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On the classification of mixed construction and demolition waste aggregate by porosity and its impact on the mechanical performance of concrete

Angulo, Sérgio Cirelli; Carrijo, Priscila Meireles; Figueiredo, Antonio Domingues de; Chaves, Arthur Pinto; John, Vanderley Moacyr
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.4%
The properties of recycled aggregate produced from mixed (masonry and concrete) construction and demolition (C&D) waste are highly variable, and this restricts the use of such aggregate in structural concrete production. The development of classification techniques capable of reducing this variability is instrumental for quality control purposes and the production of high quality C&D aggregate. This paper investigates how the classification of C&D mixed coarse aggregate according to porosity influences the mechanical performance of concrete. Concretes using a variety of C&D aggregate porosity classes and different water/cement ratios were produced and the mechanical properties measured. For concretes produced with constant volume fractions of water, cement, natural sand and coarse aggregate from recycled mixed C&D waste, the compressive strength and Young modulus are direct exponential functions of the aggregate porosity. Sink and float technique is a simple laboratory density separation tool that facilitates the separation of cement particles with lower porosity, a difficult task when done only by visual sorting. For this experiment, separation using a 2.2 kg/dmA(3) suspension produced recycled aggregate (porosity less than 17%) which yielded good performance in concrete production. Industrial gravity separators may lead to the production of high quality recycled aggregate from mixed C&D waste for structural concrete applications.; FINEP (Fundo Verde e Amarelo/Habitare); SINDUSCON-SP; FAPESP; CNPq; CAPES

Influência dos ciclos de execução nas deformações das estruturas de concreto armado de edifícios de andares múltiplos; Construction cycles influence on the deformation of reinforced concrete structures of multistory buildings

Salvador, Paulo Fernando
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.44%
Este trabalho discute as conseqüências nas deformações de estruturas de concreto armado de edifícios de andares múltiplos, moldadas através de ciclos de execução rápidos. Em recente revisão, as normas da ABNT sugerem uma maior preocupação com as solicitações aplicadas nas estruturas, quando o concreto apresenta idade inferior a vinte e oito dias. A literatura pesquisada também indica a ocorrência de manifestações patológicas decorrentes de deformações excessivas nas estruturas devido às ações de construção, que inclusive podem superar o que é previsto em projeto. Neste trabalho é mostrado um estudo experimental de caráter exploratório, buscando analisar a influência do carregamento precoce, nas deformações de vigas de concreto armado. Foram propostos dois tipos de pré-carregamento, um de curta duração, onde são aplicados três níveis de carregamento aos três dias de idade, e outro de longa duração, onde são aplicados carregamentos em idades de acordo com as ações construtivas decorrentes de dois ciclos de execução rápidos.Foram utilizados concretos produzidos com dois tipos de cimento, um de cura rápida (CP V-ARI) e outro de cura lenta (CP IV-32RS). Os resultados apontam para a confirmação do que preconizam a literatura e as normas nacionais e internacionais...

Steel bars identification in reinforced concrete structures by using ANN and magnetic fields

De Alcantara, N. P.; Gasparini, M. E L
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 428-431
ENG
Relevância na Pesquisa
46.19%
This work proposes a methodology for non destructive testing (NDT) of reinforced concrete structures, using superficial magnetic fields and artificial neural networks, in order to identify the size and position of steel bars, embedded into the concrete. For the purposes of this paper, magnetic induction curves were obtained by using a finite element program. Perceptron Multilayered (PML) ANNs, with Levemberg-Marquardt training algorithm were used. The results presented very good agreement with the expect ones, encouraging the development of real systems based upon the proposed methodology.

Identification of steel bars immersed in reinforced concrete based on experimental results of eddy current testing and artificial neural network analysis

De Alcantara, Naasson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 58-71
ENG
Relevância na Pesquisa
46.21%
This paper presents an experimental research on the use of eddy current testing (ECT) and artificial neural networks (ANNs) in order to identify the gauge and position of steel bars immersed in concrete structures. The paper presents details of the ECT probe and concrete specimens constructed for the tests, and a study about the influence of the concrete on the values of measured voltages. After this, new measurements were done with a greater number of specimens, simulating a field condition and the results were used to generate training and validation vectors for multilayer perceptron ANNs. The results show a high percentage of correct identification with respect to both, the gauge of the bar and of the thickness of the concrete cover. © 2013 Copyright Taylor and Francis Group, LLC.

