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Unformatted text preview: Sec_2.5.qxd 9/25/08 3:00 PM Page 165 SECTION 2.5 Thermal Effects (b) DISPLACEMENTS AT B & C
use superposition of displacements in the two
a ¢ T1 L12 dB RA a L1
E A1 a ¢ T 1 L12
[ s + a ¢ T1 L1 + L22] dB L1
k3 ; a¢ T1 L1 + L22 dC RAa
E A2 ; a ¢ T1 L1 + L22
[ a 165 s + a ¢ T1 L1 + L22] L1
E A1 a L1
E A2 Problem 2.5–17 Wires B and C are attached to a support at the left-hand
end and to a pin-supported rigid bar at the right-hand end (see figure).
Each wire has cross-sectional area A 0.03 in.2 and modulus of elasticity
E 30 106 psi. When the bar is in a vertical position, the length of each
wire is L 80 in. However, before being attached to the bar, the length of
wire B was 79.98 in. and of wire C was 79.95 in.
Find the tensile forces TB and TC in the wires under the action of a force
P 700 lb acting at the upper end of the bar. 700 lb
B b C b
b 80 in. Solution 2.5–17 Wires B and C attached to a bar
2TB P 700 lb A 0.03 in.2 E 30 106 psi LB 79.98 in. LC 79.95 in. 0
TB(2b) TC 3P ;
(Eq. 1) ...
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