Navegando por Assunto "Punching"

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 lisas unidirecionais de concreto armado ao puncionamento simétrico ou assimétrico
(Universidade Federal do Pará, 2006-03-02) FERREIRA, Maurício de Pina; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
Punching is normally a critical case in the design of reinforced concrete flat slabs. According to many design codes, punching develops in a more unfavorable way in cases where the load is asymmetrically applied, due to unbalanced bending moments at slab-column connections. In order to evaluate the normative prescriptions in these cases, 12 reinforced concrete oneway flat slabs ( c f ' between 36 and 58 MPa) were submitted to symmetric or asymmetric punching. The slabs dimensions were (1.800 x 1.800 x 110) mm with the load being applied through a metallic plate simulating a square column with (85 x 85 x 50) mm. This research had as variables, in addiction to the load position, the reinforcement rate in transversal direction, in order to evaluate their influence in the punching ultimate resistance of one-way slabs. Results for vertical deflections, concrete surface and flexural reinforcement strains, cracking pattern, observed ultimate loads and failure modes are presented and analyzed. Also were analyzed the estimates of 6 design codes, with 3 European and 1 North-American, beyond the versions from 1978 and 2003 of the Brazilian structural concrete design code. A numerical analysis using the Finite Elements Method to simulate the slabs behavior is presented and its results are compared to the experimentally observed ones. The results showed that, unlike the normative previsions, punching resistance doesnt reduce linearly with the increments in the loads eccentricities, with the flexural effects significantly influencing the ultimate punching resistance. Even in one-way slabs, the transversal reinforcement rate showed significant influence on the slabs force distribution, interfering in the punching resistance.
Acesso aberto (Open Access)
Análise experimental de lajes lisas unidirecionais de concreto armado com pilares retangulares ao puncionamento
(Universidade Federal do Pará, 2007-12-20) DAMASCENO, Lins Sandro Resque; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
They were analyzed 8(eight) experimentally one-way flat slabs of reinforced concrete, without punching shear reinforcement, for that the reinforcement rate in secondary direction and the largest dimension of the pillars (cmax). The flat slab were dimensions of (1.800 x 1.800 x 110) mm, same flexing reinforcement, to smallest dimension of the columns (cmin) constant and equal to 85 mm, resistance to the compression of the concrete around 40 MPa and submitted to the load in the center (symmetrical punching shear), that it simulates an internal column of a pavement. The application of the load was accomplished in passages of columns linked moliticamente to the flat slab with height 150 mm, with retangularidade rate (r = cmax/cmin) varying from 1 to 7. The objective was to evaluate the influence of the retangularidade rate, that contemplated in the increase of the control perimeter in this case, in the behavior of the slabs under flexing, and possibly a more ductile failure. The objective went to also analyze the dear rupture loads starting from the recommendations of six national and international project codes, comparing with the obtained experimental results and evaluating the estimates to the punching shear, once, when the dimensions of the pillars are substantially different can happen the polarization of tensions and the resistance earnings doesn't happen in way directly proportional to the increase of the perimeter of the columns. After analyzing the influences of the retangularidade rate of the columns and the contributions that the reinforcement rate in secondary the last loads of the flats slabs and in the failure modes, it was observed that the experimental results indicated that those varied besides elevating the resistance of the connection can supply certain ductility to the failure of the slabs. It was observed that the rate of growth of the resistances obtained in the rehearsals decreases with increments in the control perimeter. Of the observations regarding the comparison among the values of resistances of the flats slabs, it was verified that the increase of the load of experimental rupture didn't come in a lineal way, indicating that the rate of growth of the load decreases with the increase of the perimeter of the column or of the rate cmax/cmin when stays constant to smallest dimension of the column (cmin).
Acesso aberto (Open Access)
Lajes lisas nervuradas bidirecionais de concreto armado sem armadura de cisalhamento com furos adjacentes ao pilar
(Universidade Federal do Pará, 2019-08-23) AGUIAR, Amaury José Oliveira de; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
With the need for a better understanding of the structural behavior of bidirectional ribbed flat slabs of reinforced concrete with opening adjacent to the column, aiming at the passage of installation ducts or ventilation, 15 square slabs measuring 2300 mm sides and 150 mm thickness with different opening configurations. The influence of the rectangularity of the columns was also an important topic analyzed, considering the concentration of tensions in the vertices of the loaded area. In order to do, 5 consecrated standards were used as a calculation parameter to estimate the final loads of the slabs and also to develop a new approach to estimate the loads of ruin. It is worth remembering that the analyzed slabs did not have shear reinforcement, that is, only the concrete contribution was considered to estimate the ultimate strength, although some standards associate this portion of resistance with the flexural reinforcement ratio, assigning an increase on ultimate strength. The results showed that the elongation of the opening and the column affected considerably the behavior of the slabs as well, the distribution of the stresses in the regions of the vertices of the openings. Based on data bases, it was possible to establish new parameters in the normative equations (Hi) which in turn approximated the results and decreased the dispersions of the same ones, besides a non-linear numerical analysis to have provided reliability standards in the models analyzed.
Acesso aberto (Open Access)
Punção em lajes lisas unidirecionais de concreto armado com diferentes taxas de armadura secundária e pilares retangulares.
(Universidade Federal do Pará, 2022-09-29) BRANCO, Vitor Hugo Lopes; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
Symmetric punching tests and experimental analyses were conducted to evaluate the behavior of nine one-way reinforced concrete flat slabs. The slabs measured (1800 x 1800 x 120) mm, and loads were applied through three types of columns: A (85 × 85) mm, B (85 × 255) mm and C (85 × 425) mm. All slabs were made with constant longitudinal reinforcement ratio at around 1% (ρx) and different secondary flexural reinforcement ratios (ρy), namely type 1 (0.5%), type 2 (1%) and type 3 (2%), approximately. Concrete compressive strength of 28 MPa and elasticity modulus of 27 GPa. Reinforcement yield stress of 573 MPa and elasticity modulus of 244 GPa. Column rectangularity index (cmax/cmín) and secondary reinforcement ratio were the main research variables, and the present study evaluated their influence on the ultimate punching strength of the sampled one way reinforced concrete flat slabs. The experimental results were compared with four current international standards: ACI 318 (2019), EC2 (2004), MC 2010 (2011) and NBR 6118 (2014). They were also compared with the findings from a nonlinear numerical analysis made with the software ABAQUS CAE 6.14, based on the Finite Element Method (FEM) and on the Concrete Damage Plasticity (CDP) model. The results indicated that the standards need to be updated, and that there is a proportional increase of up to 50% approximately in slab punching strength when the secondary reinforcement ratio is increased by up to 2%.