Civil Engineering - UPSC Civil Service Exam Questions - Discussion
Discussion Forum : UPSC Civil Service Exam Questions - Section 1 (Q.No. 5)
5.
Two simply supported beams B1 and B2 have spans l and 2l respectively. Beam B1 has a cross-section of 1 x 1 units and beam B2 has a cross-section of 2 x 2 units. These beams are subjected to concentrated loads W each at the centre of their spans. The ratio of the maximum flexural stress in these beams is
4
2
Discussion:
12 comments Page 2 of 2.
Avenso said:
4 years ago
Stress = load/x - sectional area.
For B1 flexural stress = w/1 * 1 = w/1,
& for B2 flexural stress= w/2 * 2 = w/4,
Hence, the ratio of max. flex stress = w/(w/4) = 4.
For B1 flexural stress = w/1 * 1 = w/1,
& for B2 flexural stress= w/2 * 2 = w/4,
Hence, the ratio of max. flex stress = w/(w/4) = 4.
(2)
Jawad Ali said:
3 years ago
Flexural stress = MY/I,
M1=WL/4, y1=1/2, I1=1(1^3)/12 put values u will get stress 1=3wl/2
M2 = w(2L)/4=wL/2, y2=2/2=1 , I2= 2(2)^3/12=4/3
Hence stress2 =3wl/8.
Now stress1/stress 2 = 3wl/2 ÷ 3wl/8 = 3wl/2*8/3wl = 4.
M1=WL/4, y1=1/2, I1=1(1^3)/12 put values u will get stress 1=3wl/2
M2 = w(2L)/4=wL/2, y2=2/2=1 , I2= 2(2)^3/12=4/3
Hence stress2 =3wl/8.
Now stress1/stress 2 = 3wl/2 ÷ 3wl/8 = 3wl/2*8/3wl = 4.
(4)
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