Question

1. (a) Explain the difference between
columns which are short and slender
and those which are braced and
unbraced.
(b) Calculate the ultimate axial load
capacity of a short-braced column
supporting an approximately
symmetrical arrangement of beams
assuming that it is 500 mm square
and is reinforced with eight
20 mm diameter bars. Assume that
fcu = 40 N/mm2, fy = 500 N/mm2 and
the concrete cover is 25 mm. Design
the shear reinforcement for the
column.

2. (a) A braced column which is 300 mm
square is restrained such that it has an
effective height of 4.5 m. Classify the
column as short or slender.

(b) The column supports:
(1) an ultimate axial load of 500 kN
and a bending moment of
200 kNm, or
(2) an ultimate axial load of 800 kN
and bending moments of 75 kNm
about the x-axis and 50 kNm
about the y-axis.
Design the longitudinal steel for both
load cases by constructing suitable
design charts assuming fcu = 40 N/mm2,
fy = 500 N/mm2 and the covers to all
reinforcement is 35 mm.

3. An internal column in a multi-storey
building supporting an approximately
symmetrical arrangement of beams carries
an ultimate load of 2,000 kN. The storey
height is 5.2 m and the effective height
factor is 0.85, fcu = 35 N/mm2 and
fy = 500 N/mm2.
Assuming that the column is square,
short and braced, calculate:
1. a suitable cross-section for the column;
2. the area of the longitudinal
reinforcement;
3. the size and spacing of the links.
Sketch the reinforcement detail in cross-section.

Answer 1