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GATE 2020 AE – Question 39

Structures · Strength of materials: stress and strain, stress-strain curves, trusses, bars, beams and shafts, determinate and indeterminate · 2 marks · Multiple choice

A stepped cantilever carries P = 3 N at its free end. The free-end segment is 2 m long with second moment I; the segment next to the fixed end is 1 m long with second moment 3I. Material modulus is E. Neglect transverse shear and stress concentrations. Find free-end deflection.

Diagram for GATE 2020 AE question 39
  1. $23/(243EI)$
  2. $1/(3EI)$
  3. $43/(3EI)$
  4. $23/(3EI)$

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Correct answer: (C) $43/(3EI)$

Explanation

Let x run from the free end, so bending moment magnitude is Px. The unit-load method gives $\delta=P[\int_0^2x^2/(EI)dx+\int_2^3x^2/(3EI)dx]$. These integrals give $P[8/3+19/9]/(EI)=43P/(9EI)$. With P = 3 N, δ = 43/(3EI), C.

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