Construções habitacionais de concreto moldado no local; Cast in place concrete residential construction

Antonio Carlos Alvarenga Pinto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/05/2007 PT
Relevância na Pesquisa
46.34%
Descreve-se, em forma cronológica, as etapas de planejamento, projeto e construção de um empreendimento habitacional com 351 unidades, localizado na cidade de Campinas, SP. São apresentados, também, comentários, críticas e sugestões para aperfeiçoamento dos processos construtivos adotados. Apresenta-se, ainda, a análise estrutural e dimensionamento (verificação) dos elementos estruturais de concreto armado de uma residência em dois pavimentos construída com a tecnologia objeto de estudo desse trabalho; In a chronological order, the planning, the project and the construction steps of a residential enterprise, containing 351 units, in the city of Campinas, São Paulo, Brazil, are described. Comments, critical analyzes and suggestions are presented for the improvement of the construction process as well. Also, the paper details the structural analysis and dimensions of the structural elements of a two floor reinforced concrete residential building built under the technology proposed here

O Projeto da produção de formas para estrutura de concreto armado incorporando BIM; The Formwork Design for reinforced concrete structures incorporating BIM

Romeu da Silva Neiva Neto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/08/2014 PT
Relevância na Pesquisa
46.38%
Os sistemas de formas para concreto armado existentes no mercado brasileiro compõem até 30% do custo das obras de estruturas de concreto armado no país. Porém, construtoras geralmente não dão a devida atenção a essa disciplina, pois são poucos os casos em que o projeto para esse fim é desenvolvido e quando o é, geralmente carece de detalhamento e precisão. Isso resulta em desperdícios, falta de planejamento e atrasos nos cronogramas gerais das obras. Desta forma, o objetivo deste trabalho foi incorporar os preceitos da Modelagem da Informação da Construção (BIM) no Projeto Construtivo de Formas de Madeira (PCFM). Restringiu-se a estruturas de concreto armado para edifícios de múltiplos pavimentos. O método adotado foi o da pesquisa construtiva, pois desejava-se desenvolver de forma inovadora, projetos de forma, resolvendo problemas do mundo real por meio de uma teorização digital aplicada. O delineamento da pesquisa compreendeu a descrição da problemática (conhecimento prático e teórico), a formulação da solução digital para o projeto de formas, a implementação da solução e a consideração de sua aplicabilidade. A solução para o projeto de formas abarcou incrementalmente diferentes níveis de abstração do projeto: do componente (modelagem paramétrica)...

Influence of the concrete mechanical properties on the efficacy of the shear strengthening intervention on RC beams by NSM technique

Bianco, V.; Barros, Joaquim A. O.; Monti, G.
Fonte: International Institute for FRP in Construction (IIFC) Publicador: International Institute for FRP in Construction (IIFC)
Tipo: Conferência ou Objeto de Conferência
Publicado em //2007 ENG
Relevância na Pesquisa
46.12%
The occurrence of a failure mode, different from debonding, consisting on the detachment, from the beam core, of “two concrete lateral walls” containing the glued laminates, highlights the paramount importance of concrete mechanical properties on the effectiveness of NSM shear strengthening technique. A new mechanical-analytical interpretation of the phenomenon affecting the ultimate behaviour of RC beams NSM-strengthened in shear is presented along with the main findings. This approach takes into account the possibility that the shear strengthening contribution of the NSM laminates can be limited by the three following failure modes: debonding, concrete tensile fracture and laminates’ tensile rupture. The interaction between laminates can be also accounted for. The proposed mechanical interpretation of the NSM laminates behaviour can be extended to NSM rods.; Fundação para a Ciência e a Tecnologia (FCT) - programa “CUTINSHEAR - Performance assessment of an innovative structural FRP strengthening technique using an integrated system based on optical fiber sensors” s, POCTI/ECM/59033/2004. This work has been partially carried out under the program “Dipartimento di Protezione Civile – Consorzio RELUIS”, signed on 2005-07-11 (n. 540)...

