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)

446 Practical design and detailing
but at a distance from the support face equal to the effective depth d. This
is permitted by BS 8110-for details, see the Comments on Step 5 of the
solution to Example 6.4-2.
Comments on Step 7
See also Example 5.3-2 on possible remedial actions if the actual
span/depth ratio had exceeded the allowable.
Comments on Step 8
The clear distance ab between the bars, and the corner distance ac, are
calculated in the same manner as in Example 5.7-2. The ac values in Table
11.5-3 include an allowance for the fact that the links can only be bent to
an internal radius of 2(j) (see Fig. 6.6-1).
In Table 11.5-3, corner distances ac are not shown for the top bars at the
support B; the reason is as explained in Comment (b) at the end of
Example 5.7-2.
For the span AB, the moment redistribution is indicated as zero in Table
11.5-3. The reason can be found in Fig. 11.5-6, which shows that the
redistributed curve IIIR in fact coincides with the elastic curve I.
Comments on Step 9
The internal tie requirement dictates the provision of the bottom bars 2T32
at the internal support B. This explains why, in Step 5, 2T32 (1608 mm 2 )
were provided even though the area required at the time was only 476
mm 2 •
Comments on Step 10
The main bars in Fig. 11.5-12 have been curtailed in accordance with the
curtailment diagram in Fig. 11.5-10. (See also the 'Simplified rules for
curtailment of bars' in Section 4.10.)
Example 11.5-3
With reference to the braced building frame in Fig. 11.5-1, design and
detail an internal column, B9.
SOLUTION
See Fig. 11.5-13 (feu = 40 N/mm 2 ), and Comments at the end.
Step 1 Durability and .fire resistance
From Table 2.5-7,
nominal cover for mild exposure = 20 mm
cover to main bars = 30 + link (jJ = 40 mm, say
From Table 3.5-1,
(use 30 mm)
for 380 square column with 40 mm cover to main bars,
the fire resistance exceeds 1 hour
Nominal cover = 30 mm
Fire resistance 0 K