Basic HTML Version
1. Introduction
The technological development provided an advance in numeri-
cal analysis in order to describe the structures behaviour. One
of the available tools is the finite element method (FEM) in as-
sociation with failure criteria of considered materials that can be
used to simulate the structural systems, especially composite
structures. The program DIANA is a computational modeling
tool that uses this method.
The numerical analysis has been increasingly used to study the be-
haviour of structures with some degree of nonlinearity, which was
not possible before because of the lack of computational resources.
Therefore, large structures that previously could only be studied
through small-scale models, now can be analyzed with real dimen-
sions, since the required resources nowadays are easily available.
In this context, the performance of numerical modeling as a com-
plement to experimental analysis, or even to replace it when im-
practicable, has become increasingly common in academia, opin-
ion shared by many authors [1, 2]. These researchers complement
including the cost factor, because the substitution of physical mod-
els by numerical models exempts the final cost of the research.
During the review of the literature many studies about compos-
ite columns and numerical analysis were found. Most of the re-
searches involving composite structures come from countries
where the incidence with earthquakes is very common because
of their good behaviour in such situation. An example is the re-
search of [3], conducted in South Korea, which includes results
of parametric analysis performed from tests and numerical sim-
ulations of connections involving composite columns filled with
concrete and diaphragms.
Another study considered important is [4], which proposed a
typology of bolted connection with circular cross section CFT
column. In this paper it was presented an analytical study, us-
ing a refined three-dimensional model that provided an accurate
understanding of the global behaviour of the connection, includ-
ing the distribution of stresses on the contact surfaces. In Brazil
there are not many researches and technical information about
composite structures. This building system was introduced in
this country around the 1950s, but its use did not grow because
Brazil culture prefers reinforced concrete structures. Currently,
studies of this building system are growing, such as in the Fed-
eral University of Minas Gerais, where studies about bolted con-
nections between steel beam and composite column were found
[5]. In the School of Engineering of Sao Carlos - USP a research
group on composite structures has been developed, which can
emphasize the research of [6], who conducted a theoretical and
experimental study about filled columns submitted to axial com-
pression and [7] wherein composite connections were analyzed.
The model of beam-column connection studied in this pa-
per involves composite column filled with concrete which was
bolted to the beams through endplates. The numerical analy-
sis involves the variation of some structural parameters in the
computer model. The computer model considered as reference
for the parametric study was calibrated by experimental results.
The structural parameters which influence was studied were
bolts diameter, slab height and beam cross section. Each pa-
rameter was varied one at a time, being the other characteristics
maintained equal to the reference model.
It was selected for this study a composite beam-column con-
nection since the use of mixed or composite building systems
expands the solutions in reinforced concrete and steel struc-
tures, producing architectural and economic benefits. Com-
pared to the characteristics of reinforced concrete construction,
the steel-concrete composite structure is competitive when it is
used in structures with median and large spans. This composite
building system is characterized by less time of execution and
weight reduction, which provides economical foundations. The
fire protection is another factor that influences the choice among
reinforced concrete structures, steel structures and mixed struc-
tures, affecting significantly the final cost.
In prefabricated structures, the connections may not have the
same stiffness of a monolithic structure; therefore the joints per-
formance has a great importance. For a long time, structural
analysis was performed considering the connections with rigid
or pinned behaviour. With all researches performed and also
with the practice on site, it was possible to demonstrate the in-
adequacy of classifying the connections only as rigid or pinned.
The usual behaviour of connections is intermediate between
these two idealized situations and to define this behaviour it
must be use the term “semi-rigid connections.”
2. Design of the connection
In the physical model was used CFT column with square cross
section and dimensions of 200x200 mm, the walls of the steel tube
had a thickness of 8 mm and it was composed by two “U” profiles.
The steel beams with “I” cross-section had 250 mm in height and
100 mm width, the flanges had 7.5 mm of thickness and the web
6.3 mm. All profiles were made with ASTM A-36 steel.
The connection was designed with eight bolts with 16 mm of di-
ameter made with SAE 1020 steel and endplate with 22.2 mm of
thickness made with ASTM A-36 steel. The column had 1950 mm
in height and each beam had 1650 mm in length.
The shear connectors used to provide the joint action between the
steel beam and the slab had a diameter of 19 mm, 100 mm of height
and yielding stress of 415 MPa, according to the manufacturer›s
information. In each beam were welded six shear connectors, the
distance from each other was 210 mm (Figure 1).
The slab had 800 mm of width and 120 mm of height including 25 mm
of concrete cover. The steel plates used in the slab had 0.80 mm of
thickness and 59 mm of height. They were provided with 840 mm of
width and 2500 mm of length and according to manufacturer’s speci-
fication, the steel plates weighing 9.14 kgf/m². The Figure 1 shows
the complete design of the connection that was performed according
to the specifications of ABNT NBR 8800:2008 [8] code.
The cruciform format was the final configuration of the connection
model, simulating a central column connected to two cantilever
beams. The dimensions of the set up model were 1950 mm in
height and 3544.4 mm of length, as indicated in Figure 2.
As shown in Figure 3, in the slab reinforcement were used eight
bars with 12.5 mm diameter in the longitudinal direction. In another
direction were used twenty four bars with of 8.0 mm of diameter.
The continuity bars were connected to the column with steel gloves
in attempt to provide continuity to these bars and increase the con-
nection stiffness (Figure 4). The steel area used in the longitudinal
direction was 981.75 mm²
469
IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
M. N. KATAOKA
|
A. L. H. C. EL DEBS