Civil Engineering Reference
In-Depth Information
U2
U1
36'
28'
L2
6 @ 40' = 240'
Member U1-U2
1.51
0.56
Member U1-L2
-0.48
1.42
Member U2-L2
-0.63
FIGURE E5.7
Considering Section 1-1 in
Figure E5.6:
with unit load at L1 and
taking moments about P0, the force in U1-L2
=[−
(
1
/
6
)(
240
+
100
)
]
/
118.8
0.48.
Considering Section 1-1 in Figure E5.6: with unit load at L2 and taking
moments about P0, the force in U1-L2
=−
0.56 (Figure E5.7).
Considering Section 2-2 in Figure E5.6: with unit load at L2 and taking
moments about P0, the force in U2-L2
=
(
4
/
6
)(
100
)/
118.8
=
1.42.
Considering Section 2-2 in Figure E5.6: with unit load at L3 and taking
moments about P0, the force in U2-L2
=
2
/
6
(
100
+
240
)/
80
=
0.63 (Figure E5.7).
The distance,
h
p
, in Figure E5.6 illustrates the effect of the“modified panel
shear”created by the sloped chord, which participates in resisting the panel
shear force.
Influence lines for other chord and web members of the truss may be
constructed in a similar manner by applying unit loads at panel points and
determiningaxialforcesinmembersbythemethodofsectionsorthemethod
of joints.
=−
1
/
2
(
100
)/
80
=−
