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)

Chapter3
Axially loaded reinforced
concrete columns
Preliminary note: Readers interested only in structural design to BS 8110
may concentrate on the following sections:
(a) Section 3.2: Stress/strain characteristics.
(b) Section 3.4: Design to BS 8110.
(c) Section 3.5: Design details (BS 8110).
(d) Section 3.6: Design and standard method of detailing---examples.
3.1 Introduction
Structural concrete members may be subjected to axialload, flexure, shear
or torsion, or a combination of these; they may be prestressed or nonprestressed.
The principles underlying their analysis and design are
basically the same. However, the authors' experience is that a teaching
text may with advantage begin with something simple-the axially loaded
column; this provides a good opportunity to introduce the concepts of
elastic and ultimate-strength behaviour and to demonstrate the important
effects of shrinkage and creep. To avoid unnecessary distractions at this
stage, the discussion will further be restricted to short columns in this
chapter. The distinction between a short column and a slender column will
be explained in Chapter 7; it is sufficient for the time being to define a short
column as one in which the length is not more than about 15 times the
minimum lateral dimension.
3.2 Stress/strain characteristics of steel and concrete
The behaviour of reinforced concrete columns is intimately related to the
stress/strain characteristics of the reinforcement bars and the concrete.
Figure 3.2-1(a) shows typical stress/strain curves for the reinforcement;
these may be considered applicable for both tension and compression.
Both mild steel bars and hot-rolled high yield bars have definite yield
points. For mild steel, the plastic range (that is, the horizontal plateau of
the curve) may extend up to a strain of about 0.015; for hot-rolled high
yield steel, the plastic range extends up to about 0.005 strain when the
curve rises again as a result of strain hardening. Cold-worked high yield
bars do not have a definite yield point; for practicat purposes, BS 4461
F . K .K o n g e t a l., Reinforced and Prestressed Concrete
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