Page 111 - Handbook of Structural Steel Connection Design and Details

Design of Connections for Axial, Moment, and Shear Forces

96 Chapter Two

Of the two possible choices, the first is the better one because the rigid-
ity of the gusset-to-top chord interface is much greater than that of the
gusset-to-truss vertical interface. This is so because the gusset is direct
welded to the center of the top chord flange and is backed up by the chord
web, whereas the gusset-to-truss vertical involves a flexible end plate
and the bending flexibility of the flange of the truss vertical. Thus, any
couple required to put the gusset in equilibrium will tend to migrate to
the stiffer gusset-to-top chord interface.
With 18.0 and 55.07,

r [(18.0 7 0.3191 55.07 0.3040 7/0.9527) 2
1
2
/
(7 55.07 0.9527) ] 2
74.16 in
and from the equations of Fig. 2.20,

V 648 kips
C
H 298 kips
C
V 87 kips
B
H 250 kips
B
For subsequent calculations, it is necessary to convert the gusset-to-top
chord forces to normal and tangential forces as follows: the tangential
or shearing component is

P
T V cos H sin ( e tan )
C C C C r
The normal or axial component is

e P
C
N H cos V sin
C C C r
The couple on the gusset-to-top chord interface is then

M | N s 2 d |
C C
Thus

920
T (55.07 7 .3191) 5 711 k
C 74.16
920 k
N 7 5 86.6
C 74.16
M 86.6 (55.07 48.5) 569 kips-in
C

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