279
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
between the thickness and the length of the capital, the increase in
the failure load was of 21% in comparison to slab LC2 and 58% if
compared to slab LC1. However, slab LC4, which had the biggest
column capital, didn’t show improvements in the ultimate punching
strength if compared to slab LC3.
Regarding the strains in concrete, it is observed that near the
column face, slabs LC3 and LC4 presented higher compressive
strains than slab LC2.This behavior was different considering the
compressive strains in the outside of the column capitals, where
slabs LC2 presented higher strains than the others. These differ-
ences are in agreement with the position of the failure surface ob-
served after tests. Slab LC2 failed in the outside of the columns
capital whereas slabs LC3 and LC4 failed inside the capitals. The
use of column capitals was also beneficial in terms of ductility. Ten-
sile strains measured in the flexural bars showed that in the case
of slab LC1 only two bars yielded before failure, which results in a
yield radius (
r
ys
) of 3.23·
d
. For slabs LC2 and LC3 the yield radius
r
ys
was of 5.02·
d
and for slab LC4 almost all monitored bars yielded
before failure, resulting in a yield radius
r
ys
of 6.95
·
d
.
4. Computational analysis
Experimental tests are fundamental for the development and im-
provement of theoretical methods. However, the complete under-
standing of the behavior and failure mechanisms may be ham-
pered because of displacements and strains results are restricted
to the points of the experimental model in which gauges were in-
stalled. An efficient methodology to complement the analysis of ex-
Figure10 – Numerical modeling axisymmetric (Menetrey [15])
Experimental model of one
of the slabs tested by Kinnunen
and Nylander
Numeric model of theslab
tested by Kinnunen and
Nylander
Elements used in numerical models
Quadratic axisymmetric element
Ring element
Bar element
A
B
C
1...,98,99,100,101,102,103,104,105,106,107 109,110,111,112,113,114,115,116,117,118,...190