CIVIL ENGINEERING FORMULAS

90 CHAPTER THREE

(3.11)

(3.12)

COLUMN BASE PLATE DESIGN

Base plates are usually used to distribute column loads over a large enough area
of supporting concrete construction that the design bearing strength of the con-
crete is not exceeded. The factored load, Pu, is considered to be uniformly dis-
tributed under a base plate.
The nominal bearing strength, fp, kip/in^2 or ksi (MPa) of the concrete is
given by

(3.13)

wherefcspecified compressive strength of concrete, ksi (MPa)
A 1 area of the base plate, in^2 (mm^2 )
A 2 area of the supporting concrete that is geometrically similar to and
concentric with the loaded area, in^2 (mm^2 )

In most cases, the bearing strength, fpis , when the concrete support is
slightly larger than the base plate or , when the support is a spread footing,
pile cap, or mat foundation. Therefore, the required area of a base plate for a
factored load Puis

(3.14)

wherecis the strength reduction factor0.6. For a wide-flange column, A 1
should not be less than bfd, where bfis the flange width, in (mm), and dis the
depth of column, in (mm).
The length N, in (mm), of a rectangular base plate for a wide-flange column
may be taken in the direction of das

(3.15)

The width B, in (mm), parallel to the flanges, then, is

B (3.16)

A 1

N

N 2 A 1  d or 0.5(0.95d0.80bf)

A 1 

Pu

c0.85fc

1.7fc

0.85fc

fp0.85fc

B

A 1

A 1

and

B

A 2

A 1

 2

P

A

1.95

Q

A

L

r

67

Q

A



51,000,000

(L/r)^2