethaw, thermal shock, salt crystallization, dissolution and wetting-drying) and fuzzy inference system in predicting weathering degrees of some monument stones from three historical sites (Anahita Temple, Anobanini reliefs and Eshkaft-e Salman reliefs, Iran). The combined effects of natural weathering processes (heating and cooling, wetting and drying, and freezing and thawing) and climatic information were used for assessing the natural weathering degrees. Finally, the natural weathering degrees were multiplied by time effect coefficients to obtain more realistic natural weathering degrees of the monuments. The predicted natural weathering degrees for Anahita Temple, Anobanini reliefs and Eshkaft-e Salman reliefs are 56%, 61%, and 47%, respectively. These predicted values reasonably support the weathering degrees defined by progressive decay indices (calculated equal to 2.77, 3.42 and 2.66 for Anahita Temple, Anobanini reliefs and Eshkaft-e Salman reliefs, respectively), which means the fuzzy model potentially could accurately predict the weathering of stones.

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The aim of the present paper is to evaluate the gravity loads effect in the behaviour of reinforced concrete beams critical zones subjected to cyclic loads. A numerical study to assess the influence of gravity load on RC beam critical zones subjected to cyclic loading is presented, assuming the level of gravity load as a variable parameter. For this purpose, the non-linear model was previously validated with an experimental campaign carried out on RC beam connection subject to cyclic loading with and without gravity loads. The consideration of the gravity load effects led to an accumulation of negative (hogging) deformation and the formation of an unidirectional plastic hinge. In order to validate this behaviour in an overall structural response, a non-linear numerical analysis of a RC frame system under cyclic loads, subject to different levels of gravity load, is also presented. The numerical results are analysed in terms of global hysterical response, accumulated energy dissipation and equivalent viscous damping ratio. In this numerical study was observed that the hysteretic response depends on the load path. In the presence of higher gravity loads levels, the structure hysteretic behaviour exhibits higher damage levels and the failure mechanism is prone to the formation of four plastic hinges. This phenomenon is analysed and discuss in the present paper. © Federation Internationale du Beton (fib) - International Federation for Structural Concrete, 2019.

The aim of the present communication is to present an analysis of the gravity load influence on the hysteretic behaviour of a beam-column connection. For this purpose, in the experimental campaign a new procedure for RC cyclic tests is presented in order to reproduce closer demands on the beam critical zone than the traditional procedures. The Experimental campaign included cyclic tests of the specimens according with the ECCS recommendation and an innovate procedure. The test results are presented, compared and analysed. A numerical simulation of the tests is presented where the model for the hysteretic response of the beam was calibrated with the experimental results. Finally, the behaviour of a portal frame system under cyclic displacements up to a drift of 3.5% was analysed, assuming that the non-linearity is concentrated on the plastic hinges, considering different levels of gravity load. Thus it is intended to assess the influence of the gravity load on the behaviour of a structure subjected to cyclic loads.

The present study is part of an extensive research project, where the main objective is to evaluate a strengthening solution for reinforced concrete structures using a small thickness jacketing in the compression side of the RC element with unidirectional fiber reinforced grout - UFRG.
For this purpose a high performance cementitious grout reinforced with continuous and unidirectional non woven fibermat has been developed. It was expected that the use of these type of fibers allowed an optimization of its percentage and orientation. It was expected that the use of these type of fibers allowed an optimization of its percentage and orientation. Besides, for continuous fibers (with an aspect ratio, defined as the length-to-diameter ratio, l/d=∞), the composite should attain higher tensile strength since the fiber embedment length is enough to prevent fiber pullout.
The experimental campaign included a set of preliminary tests that allowed the design of the fiber reinforced grout, sustained with rheological parameters [7] and mechanical characterization tests of the materials.
Finally, an experimental campaign was carried out in order to proceed to the mechanical characterization of the unidirectional fiber reinforced grout. Compressive tests were conducted in small thickness tubular specimens that enable the determination of the compressive strength and the static modulus of elasticity of the material. The tensile strength of the material was obtained using splitting tests of cubic specimens (according the standard DIN 1048-5). The experimental results are presented and analyzed.

The main goal of the present research work is to characterise a unidirectional fibre reinforced grout (UFRG), developed as an alternative material to strengthen RC structures using small thickness jacketing. A high performance cementitious grout reinforced with continuous and unidirectional non-woven steel fibre mat has been developed for this purpose. It was expected that the optimization of the percentage and alignment of the steel fibres would yield a more efficient fibre grout. In fact, the composite should attain higher tensile strength with continuous fibres since the fibre embedment length is enough to prevent fibre pull-out. An experimental programme was carried out to characterise the UFRG’s mechanical properties. Compressive tests were conducted on small thickness tubular specimens to enable the determination of the compressive strength and the static modulus of elasticity. The tensile strength was obtained from splitting tests performed on cubic specimens (DIN 1048-5). Semi-empirical equations, based on the experimental results, are proposed to estimate UFRG’s modulus of elasticity, compressive strength and tensile strength. Two strengthening solutions for RC structures using small thickness CFRP jacketing are presented.

