Page 175 - Handbook of Civil Engineering Calculations, Second Edition

1.158 STRUCTURAL STEEL ENGINEERING AND DESIGN

DETERMINING DESIGN COMPRESSIVE
STRENGTH OF COMPOSITE COLUMNS

Determine the design compressive strength of a W8 40 (A36 steel) encased in a 16
16 in. (40.6 40.6 cm) ( f c
3.5 ksi) (24.1 MPa) normal-weight concrete column in
Fig. 46. Reinforcement is four No. 7 (Grade 60) bars longitudinally, and No. 3 ties at 10
in. (25.4 cm) horizontally.

Calculation Procedure:

1. Check the minimum requirements for the column
Checking minimum requirements

2
(a) For a W8 40, A s 11.7 sq.in., total area 16 in. 16 in. 256 sq.in. (1652 cm )
11.7 sq.in.
4.6% > 4% minimum o.k.
256 sq.in.
(b) Lateral tie spacing 10 in. (25.4 cm)

< /3 16 in. outer dimension 10.7 in. (27.2 cm) o.k.
2
(b) Minimum clear cover 1.5 in. (3.8 cm) o.k.
(b) Horizontal No.3 bars: A r 0.11 sq.in. per bar
2
> 0.007 sq.in. 10 in. spacing 0.07 sq.in. (0.45 cm ) o.k.
(b) Vertical No.7 bars: A r 0.60 sq.in. per bar
2
> 0.007 sq.in. 11.4 in. spacing 0.08 sq.in. (0.52 cm ) o.k.
(c) 3.0 ksi < ( f c
3.5 ksi) < 8.0 ksi for normal weight concrete o.k.
(d) Use F yr 55 ksi (378.9 MPa) for reinforcement in calculations, even though actual
F yr 60 ksi (413.4 MPa) for Grade 60 bars.

FIGURE 46