Basic HTML Version
858
IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 6
A study on the behavior of beam-column connections in precast concrete structures:
experimental analysis
5. Classification of connections
In Ferreira et al. [13] is presented a connection classifica-
tion system that subdivided the connections into five distinct
zones, as shown in Figure 15. This classification system is
based on fixity factor (a
R
) (equation 1) and on the coeffi-
cient of partially restrained (M
E
/M
R
). The fixity factor (a
R
) is
a non-dimensional parameter that associates the rotational
stiffness of the connection with the stiffness of the precast
beam, varying from 0 (pinned) to 1 (rigid). The coefficient of
partially restrained represents the ratio between the partially
restrained end moment (M
E
) and the fully restrained moment
(M
R
).
According to this classification, zone 1 corresponds to the pinned
connections, zones 2 to 4 correspond to semi-rigid connections
of low, medium and high strength, respectively, and zone 5 cor-
responds to rigid connections.
(1)
2
1
sec
sec
.
) (3
1
1
ef
R
LR
EI
(EI)
sec
– Secant stiffness of the beam according to [9]
L
ef
– Span between supports, distance between rotation cen-
ters of the supports
R
sec
– Secant stiffness of the beam-column connection
q
1
– Rotation at the beam end
q
2
– Combined rotation of the beam end and the connection
To analyze the connections behavior was used the Beam-Line Method.
To construct this line it was necessary to determine the maximum rota-
tion for a pinned connection as indicated in Figure 17. The analysis was
performed considering a beamwith 5.8 m of length with two concentrat-
ed loads of 180 kN. This structure was considered because in the case
of a rigid connection would generate a bending moment of 255 kNm,
which is the same value determined in the connection project.
For each model was considered the stiffness according to its cross
section. Model 1 with rectangular cross section and Model 2 with “T”
cross section, which was determined in accordance with [9], result-
ing in two different lines, one for each model. The moment of inertia
was calculated in stage I and the elastic modulus was determined
based on the specimens’ characterization tests. Assuming a bi-sup-
ported beam (Figure 17), the rotation of the beam end was calcu-
lated according to equation 2. Table 3 shows the values of rotation
for each model with their moment of inertia and elastic modulus.
(2)
) 1(
)
(2
l
a
IE
aPl
teorico
B A
Figure 15 – Classification system of connections
proposed by Ferreira et al. (2002) [13]
Figure 16 – Bending moment
versus
rotation curves with indication of secant stiffness and Beam-Line