Dênio Ramam Carvalho de Oliveira

Concretes with red mud coarse aggregates

Red mud (RM) is a mineral waste, residue of the Bayer process used to obtain alumina from bauxite. While the exploration of rolled pebble damages the environment and is much more controlled by the government, the huge RM disposal areas do not stop increasing and polluting soil, rivers and groundwater sources in Amazon. In this work, the material mixtures used to produce coarse aggregates presented up to 80% of RM, 30% of metakaolin and 30% of active silica as recycled waste. Several tests were carried out to determine the aggregates physical properties and to evaluate the mechanical performance of the concretes with the new aggregates, including hydraulic abrasion strength, and the results were compared to the reference ones, i.e. rolled pebble concretes. Additionally, the sintering process neutralizes any toxic substance as occur in some RM products like tiles and bricks, and these results have encouraged an industrial or semi-industrial production of RM aggregates for concretes.

Resistência à punção de ligações laje-pilar interno com conectores de cisalhamento

Punching shear is a brittle failure mode that may occur in slab-column connections, which may be prevented by using shear reinforcement in the slab-column connection. This paper presents comparisons between experimental results of 36 tests in internal slab-column connections with double- headed shear studs, which are largely used in North America, Europe and Asia, with theoretical results using recommendations presented by ACI 318, NBR6118, Eurocode 2 and also the Critical Shear Crack Theory (CSCT).Considering the database used it is possible to observe that ACI 318 presents conservative trends, whereas NBR 6118 showed a low coefficient of variation, but with a large number of unsafe results. Both Eurocode 2 and CSCT showed satisfactory results with Eurocode 2 presenting slightly higher performance.

Reinforced concrete ribbed slabs with wide-beam

Resumo Ribbed slabs have been widely used in buildings due to their many advantages, especially the decrease of concrete below the neutral line. This paper presents an experimental and computational study on ribbed slabs with wide-beam, two one-way slabs and two two-way slabs, with variable depths were tested to evaluate their resistance to punching and shear strength of slabs. Experimental and computational results showed that the wide-beam ribs connection is a critical point in the design of the slabs due to the difference in stiffness in the transition zone. Best results for the ultimate load estimates for ribs were provided by EC 2 (2004), while estimates of ACI 318 (2008) and NBR 6118 (2014) were respectively conservative and unsafe. Test results on slabs also revealed that the Brazilian alternative to analysis ribbed slabs as solid ones failed to give satisfactory results.

Experimental analysis of the efficiency of steel fibers on shear strength of beams

The efficiency of steel fibers for shear strength of reinforced concrete beams is assessed. Four beams were evaluated: control consisted of one beam without any steel fibers and three beams with reinforced concrete with steel fibers. All beams were reinforced for shear strength by a minimum reinforcement rate. The influence of fiber content added to concrete, at 0.5%, 0.8% and 1.0%, and the possibility of partial or total replacement of conventional shear reinforcement (stirrups) by steel fibers were evaluated. Results showed a significant increase in ductility and stiffness of the beams with steel fibers and, consequently, changes in the failure mode were observed, of shear (control beam) to flexure behavior (beams with steel fibers).

Avaliação do isolamento acústico em um templo religioso na cidade de Santarém Pará

O isolamento acustico de teatros, auditorios e casas de shows e de fundamental importância no âmbito social para que o funcionamento destes locais esteja de acordo com as tecnicas aplicadas na engenharia civil e com o codigo de postura da cidade em questao. As situacoes decorrentes de uma da ineficiencia do material empregado no isolamento acustico, associada a projetos arquitetonicos mal elaborados, podem acarretar um comprometimento da finalidade de um empreendimento ou estabelecimento, bem como causar seu embargo e fechamento. Este trabalho apresenta os resultados de medicoes de nivel de ruidos em um templo religioso para viabilizar uma avaliacao qualitativa de acordo com as normas tecnicas nacionais e o Codigo de Postura do Municipio, alem de uma proposta para isolamento acustico em estabelecimentos que precisam e devem funcionar “sem vazamentos sonoros” que possam vir a prejudicar o ambiente e a sociedade. Os niveis sonoros obtidos nos pontos perifericos foram a contento, dentro das normas tecnicas exigidas, com uma variacao de resultados mostrando uma eficiencia de revestimento dentro de padroes de baixo custo e confortaveis ao ouvido humano.