Gravity loads can affect a reinforced concrete structure’s response to seismic actions, however, traditional procedures for testing the beam behaviour do not take this effect into consideration. An experimental campaign was carried out in order to assess the influence of the gravity load on RC beam connection to the column subjected to cyclic loading. The experiments included the imposition of a conventional quasi-static test protocol based on the imposition of a reverse cyclic displacement history and of an alternative cyclic test procedure starting from the gravity load effects. The test results are presented, compared and analysed in this paper. The imposition of a cyclic test procedure that included the gravity loads effects on the RC beam ends reproduces the demands on the beams’ critical zones more realistically than the traditional procedure. The consideration of the vertical load effects in the test procedure led to an accumulation of negative (hogging) deformation. This phenomenon is sustained with the behaviour of a portal frame system under cyclic loads subject to a significant level of the vertical load, leading to the formation of unidirectional plastic hinges. In addition, the hysteretic behaviour of the RC beam ends tested was simulated numerically using the nonlinear structural analysis software – OpenSees. The beam–column model simulates the global element behaviour very well, as there is a reasonable approximation to the hysteretic loops obtained experimentally.

The aim of the present study was to proceed to a numerical analysis of the gravity load effects on the behaviour of reinforced concrete beam critical zones when subjected to cyclic loads. A parametric study to assess the influence of different levels of gravity load on RC beam critical zones subjected to cyclic loading was carried out. For this purpose, assuming the level of gravity load as a variable parameter, a nonlinear numerical model of a beam-column connection, previously calibrated with experimental data, was used. In order to evaluate the gravity load effects in the global response, a numerical study of a RC frame system is also presented. The numerical results are analysed in terms of global hysteretic response, accumulated energy dissipation and equivalent viscous damping ratio. In this numerical study, it was observed that the hysteretic response depends on the load path. In the presence of higher gravity load levels, the structure hysteretic behaviour exhibits higher damage levels, associated to a failure mechanism corresponding to the formation of four span plastic hinges. Thus, the proper test procedure should involve the imposition of a reverse cyclic displacement history starting each cycle from the gravity load effects.

O reforço à flexão de vigas de betão armado tem apresentado uma evolução com tendência para soluções onde são utilizadas armaduras à base de materiais compósitos de fibras de Carbono, Vidro, Basalto ou Aramida, aplicadas com as técnicas Externally Bonded Reinforcement (EBR) ou Near Surface Mounted (NSM). No entanto, o comportamento elástico-linear destes materiais e as roturas tendencialmente frágeis das soluções condicionam a sua utilização em estruturas onde se pretende alguma ductilidade. Por conseguinte, procurou-se desenvolver um sistema de reforço estrutural alternativo e inovador em que os materiais de reforço aplicados, conjuntamente com a solução de reforço, conseguissem minimizar ou eliminar os riscos de roturas prematuras e ao mesmo tempo aumentassem a ductilidade dos elementos reforçados. Neste trabalho, apresenta-se em pormenor este novo sistema de reforço à flexão de vigas de betão armado com armaduras de aço inoxidável ancoradas internamente por aderência. Neste sistema de reforço as armaduras são contínuas e pós-instaladas pelo exterior, ficando as extremidades ancoradas por aderência no interior do elemento estrutural. Apresentam-se e discutem-se os resultados dos ensaios realizados para avaliar o desempenho das vigas de betão armado reforçadas com esta nova técnica. Os modos de rotura observados são também motivo de análise mais detalhada. Evidenciam-se alguns benefícios na utilização deste sistema de reforço inovador, nomeadamente ao nível da capacidade resistente última das vigas de betão armado e fazem-se algumas recomendações para a sua aplicação e utilização na reabilitação de elementos estruturais degradados.

Apresentam-se neste artigo os resultados dos ensaios realizados à escala real de um conjunto de vigas de betão armado com secção em T, levados a cabo para avaliar o desempenho das armaduras de aço inoxidável no reforço à flexão de vigas de betão armado com armaduras pós-instaladas aplicadas com as técnicas de reforço EBR (Externally Bonded Reinforcement), NSM (Near Surface Mounted) e EBR com ancoragens metálicas nas extremidades. Os ensaios realizados demonstraram que as técnicas de reforço utilizadas permitem aumentar a rigidez à flexão em regime elástico. Porém, a viga reforçada através da técnica EBR teve uma rotura prematura antes de atingir o valor da carga de cedência da viga não reforçada. Já as vigas reforçadas com as técnicas NSM e EBR com ancoragens mecânicas superaram o valor da carga de cedência da viga de referência, e as ancoragens mecânicas proporcionaram bastante ductilidade à viga reforçada com esta técnica.

