Page 17 - Riem-Vol6_nº3

369 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
S. J. P. J. MARQUES FILHO | B. HOROWITZ
4.2 Parametric study of concentric joints
Substituting the values of Kcomplete and Ktor in Equation (11) one ar-
rives at the following expression:
(20)
Where g and k are correction factors. The values of g were
obtained for each type of joint in Sections 3.4.1 through 3.4.3.
In the following sections the values for k are obtained from a
parametric study, similar to the ones conducted for complete
type joints.
4.2.1 Concentric cross-type interior joints
In this new parametric study subassemblages are analyzed
with story heights of 3 and 4 meters, beams with cross-section
of 20x40, 20x60, 30x40, and 30x60cm and columns with cross-
section heights of 20, 30 and 40cm and widths of 40, 60, 80, 100,
120, 140, 160, 180 and 200cm. As in the modeling conducted for
complete joints, the horizontal translation in the bottom of the col-
umn and the vertical translation at the ends of the beams were pre-
vented. The reaction force resulting from an imposed displacement
of 1 cm applied at the top of the column of the finite element model
is computed for each subassemblage. Figure 16 shows a cross-
type joint with applied boundary conditions and external loading.
As seen in Section 3.4.1, the value of correction parameter for
complete cross-type joints is gC = 0,45. Using k=1 in Equation (20)
to compute the spring stiffness of the scissors model results in dif-
ferences of less than 5% when comparing with the finite element
analyses. Therefore the correction factor of the torsional term for
concentric cross-type interior joints is taken as, kC=1.
4.2.2 Concentric T-Lateral exterior joints
Consider now T-lateral type joints. The three-dimensional finite
element models are shown in Figure 17(a). Using gT = 0,3 and
adopting kT-Lat = 1, the maximum difference obtained with the pro-
posed model when compared with the finite elements results is in
the order of 6%.
4.2.3 Concentric T-Top exterior joints
The modeling of the T-Top joint is conducted in the same way as
for the T-lateral exterior joints, as can be seen in Figure 17(b). If
one uses gT = 0,3 and k=1 in Equation (20) for the computation of
the torsional stiffness, the resulting frame model is 20% stiffer than
the finite element model. Therefore based on the parametric study
Figure 16 – Cross-type interior joint with its
boundary conditions and load
Figure 17 – (a) Model of the T-Lateral exterior joints; (b) model of the T-Top exterior joints;
(c) model of the L-type joints
A B C