Steel Designers Manual - TheBestFriend.org

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Steel Designers' Manual - 6th Edition (2003)
678 Bolts
centre method is used. This is a redistribution system, developed by Crawford and
Kulak, 11 in which the assumed centre of rotation is continually adjusted until the
three basic equations of equilibrium are satisfied.The method is a limit-state concept
and has been shown to be less conservative than the traditional elastic methods.)
Consider first a single line of bolts subject to a torsional moment, Fig. 23.4(a). If
the area of each bolt is a, the second moment of area of a typical bolt is ay 2 and the
total Say 2 = aSy 2 .The stress in the extreme bolt due to the eccentricity then becomes:
My
I
and the force per bolt
May1
My1
= 2 2 aSy Sy
The polar inertia about the centroid for any single line group containing n bolts with
constant pitch p is
I
0
=
My
=
aSy 1 1
2
J= ( n-1)
Â
J = 0
È(
n-1-2J) ˘
p
ÎÍ 2 ˚˙
2
Consider next a double line of bolts subject to a load R with eccentricity x (Fig.
23.4(b)). The radius to the nearest bolt is given by
Fig. 23.4 Bolt group analysis
'1
'
+
+ +
(a) (b)
y