Influência do Traçado do Cabo na Resistência ao Cisalhamento de Vigas de Concreto Protendido

Poucas informacoes relativas as investigacoes experimentais sobre a colaboracao da protensao na capacidade resistente ao esforco cortante dos elementos estruturais protendidos, sao encontradas na literatura tecnica. Assim, foi avaliado experimentalmente o desempenho ao cisalhamento de seis vigas de concreto protendido com cordoalhas engraxadas, secao transversal de (150 x 450) mm2, comprimento de 2400 mm e resistencia a compressao do concreto de 30 MPa, sendo que as variaveis do trabalho foram o tracado do cabo de protensao, reto ou parabolico, e a taxa de armadura transversal. Sao apresentados os resultados para os deslocamentos verticais, deformacao do aco e do concreto e as cargas ultimas experimentais comparadas com as estimadas das normas ACI 318, EUROCODE 2 e NBR 6118: 2014. Os resultados mostraram que as vigas com tracado inclinado apresentaram aumento na resistencia ao cisalhamento em ate 16 % quando comparadas as vigas com cabos retos.

Avaliação Estrutural da Ponte sobre o Rio Sororó na Ferrovia Carajás

The Carajas railway is operated by Vale SA and is used to transport the Brazilian production of iron ore mine located in the state of Para until Itaqui harbor in Maranhao state. With 892 km in length, the railway will be doubled due to the prospect of increased production, which requires verification of the structures of bridges to ensure safety under loading up to 23% larger. The railway bridge in reinforced concrete has five hyperstatic spans with 25 m long and was built over Sororo river in the southeast of Para. To better evaluate its structural performance under current loadings, several structural elements were monitored with strain gages and the concrete was characterized by non-destructive and destructive testing on the structure. This information was used in a computer model to estimate the future structural behavior. The methodology was satisfactory as the estimated structural performance for future loadings, meeting the recommendations of the Brazilian technical standards.

Influence of the column rectangularity index and of the boundary conditions in the punching resistance of slab-column connections

Resumo Experimental evidence indicates that both the column rectangularity index and the boundary conditions of the connection may affect the ultimate punching resistance. This paper presents general aspects of these topics and, through the analysis of experimental results of tests on 131 slabs, evaluates the accuracy and suitability of recommendations presented by ABNT NBR 6118, Eurocode 2, ACI 318 and fib Model Code 2010. Experimental results showed that the security level of normative estimates trend to reduce as the column rectangularity increases, and in some cases, the punching resistance was overestimated. Finally, adjustments are suggested in equations presented by NBR 6118 and MC2010 in order to eliminate this trend of unsafe results.

Lajes lisas nervuradas bidirecionais com furos

A passagem de tubulacoes em elementos estruturais ainda merece atencao especial dos projetistas, principalmente quando o modo de ruptura dos mesmos pode ser alterado devido as mudancas em seus comportamentos. Este trabalho compara os resultados experimentais obtidos para 06 (seis) lajes lisas nervuradas bidirecionais em concreto armado, com furos retangulares adjacentes aos pilares e sem armadura de cisalhamento, com as estimativas das formulacoes dadas pelas normas ACI 318 e NBR 6118. As lajes foram moldadas e ensaiadas no Laboratorio de Engenharia Civil da UFPA e apresentaram dimensoes de 1.800 mm x 1.800 mm x 150 mm, sendo submetidas a carregamento central em placas quadradas que simularam pilares com 120 mm de lado. O material inerte entre as nervuras foi o EPS e o espacamento entre as mesmas foi de 250 mm, com largura media de 75 mm e altura 130 mm. Os resultados mostraram que as normas convergem em suas estimativas de resistencia ao cisalhamento, quando as nervuras sao tratadas isoladamente como vigas, e tambem ao puncionamento, mas neste caso tendem a ser conservadoras quando as lajes apresentam dois furos.

Análise experimental e numérica de lajes cogumelo de concreto armado

O uso de capiteis e uma das formas de se aumentar a resistencia a puncao de ligacoes laje-pilar. As recomendacoes normativas para a definicao da geometria e verificacao da resistencia ultima de ligacoes com capiteis sao pouco abrangentes, sendo poucas as pesquisas experimentais disponiveis sobre o tema. Este artigo discute aspectos relevantes do desenvolvimento historico das lajes cogumelo e apresenta resultados de 4 ensaios experimentais, sendo 1 laje lisa de referencia e 3 lajes cogumelo com capiteis de secao circular. Estes resultados sao comparados com as estimativas das normas EUROCODE 2 (2004) e NBR 6118 (2007) e com modelos numericos nao-lineares a fim de se compreender melhor a distribuicao das tensoes e o mecanismo de ruptura de lajes cogumelo.