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)

174 Reinforced concrete beams-the serviceability limit states
t--l• --b----.l
..,
• • ;.;J
(notecJ h
• •-1--lfih
sb,..250
Notes:
(a} ab ~ value specified in Table 5·4-1
(b)
ac ~ t x value specified for ab
{c) If (and only if) h> 750mm, side bars
are required to a depth of t h.
Fig. 5.4-1 Reinforcement spacing rules for crack control
Note: the minimum sizes are to guard against the bar yielding locally
at a crack.
Table5.4-l Clear distance between bars (BS 8110: Clause 3.12.11.2.3)
Redistribution to ( +) or from (-) section considered
f
(N/mm 2 ) -30 -20 -10 0 +10 +20 +30 (%)
250 210 240 270 300 300 300 300 (mm)
460 115 130 145 160 180 195 210 (mm)
Comments on Table 5.4-1
(a) The values in Table 5.4-1 have been calculated from the following
equation, which may be more convenient to use than interpolation
from the table:
I . 75000[100 - /3%] 300
c ear spacmg = !;- 100 :::; (5.4-1)
where {3% is the percentage of moment redistribution.
(b) Instead of using Table 5.4-1 or eqn (5.4-1), BS 8110: Clause
3.12.11.2.4 states that the clear spacing may be calculated from
. 47000
clear spacmg = -r :::; 300 (5.4-2)