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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
3.5. Mechanical properties of materials
3.5.1 Concrete
The compressive strength of cast on site concrete was obtained
by testing three cylindrical specimens with dimensions of 200
mm x 100 mm. The characterizations tests were conducted one
day after the test of the connections, when the specimens were
eight days old. The average of the compressive strength was
25, 7 MPa.
The values of the compressive strength of the precast concrete el-
ements were reported by manufacturer. The compressive strength
was about 40 MPa and the elastic modulus was 30270 MPa.
3.5.2 Grout
The grout was used to fill the interface between the beam and the
column, the hole of the dowels and hole in the column where the con-
tinuity reinforcement was located. The type of grout used in the pro-
totypes was a mixture based on cement Portland, natural aggregates
and additives which allow the utilization in operations of anchorage.
This product develops high mechanical strength without shrink-
age and it is indicated to grout services or to be used as mortar
repairs. This grout was chosen due to its fluidity maintained for
a long time, which allows working in hard to reach areas like
the case of the fulfillment of the holes and the interfaces. Ac-
cording to manufacturer’s data, this grout can achieve a com-
pressive strength of 20 MPa in twenty-four hours and 52 MPa
at twenty-eight days.
The characterizations tests of the cylindrical specimens of grout
were performed with 26 days and the results confirmed the data
provided by the manufacturer. Thus, it can be considered that in
the date of the connections test, when the grout was 15 days old,
it had reached 40 MPa of compressive strength.
4. Experimental results
The tests of the connections models tested presented satisfac-
tory behavior because they reached a load which exceed the
Figure 11 – Test set up
Figure 12 – Bending moment
versus
rotation curves
with the indication of secant stiffnesses (red lines)
Table 2 – Stiffnesses of Model 1 and 2
Model
Secant stiffness
kNm/rad
Project stiffness
kNm/rad
1
120 689
155 772
2
181 818
511 993