Mechanical Engineering - Strength of Materials - Discussion

Discussion Forum : Strength of Materials - Section 9 (Q.No. 3)
3.
Two beams, one of circular cross-section and the other of square cross-section, have equal areas of cross-sections. When these beams are subjected to bending,
both beams are equally economical
square beam is more economical
circular beam is more economical
none of these
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
10 comments Page 1 of 1.

Siva said:   6 years ago
Higher section modulus is more economical.

Paul said:   7 years ago
The matter of stress concentration comes across for square section while nothing like in circular. So, that is entirely possible of economical consideration. Moreover, I work in construction. Where rebars are used of circular cross-section.
(1)

Amanuel said:   7 years ago
If you compute the section modules of both section you will get square cross-section has greater section modulus than that of circular as when I calculate this I get Zs=0.116Md^3 > Zc= 0.0982Md^3.

This is done by taking a same cross-sectional area and bending moment.

Ashutosh Mukherjee said:   7 years ago
The circular cross-section is always smaller than the square cross-section (can be explained by why bubbles/droplets take the shape of sphere). For a smaller cross-section, the stress applied will be more. Thus square cross-section will be more economical.
(1)

Pradeep gk said:   8 years ago
Therfore all beams are made of a square section for buildings not a circular.

Prashant said:   9 years ago
I considered a square and circle,
Square = 50 mm x 50 mm, area = 2500 mm^2. It gives inertia 520833.3333 mm^4.
Circle = dia 56.42 mm, area = 2500 mm^2. It gives inertia 497359.1972 mm^4.

Which proves Square beam is more economical.

Arvind said:   1 decade ago
Section modulus of square beam is more than circular beam.
(1)

Amit said:   1 decade ago
As per the stress distribution diagram.

Ashish said:   1 decade ago
The higher section of modulus is trapezoidal.

Karthi said:   1 decade ago
Square beams have higher section modulus.

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