An outbreak of occupational textile dye dermatitis from Disperse Blue 106

Contact Dermatitis. 2000 Oct;43(4):235-7. An outbreak of occupational textile dye dermatitis from Disperse Blue 106. Mota F, Silva E, Varela P, Azenha A, Massa A. Dermatology Department, Hospital Geral Santo António, Braga, Portugal. PMID: 11011934 [PubMed - indexed for MEDLINE

Concepção de sistemas de restrição passiva à retracção para avaliação das tensões associadas à deformação impedida

As tensões associadas à retracção do betão em estruturas laminares sujeitas a restrições ao seu movimento livre originam, frequentemente patologias que podem comprometer a durabilidade da estrutura. Esta problemática é recorrente em pavimentos de edifícios industriais e em camadas de betão utilizadas na reparação e no aumento da capacidade de carga de pavimentos de betão. O comportamento do betão quando sujeito a condições de impedimento parcial ou total à retracção é usualmente avaliado com recurso a ensaios qualitativos de fissuração. Apesar desses ensaios serem úteis para realizar comparações do quão propensos à fissuração são distintos tipos de betões, eles não permitem estudar o mecanismo de forma quantitativa, o que é essencial para o desenvolvimento de novas estratégias e produtos que visem mitigar o problema da fendilhação do betão associado às deformações impedidas. Assim, no presente trabalho são propostos e implementados dói métodos de ensaio para avaliação, de forma quantitativa, das tensões auto-induzidas nos betões, tendo-se para tal utilizado um betão auto-compactável reforçado com fibras de aço. Neste trabalho são descritos os ensaios piloto efectuados e apresentados e comentados os resultados preliminares

Influence of casting condition on the anisotropy of the fracture properties of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC)

Identification of the tensile constitutive behaviour of Fibre Reinforced Concrete (FRC) represents an important aspect of the design of structural elements using this material. Although an important step has been made with the introduction of guidance for the design with regular FRC in the recently published fib Model Code 2010, a better understanding of the behaviour of this material is still necessary, mainly for that with self-compacting properties. This work presents an experimental investigation employing Steel Fibre Self-Compacting Concrete (SFRSCC) to cast thin structural elements. A new test method is proposed for assessing the post-cracking behaviour and the results obtained with the proposed test method are compared with the ones resulted from the standard three-point bending tests (3PBT). Specimens extracted from a sandwich panel consisting of SFRSCC layers are also tested. The mechanical properties of SFRSCC are correlated to the fibre distribution by analysing the results obtained with the different tests. Finally, the stress-crack width constitutive law proposed by the fib Model Code 2010 is analysed in light of the experimental results.This work is part of the research project QREN number 5387, LEGOUSE, involving the companies Mota-Engil, CiviTest, the ISISE/University of Minho and PIEP. The first author would like to thank the FCT for the financial support through the PhD Grant SFRH/BD/64415/2009. The authors would like to express their sincere gratitude and appreciation to Ibermetais, Secil and SIKA, for supplying, respectively, the fibres, the cement and the super-plasticizer, respectively

Otimização do faseamento construtivo de estruturas constituídas por grandes volumes de betão : estudo do canal do descarregador de cheias de uma barragem