Neste artigo apresentam-se as principais características da técnica de reforço Continuous Reinforcement Embedded at Ends (CREatE), os procedimentos de aplicação e as vantagens e limitações da sua utilização. Apresentam-se também os resultados dos ensaios realizados para avaliar o desempenho desta técnica no reforço à flexão de vigas de betão armado com secção transversal em T, reforçadas com armaduras pós-instaladas de aço inoxidável, coladas pelo exterior ou inseridas na zona de recobrimento. As vigas reforçadas com a técnica CREatE e ensaiadas à flexão em quatro prontos apresentaram elevados acréscimos de resistência e ductilidade quando comparadas com as vigas reforçadas com as técnicas tradicionais - Externally-Bonded Reinforcement (EBR) e Near Surface Mounted (NSM). As vigas reforçadas com a técnica CREatE foram sujeitas a carregamentos monotónicos ou cíclicos, tendo-se constatado que as roturas prematuras que estão associadas às técnicas tradicionais anteriormente referidas nunca foram observadas nas vigas reforças com esta técnica. Desenvolveu-se um modelo numérico simples, e com boa precisão, para modelar o desempenho das vigas de betão armado, sendo os resultados apresentados e discutidos.

A procura de soluções de reforço mais eficientes que permitam aumentar a capacidade resistente de elementos estruturais sujeitos a flexão levou ao desenvolvimento de um sistema inovador de aplicação de armaduras de reforço coladas pelo exterior. Neste artigo descrevem-se os ensaios experimentais realizados e analisam-se os resultados obtidos com vigas de betão armado reforçadas com armaduras pós-instaladas de aço inoxidável com diferentes técnicas: Externally Bonded Reinforcement (EBR), Near Surface Mounted (NSM) e com o novo sistema de reforço desenvolvido - Continuous Reinforcement Embedded at Ends (CREatE). As vigas ensaiadas monotonicamente até à rotura em flexão de quatro pontos têm seção transversal em T e um vão livre de três metros. No novo sistema de reforço as armaduras são ancoradas por aderência no interior do elemento estrutural, o que associado à utilização de armaduras em aço inoxidável, possibilita aumentos de resistência e ductilidade consideráveis face às técnicas tradicionais de colagem pelo exterior.

This article presents the comparison between 6 theoretical models of axially confined concrete columns with the experimental results of 7 tested columns of different authors. This study analysed the accuracy of 6 different confinement models for square columns taking into account the results of experimental tests on 7 RC columns confined with CFRP sheets with different dimensions and carried out by different authors. The profile of curves, the peak/failure values, the stress–strain and axial–to–lateral relations were studied to conclude which models show the best correlation with the experimental test results. Quantification of this deviation was carried out for key parameters. Some models predicted peak values with reasonable accuracy – Manfredi & Realfonzo, Campione & Miraglia, Lam & Teng, Pellegrino & Modena – although for the whole load–strain behaviour only the model of Faustino, Chastre & Paula seemed to be reasonably accurate in most cases.

Reinforced concrete (RC) columns with various strengthening systems and different conditions were tested to cyclic lateral and axial loading for the purpose of performance assessment. Tests included confinement strengthening with carbon-fiber-reinforced polymer (CFRP) sheets, longitudinal strengthening with CFRP laminates and confining CFRP jacket, longitudinal strengthening with stainless steel bars and confining CFRP jacket, tested column until reinforcing steel failure, repair and CFRP confining jacket, and longitudinal strengthening with stainless steel bars. The analysis of the tests results as to load-displacement relationship and energy dissipation led to the conclusion that the use of external longitudinal strengthening with CFRP confinement is effective for performance retrofitting and upgrading, and viable in terms of execution. The load capacity increase due to strengthening reached 36–46% with good ductile behaviour. Nonlinear numerical modelling was carried out using two approaches which represent reasonably well the global performance of the studied columns for the prediction of the ascending load-displacement relationship and the peak load values in each cycle.

Five experimental cyclic tests were carried out on reinforced concrete rectangular columns with rounded corners, different condition (new and damaged) and different strengthening systems: that included confinement through carbon fiber (CFRP) jackets, anchor dowels, high strength repair mortar and external longitudinal stainless steel bars. Lateral load - displacement relationship, energy dissipation, ductility and curvature results were analyzed together with two different damage assessment classifications. The overall evaluation concludes that the use of external confinement with CFRP on RC columns is viable and of effective performance enhancement alone and combined with other techniques. Damaged columns that were retrofitted showed an increased load capacity up to 20% along with good ductile behavior within the limits of the US, European, Canadian and Japanese codes, with minor/moderate degree of damage at 1% drift ratio and moderate degree of damage at 2% drift ratio.

