Civil Engineering Reference
In-Depth Information
Case 1 (NEITHER FIBERS NOR STIRRUPS). Beams ordered by f
cm
2.50
90
CONSERVATIVE
80
2.25
70
2.00
60
1.75
50
1.50
40
1.25
30
1.00
20
0.75
10
UNCONSERVATIVE
0.50
0
fcm (Reinforced beams)
fcm (Prestressed beams)
SM (EHE-08)
SM (MC2010)
SM (RILEM)
Case 2 (ONLY STIRRUPS). Beams ordered by f
cm
2.00
90
CONSERVATIVE
80
1.75
70
1.50
60
50
1.25
40
1.00
30
20
0.75
10
UNCONSERVATIVE
fcm (Reinforced beams)
0.50
0
fcm (Prestressed beams)
SM (EHE-08)
SM (MC2010)
SM (RILEM)
Fig. 8.44
In
fl
uence of the concrete compressive strength (f
c
) on shear safety margins
8.8.6 In
fl
uence of the Stress Due to the Prestressing
Actions,
σ
c
Codes were always conservative for prestressed beams since they underestimate the
effective shear strength experimentally determined. However,
in beams with
combined shear reinforcement (
bers and stirrups), prestressed beams had SM
levels similar of those of beams without prestressing (Fig.
8.49
).
For beams without any shear reinforcement, SM of the prestressed beams had a
clear dependence of prestressing, since the SM increased with the prestressing
stress. In beams with shear reinforcement only, a larger scatter was observed
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