6 research outputs found
An investigation into the relationship between surface concrete resistivity and chloride conductivity test
No full textIncludes bibliographical references.The chloride conductivity test (CCT) is a South African-developed Durability Index (DI) test used for the evaluation and quantification of the quality of concrete cover. It is also used as an input parameter for service life prediction (SLP) of RC structures in the marine environment, using a modified version of Crank’s solution to Fick’s second law of diffusion. The surface concrete resistivity test is an electrochemical test that has a good correlation with the concrete chloride diffusion process. The surface concrete resistivity test is used as a quick way to determine the durability of concrete. The purpose of this study was to provide an in-depth literature review on surface concrete resistivity and investigate its use for the design and prediction of durability in RC structures. The study also compared and contrasted surface concrete resistivity with CCT, using results from previous work, in terms of their application in the design of RC structures. Thereafter, the study investigated the relationship between surface concrete resistivity and CCT. The study was carried out by comparing laboratory and field surface concrete resistivity with CCT results. Then, corrosion initiation periods (CIP’s) and diffusion coefficients were estimated using Mackechnie’s (1996) CCT SLP model as well as surface concrete resistivity models by Andrade (2004) and Baroghel-Bouny et al. (2009). Input parameters for the model such as surface concrete resistivity and CCT results were based on measurements from a previous study. It was found that moisture gradients, chloride contamination and temperature gradients easily influence concrete electrical resistivity testing done in-situ. The input parameters for the surface concrete resistivity models were restricted to laboratory results. The analysis revealed that for blended cement concrete, w/b ratio has a greater influence on chloride conductivity than binder type. It was observed that using a different binder type has a greater influence on surface concrete resistivity at a high w/b ratio than a low one. In addition, decreasing the w/b ratio for GGBS concrete is more effective than decreasing it for FA concrete in influencing the surface concrete resistivity. Andrade’s surface concrete resistivity SLP model resulted in similar CIP values as the CCT model for CEM I only concrete and slag concrete at 0.40 w/b. A constant links the diffusion coefficients from surface concrete resistivity and CCT models. An inverse relationship was found between surface concrete resistivity and the diffusion coefficient calculated from the CCT SLP model
Collaborative BIM-based workflows for a new sustainable compression-only structural block construction system
No full textDissertação de mestrado em European Master in Building Information ModellingCurrently, the construction industry is the largest industry in the world and contributes 8% per year to
greenhouse gas emissions mostly due to concrete which is the most common material used for
construction. Reinforced concrete needs steel reinforcement which is prone to rust when the concrete
cracks and deleterious materials reach the steel. Widespread steel corrosion affects the durability of the
entire structure, reduces its service life, and increases the need for rehabilitation and maintenance during
its lifecycle. An interesting alternative, for the sake of optimisation, durability, and material waste
minimisation, would be to make concrete structures solely endure compression forces and hence avoid
the need to use steel reinforcement. This can be achieved through applying form-finding methods to
achieve optimised structural shapes. Precast systems can further optimise and increase the industry’s
productivity more than the traditional on-site construction systems can. Additionally, digitalisation
through BIM and computational design processes can automate and assist in cost savings and quality
assurance.
This dissertation proposes the use of low-strength concrete to create precast compression-only concrete
structures. Each discrete part of the structure is made through flexible moulds that are adaptable to a
wide range of geometries. The structural components are connected by prestressing cables (not made of
steel and not prone to corrosion) which are installed in-situ thereby creating a new construction system.
In short, the system aims to satisfy the following requirements i) self-supporting during construction, or
only needing some propping ii) optimised structural behaviour (compression-only – no bending
moments), iii) high durability and long service life (no reinforcement).
Computational and parametric design were used to create a compression-only shell structural shape
through the Particle Spring form-finding method in Rhinoceros/Grasshopper 3D. Once the overall
structural shape was obtained, it was thickened and tessellated thereby defining its discrete elements.
The construction sequence of precast elements was implemented automatically with a cellular automata
algorithm. Then, a custom tool was created that linked the structural shape generated to the structural
analysis software DIANA and automated the phased analysis which incorporated the construction
sequencing. Thereafter, finite element analysis (FEA) was used to assess the structural behaviour.
Finally, a collaborative workflow was set up such that engineers and architects can work together to
create the most optimal structural shape in a BIM environment.