The enhancement of the mechanical behaviour of reinforced concrete (RC) columns with regard to axial compression is an up-to-date concern, namely if the strengthening of existing structures is to be considered. In view of this, external confinement with FRP systems has been tested in order to become a feasible technique, since it seems to have important advantages over other systems such as its high strength and stiffness in relation to weight and its improvement of strength and ductility while confining RC columns. Square columns confined with FRP show a more complex interpretation of their behaviour, when compared to circular columns. Accordingly, the present work includes the analysis of two experimental programs regarding axial compression on CFRP confined RC columns: one on circular and square specimens with different corner radii; the other on square specimens with side lengths ranging from medium to large. Based on this, modelling equations are proposed to predict maximum axial load, axial strain and lateral strain, as well as the entire behaviour until failure with curves of axial load-axial strain and axial load-lateral strain. The modelling results show that the analytical curves are in general agreement with the presented experimental curves for a wide range of dimensions.

This study presents the testing, completion, and analysis of different external strengthening systems applied to rectangular reinforced concrete columns with rounded corners. The experimental study included confinement strengthening with carbon-fiberreinforcedpolymer (CFRP) sheets, longitudinal strengthening with CFRP laminates and confining CFRP jacket, longitudinal strengtheningwith stainless steel bars and confining CFRP jacket, tested column until reinforcing steel failure, repair and CFRP confining jacket,and longitudinal strengthening with stainless steel bars. The analysis of the experimental results included lateral load-displacement relationship, energy dissipation, ductility, and curvature damage assessment classifications. It was concluded that the use of externallongitudinal strengthening combined with CFRP confinement is effective for enhancing performance and is viable in terms of execution. The load capacity increase due to strengthening reached 36–46% with good ductile behavior (failure was reached at 4.4% drift ratio). Despite some differences between CFRP laminates and stainless steel, all columns presented moderate degrees of damage between 1 and 2% drift ratio and minor damage degree until 1% drift ratio.

This article discusses mathematical modelling of the long-term performance of concrete with different supplementary cementitious materials in a maritime environment. The research was carried out in the light of the national Portuguese application of the CEN standards with mandatory requirements for a performance-based design approach. Laboratory investigations were performed on concrete compositions based on CEM I and CEM II/B-L in which the cement was partially replaced by either 0% (reference composition) or 50% of low calcium fly ash (FA). Concrete compositions were made with the objective to achieve service lives of 50 and 100 years with regard to steel corrosion. Test results of compressive strength, chloride potential diffusion and electrical resistivity are reported for different curing ages of 28, 90, 180 and 365 days. Chloride diffusion results were used for the implementation of modelling equations in order to estimate the design lifetime regarding reinforcing steel corrosion. A performance-based approach using a probabilistic method was carried out and the results obtained are compared with the requirements according to the Portuguese prescriptive approach. The modelling results show that FA blended compositions have better performance compared to those with Portland cements, especially if curing ages beyond 28 days are considered.

Cement bonded particle board (CBPB) is a composite material produced in plates consisting mainly of wood and cement, and may contain additives. This material is currently used in cladding, raised floors, dropped ceilings, prefabricated houses, office containers and various supplies to the building industry such as kitchens, bathrooms and furniture. It is composed of a type of wood Pinus pinaster and/or Pinus pinea, Portland cement type II, sodium silicate and aluminium sulphate. CBPB has been the subject of several studies with the purpose of enabling the use of other types of wood or even vegetable biomass, as the chemical compounds from wood (extractives and sugars) tend to inhibit of cement hydration. A study on the behaviour of short CBPB elements under compression was carried out in the Department of Civil Engineering of Universidade NOVA de Lisboa with the aim of enabling its use in structural elements. The study was supported by VIROC, the company which produces CBPB in Portugal. This paper presents and analyses the most significant results of a campaign of axial compression tests performed on 111 specimens of different heights and cross sections. The behaviour of CBPB specimens of varying slenderness was subjected to a more detailed analysis.

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The seismic retrofit of reinforced concrete columns with FRP jackets has received a considerable increment in recent years due the high strength-weight and stiffness-weight ratios of FRP compared to other materials. The FRP outer shell also contributes to prevent or delay environmental degradation of the concrete and corrosion of the steel reinforcement. An experimental program conducted in order to analyze the behavior of reinforced concrete columns jacketed with FRP composites or repaired with polymeric concrete and subjected to axial compression and cyclic horizontal loads is described. The dimensions of the cylindrical columns were 1500 mm height by 250 mm diameter. The influence of various parameters on the response, including the type of confining material and the number of FRP layers, is reported. The results of the tests are shown and interpreted.

