Civil Engineering Reference
In-Depth Information
Fig. 4.10 Crack widths (mm) on beams for different shear reinforcement combinations
In the
ber-only beams (HF600/4) only a few cracks developed at low loads
(
600 kN), but one of them opened quickly. In H600TR/3, which had only tra-
ditional reinforcement, the cracks were more noticeable, very straight and highly
parallel. At very low loads (
≈
600 kN) some crack openings of about 0.3 mm were
noted and advanced rapidly. In all the SCFRC and stirrups-only beams the crack
which produced the failure either coincided with a previous crack or was generated
from previous cracks. HF600TR/2 (traditional reinforcement and
≈
bers) developed
a larger number of smaller cracks fairly close together. Shear cracks only appeared
at high loads and reached widths of 0.2 mm only near ultimate loads. The cracks
grew slowly but were easy to control. The crack that
nally caused the failure
appeared at a very high load from two existing parallel cracks and had a
fl
atter
nal
crack slope.
To sum up, clearly improved ductility was detected only in SCFRC beams with
stirrups and when
bers plus traditional transverse reinforcement led to a 35 %
increment in maximum load for the same crack width. In fact, the crack width of the
beam with traditional transverse reinforcement only (H600TR/3) was 0.4 mm for a
load of 750 kN. The same beam with
bers (HF600TR/2) reached an ultimate load
(1,150 kN) 35 % higher than the
ber-only beams.
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