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)

Real behaviour of columns 71
with a maximum stress of 0.67 !e)Ym; concrete is assumed to fail at an
ultimate strain, Eeu, of 0.0035.
3.3 Real behaviour of columns
Figure 3.3-1 shows schematically a reinforced concrete column subjected
to an axial load N. The four longitudinal bars are enclosed by lateral ties,
or links as they are of ten called, the function of which will become clear
later ono We shall consider the response of the column as the load N is
progressively increased to the ultimate value.
Elastic behaviour
When the stresses in the concrete and the reinforcement are sufficiently
low, the stress/strain relations may be considered linear (Figs 3.2-1(a) and
3.2-2(a)); therefore the usual elastic theory applies. From the condition of
equilibrium,
N = !eAe + !sAse (3.3-1)
where N = applied axial load;
!e = compressive stress in the concrete;
!s = compressive stress in the longitudinal reinforcement;
Ac = cross-sectional area of the concrete;
Ase = cross-sectional are a of the longitudinal reinforcement.
Longitudinal bars
Lateral ties
Concrete cover
Cross section
t t t t 1
N
Fig. 3.3-1