Page 110 - Riem-Vol6_nº2

281 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 2
A. F. LIMA NETO | M. P. FERREIRA | D. R. C. OLIVEIRA | G. S. S. A. MELO
perimental results and is to carry computational non-linear finite el-
ement analysis, which after calibration may return comprehensive
results. This topic presents results from nonlinear finite element
analysis carried using commercial software MIDAS FEA. Axisym-
metric computational models were generated using as reference
analyzes made by Ferreira [14], Menétrey [15] and Trautwein [16].
In these analyses authors adapted the geometry and the reinforce-
ment of slabs in order to use axisymmetric models. Flexural re-
inforcement which were originally placed in orthogonal arrange-
ments were adjusted and changed to axisymmetric reinforcement
formed by rings and by radial bars, as shown in the Figure 10.
Comparisons between experimental and computational results pre-
sented by Ferreira [14] and Menétrey [15] indicate that the axisym-
metric theoretical models present load-displacement response stiffer
than what is observed in tests with experimental models with orthogo-
nal reinforcement. According to the authors, these results indeed de-
scribe the expected behavior once axisymmetric reinforcement are
more effective than orthogonal reinforcement in terms of bending
and cracking. They use results from Kinnunen and Nylander [7] as
experimental evidence and show that, despite the significantly differ-
ent flexural behavior, the ultimate punching resistance of slabs with
orthogonal or axisymmetric reinforcement are similar. Therefore, axi-
symmetric computational analyses are valid and may provide a better
understanding of the punching shear failure mechanism.
Based on literature, the input data used in the computational non-
linear analysis to define the properties of concrete and steel were:
Poisson’s ratio of the concrete νc = 0,15; compressive strength of
concrete fc = 32 MPa; modulus of elasticity of concrete Ec = 27
GPa; Fixed Total Strain Crack Model; Effect of lateral cracking ac-
cording to Vecchio and Collins [17];Confinement effect neglected;
basic value of fracture energy for a maximum aggregate size of 9.5
mm Gf0 N.mm/mm2 = 0.0259; compressive fracture energy Gc = 10
N.mm/mm2 ; modulus of elasticity of steel Es = 200 GPa, Poisson’s
ratio of the steel νs = 0.30; Yield stress of steel fys = 550 N/mm2.
The fracture energy was calculated using Equation 10.
(10)
7,0
0
0 





 
cm
cm
f f f
f
G G
Figure 12 – Computational and experimental load-displacement curves of slabs
Displacements of slab LC1
Displacements of slab LC3
A
C
Displacements of slab LC
Displacements of slab LC4
B
D