Tendo em vista evitar riscos elevados de fissuração em construções constituídas por grandes volumes de betão, são geralmente estabelecidas limitações construtivas, tais como imposição de altura máxima das camadas e de tempos mínimos entre os inícios de betonagens de camadas sequenciais. Geralmente estes limites são estabelecidos pelo dono de obra, com base em experiências prévias ou com base em exigências regulamentares. No entanto, esta abordagem é demasiado simplificada por não considerar as complexidades envolvidas no risco de fissuração de cada caso específico. O presente trabalho descreve os estudos realizados para a avaliação da possibilidade de diminuir o tempo entre duas fases subsequentes de betonagem da zona corrente do descarregador de cheias de uma barragem. Adota-se uma metodologia de simulação numérica do comportamento termo-químico-mecânico na fase de construção, com recurso a software baseado no Método dos Elementos Finitos. O problema térmico é simulado recorrendo a um modelo em regime transiente que permite determinar a evolução da temperatura no betão tendo em conta o calor de hidratação do cimento, as condições ambientais e a geometria da estrutura. A capacidade de previsão das ferramentas de análise do problema térmico é validada através de resultados da monitorização de temperaturas realizada durante uma das betonagens da obra. Por fim, são realizadas análises paramétricas com o objetivo de avaliar as consequências da alteração do ciclo construtivo.In order to avoid high cracking risk in construction of massive elements, limitations are generally established on the construction process, such as the imposition of maximum height of concreting layers and minimum time between consecutive casting phases. Construction phasing/schedules are generally set by owners and contractors based on previous experiences or on regulation requirements. However, this approach tends to be conservative as it overlooks several factors that influence cracking risk. This paper describes a study conducted to evaluate the possibility of optimizing the height and time interval between two subsequent concreting stages of a channel of a dam spillway. The study is based on the numerical simulation of construction through coupled thermo-chemo-mechanical FEM based software. The thermal problem is simulated using a transient model for determining the temperature evolution in the concrete taking into account the heat hydration, environmental conditions and the geometry of the structure. The predictive performance of the numerical tools adopted for the thermal problem is validated by considering the temperatures measured during one of the concreting phases. Special emphasis is given to choice of modeling parameters based on previous experiences of the research team. Finally, the evaluation of alternative construction scenarios and their cracking risk is made using the validated model

Construction phasing of a dam spillway : thermo-mechanical simulation

One of the most important issues to be taken into account while defining the construction phasing of massive elements, such as dams or thick walls, is the height of each construction stage. In fact, if the height of casting of each construction stage is increased, the temperature variations associated to heat of hydration are raised, with a consequent increase of concrete cracking risk. On the other hand, if the height of each construction phase is reduced, overall construction schedules are penalized, and costs are increased. The thickness of the concrete elements to be cast in each stage should be then as large as possible without causing thermal cracks. The evaluation of alternative construction scenarios and their cracking risk can be assessed with thermo-mechanical models. This paper aims to present an application of thermo-mechanical modeling to the central wall of a dam spillway entrance. The case study has added interest in view of the extensive material characterization, in-situ monitoring of temperature/strain, and the use of air-cooled pipes to reduce temperature increase in concrete

Conception of sandwich structural panels comprising thin walled steel fibre reinforced self-compacting concrete (SFRSCC) and fibre reinforced polymer (FRP) connectors

In this paper, an innovative thermally efficient sandwich structural panel is proposed for the structural walls of a pre-fabricated modular housing system. Traditionally, sandwich concrete panels consist of conventional reinforced concrete wythes as external layers, polystyrene foam as core material and steel connectors. However, steel connectors are known to cause thermal bridges on the building envelope and possibly condensation and mould problems. Furthermore, the possibilities for thickness reduction/optimization of conventionally reinforced concrete layers are frequently limited by minimum cover requirements. To overcome these issues, the proposed sandwich panel comprises Fibre Reinforced Polymer (FRP) connectors and two thin layers of Steel Fibre Reinforced SelfCompacting Concrete (SFRSCC). This paper presents the basic conception of the proposed building system together with preliminary parametric numerical analyses to define the arrangement and geometry of the elements that constitute the sandwich panels. Finally, the feasibility of using the proposed connector and SFRSCC on the external wythes is experimentally investigated through a series of pull-out tests where failure modes and load capacity of the connections are analysed

Development of sandwich panels combining fibre reinforced concrete layers and fibre reinforced polymer connectors: part I: conception and pull-out tests