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This thesis deals with the analysis of the behaviour of retrofitting reinforced concrete circular columns with FRP materials which were subjected either to axial cyclic compression or axial compression and alternated cyclic horizontal loads. The choice of this topic derived from the need to investigate the behaviour of the strengthening of reinforced concrete columns to seismic actions, especially with new materials such as carbon and glass fibres or polymeric mortars. Another reason for such choice is linked to the strong seismicity of the Portuguese territory.
It has been verified that confined concrete columns with FRP jackets have their resistance and ductility highly increased as these considerably reduce the columns transversal deformation, thus preventing the buckling of longitudinal reinforcement. There has been an increasing use of FRP composites in the strengthening of structures, mainly with GFRP (Glass Fibre Reinforced Plastics) or CFRP (Carbon Fibre Reinforced Plastics). This is due to their attractive characteristics such as high resistance to corrosion, lowratio for weight/strength, moldability, easy application and the fact that there is no need of support structures.
Forty-five experimental tests were carried out, dealing with retrofitting reinforced concrete columns with axial monotonic or cyclic compression reinforced with FRP composites. The column height of 750 mm was maintained in order to evaluate the influence of several parameters in its behaviour: the column geometry (change in its diameter), the type of column (plain or reinforced concrete), transversal reinforcement ratio of concrete columns, the type of external confinement with FRP (C or GFRP), the number of FRP layers and the type of axial loading (monotonic or cyclic).
Twelve additional experimental tests were conducted in order to analyse the behaviour of reinforced concrete columns jacketed with FRP composites and subjected to axial cyclic compression and alternated cyclic horizontal loads. The columns’ dimension was maintained (1500 mm height by 250 mm diameter) and the models were subjected to a series of cyclic and alternated loadings. This enabled the study of the various parameters’ influence in their behaviour such as the type of FRP confinement, the number of FRP layers, the level of axial loading, the jacket’s height or the strengthening of the plastic hinge by replacing the cover concrete with polymeric mortar.
Based on the numerical models presented and experimental analysis carried out, models were proposed and developed to simulate the behaviour of columns jacketed with FRP composites.

Neste artigo é apresentado um resumo das intervenções de conservação realizadas no século passado e dos estudos e testes não destrutivos realizados na última década na Igreja de São Leonardo na Atouguia da Baleia. Em seguida mostra-se o padrão de degradação que ocorre nos portais de arenito da igreja e é analisada a evolução da alveolização que ocorreu nos portais de arenito ao longo dos últimos sessenta a setenta anos. No final, a inspeção visual dos portais de arenito é comparada com um levantamento realizado através de varrimento por laser 3D.

Sandstone building stones are important in the building elements of Portuguese monuments, particularly in the western and southern regions. Alveolization due to salt crystallization was the most important degradation pattern found in the old sandstone façades of St. Leonardo’s Church, a Portuguese monument built in Atouguia da Baleia village in the Middle Age. Its sandstone façades have a widespread distribution of deep and large alveolization patterns mainly on portals and vaults that appeared as a result of the past and present vicinity of seashore. In this paper a summary of conservation interventions carried out in the past century in St. Leonardo’s Church is presented, as well as a summary of the studies carried out in the last decade. Then the degradation patterns on the sandstone walls of St. Leonard’s Church are shown and finally the evolution of the alveolization occurred on the sandstone walls over the last sixty to seventy years is analysed. Visual inspection of sandstone walls is compared with a survey performed by laser scanning, which seems to be a powerful technology to carry out 3D geometric modelling of the building elements of stone monuments and also the 3D mapping of stone degradation patterns.

Neste artigo é apresentado um resumo das intervenções de conservação realizadas no século passado na Igreja de São Leonardo, bem como um resumo dos estudos realizados na última década. Em seguida mostra-se o padrão de degradação que ocorre nos portais de arenito da igreja e é analisada a evolução da alveolização que ocorreu nos portais de arenito ao longo dos últimos sessenta a setenta anos. No final, a inspeção visual dos portais de arenito é comparada com um levantamento realizado através de varrimento por laser tridimensional.

The retrofit of reinforced concrete columns with FRP jackets has received considerable attention in recent years. The advantages of this technique compared to other similar techniques include the high strength-weight and stiffness-weight ratios of FRP (Fibre Reinforced Plastics), the strength and ductility increase of RC columns confined with FRP jackets as well as the fact that FRP external shells prevent or mitigate environmental degradation of the concrete and consequent corrosion of the steel reinforcement. Furthermore, this method also reduces the column transversal deformation and prevents the buckling of longitudinal reinforcement. Twenty five experimental tests were carried out on reinforced concrete columns confined with CFRP composites, and subjected to axial monotonic compression. In order to evaluate the influence of several parameters on the mechanical behavior of the columns, the height of the columns was maintained, while changing other parameters: the diameter of the columns, the type of material (plain or reinforced concrete), the steel hoop spacing of the RC columns and the number of CFRP layers. Predictive equations, based on the experimental analysis, are proposed to estimate the compressive strength of the confined concrete, the maximum axial load and the axial or the lateral failure strain of circular RC columns jacketed with CFRP. A stress-strain model for CFRP confined concrete in compression, which considers the effect of the CFRP and the transversal reinforcement on the confined compressive strength of the column is also proposed. The curves, axial load versus axial or lateral strain of the RC column, are simulated based on the stress-strain model and include the longitudinal reinforcement effect. The results demonstrate that the model and the predictive equations represent very well the axial compression behavior of RC circular columns confined with CFRP. The applicability of this model to a large spectrum of RC column dimensions is its main advantage.