13th International Congress on Polymers in Concrete

Aguiar, J. L. Barroso de, ed. lit.; Jalali, Said, ed. lit.; Camões, Aires, ed. lit; Ferreira, Rui Miguel, ed. lit.; International Congress on Polymers in Concrete, 13, Madeira, 2010
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /02/2010 ENG
Relevância na Pesquisa
46.35%
The 13th International Congress on Polymers in Concrete 2010 (13th ICPIC 2010) follows a series of 12 earlier successful congresses, which has been started in London in 1975. These congresses, being held every three years, played a key role in disseminating R&D findings between researchers, academics, industrials and students. The 13th ICPIC was again a forum to exchange knowledge and most recent research findings among participants. It represented a contribution to the development of this important subject. The 13th ICPIC was held in Funchal, capital of Madeira Islands, Portugal. 120 participants coming from thirty different countries presented and discussed about 100 contributions submitted to the congress. The main topics covered had been: (a) Concrete-Polymer Composites (Micro and nanostructure, Ecological aspects, Properties, Test methods and Applications), (b) Interface Zone Polymer/Concrete (Micro and nanostructure, Penetration process, Adhesion strength, Durability and Test methods), (c) Coatings and Crack Injection (Adhesion strength, Permeability, Durability, Test methods and Applications), and (d) Concrete Rehabilitation (Innovations, Durability, Test methods and Case studies). Nowadays, the field “polymers in concrete” is rather consolidated in the construction industry. The future of polymers in concrete will be oriented to take full benefit of the synergic actions between these organic and mineral materials...

Management of precast concrete construction.

Jost, Daniel Adam
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 79 leaves; 4023082 bytes; 4022841 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
46.13%
Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering.; Bibliography: leaves 70-72.

An experimental study into the evolution of loads on shores and slabs during construction of multistory buildings using partial striking; Engineering Structures

Alvarado, Yezid A; Calderón, Pedro A; Adam, Jose M; Payá Zaforteza, Ignacio J; Pellicer, Teresa M; Pallarés, Francisco J.; Moragues, Juan J.
Fonte: Pontifícia Universidade Javeriana Publicador: Pontifícia Universidade Javeriana
Formato: 2132-2140
Relevância na Pesquisa
46.27%
31-9; This paper describes a full-scale test on a building constructed so as to enable study of the transmission of loads between slabs and shores during the processes of shoring and striking. The experimental model consisted of a 3-storey building with slabs made up of reinforced concrete. The structure was built using a procedure which includes an intermediate stage during striking, known as clearing. This involves removing the formwork boards and a certain number of shores before the pouring of concrete of the uppermost slab. This operation helps optimise the construction process since most of the formwork and shoring material is recovered in only a few days. The loads on the shores were measured by placing 3 strain gauges on each one of them. The results obtained differ notably from those estimated by the simplified methods commonly used. They show that, due to the clearing operation, the shores experience an average unloading of up to 49%, transferring this load to the slab that has been subject to clearing. In the stages that follow the hardening of the concrete, the spread of the loads among the shores is not uniform as the shores furthest away from the columns suffer more loading than the rest.

Environmental and Social Management System Implementation Handbook : Construction

International Finance Corporation
Fonte: Washington, DC Publicador: Washington, DC
EN_US
Relevância na Pesquisa
46.07%
This Handbook is intended to be a practical guide to help companies in the construction industry develop and implement an environmental and social management system, which should help to improve overall operations. In the current economic climate, companies are under pressure to perform or even just survive. New initiatives are often met with resistance as people struggle to keep up with their day-to-day responsibilities. Some people think that an environmental and social management system must be big, complicated and expensive. But that is not really true. To be effective, a management system needs to be scaled to the nature and size of the company. If a company has existing management systems for quality or health and safety, this Handbook will help to expand them to include environmental and social performance. Sections I and II provide background on environmental and social management systems (ESMS) in the construction industry. Section III provides step-by-step instructions on how to develop and implement an ESMS. The ESMS Toolkit and Case Studies section gives: 1) tools to help develop and implement the systems described in the Handbook; and 2) case studies presenting two companies in the construction industry that implemented an ESMS.

Non-linear overload behaviour and ductility of reinforced concrete flexural members containing 500MPa grade steel reinforcement / by Rebecca Jane Gravina

Gravina, Rebecca Jane
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 236304 bytes; application/pdf
Publicado em //2002 EN
Relevância na Pesquisa
46.38%
Investigates the overload behaviour and modes of collapse of reinforced concrete flexural members containing 500MPa grade reinforcing steel and evaluates the adequacy of current ductility requirements for design according to AS 3600 to ensure strength and safety.; Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2002; Includes corrigenda (inserted after title page) and list of publications published as a result of this research.; Includes bibliographical references (leaves 192-199); xxvii, 223 leaves : ill. ; 30 cm.