Through a case study to evaluate the framework, results show that with the proposed workflow, any
arbitrary compression-only structural shape can be defined using form-finding principles. FEA can be
performed for structural analysis and a BIM model produced for construction. Although, there are some
tensile stresses present during the phased construction they can be almost eliminated with the use of
minimal construction supports.Atualmente, a indústria da construção é a maior do mundo, sendo responsável por 8% das emissões de
gases de efeito estufa, principalmente devido ao betão, que é o material mais comum usado na construção.
O betão armado recorre a armaduras em aço, que estão particularmente sujeitas à corrosão quando ocorre
fissuração e decorrente penetração de agentes agressivos do exterior. A corrosão generalizada do aço afeta
a durabilidade de toda a estrutura, reduz sua vida útil e aumenta a necessidade de reabilitação e manutenção
durante seu ciclo de vida. Uma alternativa interessante, em prol da otimização, durabilidade e minimização
do desperdício de material, conceber estruturas de betão unicamente sujeitas a esforços de compressão e,
evitando portanto a necessidade de utilização de armaduras. Isso pode ser alcançado através da aplicação
de métodos de otimização da forma da estrutura. É também sabido que os sistemas pré-fabricados
permitem otimização e aumento de produtividade na indústria da construção, por comparação com os
métodos tradicionais de construção in-situ. Além disso, a digitalização por meio de BIM e processos de
projeto computacional podem automatizar e auxiliar na redução de custos e garantia de qualidade.
Esta dissertação propõe o uso de betão de baixa resistência para criar estruturas pré-fabricadas de betão,
sujeitas unicamente a esforços de compressão. Cada parte discreta da estrutura (módulos de cerca de um
metro quadrado de área) é feita por meio de moldes flexíveis que se adaptam a uma ampla gama de
geometrias. Os componentes estruturais são conectados por cabos de pré-esforço (em material não
metálico, evitando efeitos de corrosão) que são instalados no local, criando assim um novo sistema de
construção. Em suma, o sistema visa satisfazer os seguintes requisitos: i) ser autoportante durante a
construção, ou precisando apenas de escoramento limitado; ii) comportamento estrutural otimizado
(somente compressão - sem momentos de flexão), iii) alta durabilidade e longa vida útil (sem armaduras
metálicas).
No âmbito da dissertação são utilizados algoritmos computacionais para criar uma forma estrutural de
casca somente de compressão por meio de métodos conhecidos por ‘form finding’ no Rhinoceros /
Grasshopper 3D. Uma vez obtida a forma estrutural geral, foi-lhe atribuída espessura e compartimentação
(tecelagem), definindo assim seus elementos discretos. A sequência de construção dos elementos préfabricados
foi implementada automaticamente com algoritmos de automação celular. Em seguida, foi
criada uma ferramenta customizada que permite interoperabilidade automática do modelo criado para o
software de análise estrutural DIANA e automatizou a análise em fases que incorporou a sequência
construtiva. Posteriormente, foi usada a análise pelo método dos elementos finitos para avaliar o
comportamento estrutural. Por fim, é proposto um fluxo de trabalho colaborativo entre engenheiros e
arquitetos, rumo à definição conjunta de formas otimizadas com o procedimento desenvolvido nesta
dissertação.
Por meio de um estudo de caso para testar a estrutura, os resultados mostram que o fluxo de trabalho
proposto é viável, podendo ser aplicável a outras geometrias mais complexas. Refira-se que embora
existam algumas tensões de tração presentes durante a construção em fases, elas podem ser quase
eliminadas com o uso de suportes de construção provisórios (meros escoramentos tipicamente usados na
construção) com pouco impacto nos custos e tempo de construção
Compression‑only precast block construction system using BIM and custom interoperability tools for collaboration between engineers and architects
No full textCurrently, the construction industry contributes 8% per year to greenhouse gas emissions
which is more than 3 times that of the aviation industry. Steel corrosion affects
the durability of reinforced concrete structures, reduces their service life, and
increases the lifecycle maintenance costs. For these reasons, this study proposes
collaborative BIM‑based
workflows and design for a new sustainable compression‑only
structural block construction system. Computational and parametric design
were used to create a compression‑only
shell structural shape through form‑finding
in Rhinoceros/Grasshopper 3D. Once the overall structural shape was obtained, it
was thickened and tessellated thereby defining its discrete elements. The construction
sequence of precast elements was implemented automatically with a cellular
automata algorithm. Then, a custom tool was created that linked the structural shape
generated to the structural analysis software DIANA and automated the phased
analysis which incorporated the construction sequencing. Thereafter, finite element
analysis (FEA) was used to evaluate the structural behaviour. Additionally, a collaborative
workflow was set up such that engineers and architects can work together to
create the most optimal structural shape in a BIM environment mediated through
computational design tools. Through a case study to evaluate the framework, results
show that with the proposed workflows, an infinite number of arbitrary compression‑only
structural shapes can be defined using form‑finding
principles. Although, there
were tensile stresses present during the phased construction they can be further
minimised with the use of minimal construction supports.The first author acknowledges the Erasmus Mundus Joint Master’s Degree Scholarship from the European Union for the BIM A+ European Masters Course 2020/2021, during which the work was conducted. This work was partly financed by FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020 and
the R&D Unit Landscapes, Heritage and Territory Laboratory (Lab2PT), under reference UIDB/04509/2020
Te Toi Poto, Te Toi Roa A Critical Evaluation of Māori-State Inclusion in the Ohiwa Harbour Strategy, Aotearoa New Zealand.