Os edifícios históricos como os palácios, castelos, igrejas e templos, são exemplos do património construído e constituem uma parte importante do nosso património cultural. Estas construções históricas incluem normalmente paredes de alvenaria maciça e pedra natural. A salvaguarda do património construído em pedra é de importância inquestionável, pelo que devem ser desenvolvidas e estudadas técnicas de intervenção adequadas em materiais e estruturas. Neste artigo, é apresentada uma metodologia de ensaios não destrutivos para avaliar a conservação de edifícios históricos de pedra e, com base nesta metodologia, é mostrado um caso de estudo na Igreja de São Leonardo, monumento português construído na Atouguia da Baleia no século XIII.

Earthquakes, soil settlements, traffic vibrations, and air pollution are some of the actions that can affect historic old buildings. Besides these, the lack of continuous maintenance puts a large part of this heritage in risk due to structural problems that reduce their own safety and that of their users. The preservation and risk mitigation of built cultural heritage require the use of reliable tools in order to assess its state of conservation and to identify and prevent potential vulnerabilities. Having this in mind, it is not possible to carry out destructive tests in most historic old buildings, so it is preferable to opt for nondestructive tests (NDT) or alternative methodologies that allow the physical and mechanical characterization of materials and structure. In this chapter, a general view of NDT methods used in historic buildings to obtain the geometrical information, the damage mapping, the mechanical and physical characterization, and the petrographic analysis of stones is presented. An alternative methodology to physically and mechanically characterize the stone of historic buildings using NDT tests is also proposed. The chapter ends with a case study carried out in the St. Leonard’s Church, a Portuguese monument built in Atouguia da Baleia village in the 13th century, where the alternative methodology here presented was applied. The final results of this study show that the methodology proposed allows the obtention of stress-strain curves in a completely nondestructive way, based on the water absorption coefficient at low pressure.

The strengthening of reinforced concrete structures with FRP materials has received a considerable increment in recent years due to their durability characteristics, high strength-weight and stiffness-weight ratios of FRP compared to other materials.An experimental program was conducted in order to analyse the behaviour of different structural solutions to strengthen reinforced concrete beams with carbon FRP composites: EBR (Externally-Bonded Reinforcement), NSM (Near Surface Mounted) reinforcement and an innovative technique externally-bonded using continuous reinforcement embedded at ends (CREatE). The RC beams had a 3m span by 0.3m height and were tested until rupture in a 4-point bending test system.The CREatE technique has proved to be the most effective of the three alternatives tested, with the full utilisation of the CFRP and the highest strength, combined with the highest ductility.

