275
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
2.2 Eurocode 2
EUROCODE 2 [11] assumes that the punching strength of flat slabs
with column capitals or drop panels must be checked in three control
perimeters as shown in Figure 5. This means that it must be checked
the maximum shear strength of the slab-column connection, using
Equation 4, and that the tensile diagonal strength inside and outside
the capital or drop panel should be checked using Equations 5 and 6.
(4)
0
0,3 1
250
c
R max
c
f
V
u d
f
 
  
Where:
f
c
is the compressive strength of (
f
c
90 MPa);
u
0
is the column perimeter in mm;
d
is the effective depth of the slab, in mm.
(5)
H
c
H
du f
V
�  
1
3
int
Rc,
100
18,0
Where:
ξ
H
is the
size effect
, taken as
(
)
0,2
200
1
≤ +
+=
H
H
h d
ξ
for a
failure surface inside the column capital, with
d
and
h
H
in mm;
ρ
is the geometric flexural reinforcement ratio expressed by
, where
ρ
x
and
ρ
y
are the flexural reinforce-
ment ratios in orthogonal directions x and y, considering only bars
within a region away
3∙
d
from the faces of the column;
u
1
is the length of a control perimeter taken 2·
d
from the column
faces, in mm;
d
H
is the effective depth of the slab in the ends of the column faces, inmm;
h
H
is the thickness of the capital, in mm.
(6)
d u f
V
out
c
�   
 
3
ext
Rc,
100
0,18
Where:
u
out
is the length of a control perimeter taken 2·
d
from the ends of
capital, in mm.
2.3 Critical shear crack theory (CSCT)
Muttoni [12] idealized his theory based on the idea that the punch-
ing resistance decreases with increasing rotation of the slab.
Such behavior may be attributed to formation of a critical shear
crack that propagates along the slab thickness cutting the com-
pression strut, which transmits shear forces to the column (see
Figure 6 – Adaptations in the critical shear crack theory as presented by [12]
1...,94,95,96,97,98,99,100,101,102,103 105,106,107,108,109,110,111,112,113,114,...190