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)

416 Practical design and detailing
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28 162
Fig. 11.4-5 Storey sub-frame bending moments (kNm)-loading as in Fig. 11.4-4
Fixed end moments (FEM) (Table 11.4-3):
Spans AB, CD:
Span BC:
w/ 2 /12 = 36 - 8 2 /12 = 192 kNm
w/ 2 /12 = 122 x 10Z/12 = 1020 kNm
With the 'free' bending moment in span BC equal to 1525 kNm (i.e.
122 x 10 2 /8), the maximum sagging moment at the centre of span BC
is 533 kNm (i.e. 1525-972). This is to be compared with the value of
769 kNm, as given in Fig. 4.9-6, Case 2, and the difference is due to the
introduction of column restraint. Figure 11.4-5 shows the corresponding
bending moment diagram.
Example 11.4-l(c)
With reference to the braced frame in Example 11.4-1(a) and Fig. 11.4-3,
calculate the bending moments in the beam AB; use the sub-frame of
Fig. 11.4-l(e).
SOLUTION
For clarity, Fig. 11.4-1(e) is redrawn as Fig. 11.4-6 with appropriate
dimensions and loadings included.
Distribution factors (DF) (Table 11.4-4):
At A: (~cols): AB = 84%: 16% (as in Example 11.4-
1(b))
T.
3m
122 kN/m 36kN/m
+·A 8
(half stiffness)
3m
_l__
8m 10m
I· . I·
Fig. 11.4-6 . Sub-frame for beam AB
'
-I
c