In this paper, an innovative and thermally efficient sandwich panel is proposed for the structural walls of a pre-fabricated modular housing system. Traditionally, sandwich concrete panels consist of reinforced concrete wythes as outer layers, polystyrene foam as core material and steel connectors. However, steel connectors are known to cause thermal bridges on the building envelope, with possible consequent occurrence of condensation and mould problems. Furthermore, the reduction/optimization of the thickness of conventionally reinforced concrete layers is frequently limited by minimum concrete cover requirements for the protection of the reinforcement from corrosion. To overcome these issues, the proposed sandwich panel comprises Glass Fibre Reinforced Polymer (GFRP) connectors and two thin layers of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC). This paper presents the material and structural concept of the proposed building system. Moreover, the feasibility of using the proposed connectors and SFRSCC on the outer wythes is experimentally investigated through a series of pull-out tests where failure modes and load capacity of the connections are analysed.QREN-ADI and Fundação para a Ciência e a Tecnologia (FCT)This work is part of the research project QREN number 5387, LEGOUSE, involving the companies Mota-Engil, CiviTest, the ISISE/University of Minho and PIEP. The first author would like to thank the FCT for the financial support through the PhD Grant SFRH/BD/64415/2009. The authors also thank the collaboration of the following companies: Maccaferri and RADMIX™ for supplying the fibres, Secil and SIKA for providing the cement and the superplasticizers, respectively, and S&P – Clever Reinforcement Ibérica for supplying the epoxy adhesive

Comportamento térmico de painéis sanduíche constituídos por lâminas em betão e conectores de compósito de polímero reforçado com fibras

Relatório 10-DEC/E-2

Development of sandwich panels combining fibre reinforced concrete layers and fibre reinforced polymer connectors: part II : evaluation of mechanical behaviour

In the first part of this paper the authors describe an innovative sandwich panel that comprises Glass Fibre Reinforced Polymer (GFRP) connectors and two thin layers of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC). This second part of the paper reports the investigation performed by the authors based on the numerical simulation of these sandwich panels. The simulations use the Finite Element Method (FEM) software implemented by the second author (FEMIX). Through linear static analyses and consideration of Ultimate Limit State loading scenarios, parametric studies were performed in order to optimise the arrangement of the GFRP connectors and the thickness of the SFRSCC layers. Moreover, models considering a specific nonlinear behaviour of SFRSCC were also constructed in order to simulate the progressive damage of the panel induced by cracking. In the scope of the nonlinear analyses, emphasis is given to parameter estimation of fracture modelling parameters for the fibre reinforced concrete based on both inverse analysis and the fib Model Code.QREN-ADI and Fundação para a Ciência e a Tecnologia (FCT)This work is part of the research project QREN number 5387, LEGOUSE, involving the companies Mota-Engil, CiviTest, the ISISE/University of Minho and PIEP. The first author would like to thank the FCT for the financial support through the PhD Grant SFRH/BD/64415/2009. The authors also thank the collaboration of the following companies: Maccaferri and RADMIX™ for supplying the fibres, Secil and SIKA for providing the cement and the superplasticizers, respectively, and S&P – Clever Reinforcement Ibérica for supplying the epoxy adhesive

Flexural and shear behaviour of precast sandwich slabs comprising thin walled steel fibre reinforced self-compacting concrete

Publicado em "Rheology and processing of construction materials", ISBN 978-2-35158-137-7Insulated sandwich panels are often composed of external concrete layers, mechanically connected through metallic elements, such as trusses. Due to their high thermal conductivity, metallic connectors tend to cause thermal bridges on the building envelope. In view of this problem, an innovative solution for sandwich slabs is proposed within the framework of a pre-fabricated modular housing system. The referred slabs are based on a sandwich solution composed by two thin layers of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) that are connected by thin perforated plates of Glass Fibre Reinforced Polymer (GFRP), used together with a thermal insulation core-layer. The bottom concrete layer is reinforced with conventional steel rebars and steel fibres, whereas the upper one does not have conventional reinforcement. This paper presents a preliminary experimental program aiming to assess the flexural and shear behaviour of this type of sandwich panel solution. The obtained results confirm the feasibility of the proposed sandwich slab system, revealing its capacity in terms of load carrying capacity and ductility performance. In addition, the flexural behaviour of the tested specimens was numerically analysed for the serviceability limit states using the finite element method with consideration of the material non-linearity.Fundação para a Ciência e a Tecnologia (FCT