Civil Engineering Reference
In-Depth Information
The smallest variation was obtained for compressive strength, with 8 % CoV.
The residual
exural strengths values were in a wider range, with CoV between 13
and 22 %. This means that for residual
fl
exural strength, dispersion can only be
controlled at levels higher than those obtained for compression strength in tradi-
tional concrete production. In fact, it should be noted that high CoV for residual
strength values is very common in
fl
exural testing, no matter how it was cast (FRC
cast in a controlled laboratory environment typically has a CoV of 20 % [
4
]).
di Prisco et al. [
5
] obtained a higher dispersion for the residual parameters from
an SCFRC used as a top slab (26.8
fl
34.6 %) when casting concrete with a small
-
proportion of
bers and under in situ production conditions.
4.4 Experimental Program and Results Analysis
4.4.1 Main Variables and Beams Production
Nine six meter-long prestressed I-beams were cast with different
fl
ange dimensions.
Figure
4.3
shows the beams
cross-section and reinforcement.
Prestressed beams were over-reinforced longitudinally with 11 tendons (0.6
'
″
diameter with a nominal cross-section equal to 140 mm 2) of 7 wires (Y 1860 S7).
Their initial tension was 1,354 MPa (before pre-stress losses, which can account for
approximately 26.2 %). This reinforcement guarantees the shear failure of the
beam. This longitudinal reinforcement means that
ˁ
l = 1.83 % for all the beams,
except for specimen HF400h/6, with
l = 1.71 %. All the rebars used for stirrups or
additional reinforcement were made out of type B 500 S steel.
ˁ
Fig. 4.3 Cross-section. Dimensions in mm
Search WWH ::
Custom Search