A procura de soluções de reforço mais duráveis e de fácil aplicação tem levado à utilização crescente dos compósitos de FRP (Fiber Reinforced Polymer) no reforço de estruturas, dada a sua resistência à corrosão, o baixo quociente peso/resistência mecânica, a sua moldabilidade, a facilidade de aplicação e a eliminação de estruturas de suporte. No reforço estrutural de vigas de betão armado com compósitos de FRP, são tradicionalmente utilizados dois tipos de técnicas: os sistemas em que o laminado é colado pelo exterior (EBR - Externally-Bonded Reinforcement) ou aqueles em que o laminado é inserido em rasgos previamente abertos na camada de recobrimento (NSM - Near Surface Mounted). No entanto, as técnicas utilizadas, o comportamento elástico-linear destes materiais e as roturas tendencialmente frágeis das soluções condicionam a sua utilização em estruturas onde se pretende alguma ductilidade. A técnica de reforço NSM apresenta algumas vantagens em relação à técnica EBR, nomeadamente ao nível da proteção das armaduras [1]. Além disso, o desempenho em termos de ductilidade do sistema e resistência final excede a técnica EBR. Contudo, diversos ensaios experimentais [2-5] têm mostrado que roturas prematuras [6] da ligação na interface ou o destacamento do betão na zona do recobrimento entre a face inferior das armaduras ordinárias e as armaduras de reforço podem limitar significativamente a eficiência do sistema, originando modos de rotura frágeis e desperdício de material por falta de otimização da quantidade de material aplicado [1]. A fim de evitar a rotura prematura das soluções de reforço tradicionais (EBR e NSM), foi concebido na Universidade NOVA um sistema inovador de reforço intitulado CREatE (Continuous Reinforcement Embedded at Ends). O sistema CREatE foi idealizado para ser utilizado com diversos materiais [1, 5] e diferentes elementos estruturais, tais como vigas [1, 3], pilares [7], pavimentos [8], lajes ou paredes, em que é necessário aumentar a sua capacidade resistente através de armaduras pós-instaladas. A solução de reforço CREatE caracteriza-se pela utilização de armaduras contínuas embutidas nas extremidades do elemento estrutural sem o uso de dispositivos mecânicos para as fixar. Antes da ancoragem da armadura de reforço no interior do elemento, é necessário utilizar uma curva de transição suave para al terar a forma da armadura de reforço e evitar a concentração de tensões no la minado de CFRP (Carbon Fiber Reinforced Polymer) ou na interface e, desta forma, ter um fluxo gradual de tensões transmitidas à zona de ancoragem existente no interior do elemento. Para validar a solução CREatE foi realizada uma campanha de ensaios à flexão de vigas de betão armado com seção em T, uma altura total de 0,3m, um vão livre de 3,0m e reforçadas com laminados de CFRP recorrendo a diferentes técnicas (EBR, NSM e CREatE). As vigas foram testadas à flexão em 4 pontos, tendo-se obtido resultados promissores (Figura 1), com a eliminação na técnica CREatE dos modos de rotura prematuros. Na Figura 2 é possível observar uma viga ensaiada com a técnica CREatE em que se detetam aberturas de fendas significativas sem que se verifique qualquer rotura prematura do sistema. Além da eliminação dos modos de rotura prematuros, os ensaios comprovam que a técnica CREatE permite o incremento da ductilidade (Figura 1) e a exploração total da capacidade do CFRP [1, 3, 5].

Apresentam-se e analisam-se um conjunto de ensaios realizados em vigas de betão armado reforçadas com armaduras pós-instaladas de aço ou de FRP, incluindo os referentes a uma nova técnica (CREatE) desenvolvida na FCT NOVA, tendo-se concluído que a técnica CREatE possibilita aumentos de resistência e ductilidade consideráveis face às técnicas tradicionais.

O aumento da resistência e/ou da ductilidade é um objetivo primordial quando se procede ao reforço de pilares. Um método bastante eficaz de aumentar a ductilidade, particularmente em regiões sísmicas, é através do encamisamento com coletes de FRP, uma vez que esta técnica permite uma diminuição da deformação transversal do pilar e a limitação da encurvadura das armaduras longitudinais, aumentando consequentemente a ductilidade do mesmo. Diversos ensaios experimentais permitiram detetar que os incrementos são maiores em secções circulares do que em secções quadradas ou retangulares [1, 2]. A atenuação deste efeito é obtida através do arredondamento dos cantos nos pilares de secção retangular. Contudo, o encamisamento com coletes de FRP, por si só, não aumenta significativamente a resistência do pilar à flexão composta. Para que isso aconteça e se mantenha um nível elevado de ductilidade, é necessário adicionar armaduras longitudinais à armadura do pilar e posteriormente proceder ao encamisamento com colete de FRP. Uma forma muito eficiente de o conseguir, mantendo a seção transversal do pilar, é utilizando o sistema CREatE (Continuous Reinforcement Embedded at Ends) desenvolvido na Universidade NOVA e já anteriormente apresentado nesta coluna, na edição de Junho/Agosto de 2017 [3], para o caso do reforço de vigas. O sistema CREatE foi idealizado para ser utilizado com diversos materiais e diferentes elementos estruturais [4-7], em que é necessário aumentar a sua capacidade resistente através de armaduras pós-instaladas, caracterizando-se pela utilização de armaduras contínuas embutidas nas extremidades do elemento estrutural sem o uso de dispositivos mecânicos para as fixar. Antes da ancoragem da armadura de reforço no interior do elemento, é necessário utilizar uma curva de transição suave para alterar a forma da armadura de reforço e evitar a ocorrência de concentrações de tensões na armadura ou na interface [4, 7, 8]. Este conceito foi aplicado no reforço de pilares realizado no âmbito da tese de doutoramento de Faustino Marques [9].Na Figura 1 é possível observar dois pilares de seção retangular (20x40cm2) encamisados com coletes de 3 camadas de CFRP (200gr/m2) em que foi utilizado o sistema CREatE com armaduras pós-instaladas de aço inox (2x20x5mm2) ou de laminados de CFRP (2x(10+20)×1.4 mm2/face) para reforço longitudinal [7, 8]. Na Figura 2 pode observar-se os resultados dos ensaios experimentais de um conjunto de pilares de seção retangulares sujeitos a esforço axial e a ações horizontais cíclicas. O pilar P11 é o de referência pois, não foi reforçado, enquanto os pilares P12, P15 e P16 foram encamisados com coletes de 3 camadas de CFRP e nos pilares P15 e P16 foi utilizado adicionalmente o sistema CREatE com armaduras pós-instaladas de aço inox (P15) ou de laminados de CFRP (P16) para reforço longitudinal [7]. Na Figura 3 mostra-se a envolvente dos diagramas Força-Deslocamento dos ensaios dos diferentes pilares de seção retangular (P11; P12; P15 e P16), sendo possível de constatar um excelente desempenho não só em termos de ductilidade (incremento de 67%) como de resistência (incrementos entre 29% e 43%, para drifts entre 2 e 4%) dos pilares reforçados com o sistema CREatE relativamente ao pilar de referência não reforçado.

