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)

Design and detailing-illustrative examples 193
Fig. 5. 7-3 Tension bars at support
clear distance between bars = 160 mm.
From Fig. 5.7-3,
Comments
(a)
ab + 2( 40 + 16 + 20 + 20) = 325
ab = 133 mm < 160 mm OK
(ac + 2~y = (4o + 2~y + (76 + 2~y
ac = 89.48 mm > ~ of 160 mm
(see Comment (a) below)
The corner distance ac is 89.48 mm and exceeds the BS 8110 limit in
Fig. 5.4-1. One possible remedial action is, of course, to carry out a
crack-width calculation (see Section 5.6). However, Example 5.4-1:
solution part (c) explains an easier remedial action. That is, we shall
take advantage of the fact that As, prov is greater than As, req and
use the reduced Is value to obtain a relaxed bar spacing from eqn
(5.4-2).
From Example 4.11-1, As,req = 572 mm 2 and As.prov = 628 mm 2 •
Hence, from eqn (5.3-1(b)),
f, = ~ f, As. req _!_
s 8 y As. prov /Jb
= i(460)(~~~)(t)
= 261 N/mm 2
Substituting into eqn (5.4-2),
. 47000 47000
clear spacmg = ---rs- = 261 = 180 mm
Therefore, we now have
ac = 89.48 mm <!of 180 mm OK