Basic HTML Version
850
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
3.1 Design of the connection
The two prototypes were dimensioned to resist the application of
150 kN on each beam and the design was done according to the
requirements of [1], [9] and [10]. The column had cross section
area of 500 mm x 400 mm and 1400 mm of height, concrete corbel
with 400 mm x 250 mm and dowels with 20 mm in diameter. The
beams had cross section area of 400 mm x 400 mm in their precast
part and after the assembly, 200 mm of cast on site concrete were
added. This concrete cover filled the beams and the slab at the
same time and it promoted the integration with the negative rein-
forcement. The reinforcement details of these elements are shown
in Figures 2 and 3.
The negative reinforcement was located on the side of the col-
umn and passing through the column by holes. In prototype called
Model 1, the reinforcement just passed through the column and in
the prototype called Model 2, the bars were distributed in the side
of the column and crossing it, both on the precast slab. The slab
used on Model 2 was the hollow core slab with 200 mm in height
and cast on site concrete cover with 70 mm of thickness. The can-
tilever slab had 400 mm of length which was measured from the
face of the beam. The bars on side of the column were distributed
on a range of 250 mm, which also was measured from the face of
the column. Figure 4 shows the dimensions of the pieces of hollow
core slabs used on Model 2.
The longitudinal continuity reinforcement was integrated to the
structure with 270 mm of height of concrete casting on site on
the precast beams in order to improve the flexural strength
of the connection. This height was constituted by two layers:
200 mm of the beams and 70 mm of concrete cover on the
hollow core slab.
The steel area (As) used in the models was 804 mm². In the situ-
ation that 100% of the reinforcement passed inside the column
(Model 1), this reinforcement consisted of 4 bars of 16 mm of di-
ameter. It is important to say that Model 1 had no slab. In Model 2,
which had 50% the reinforcement passing inside the column and
50% outside, two bars of 16 mm of diameter passing inside the
column and 4 bars of 8 mm of diameter on each side were used.
ies. Saqan [5], a researcher of the University of Texas, tested
various configurations of connections that would provide to the
structure a rigidity behavior when subjected to earthquakes.
The connections developed did not have concrete cast on site
and should be economical and ductile. This research had an
objective to increase the knowledge about the behavior of this
type of connection in order to increase the utilization of precast
concrete structures in the United States.
Many researches about precast concrete connections were also
performed in Brazil. A current search that can be mention is Olivei-
ra Junior [6] which studied the behavior of a type of beam-column
connection for use in hydroelectric power plants. This connection
was made with cast on site concrete, using concrete fiber and steel
threaded sleeves to provide continuity to the reinforcement and
consequently high rigidity.
Baldissera [7] studied a type of connection with inclined dow-
els. To analyze the behavior of this connection, the results
of the test of this connection with inclined dowels were com-
pared to the behavior of the conventional connections with
straight dowels. The conclusion of the comparison was the
rigidity increase with the innovated detail. In this context, this
paper aims to analyze the behavior of the beam-column con-
nections in precast concrete structures with the focus on the
details of the slab reinforcement. The influence of the distri-
bution of the bars in the slab in order to improve the transfer
of stress was analyzed, even as the distribution of cracking
in this region.
3. Experimental program
The experimental program of this paper was performed in Kata-
oka [8] and it aimed to analyze the interaction of the beam end
with the column. Two prototypes with cruciform arrangement were
constructed to be tested. They were constituted by a central con-
tinuous column with two cantilever beams. The vertical action was
applied at the end of the beams, as illustrated in Figure 1. This ar-
rangement enabled the simulation of a region near a central node
of a porch structure.
Figure 2 – Details of beams reinforcement