F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

(c)
Shear failure of beams without shear reinforcement 201
collapse occurs. This failure mode is of ten called shear-tension failure
or shear-bond failure; again the ultimate load is not much higher than
the diagonal cracking load.
2.5> avid> 1: For avId lower than about 2.5 but greater than 1, the
diagonal crack of ten forms independently and not as a development
of a ftexural crack (Fig. 6.2-3) [10]. The beam usually remains stable
after such cracking. Further increase in the force V will cause the
diagonal crack to penetrate into the concrete compression zone at the
loading point, until eventually crushing failure of the concrete occurs
there, sometimes explosively (Fig. 6.2-3; shaded portion). This
failure mode is usually called shear-compression failure; for this
mode, the ultimate load is sometimes more than twice that at
diagonal cracking.
(d) avId < 1: The behaviour of beams with such low avId ratio
approaches that of deep beams [12-21]. The diagonal crack forms
approximately along a line joining the loading and support points
(Fig. 6.2-4). It forms mainly as a result of the splitting action of the
compression force that is transmitted directly from the loading point
to the support; it initiates frequently at about dl3 above the bottom
Ţ
d
1
Fig. 6.2-3
2·S>Ov/d >1
T
d
1
V
(
1
V Ov/d <1
Fig. 6.2-4