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)

Bond and anchorage (BS 8110) 223
Table 6.6-2 Effective anchorage lengths of standard hooks and bends (BS 4466)
fy = 250 N/mm 2 fy = 460 N/mm 2
Bar size
(jJ Bend Hook Bend Hook
8 15(jJ 15(jJ
10 13(jJ 15(jJ
12 11(jJ AII 14(jJ AII
16 9(jJ 16(jJ 12(jJ 24(jJ
20 8(jJ 12(jJ
25 8(jJ 12(jJ
32 8(jJ 12(jJ
40 8(jJ 12(jJ
eqn (6.6-3(b». For the purpose of illustration, we shall assume that the
bar stresses are not known. From Fig. 6.4-1,
As (4 size 32 bars) = 3216 mm 2
e = 3216/(350) (800) = 1.15%
A~ (3 size 32 bars) = 2412 mm 2
e' = 2412/(350) (800) = 0.86%
From the beam design chart (Fig. 4.5-2),
M
btf. = 4 N/mm 2
Actual M/btP = (768) (10 6 )/(350) (800 2 ) = 3.43 N/mm 2
For anchorage length calculations, the bar stresses may be taken
approximately as
fs = 3.:3 (0.87fy) = 343 N/mm 2 (for fy = 460 N/mm 2 )
From eqn (6.6-3(a» and Table 6.6-1, the anchorage bond lengths 1 are
. (343) (32)
1 (tenslon bars) = (4) (0.5) (~40) = 868 mm
. (343) (32)
1 (compresslOn bars) = (4) (0.63) (~40) = 689 mm
Example 6.6-2
For many years, successive British Codes of Practice such as CP 110 and
CP 114 required designers to check local bond stresses. BS 8110, however,
does not require such checking. Comment.
SOLUTION
In the past, British designers check local bond stresses partly from habit
and partly because successive codes of practice have referred to such