Deep beams with web openings - Reinforced Concrete Deep Beams - page 87

Figure 3.16 Comparison of tested and computed ultimate shear strengths of beams with and
without opening in web under four-point loading (Ray, 1980; 1985).
where, the subscripts 1 and 2 refer to the values with respect to critical paths
I and II respectively.
Eqns (3.41) and (3.42) can be utilised in predicting the ultimate strength of
beams with web openings. Moreover, the failure load path can be predicted in
advance and with greater certainty by computing the resistance of the two
critical paths, unless the difference is only marginal. Eqns (3.4.1) and (3.42)
developed for a general case of reinforced concrete deep beams with web
openings and provided with main and web steel, however, can be utilised for
finding out the ultimate strengths of reinforced concrete beams with main steel
only and of plain concrete beams by deleting the terms not involving.
However, in the four-point loading, unlike the two-point system, the
admissible size of the opening will be fixed on the basis of the larger shear
span ( Figure 3.15) and the restrictions stipulated for the opening parameters
will apply in this case also.
The validity of the Eqns (3.41) and (3.42) has been verified for a few
beams available (Kong et al., 1977; Ray, 1980; 1985) and found satisfactory.
Variations beyond ±20% are limited to only few beams and within a
variation of ±30%, 80% of the beams under four-point loading can be
covered (Figure 3.16).