Question

A beam of uniform flexural rigidity supports a set of loads as shown in figure below.


What is the value of W if the magnitude of bending moment at midspan and at support of the beam are numerically equal?

• A. 20 kN
• B. 40 kN
• C. 60 kN
• D. 80 kN

Answer 1

The correct option is B 40 kN

(b)
Since the beam is symmetrically loaded, hence the vertical reaction.

$R=\frac{W}{2}+10$

Bending moment at support

$=(\frac{W}{2}+10)\times 2-10\times 4$

= W + 20-40 = -20

Bending moment at support

$=-10\times 2=20kN-m$

But bending moment at mid span and at support are numerically equal.

$\therefore W-20=20=40kN$