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)

Shear resistance in design calculations (BS 8110) 209
restricting the widening of the diagonal crack [1]; but links can
perform the important function of preventing the pressing down of
the longitudinal reinforcement and hence maintaining the dowel
capacity.
Example 6.3-1
With reference to the truss analogy illustrated in Fig. 6.3-4, derive an
expression for the number of links that will be crossed by the line A-A.
Hence comment on the maximum permissible link spacing.
SOLUTION
With reference to Fig. 6.3-5, the horizontal projection of A'-A' = (d -
d') cot {3. Similarly the horizontal projection of a link is (d - d') cot a.
Thus, the line A-A will intersect alI the links within the horizontal
distance (cot a + cot (3) (d - d'). That is,
[ Number of links] = (cot a + cot (3) (d - d')
crossed by A-A
SV
* [cot a ~ cot {3] d
The maximum permissible link spacing is that which will enable the line
A - A to cross one link only, so that
sv,max = (cot a + cot (3)d
For the particular case of vertical links, a = 90° and (see explanation
folIowing eqn 6.3-3) (3 = 45°, so that
sv.max(vertical links) = d
A
A
1. (Colcx+Col,alld-d"
Fig. 6.3-5 Effective region for a web bar [See also Ref. 7]
6.4 Shear resistance in design calculations (BS 8110)
BS 8110's design procedure is based on the principles explained in Sections
6.2 and 6.3. The procedure is summarized below, with comments on the
various steps listed at the end.