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)

412 Practical design and detailing
exceeding ultimate ground pressure values, may have been taken care of
by proper consideration of the foundation material, it is still possible for a
tall, narrow building to fail by overturning. Such a mode of failure should
be investigated with a load application of l.OGk + 1.4Wk (BS 8110:
Clause 3.2.1.3.2).
Some examples of the application of these loading arrangements to the
given sub-frames will be given in Sections 11.4(b) and (c).
We have explained the analysis for braced and unbraced frames. It is
necessary to bear in mind that the designer should aim for safe, robust and
durable structures; unbraced frames should be avoided if possible. Indeed
the I.Struct.E. Manual [20] specifically recommends that 'lateral stability
in two orthogonal directions should be provided by a system of strongpoints
within the structure so as to produce a braced structure, i.e. one in which
the columns will not be subject to sway moments'. Examples of such
strongpoints are the shear walls and core walls referred to earlier in this
section.
Robustness (BS 8110: Clause 3.1.4)
All members of the structure should be effectively held together with ties in
the longitudinal, transverse and vertical directions [20]. Detailed provisions
are given in BS 8110: Clause 3.1.4 and in the I.Struct.E. Manual
[20]: Clause 4.11. The applications of the BS 8110 provisions are illustrated
in Section 11.5: in Step 9 of Example 11.5-1 and Step 9 of Example
11.5-2.
11.4(b) Braced frame analysis
Example 11.4-l(a)
Figure 11.4-3 shows a braced structural frame, such that the lateral
loading is resisted by suitable shear walls or other means. Calculate the
moments in the beams AB, BC and CD if the characteristic dead load gk is
IOkN
-J
"l
N
Bm 10m
·I Bm ·I
Fig. 11.4-3 Structural frame--relative El values as shown in boxes