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
13.33 kg/cm2 tensile
13.33 kg/cm2 compressive
26.67 kg/cm2 tensile
26.67 kg/cm2 compressive
none of these.
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
16 comments Page 2 of 2.

Shraddha said:   5 years ago
@Vipin Sainath.

Why Σ = (M/Z)*(P/A)?

Kajal said:   5 years ago
@Vipin Sainath.

Why multiplying p/A?
(1)

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.

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.
(2)

B.Singh said:   3 years ago
Great solution, thanks @Vipin Sainath.
(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?


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