Intermediate crack debonding of plated reinforced concrete beams

Liu, Irene S. T.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 1973162 bytes; 2527928 bytes; 1902241 bytes; 774635 bytes; 2818500 bytes; 129203 bytes; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf
Publicado em //2006 EN
Relevância na Pesquisa
46.23%
With increasing number of structures reaching their designed life or capacities everyday, retrofitting has become an important area in civil engineering. A popular method of strengthening and stiffening reinforced concrete ( RC ) beams is by adhesively bonding steel or FRP plates to the external surfaces. This technique has been proven to be efficient, inexpensive, unobtrusive and can be applied while the structure is in use. However, it has been found that adhesively bonded plates are prone to premature debonding prior to reaching their designed capacities, which restricts the use of existing design rules and guidelines for retrofitting RC beams using this relatively new form of structure. There are various forms of debonding including : plate end ( PE ) debonding ; critical diagonal crack ( CDC ) debonding ; and intermediate crack ( IC ) debonding. IC debonding is an especially important mechanism as it will occur at plated hinges of continuous members, and unlike other premature debonding mechanisms, IC debonding is very difficult to prevent. This debonding mechanism is associated with the formation of flexural or flexural - shear cracks in the vicinity of the plates, which causes slip to occur at the plate / concrete as well as the bar / concrete interfaces. Most research to date has been focusing on the bond - slip relationship at the plate / concrete interface...

Deformation Capacity and Moment Redistribution of Partially Prestressed Concrete Beams

Rebentrost, Mark
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 5564067 bytes; 196399 bytes; 9596673 bytes; 3946117 bytes; 2543466 bytes; 126665 bytes; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf
Publicado em //2004 EN
Relevância na Pesquisa
46.24%
Ductility is a measure of the ability of a material, section, structural element or structural system to sustain deformations prior to collapse without substantial loss of resistance. The Australian design standard, AS 3600, imposes minimum ductility requirements on structural concrete members to try to prevent premature non-ductile failure and hence to ensure adequate strength and ductile-type collapse with large deflections. The requirements also enable members to resist imposed deformation due to differential settlement, time effects on the concrete and temperature effects, whilst ensuring sufficient carrying capacity and a safe design. Current AS 3600 requirements allow a limited increase or reduction in elastically determined bending moments in critical regions of indeterminate beams, accommodating their ability to redistribute moment from highly stressed regions to other parts of the beam. Design moment redistribution limits and ductility requirements in AS 3600 for bonded partially prestressed beams are a simple extension of the requirements for reinforced members. The possibility of premature non-ductile failure occurring by fracture of the reinforcement or prestressing steel in partially prestressed members has not adequately addressed. The aim of this research is to investigate the overload behaviour and deformation capacity of bonded post-tensioned beams. The current ductility requirements and design moment redistribution limits according to AS 3600 are tested to ensure designs are both safe and economical. A local flexural deformation model based on the discrete cracked block approach is developed to predict the deformation capacity of high moment regions. The model predicts behaviour from an initial uncracked state through progressive crack development into yielding and collapse. Local deformations are considered in the model using non-linear material laws and local slip behaviour between steel and concrete interfaces...

Towards a generic model of the intermediate crack debonding resistance of plates adhesively bonded to concrete

Seracino, R.; Oehlers, D.; Raizal Saifulnaz, M.
Fonte: International Institute for FRP in Construction; Hong Kong Publicador: International Institute for FRP in Construction; Hong Kong
Tipo: Conference paper
Publicado em //2005 EN
Relevância na Pesquisa
46.21%
Numerous models have been published to predict the maximum intermediate crack (IC) debonding force in adhesively bonded plate-to-concrete joints. However, none of the models are generic in that they are only applicable to a particular retrofitting technique, and they are not explicitly a function of the fundamental property of adhesively bonded plate-to-concrete joints, that is the interface shear stress – slip relationship. This paper presents a generic model to determine the IC debonding force that is a function of the interface shear stress and slip and the debonding failure plane, which is applicable to both the externally bonded and nearsurface mounted retrofitting techniques.; R. Seracino, D.J. Oehlers and M.R. Raizal Saifulnaz; © 2005 International Institute for FRP in Construction

Seismic behavior and design of reinforced concrete columns confined with FRP stay-in-place formwork

