Question

Identify, from the following, the correct value of the bending moment $M_A\left(inkNmunits\right)$ at the fixed end A in the statically determinate beam shown below (with internal hinges at B and D), when a uniformly distributed load of 10kNm is placed on the spans. (Hint: Sketching the influence line for $M_A$ or applying the Principle of virtual Displacements makes the solution easy).

• A. -80
• B. 0
• C. +40
• D. -40

Answer 1

The correct option is B 0

By using Muller Breslau principle we obtain the ILD for bending moment $M_A$.
ILD for $M_A$

Now total $M_A$ at A due to UDL 10 kN/m is net area of ILD multiplied by 10 kN/m.
Net area of ILD = 0
$\therefore M_A=0$