Page 124 - Handbook of Structural Steel Connection Design and Details

Design of Connections for Axial, Moment, and Shear Forces

Design of Connections for Axial, Moment, and Shear Forces 109

2.2.4 Column base plates
The geometry of a column base plate is shown in Fig. 2.26. The area of
the base plate is A B N. The area of the pier that is concentric with
1
A is A . If the pier is not concentric with the base plate, only the portion
1 2
that is concentric can be used for A . The design strength of the concrete
2
in bearing is
A 2
F 5 0.6 3 0.85f c
c p
BA 1
where fr c is the concrete compressive strength in ksi and
A
1 # 2 # 2
BA 1

The required bearing strength is
P
f 5
p
A 1
where P is the column load (factored) in kips. In terms of these variables,
the required base plate thickness is
2f p
t p 5 l
B F y

where l max {m,n, n }
F base plate design strength 0.9 F
y y
N 2 0.95d
m 5
2
B 2 0.8bf
n 5
2
nr 5 2dbf
4
22x
l 5 # 1
1 1 21 2 x
f
4db f p
x 5 2
sd 1 b d F
c p
f
d depth of column
b flange width of column
f
For simplicity, can always be conservatively taken as unity. The for-
mulation given here was developed by Thornton (1990a, 1990b) based
on previous work by Murray (1983), Fling (1970), and Stockwell (1975).
It is the method given in the AISC Manual (2005).

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