Este livro apresenta diferentes perspetivas sobre o património arquitetónico em Espanha e Itália, debruçando-se sobre temas que estão na ordem do dia, como a reabilitação do património arquitetónico ou as acessibilidades ao mesmo, sejam elas na forma física ou digital, sendo os autores profundos conhecedores desta área. Nas intervenções a realizar no património edificado é fundamental ter um conhecimento aprofundado do projeto, da história e do processo construtivo da obra, bem como do seu comportamento estrutural. De acordo com o ICOMOS estas intervenções devem ser realizadas utilizando as técnicas mais adequadas, baseadas num diagnóstico apropriado e na compreensão dos materiais existentes. De igual forma, os estudos no edificado monumental devem ser realizados com o menor grau de intrusão e o máximo respeito pela sua integridade física, seguindo os princípios de salvaguarda do património arquitetónico definidos na carta internacional de Atenas.O livro divide‐se em duas grandes áreas: numa, abordam‐se os assuntos que se enquadram essencialmente no âmbito da conservação e reabilitação do património arquitetónico e na outra são apresentados os temas mais dedicados à acessibilidade do público ao património arquitetónico e à sua divulgação online. Os trabalhos apresentados no âmbito da conservação e reabilitação do património arquitetónico seguem na essência as recomendações do ICOMOS em relação à necessidade de compreensão da construção existente, ao desenvolvimento de novas técnicas e dos materiais mais adequados aos trabalhos de conservação e reabilitação, assim como na realização de testes em modelos experimentais à escala, tendo por objetivo avaliar o comportamento da estrutura antes e após a reabilitação. O património arquitetónico construído constitui uma parte importante da história da civilização humana e é um fator determinante da nossa identidade coletiva que importa preservar para as gerações futuras. Com a sua intervenção na conservação, reabilitação, valorização e divulgação do património construído, os autores deste livro estão a cumprir um importante papel na nossa sociedade, preservando um legado que nos foi deixado pelos nossos antepassados.

A reabilitação de estruturas de betão armado com compósitos de FRP tem tido uma grande aceitação em especial devido às excelentes características de durabilidade dos materiais compósitos, ao seu baixo peso e às suas elevadas prestações mecânicas. Contudo, o comportamento elástico-linear dos compósitos de FRP e a sua forma de aplicação pode originar roturas prematuras, quer na técnica de reforço EBR (Externally Bonded Reinforcement), em que o compósito é colado externamente, quer na técnica NSM (Near Surface Mounted) em que o compósito é inserido na zona do recobrimento. No sentido de minimizar o risco de roturas prematuras e ao mesmo tempo aumentar a ductilidade dos elementos reforçados, desenvolveu-se um novo sistema de reforço estrutural em que as armaduras são ancoradas internamente por aderência. A fim de validar o novo sistema de reforço estrutural com compósitos de FRP foi realizado um programa experimental que incluiu o ensaio de vigas de betão armado (BA) reforçadas com as seguintes técnicas de reforço: EBR, NSM e pela nova técnica CREatE (continuous reinforcement embedded at ends). Neste artigo descrevem-se os ensaios experimentais realizados e analisam-se os resultados obtidos. As vigas de BA ensaiadas tinham seção em T, com um vão de 3,0 m e uma altura de 0,3 m e foram solicitadas em flexão em 4 pontos e testadas até a rotura. A técnica CREatE provou ser a mais eficaz das três alternativas testadas mobilizando a totalidade do CFRP e apresentando a maior capacidade resistente e a ductilidade mais elevada.

Neste artigo apresentam-se e analisam-se um conjunto de ensaios realizados em vigas de betão armado reforçadas com armaduras pós-instaladas de aço ou de FRP, incluindo os referentes a uma nova técnica (CREatE) desenvolvida na FCT NOVA. Os resultados experimentais permitiram concluir que a técnica CREatE possibilita aumentos de resistência e ductilidade consideráveis face às técnicas tradicionais.

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