Navegando por Assunto "Fissura"

Agora exibindo 1 - 5 de 5

Acesso aberto (Open Access)
Análise experimental e numérica de lajes cogumelo de concreto armado
(Universidade Federal do Pará, 2013-04) LIMA NETO, Aarão Ferreira; FERREIRA, Maurício de Pina; OLIVEIRA, Dênio Ramam Carvalho de; MELO, Guilherme Sales Soares de Azevedo
The use of column capitals is one way to increase the punching strength of slab-column connections. Recommendations presented by codes of practice for defining the geometry and checking the resistance of slab-column connections with capitals are not comprehensive, with few experimental studies available on the topic. This paper discusses important aspects of the historical development of mushroom slabs and also presents experimental results of 4 tests, with 1 test in a reference flat slab and 3 tests in mushroom slabs with circular column capitals. These results are compared with theoretical results estimated using Eurocode 2 (2004) and NBR 6118 (2007). They were also compared with a series of non-linear finite element analysis in order to get insight of the stress distribution and of the failure mechanism of mushroom slabs.
Acesso aberto (Open Access)
Influence of the column rectangularity index and of the boundary conditions in the punching resistance of slab-column connections
(Universidade Federal do Pará, 2015-06) PAIVA, Odilson da Silva de; FERREIRA, Maurício de Pina; OLIVEIRA, Dênio Ramam Carvalho de; LIMA NETO, Aarão Ferreira; TEIXEIRA, Marcelo Rassy
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.
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)
Punching strength of reinforced concrete flat slabs without shear reinforcement
(Universidade Federal do Pará, 2012-10) SACRAMENTO, Paulo Victor Prazeres; FERREIRA, Maurício de Pina; OLIVEIRA, Dênio Ramam Carvalho de; MELO, Guilherme Sales Soares de Azevedo
Punching strength is a critical point in the design of flat slabs and due to the lack of a theoretical method capable of explaining this phenomenon, empirical formulations presented by codes of practice are still the most used method to check the bearing capacity of slab-column connections. This paper discusses relevant aspects of the development of flat slabs, the factors that influence the punching resistance of slabs without shear reinforcement and makes comparisons between the experimental results organized in a database with 74 slabs carefully selected with theoretical results using the recommendations of ACI 318, EUROCODE 2 and NBR 6118 and also through the Critical Shear Crack Theory, presented by Muttoni (2008) and incorporated the new fib Model Code (2010).
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.