Navegando por Assunto "Laje nervurada"

Agora exibindo 1 - 5 de 5

Acesso aberto (Open Access)
Análise experimental de lajes lisas nervuradas de concreto armado com armadura de cisalhamento
(Universidade Federal do Pará, 2007-11-01) SOUZA, Shirley do Socorro Melo de; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
Two-way waffle flat slabs are structural elements of reinforced concrete supported directly on columns, under bending moments over the two directions, they improve the speed of the execution and save moulds and concrete and, consequently, labor. This work seeks to contribute for the study of the behavior of this kind of slab, as the shear resistance of the ribs and the punching in the solid area, through tests of 8 two-way reinforced concrete waffle flat slabs. Comparative analyses between the experimental results and estimated by national and international design codes had been carried out. The slabs were square, with 1.800 mm of side and total height of 140 mm. The cross section of the slabs was formed by ribs with 50 mm of width for the base and 100 mm for the upper base and the spaces between the ribs had been filled with EPS blocks (expanded polystyrene). The main variables considered were the type of shear reinforcement in the ribs (trusses, closed vertical stirrup and 45 inclined stirrup) and the use of 45 inclined stirrup as shear reinforcement in the solid region. They were presented and analyzed the results observed for the vertical displacements, deformation in the flexural and shear reinforcement, and the propagation of cracks. The values observed for failure loads were compared with the estimated ones. It was observed that the shear reinforcement in the ribs did not increase the failure loads and that the shear reinforcement in the solid region increased significantly the resistance of the slabs.
Acesso aberto (Open Access)
Análise experimental de lajes nervuradas de concreto armado com viga faixa de altura variável
(Universidade Federal do Pará, 2014-11-21) SACRAMENTO, Paulo Victor Prazeres; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
The ribbed slabs have been widely used in the buildings it has several advantages in its execution and performance. In order to get a good design of this type of slab is necessary ensure that the stresses are properly supported, mainly those considered critical, which can lead the structure to the collapse suddenly, as is the case of punching in connection wide beam-column or of the shear in the region of the ribbed. In order to evaluate the punching strength of the slab-column connection and the shear strength of the ribs were manufactured four reinforced concrete ribbed slabs, two slabs one-way and two slabs two-way. The flexural reinforcement rate was constant in all slabs. All slabs were square of side 2200 mm and thickness equal to 150 mm. The main variable in this study was the change in height of the wide beam. This variation has to evaluate the performance of the ribs, even when the limit of spacing between them is ensured. Also, check if the punching is a possibility of rupture in this case. The estimates in this step design were based on three different standards. These were ACI 318 (2008), Eurocode 2 (2004) and NBR 6118 (ABNT, 2014). Studies with ribbed slabs have shown that the estimates of design standards are conservative. In addition, this predictions may lead to inadequate results for resistance slabs. The experimental results of this series of tests were compared to the standard recommendations in order to assess the accuracy of these three standards, which refer to the ribbed slabs. Were also built computational models in order to verify that the behavior of slabs as the stress distribution both in connection wide beam-column range as the beam connection wide beam-ribbed. The results showed that the slabs connection wide beam-ribs must be treated in a careful manner due to the difference in stiffness between the solid area and the ribs.
Acesso aberto (Open Access)
Lajes lisas nervuradas bidirecionais com furos
(Universidade Federal do Pará, 2014-08) MATEUS, Gustavo Menezes; AGUIAR, Amaury José Oliveira de; FERREIRA, Maurício de Pina; OLIVEIRA, Dênio Ramam Carvalho de
The position of pipes and hoses for several installations still deserves special attention from designers mainly when the failure mode can be modified due to changes in behavior. This work compares experimental results of six two-way reinforced concrete ribbed flat slabs with rectangular holes close to the column and without shear reinforcement with the estimates obtained from codes ACI 318 and NBR 6118 equations. All slabs were casted and tested in the Civil Engineering Laboratory of UFPA and had dimensions of 1.800 mm x 1.800 mm x 150 mm and were submitted to central loading applied through 120 mm side square steel plates simulating the columns. EPS was used as inert material and the ribs were spaced 250 mm with 130 mm height and 75 mm average wide. The results showed that the codes’ shear equations estimates agree when the ribs are considered as beam and also for punching shear, but trend to be safer when the slabs present two shafts.
Acesso aberto (Open Access)
Lajes lisas nervuradas de concreto armado ao cisalhamento
(Universidade Federal do Pará, 2011-10) SOUZA, Shirley do Socorro Melo de; OLIVEIRA, Dênio Ramam Carvalho de
The structural systems with waffle flat slabs are the most used in Brazil when the main requirement is flexible "layouts" and long spans with reasonable economy. However, few studies have been developed in Brazil regarding the behavior of these slabs when the flexural resistance is satisfactory and the shear in the ribs and punching resistances become competitive. This work shows the experimental analysis of 8 two-way reinforced concrete waffle flat slabs under centered load. The dimensions of the slabs were the same and equal to 1800 mm x 1800 mm x 140 mm. The ribs were 80 mm (height) by 50 mm (width) and the compressive concrete strength was approximately 40 MPa. The experimental results were compared to those estimated by the Brazilian code NBR 6118:2003. It was verified that the resistance of the ribs is not satisfactorily estimated by the code, which excessively underestimates the results for ribs with and without shear reinforcement.
Acesso aberto (Open Access)
Resistência ao cisalhamento de lajes nervuradas unidirecionais de concreto armado
(Universidade Federal do Pará, 2014-08) SOUZA, Wallace Maia de; CAETANO, Thiago Rodrigues Gonçalves; FERREIRA, Maurício de Pina; OLIVEIRA, Dênio Ramam Carvalho de
The shear strength of one-way reinforced concrete ribbed slabs without stirrups in the ribs is still controversial when its estimate does not consider the contribution of the monolithic flange. To contribute to a better understanding of the behavior of these slabs were fabricated in the laboratory 8 one-way reinforced concrete ribbed slab panels where the main variables were the distance between the ribs and the thickness of the flange. The normative recommendations of NBR 6118, ACI 318 and EUROCODE 2 for the ultimate resistance of these slabs were evaluated. The experimental results showed an increase of shear strength with increasing thickness of the flange, also resulting in greater reinforcement strains and higher deflections.