Shear Database and Study of the Parameters Influencing Shear Behavior - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 147

With this graph it has been possible to observe that for a/d > 3.5 the MC2010
was the most conservative (Fig. 8.4 ).

8.3.2 In fl uence of the Effective Depth, d. Size Effect

If experimental shear stress (v u =V test /b d) is represented versus effective depth

(d), a clear tendency (size effect) is observed, as expected; in fact, shear stress
decreased when effective depth increase (Fig. 8.5 ).
It can be observed that, when d > 900 mm (speci

·

cally d = 1,440 mm in this
case), all Codes are unsafe (Fig. 8.6 ). On the other hand, for d < 900 mm, all Codes
give similar values.
Figure 8.6 also shows that all Codes are conservative for d < 200 mm, although
MC2010 underestimates the effect of the effective depth (d) in this range (see square
a, in Fig. 8.6 ). Codes are unconservative for reinforced beams with d > 900 mm (see
square b, in Fig. 8.6 ). Prestressed beams are always conservative for all Codes (see
square c, in Fig. 8.6 ). Finally it is noted that, for one of the prestressed beams, the
MC2010 gives higher SM, it appears that the MC2010 underestimates the effect of
prestressing, as discussed below (see square d, in Fig. 8.6 ).

8.3.3 In fl uence of the Concrete Compressive Strength, f c

Trends on SM due to concrete compressive strength are not observed in beams
without shear reinforcement.

Fig. 8.5 Beams without
shear reinforcement (neither
bers nor stirrups). Size effect

6.00

Reinforced beams Prestressed beams

5.00

4.00

3.00

2.00

1.00

0.00

0 200 400 600 800 1000 1200 1400 1600

d (mm)