No full textIn New Zealand, the State Owned Enterprises Act 1988 [SOE], Local Government Act 2002 [LGA], the Resource Management Act 1991 [RMA] require that government include the voices of Māori, and ensure their contribution to the decision-making processes of local authorities. Accordingly, central and local government have embraced the idea of inclusive partnership as part of policymaking processes informed by shared values both of government and iwi.
Thus, it is not uncommon to see consultations, partnerships and engagement between Māori-state on a range of issues in line with Tikanga and protocols of Māori culture. These transitions reflect contemporary critical policy scholarship that underscores the need to include marginalised voices policymaking, specifically through processes that reflect diverse values. Termed here as ‘procedural inclusion’, these efforts are framed within the wider goal of participatory democracy as part of the efforts to realise an inclusive society. The present research is a critical evaluation of the inclusion of Māori in the processes of policymaking, especially when those processes have been especially designed to be culturally sensitive.
This core objective is developed through the analysis of the case study of iwi/hapū-local government engagement in creating and implementing the Ohiwa Harbour Strategy in New Zealand’s Eastern Bay of Plenty region between 2002- 2008. The strategy engagement, which culminated in a long-term plan to manage and conserve the Ohiwa harbour, is uniquely positioned for this investigation. It is often regarded by its iwi/hapū and local government stakeholders as a success story in iwi/hapū-government engagement. Using a critical qualitative research methodology informed by kaupapa Māori, the study sought to critically evaluate this exemplar of procedural inclusion at multiple levels. At an operational policy level, the research identified the factors that either facilitated or inhibited Māori inclusion in the strategy development process. At another, more substantive level, the study explored the politics of this engagement, and if the goals of procedural inclusion could accommodate the transformative claims of self-determination and kaitiakitanga made by iwi/hapū.
The analysis of interview data with key stakeholders and documents of the strategy process revealed that a range of factors enhance inclusive policymaking for Māori. At a practical level, legislative frameworks, commitment to Tikanga by all parties, and key strategic cultural brokers facilitated the inclusion of Māori, while limited capacity, fear of change and inter-tribal tensions hinder inclusion. The results also show, at another level, that the ability to productively participate in these engagement processes are framed by discursive politics – of the meanings and interpretations emanating from historical contexts, nature of power relationships, and of decisions regarding who represents whom and what is represented. In all, the study points to both advantages and limitations of procedural inclusion. Inclusive policymaking can open possibilities for better management of environmental resources, strengthening Māori political voice, and creating opportunities for livelihoods and with it greater economic and social inclusion. Equally, there are also limits of government-sponsored engagement.
Māori inclusion in policymaking, while positive, does not deliver opportunities for self determination or rangatiratanga in keeping with the Treaty principles of partnership
High measles and rubella vaccine coverage and seroprevalence among Zambian children participating in a measles and rubella supplementary immunization activity
No full text4º Congresso Português de Building Information Modelling vol. 1 - ptBIM
No full textLivro de atas do Congresso ptBIM 2022, onde se promove um fórum de discussão técnico-científica em língua Portuguesa nas metodologias ‘Building Information Modelling’ (BIM), envolvendo a participação ativa das comunidades profissional e académica das áreas de Arquitetura e Engenharia. Pretende-se enfatizar os problemas e esforços de implementação na Indústria da Construção e reforçar as redes de profissionais que incorporam práticas BIM nas suas atividades.https://ptbim.org
