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)

Problems 287
7.8 Computer programs
(in collaboration with Dr H. H. A. Wong, University of Newcastle upon
Tyne)
The FORTRAN programs for this chapter are listed in Section 12.7. See
also Section 12.1 for 'Notes on the computer programs'.
Problems
7.1 Is the moment-carrying capacity M of a column section increased by
an increase in the axial load N?
Ans.
Yes and no. See Fig. 7.1-7, which shows that (a) in the region of
tension failure, i.e. when a is less than that of point H, the answer is
'yes' and (b) in the region of compression failure, i.e. when a is
greater than that of point H, the answer is 'no'.
7.2 Is the load-carrying capacity N of a column section increased by an
increase in the bending moment M?
Ans.
No. (Study Fig. 7.1-7 and think carefully.)
7.3 In Section 7.1, the principles of interaction diagrams were discussed
with reference to a rectangular column section. Explain how these
principles can be applied to the construction of an interaction diagram for a
circular column.
~~4icu
Problem7.3
Ans.
(The numerical calculations tend to be tedious, but no new
principles are involved.) For each assumed value of x, determine
the steel strains from compatibility and read off the corresponding
steel stresses from the stress/strain curve. Then determine Nand M
from equilibrium consideration. Repeat the process for various x
values and complete the N - M curve.
7.4 BS 8110: Clause 3.8.4.5 gives the following equations for the design
of columns under biaxial bending: