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Unformatted text preview: 05Ch05.qxd 9/24/08 4:59 AM Page 395 SECTION 5.5 Normal Stresses in Beams q xmax2
22 Mmax RAxmax Mmax 9.40376 * 10 Mmax 2 2
1 xmax q xmax
3 qL2 8.727 kN # m smax Mmax
S smax 6.493 * 103 395 N
m2 smax 6.49 MPa ; 21.6 ksi ; Problem 5.5-5 Each girder of the lift bridge (see figure) is
180 ft long and simply supported at the ends. The design load
for each girder is a uniform load of intensity 1.6 k/ft. The girders
are fabricated by welding tree steel plates so as to form an
I-shaped cross section (see figure) having section modulus
S 3600 in.3.
What is the maximum bending stress smax in a girder due
to the uniform load? Solution 5.5-5 Bridge girder
S 180 ft q 1.6 k/ft 3 3600 in. Mmax qL2
8 smax Mmax
S smax qL2
8S (1.6 k/ft)(180 ft)2(12 in./ft)
8(3600 in.3) ...
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This note was uploaded on 12/22/2011 for the course MEEG 310 taught by Professor Staff during the Fall '11 term at University of Delaware.
- Fall '11