Saatcioglu, M.; Ozbakkaloglu, T.; Elnabelsy, G.
Fonte: Amer Concrete Inst Publicador: Amer Concrete Inst
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
46.32%
One of the applications of fiber-reinforced polymers (FRP) in building and bridge construction is stay-in-place formwork. FRP stay-in-place formwork, in the form of preformed tubes, provides easy form assembly protection of steel reinforcement and concrete against corrosion and chemical attacks while also improving the strength and ductility of structural elements in earthquakeresistant construction. Seismic performance of FRP tubes in building and bridge columns has been investigated through tests of large-scale specimens under simulated seismic loading. The experimental program consisted of tests of circular and square columns confined with carbon FRP (CFRP) tubes. The results indicate that the use of CFRP tubes increases column inelastic deformability significantly. Bridge columns under low levels of axial compression exhibit inelastic drift capacities in excess of 4% before failing in flexural tension due to the rupturing of longitudinal reinforcement. Building columns under higher levels of axial compression show drift capacities in excess of 8% when the behavior is governed by confined concrete. These observations and experimental results were used to develop a displacement-based design procedure for concrete confinement for FRP-encased concrete columns. The paper presents an overview of the experimental program and the design approach developed.; http://www.concrete.org/PUBS/JOURNALS/OLJDetails.asp?Home=SP&ID=20245; M. Saatcioglu...

A confinement model for FRP-confined normal and high-strength concrete in square and rectangular sections

Lim, J.; Ozbakkaloglu, T.
Fonte: International Institute for FRP in Construction; online Publicador: International Institute for FRP in Construction; online
Tipo: Conference paper
Publicado em //2013 EN
Relevância na Pesquisa
46.21%
The confinement of concrete with fiber reinforced polymer (FRP) composites can significantly enhance its strength and deformability. However, the effectiveness of FRP confinement on square and rectangular concrete sections, in which the concrete is non-uniformly confined, is much lower than the effective confinement of circular sections. To investigate the shape factors influencing the compressive behavior of FRP-confined concrete in square and rectangular sections, a database of existing test results was assembled. The database was then studied, together with a companion database consisting of the test results of FRP-confined concrete in circular sections, in order to capture the change in the effectiveness of confinement due to the change in the sectional shape. The combined database catalogued the compression test results of 1547 specimens with unconfined concrete strengths ranging from 6.2 to 169.7 MPa. It provided a significantly extended parameter space, thereby allowing clearer observations of the important factors influencing the compressive behavior of FRP-confined concrete in various sections. Based on the test database, a unified model for FRP-confined concrete in circular, square and rectangular sections was developed and presented in this paper.; http://web.archive.org/web/20130422092859/http://www.apfis2013.org; J. C. Lim and T. Ozbakkaloglu

Circus of Maxentius, concrete construction detail

Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Imagem
ENG
Relevância na Pesquisa
46.03%
Incorporation of terracotta storage jars into fabric of concrete wall, characteristic of early 4th CE

Concrete Construction Employees: When does procedural fairness shape self-evaluations?

Smith, Heather J.; Thomas, Timothy R.; Tyler, Tom R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/2006 EN
Relevância na Pesquisa
46.22%
According to the Group Value Model, group authorities and procedures communicate symbolic information to people about whether the group values or respects them. Employees for a concrete construction company completed a questionnaire about their work experiences in either English or Spanish. Among employees who identified more strongly with the concrete construction company, the quality of supervisor treatment predicted employees' feelings of respect and personal self-efficacy. Further, for employees who identified with the company, feeling respected by their colleagues mediated the relationship between fair treatment by a single supervisor and self-efficacy. Even when the working context encourages short term and instrumental goals, these results suggest that employees who identify with the company still care about fair treatment because of the self-relevant information it communicates to them.

Cradle-to-gate environmental impacts of the concrete industry in South Africa

Muigai,R; Alexander,M G; Moyo,P
Fonte: Journal of the South African Institution of Civil Engineering Publicador: Journal of the South African Institution of Civil Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2013 EN
Relevância na Pesquisa
46.19%
The objective of the paper is to provide an understanding of the South African concrete industry's environmental burden in terms of natural resource consumption and carbon dioxide equivalent emissions (CO2-e). The review covers current practices in the concrete construction field in South Africa (SA) and their implications for the environment. Elaboration in terms of detail and quantification is given for the environmental burden generated during the manufacture of raw materials for concrete and their transportation to site. Four-year average (2005-2008) data is provided for resources consumed and wastes emitted during the quarrying and manufacture of raw materials for concrete. Carbon dioxide-equivalent emissions data per unit of material produced was obtained from the InEnergy Report produced for the Cement and Concrete Institute (C&CI) of South Africa. The study determined that, on average, 39.7 Mt of raw materials are consumed per year and 4.92 x 10(9) kg CO2-e emissions are emitted per year to produce cement and aggregates for concrete production in South Africa.