Experimental Tests on Fibers Influence on the Size Effect on Shear - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 79

dissipating a small energy. On the other hand, depending on the content, bers

enhance concrete toughness. Consequently, more energy is dissipated by cracks in

ber reinforced concrete.
Table 5.3 shows the mechanical properties of the different types of concrete
used: the average compressive strength (f cm ); the average tensile strength (f ctm ); the
Young s modulus (E cm ) and the average post-cracking residual strength (f R1 ,f R2 ,

f R3 ,f R4 ).
Also, round panel tests [ 1 ] were made using centrally loaded small round panels
of 600 mm of diameter [ 2 ], see Fig. 5.7 . In these tests, energies of fracture after
cracking were determined (Fig. 5.8 and Table 5.4 ).
The yielding and tensile ultimate strength of the longitudinal deformed rein-
forcing bars were, respectively: 506 and 599 MPa for

'

ϕ 14 bars; 555 and 651 MPa

for 24 bars. These are typical values for S500

steel, according to the current EC2 (2005).

ϕ 20 bars and, 518 and 612 MPa for ϕ

Table 5.3 Mechanical
properties of concrete and
post-cracking residual
strengths according to
EN 14651

Beams PC FRC50 FRC75

Fibres V f (%) 0.00 0.64 1.00

f cm (MPa) 38.7 32.1 33.1

f ctm (MPa) 3.0 2.4 2.5

E cm (MPa) 33,500 30,800 32,100

f R,1 (MPa) 5.4 6.0

-

f R,2 (MPa) - 5.6 6.1

f R,3 (MPa) - 5.0 6.0

f R,4 (MPa) 4.5 5.5

-

Fig. 5.7 Round panel during
the test