Structures·MCQ explained

What is the slope at the end of a simply supported beam of span 2 m carrying a load of 5 kg per unit length over the entire span?

Try it first: pick an option, then read the explanation.

Correct answer: B. 5/(3EI)

Asked in SSC JE 02/03/2017 (Morning)

Detailed Explanation

For a simply supported beam with a UDL over the whole span, the slope at each support is wL³/24EI.

\[ \theta = \frac{wL^3}{24EI} = \frac{5\times2^3}{24EI} = \frac{40}{24EI} = \frac{5}{3EI} \]

Why “5/(3EI)” Is Correct

The end slope is 5/(3EI) (in kg and m units).

w per unit lengthABLBMDwL²/8δ5wL⁴/384EI
Simply supported beam with UDL w: parabolic BMD with wL²/8 at the centre; maximum deflection 5wL⁴/384EI at mid-span and slope wL³/24EI at each support.

Why the Other Options Are Wrong

  • A. 1/(16EI): 1/16EI uses the central-point-load coefficient without the load values.
  • C. 1/(3EI): 1/3EI is five times too small.
  • D. 1/(20EI): 1/20EI has no basis.

Key Point

Simply supported UDL: θend = wL³/24EI.

Key Concepts for Students

  • Central point load: θend = WL²/16EI.
  • Maximum deflection: 5wL⁴/384EI.
  • Write the answer in the same units as the data.

Practice more: this is question 34 in Slope and Deflection MCQs – Part 3. Try the whole set and check every answer instantly.