Civil Engineering - Strength of Materials - Discussion
Discussion Forum : Strength of Materials - Section 3 (Q.No. 5)
5.
The section modulus of a rectangular light beam 25 metres long is 12.500 cm3. The beam is simply supported at its ends and carries a longitudinal axial tensile load of 10 tonnes in addition to a point load of 4 tonnes at the centre. The maximum stress in the bottom most fibre at the mid span section, is
Discussion:
16 comments Page 1 of 2.
Supriya said:
3 years ago
Why using m/z+p/a?
It is like bending stress=M/Z know from the flexural formula. Am I right?
It is like bending stress=M/Z know from the flexural formula. Am I right?
B.Singh said:
3 years ago
Great solution, thanks @Vipin Sainath.
(2)
Shahid Khan said:
4 years ago
Here is the solution:
Length= 2.5m=250 cm,
Z=12500 cm^3,
Z=bh^2/6=12500,
Bh^2=75000,
H=50cm.
B=30 cm.
Sigma=m/z + p/A.
M=4000*250/4=250000,
A=1500 cm2.
Sigma =250000/12500 +10000/1500,
= 20+6.66,
= 26.66 kg/cm2.
Length= 2.5m=250 cm,
Z=12500 cm^3,
Z=bh^2/6=12500,
Bh^2=75000,
H=50cm.
B=30 cm.
Sigma=m/z + p/A.
M=4000*250/4=250000,
A=1500 cm2.
Sigma =250000/12500 +10000/1500,
= 20+6.66,
= 26.66 kg/cm2.
(2)
Chris said:
4 years ago
@Shraddha @Kajal.
P/A represents stress.
The bending formula:
M/I = f/y.
Stress f = P/A.
Section Modulus Z = I/y.
P/A represents stress.
The bending formula:
M/I = f/y.
Stress f = P/A.
Section Modulus Z = I/y.
Kajal said:
5 years ago
@Vipin Sainath.
Why multiplying p/A?
Why multiplying p/A?
(1)
Shraddha said:
5 years ago
@Vipin Sainath.
Why Σ = (M/Z)*(P/A)?
Why Σ = (M/Z)*(P/A)?
Vipin sainath said:
5 years ago
Bending Stress (Sigma) = M/Z x P/A.
First, we have to calculate Depth and Breadth ..From span/depth ratio we get Depth
Span/20 = 25m/20 = 1.25m or 125cm so D= 125cm, Then B/D=0.5 to 0.67 from this ratio we get breadth B,
B = Dx0.5 = 125X0.5 = 62.5 say B= 60cm, So we got B and D.
M/Z = (4000x2500/4) / 12.6 = 2,00,000 kg/cm2.
P/A = 10000/7500 =1.33 kg/cm2.
Therefore, Sigma = 200000 kg/cm2 x 1.33 kg/cm2 = 266000 Kg/cm2 or 26.6 Kg/m2
finally we got Max stress = 26.6kg/m2.
First, we have to calculate Depth and Breadth ..From span/depth ratio we get Depth
Span/20 = 25m/20 = 1.25m or 125cm so D= 125cm, Then B/D=0.5 to 0.67 from this ratio we get breadth B,
B = Dx0.5 = 125X0.5 = 62.5 say B= 60cm, So we got B and D.
M/Z = (4000x2500/4) / 12.6 = 2,00,000 kg/cm2.
P/A = 10000/7500 =1.33 kg/cm2.
Therefore, Sigma = 200000 kg/cm2 x 1.33 kg/cm2 = 266000 Kg/cm2 or 26.6 Kg/m2
finally we got Max stress = 26.6kg/m2.
(3)
Basanth Babu said:
6 years ago
The cross sectional area of the beam is needed to solve this problem.
(2)
Pranjul said:
6 years ago
Area calculate from bending equation M = f * Z and f = force/area.
Muthu said:
6 years ago
Please explain the answer.
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