Page 67 - vol5_n4

480 IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
Parametric study on the behaviour of bolted composite connections
7.2 Slab height
In reference connection model was used slab with 120 mm of
height and to study the influence of this parameter was used height
of 140 mm, 160 mm and 180 mm. It should be noted that in all of
the models were used a concrete cover equal to 25 mm, like in the
tested model, as specified in [13].
In Figure 17, the envelope curves from parametric analysis of the
slab height compared with the envelope curve of the reference
model are presented. As expected, all models with slab with higher
height than the slab of reference model showed higher stiffness,
but the differences were not significant. As shown in Table 5, for
the slab with 140 mm of height, almost no difference in the stiffness
was observed in comparison with the reference model, called Mod-
el 1 in Figure 21. For connection with slab with 160 mm of height
the difference was 6% and for the highest slab, 180 mm, the dif-
ference was 8%. As can be seen also in Figure 21, the stiffness to
the negative bending moment was higher in all cases, showing that
the slab contributes with the increased of the stiffness. Another
observation that can be made is that the height of the slab affects
the connection stiffness in the same way for positive and negative
bending moment. For positive and negative bending moment the
tendency was equal for all heights.
Table 4 – Relationship between the stiffnesses
of the parametric analysis of the bolts diameter
Bolts diameter (mm) Stiffness (kNm/rad) k/ki f16
16 42552,23 -
12,5 29385,91 0,69
20,0 42219,78 0,99
25,0 49017,47 1,15
7.3 Cross section of the beam
For the parametric analysis of the influence of the steel beam cross
section on the behaviour of the connection were varied the thick-
nesses of the flanges and the web and the width of the flanges.
These changes were made comprising three different cross sec-
tions: the first one with flange with 10 mm of thickness, the second
one with flanges with width equal to 140 mm and in an attempt to
increase the stiffness, the third cross section had flanges and web
with thickness equal to 10 mm. The cross sections used in the
parametric analysis are detailed herein Figure 22.
Comparing the bending moment versus rotation curves for all
cross sections analyzed with the curve of the reference model (Fig-
ure 23), it was noted that the stiffness of all connections with robust
beams was considered inferior and less rigid.
Examining the design process of the connection, the justification
for the lower stiffness of the models of beam cross section para-
metric analysis was found. Therefore, as all other parameters of
the connection were maintained, including the diameter of the bolts
and their properties, and with the use of robust and less deform-
able beams, the bolts were more requested, becoming the weak
point of connection, incompatible with the connected elements.
Figure 20 – Comparison of bending moment versus rotation curves and
envelope curves used for parametric analysis of the bolts diameter
Bending moment versus rotation curves Envelope curves
Table 5 – Relationship between the stiffnesses
of the parametric analysis of the slab height
Slab height Stiffness(kNm/rad) k/ki reference
Reference L = 120 mmlaje 42552,23 -
L laje = 140 mm 42171,03 0,99
L laje = 160 mm 45381,65 1,06
L laje = 180 mm 46042,11 1,08