GATE 2021 AR – Question 60
A simply supported steel I-beam spans 8 m under 15 kN/m UDL. Overall depth 450 mm and second moment of area 18000 cm⁴. Find maximum bending stress in N/mm², as an integer.
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Correct answer: 150 to 150
Explanation
Maximum moment iswL²/8=15×8²/8=120 kN·m=120000000 N·mm. Extreme-fibre distance is 225 mm and I=18000×10000=180000000 mm⁴. Thus σ=My/I=150 N/mm². Convert cm⁴ using the fourth power of the length conversion.